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1871 semiconductor march 1998 hi7190 24-bit, high precision, sigma delta a/d converter features ? 22-bit resolution with no missing code ? 0.0007% integral non-linearity (typ) ? 20mv to 2.5v full scale input ranges ? internal pgia with gains of 1 to 128 ? serial data i/o interface, spi compatible ? differential analog and reference inputs ? internal or system calibration ? -120db rejection of 60/50hz line noise ? settling time of 4 conversions (max) for a step input applications ? process control and measurement ? industrial weight scales ? part counting scales ? laboratory instrumentation ? seismic monitoring ? magnetic field monitoring ? additional reference literature - tb348 hi7190/1 negative full scale error vs conversion frequency - an9504 a brief intro to sigma delta conversion - tb329 harris sigma delta calibration technique - an9505 using the hi7190 evaluation kit - tb331 using the hi7190 serial interface - an9527 interfacing hi7190 to a microcontroller - an9532 using hi7190 in a multiplexed system - an9601 using hi7190 with a single +5v supply description the harris hi7190 is a monolithic instrumentation, sigma delta a/d converter which operates from 5v supplies. both the sig- nal and reference inputs are fully differential for maximum ?exi- bility and performance. an internal programmable gain instrumentation ampli?er (pgia) provides input gains from 1 to 128 eliminating the need for external pre-ampli?ers. the on- demand converter auto-calibrate function is capable of remov- ing offset and gain errors existing in external and internal cir- cuitry. the on-board user programmable digital ?lter provides over -120db of 60/50hz noise rejection and allows ?ne tuning of resolution and conversion speed over a wide dynamic range. the hi7190 and hi7191 are functionally the same device so all discussion will refer to the hi7190 for simplicity. the hi7190 contains a serial i/o port and is compatible with most synchronous transfer formats including both the motor- ola 6805/11 series spi and intel 8051 series ssr protocols. a sophisticated set of commands gives the user control over calibration, pgia gain, device selection, standby mode, and several other features. the on-chip calibration registers allow the user to read and write calibration data. pinout hi7190 (pdip, soic) top view ordering information part number temp. range ( o c) package pkg. no. hi7190ip -40 to 85 20 ld pdip e20.3 HI7190IB -40 to 85 20 ld soic m20.3 hi7190eval evaluation kit 11 12 13 14 15 16 17 18 20 19 10 9 8 7 6 5 4 3 2 1 sclk sdo sdio cs drd y dgnd v rlo av ss v rhi v cm mode reset osc 1 osc 2 sync dv dd agnd av dd v inhi v inlo caution: these devices are sensitive to electrostatic discharge. users should follow proper ic handling procedures. copyright ? harris corporation 1998 file number 3612.5
1872 functional block diagram typical application schematic ? digital filter ? - d modulator pgia ? 1-bit d/a 1 control and serial interface unit control register serial interface unit clock generator av dd transducer burn-out current v inhi v inlo v cm osc 1 osc 2 drd y reset sync cs mode s clk sdio sdo v rhi v rlo reference inputs 10mhz osc 1 osc 2 v rhi v rlo +2.5v av dd +5v 0.1uf v cm v inhi v inlo agnd dv dd dgnd sclk cs drd y sync sdo sdio +5v 4.7 m f + 0.1 m f 4.7 m f + reset input input av ss -5v 0.1 m f 4.7 m f + data i/o data out sync cs drd y reset 13 17 16 15 12 11 10 9 8 7 14 6 18 5 4 19 2 3 1 mode 20 reference + - r 1 hi7190
1873 absolute maximum ratings thermal information supply voltage av dd to agnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5.5v av ss to agnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -5.5v dv dd to dgnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +5.5v dgnd to agnd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.3v analog input pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . av ss to av dd digital input, output and i/o pins . . . . . . . . . . . . . . . dgnd to dv dd esd tolerance (no damage) human body model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 500v machine model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +100v charged device model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1000v operating conditions temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . -40 o c to 85 o c thermal resistance (typical, note 1) q ja ( o c/w) pdip package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 soic package . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 maximum junction temperature plastic packages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150 o c maximum storage temperature range . . . . . . . . . .-65 o c to 150 o c maximum lead temperature (soldering, 10s) . . . . . . . . . . . . 300 o c (soic - lead tips only) caution: stresses above those listed in absolute maximum ratings may cause permanent damage to the device. this is a stress o nly rating and operation of the device at these or any other conditions above those indicated in the operational sections of this speci?cation is not im plied. electrical speci?cations av dd = +5v, av ss = -5v, dv dd = +5v, v rhi = +2.5v, v rlo = agnd = 0v, v cm = agnd, pgia gain = 1, osc in = 10mhz, bipolar input range selected, f n = 10hz parameter test conditions min typ max units system performance integral non-linearity, inl end point line method (notes 3, 5, 6) - 0.0007 0.0015 %fs differential non-linearity (note 2) no missing codes to 22-bits lsb offset error, v os see table 1 - -- - offset error drift v inhi = v inlo (notes 3, 8) - 1 - m v/ o c full scale error, fse v inhi - v inlo = +2.5v (notes 3, 5, 8, 10) - - - - noise, e n see table 1 - - - - common mode rejection ratio, cmrr v cm = 0v, v inhi = v inlo from -2v to +2v -70 - db normal mode 50hz rejection filter notch = 10hz, 25hz, 50hz (note 2) -120 - - db normal mode 60hz rejection filter notch = 10hz, 30hz, 60hz (note 2) -120 - - db step response settling time - 2 4 conversions analog inputs input voltage range unipolar mode (note 9) 0 - v ref v input voltage range bipolar mode (note 9) - v ref -v ref v common mode input range (note 2) av ss -av dd v input leakage current, i in v in = av dd (note 2) - - 1.0 na input capacitance, c in - 5.0 -pf reference voltage range, v ref (v ref = v rhi - v rlo ) 2.5 - 5 v transducer burn-out current, i bo - 200 - na calibration limits positive full scale calibration limit - - 1.2(v ref /gain) - negative full scale calibration limit - - 1.2(v ref /gain) - offset calibration limit - - 1.2(v ref /gain) - input span 0.2(v ref /gain) - 2.4(v ref /gain) - digital inputs input logic high voltage, v ih (note 11) 2.0 - - v input logic low voltage, v il - - 0.8 v input logic current, i i v in = 0v, +5v - 1.0 10 m a hi7190
1874 input capacitance, c in v in = 0v - 5.0 - pf digital outputs output logic high voltage, v oh i out = -100 m a (note 7) 2.4 - - v output logic low voltage, v ol i out = 3ma (note 7) - - 0.4 v output three-state leakage current, i oz v out = 0v, +5v (note 7) -10 1 10 m a digital output capacitance, c out -10- pf timing characteristics sclk minimum cycle time, t sclk 200 - - ns sclk minimum pulse width, t sclkpw 50 - - ns cs to sclk precharge time, t pre 50 - - ns drdy minimum high pulse width (notes 2, 7) 500 - - ns data setup to sclk rising edge (write), t dsu 50 - - ns data hold from sclk rising edge (write), t dhld 0- - ns data read access from instruction byte write, t acc (note 7) - - 40 ns read bit valid from sclk falling edge, t dv (note 7) - - 40 ns last data transfer to data ready inactive, t drdy (note 7) - 35 -ns reset low pulse width (note 2) 100 - - ns sync low pulse width (note 2) 100 - - ns oscillator clock frequency (note 2) 0.1 - 10 mhz output rise/fall time (note 2) - - 30 ns input rise/fall time (note 2) - - 1 m s power supply characteristics iav dd - - 1.5 ma iav ss - - 1.5 ma idv dd sclk = 4mhz - - 3.0 ma power dissipation, active pd a sb = 0 - 15 30 mw power dissipation, standby pd s sb = 1 - 5 - mw psrr (note 3) - -70 - db notes: 1. q ja is measured with the component mounted on an evaluation pc board in free air. 2. parameter guaranteed by design or characterization, not production tested. 3. applies to both bipolar and unipolar input ranges. 4. these errors can be removed by re-calibrating at the desired operating temperature. 5. applies after system calibration. 6. fully differential input signal source is used. 7. see load test circuit, figure 10, r1 = 10k w , c l = 50pf. 8. 1 lsb = 298nv at 24 bits for a full scale range of 5v. 9. v ref = v rhi - v rlo 10. these errors are on the order of the output noise shown in table 1. 11. all inputs except osc 1 . the osc 1 input v ih is 3.5v minimum. electrical speci?cations av dd = +5v, av ss = -5v, dv dd = +5v, v rhi = +2.5v, v rlo = agnd = 0v, v cm = agnd, pgia gain = 1, osc in = 10mhz, bipolar input range selected, f n = 10hz (continued) parameter test conditions min typ max units hi7190
1875 timing diagrams figure 1. data write to hi7190 figure 2. data read from hi7190 figure 3. data read from hi7190 1st bit 2nd bit cs sclk sdio t sclk t dsu t dhld t sclkpw t sclkpw t pre cs sclk sdio sdo t acc t dv 1st bit 2nd bit sclk cs drd y sdio t drd y 8 7 6 5 1 hi7190
1876 pin descriptions 20 lead dip, soic pin name description 1 sclk serial interface clock. synchronizes serial data transfers. data is input on the rising edge and output on the falling edge. 2 sdo serial data out. serial data is read from this line when using a 3-wire serial protocol such as the motorola serial peripheral interface. 3 sdio serial data in or out. this line is bidirectional programmable and interfaces directly to the intel standard serial interface using a 2-wire serial protocol. 4 cs chip select input. used to select the hi7190 for a serial data transfer cycle. this line can be tied to dgnd. 5 drd y an active low interrupt indicating that a new data word is available for reading. 6 dgnd digital supply ground. 7av ss negative analog power supply (-5v). 8v rlo external reference input. should be negative referenced to v rhi . 9v rhi external reference input. should be positive referenced to v rlo . 10 v cm common mode input. should be set to halfway between av dd and av ss . 11 v inlo analog input lo. negative input of the pgia. 12 v inhi analog input hi. positive input of the pgia. the v inhi input is connected to a current source that can be used to check the condition of an external transducer. this current source is controlled via the control register. 13 av dd positive analog power supply (+5v). 14 agnd analog supply ground. 15 dv dd positive digital supply (+5v). 16 osc 2 used to connect a crystal source between osc 1 and osc 2 . leave open otherwise. 17 osc 1 oscillator clock input for the device. a crystal connected between osc 1 and osc 2 will provide a clock to the device, or an external oscillator can drive osc 1 . the oscillator frequency should be 10mhz (typ). 18 reset active low reset pin. used to initialize the hi7190 registers, filter and state machines. 19 sync active low sync input. used to control the synchronization of a number of hi7190s. a logic 0 initializes the converter. 20 mode mode pin. used to select between synchronous self clocking (mode = 1) or synchronous external clocking (mode = 0) for the serial port. load test circuit figure 4. v 1 r 1 c l (includes stray dut capacitance) esd test circuits figure 5a. figure 5b. dut human body c esd = 100pf machine model c esd = 200pf r 1 c esd r 1 = 10m w r 1 = 10m w r 2 r 2 = 1.5k w r 2 = 0 w v charged device model r 1 r 1 = 1g w r 2 r 2 = 1 w v dut dielectric hi7190
1877 table 1. noise performance with inputs connected to analog ground hertz snr enob p-p noise ( m v) rms noise ( m v) gain = 1 10 132.3 21.7 9.8 1.5 25 129.5 21.2 13.6 2.1 30 127.7 20.9 16.6 2.5 50 126.3 20.7 19.5 3.0 60 125.6 20.6 21.2 3.2 100 122.4 20.0 30.7 4.6 250 107.7 17.6 166.7 25.3 500 98.1 16.0 505.3 76.6 1000 85.7 13.9 2101.8 318.5 2000 68.8 11.1 14661.6 2221.4 gain = 2 10 129.2 21.2 14.0 2.1 25 125.7 20.6 20.9 3.2 30 124.5 20.4 24.1 3.7 50 123.4 20.2 27.3 4.1 60 122.5 20.1 30.3 4.6 100 118.1 19.3 50.0 7.6 250 106.1 17.3 199.5 30.2 500 96.9 15.8 580.1 87.9 1000 84.4 13.7 2435.6 369.0 2000 67.8 11.0 16469.7 2495.4 gain = 4 10 125.9 20.6 20.5 3.1 25 123.1 20.1 28.4 4.3 30 121.8 19.9 32.8 5.0 50 119.9 19.6 40.9 6.2 60 119.9 19.6 40.9 6.2 100 116.1 19.0 63.2 9.6 250 105.7 17.3 209.7 31.8 500 96.6 15.8 597.8 90.6 1000 84.3 13.7 2469.5 374.2 2000 68.2 11.0 15656.1 2372.1 gain = 8 10 124.7 20.4 23.4 3.5 25 120.6 19.7 37.8 5.7 30 119.2 19.5 44.3 6.7 50 117.5 19.2 53.8 8.2 60 116.8 19.1 58.6 8.9 100 112.1 18.3 100.0 15.2 250 101.4 16.5 345.2 52.3 500 95.3 15.5 691.1 104.7 1000 83.1 13.5 2838.6 430.1 2000 68.3 11.1 15494.7 2347.7 gain = 16 10 120.1 19.7 39.8 6.0 25 114.8 18.8 73.4 11.1 30 113.5 18.6 85.1 12.9 50 111.0 18.1 114.4 17.3 60 109.6 17.9 134.0 20.3 100 105.5 17.2 214.8 32.5 250 95.2 15.5 699.1 105.9 500 89.1 14.5 1417.7 214.8 1000 83.5 13.6 2686.0 407.0 2000 62.6 10.1 30110.0 4562.1 gain = 32 10 113.2 18.5 88.8 13.5 25 109.0 17.8 142.7 21.6 30 108.2 17.7 157.4 23.8 50 104.7 17.1 235.8 35.7 60 105.0 17.1 227.8 34.5 100 102.3 16.7 310.5 47.0 250 93.4 15.2 861.1 130.5 500 87.1 14.2 1782.7 270.1 1000 78.2 12.7 4990.4 756.1 2000 57.0 9.2 57311.1 8683.5 gain = 64 10 106.7 17.4 186.2 28.2 25 102.9 16.8 288.4 43.7 30 101.9 16.6 325.8 49.4 50 98.5 16.1 479.8 72.7 60 98.9 16.1 459.8 69.7 100 96.3 15.7 620.2 94.0 250 85.5 13.9 2133.5 323.3 500 78.1 12.7 5025.0 761.4 1000 66.7 10.8 18693.5 2832.3 2000 50.5 8.1 120163.0 18206.5 gain = 128 10 101.1 16.5 356.5 54.0 25 96.0 15.7 638.3 96.7 30 95.2 15.5 704.8 106.8 50 93.2 15.2 882.2 133.7 60 92.2 15.0 996.7 151.0 100 91.4 14.9 1086.6 164.6 250 79.4 12.9 4346.4 658.5 500 71.8 11.6 10439.2 1581.7 1000 60.1 9.7 39923.0 6048.9 2000 44.8 7.1 233238.2 35339.1 hertz snr enob p-p noise ( m v) rms noise ( m v) hi7190
1878 de?nitions integral non-linearity, inl, is the maximum deviation of any digital code from a straight line passing through the end- points of the transfer function. the endpoints of the transfer function are zero scale (a point 0.5 lsb below the ?rst code transition 000...000 and 000...001) and full scale (a point 0.5 lsb above the last code transition 111...110 to 111...111). differential non-linearity, dnl, is the deviation from the actual difference between midpoints and the ideal difference between midpoints (1 lsb) for adjacent codes. if this differ- ence is equal to or more negative than 1 lsb, a code will be missed. offset error, v os , is the deviation of the ?rst code transition from the ideal input voltage (v in - 0.5 lsb). this error can be calibrated to the order of the noise level shown in table 1. full scale error, fse, is the deviation of the last code transition from the ideal input full scale voltage (v in -+v ref /gain - 1.5 lsb). this error can be calibrated to the order of the noise level shown in table 1. input span, de?nes the minimum and maximum input voltages the device can handle while still calibrating properly for gain. noise, e n , table 1 shows the peak-to-peak and rms noise for typical notch and -3db frequencies. the device program- ming was for bipolar input with a v ref of +2.5v. this implies the input range is 5v. the analysis was performed on 100 conversions with the peak-to-peak output noise being the difference between the maximum and minimum readings over a rolling 10 conversion window. the equation to convert the peak-to-peak noise data to enob is: enob = log 2 (v fs / v nrms ) where: v fs = 5v, v nrms = v np-p / cf and cf = 6.6 (imperical crest factor) the noise from the part comes from two sources, the quantization noise from the analog-to-digital conversion pro- cess and device noise. device noise (or wideband noise) is independent of gain and essentially ?at across the frequency spectrum. quantization noise is ratiometric to input full scale (and hence gain) and its frequency response is shaped by the modulator. looking at table 1, as the cutoff frequency increases the output noise increases. this is due to more of the quantization noise of the part coming through to the output and, hence, the output noise increases with increasing - 3db frequencies. for the lower notch settings, the output noise is dominated by the device noise and, hence, altering the gain has little effect on the output noise. at higher notch frequencies, the quantization noise dominates the output noise and, in this case, the output noise tends to decrease with increasing gain. since the output noise comes from two sources, the effective resolution of the device (i.e., the ratio of the input full scale to the output rms noise) does not remain constant with increasing gain or with increasing bandwidth. it is possible to do post-?ltering (such as brick wall ?ltering) on the data to improve the overall resolution for a given -3db frequency and also to further reduce the output noise. circuit description the hi7190 is a monolithic, sigma delta a/d converter which operates from 5v supplies and is intended for measurement of wide dynamic range, low frequency signals. it contains a programmable gain instrumentation ampli?er (pgia), sigma delta adc, digital ?lter, bidirectional serial port (compatible with many industry standard protocols), clock oscillator, and an on-chip controller. the signal and reference inputs are fully differential for maximum ?exibility and performance. normally v rhi and v rlo are tied to +2.5v and agnd respectively. this allows for input ranges of 2.5v and 5v when operating in the unipo- lar and bipolar modes respectively (assuming the pgia is con?gured for a gain of 1). the internal pgia provides input gains from 1 to 128 and eliminates the need for external pre- ampli?ers. this means the device will convert signals rang- ing from 0v to +20mv and 0v to +2.5v when operating in the unipolar mode or signals in the range of 20mv to 2.5v when operating in the bipolar mode. the input signal is continuously sampled at the input to the hi7190 at a clock rate set by the oscillator frequency and the selected gain. this signal then passes through the sigma delta modulator (which includes the pgia) and emerges as a pulse train whose code density contains the analog signal information. the output of the modulator is fed into the sinc 3 digital low pass ?lter. the ?lter output passes into the calibration block where offset and gain errors are removed. the calibrated data is then coded (2s complement, offset binary or binary) before being stored in the data output register. the data output register update rate is deter- mined by the ?rst notch frequency of the digital ?lter. this ?rst notch frequency is programmed into hi7190 via the control register and has a range of 10hz to 1.953khz which corresponds to -3db frequencies of 2.62hz and 512hz respectively. output data coding on the hi7190 is programmable via the control register. when operating in bipolar mode, data out- put can be either 2s complement or offset binary. in unipolar mode output is binary. the drd y signal is used to alert the user that new output data is available. converted data is read via the hi7190 serial i/o port which is compatible with most synchronous transfer formats including both the motorola 6805/11 series spi and intel 8051 series ssr protocols. data integrity is always maintained at the hi7190 output port. this means that if a data read of conversion n is begun but not ?nished before the next conversion (conversion n + 1) is complete, the drd y line remains active (low) and the data being read is not overwritten. the hi7190 provides many calibration modes that can be initiated at any time by writing to the control register. the device can perform system calibration where external com- ponents are included with the hi7190 in the calibration loop hi7190
1879 or self-calibration where only the hi7190 itself is in the cali- bration loop. the on-chip calibration registers are read/write registers which allow the user to read calibration coef?cients as well as write previously determined calibration coef?cients. circuit operation the analog and digital supplies and grounds are separate on the hi7190 to minimize digital noise coupling into the analog circuitry. nominal supply voltages are av dd = +5v, dv dd = +5v, and av ss = -5v. if the same supply is used for av dd and dv dd it is imperative that the supply is sepa- rately decoupled to the av dd and dv dd pins on the hi7190. separate analog and digital ground planes should be maintained on the system board and the grounds should be tied together back at the power supply. when the hi7190 is powered up it needs to be reset by pull- ing the reset line low. the reset sets the internal registers of the hi7190 as shown in table 2 and puts the part in the bipolar mode with a gain of 1 and offset binary coding. the ?lter notch of the digital ?lter is set at 30hz while the i/o is set up for bidirectional i/o (data is read and written on the sdio line and sdo is three-stated), descending byte order, and msb ?rst data format. a self calibration is performed before the device begins converting. drd y goes low when valid data is available at the output. the con?guration of the hi7190 is changed by writing new setup data to the control register. whenever data is written to byte 2 and/or byte 1 of the control register the part assumes that a critical setup parameter is being changed which means that drd y goes high and the device is re-syn- chronized. if the con?guration is changed such that the device is in any one of the calibration modes, a new calibra- tion is performed before normal conversions continue. if the device is written to the conversion mode, a new calibration is not performed (a new calibration is recommended any time data is written to the control register.). in either case, drd y goes low when valid data is available at the output. if a single data byte is written to byte 0 of the control register, the device assumes the gain has not been changed. it is up to the user to re-calibrate the device if the gain is changed in this manner. for this reason it is recommended that the entire control register be written when changing the gain of the device. this ensures that the part is re-calibrated (if in a calibration mode) before the drd y output goes low indicating that valid data is available. the calibration registers can be read via the serial interface at any time. however, care must be taken when writing data to the calibration registers. if the hi7190 is internally updating any calibration register the user can not write to that calibration register. see the operational modes section for details on which calibration registers are updated for the various modes. since access to the calibration registers is asynchronous to the conversion process the user is cautioned that new calibration data may not be used on the very next set of valid data after a calibration register write. it is guaranteed that the new data will take effect on the second set of output data. non-calibrated data can be obtained from the device by writing 000000 (h) to the offset calibration register, 800000 (h) to the positive full scale calibration register, and 800000 (h) to the negative full scale calibration regis- ter. this sets the offset correction factor to 0 and the positive and negative gain slope factors to 1. if several hi7190s share a system master clock the sync pin can be used to synchronize their operation. a common sync input to multiple devices will synchronize operation such that all output registers are updated simultaneously. of course the sync pin would normally be activated only after each hi7190 has been calibrated or has had calibration coef?cients written to it. the sync pin can also be used to control the hi7190 when an external multiplexer is used with a single hi7190. the sync pin in this application can be used to guarantee a max- imum settling time of 3 conversion periods when switching channels on the multiplexer. analog section description figure 6 shows a simpli?ed block diagram of the analog modulator front end of a sigma delta a/d converter. the input signal v in comes into a summing junction (the pgia in this case) where the previous modulator output is subtracted from it. the resulting signal is then integrated and the output of the integrator goes into the comparator. the output of the comparator is then fed back via a 1-bit dac to the summing junction. the feedback loop forces the average of the fed back signal to be equal to the input signal v in . table 2. register reset values register value (hex) data output register xxxx (undefined) control register 28b300 offset calibration register self calibration value positive full scale calibration register self calibration value negative full scale calibration register self calibration value pgia integrator comparator v rhi v rlo dac v in + - ? + - figure 6. simple modulator block diagram hi7190
1880 analog inputs the analog input on the hi7190 is a fully differential input with programmable gain capabilities. the input accepts both unipolar and bipolar input signals and gains range from 1 to 128. the common mode range of this input is from av ss to av dd provided that the absolute value of the analog input voltage lies within the power supplies. the input impedance of the hi7190 is dependent upon the modulator input sam- pling rate and the sampling rate varies with the selected pgia gain. table 3 below shows the sampling rates and input impedances for the different gain settings of the hi7190. note that this table is valid only for a 10mhz master clock. if the input clock frequency is changed then the input impedance will change accordingly. the equation used to calculate the input impedance is: where c in is the nominal input capacitance (8pf) and f s is the modulator sampling rate. bipolar/unipolar input ranges the input on the hi7190 can accept either unipolar or bipolar input voltages. bipolar or unipolar options are chosen by pro- gramming the b/ u bit of the control register. programming the part for either unipolar or bipolar operation does not change the input signal conditioning. the inputs are differential, and as a result are referenced to the voltage on the v inlo input. for example, if v inlo is +1.25v and the hi7190 is con?gured for unipolar operation with a gain of 1 and a v ref of +2.5v, the input voltage range on the v inlo input is +1.25v to +3.75v. if v inlo is +1.25v and the hi7190 is con?gured for bipolar mode with gain of 1 and a v ref of +2.5v, the analog input range on the v inhi input is -1.25v to +3.75v. programmable gain instrumentation ampli?er the programmable gain instrumentation ampli?er allows the user to directly interface low level sensors and bridges directly to the hi7190. the pgia has 4 selectable gain options of 1, 2, 4, 8 which are implemented by multiple sampling of the input signal. input signals can be gained up further to 16, 32, 64 or 128. these higher gains are implemented in the digital section of the design to maintain a high signal to noise ratio through the front end ampli?ers. the gain is digitally programmable in the control register via the serial interface. for optimum pgia performance the v cm pin should be tied to the mid point of the analog supplies. differential reference input the reference inputs of the of the hi7190, v rhi and v rlo , provide a differential reference input capability. the nominal differential voltage (v ref = v rhi - v rlo ) is +2.5v and the common mode voltage cab be anywhere between av ss and av dd . larger values of v ref can be used without degradation in performance with the maximum reference voltage being v ref = +5v. smaller values of v ref can also be used but performance will be degraded since the lsb size is reduced. the full scale range of the hi7190 is de?ned as: and v rhi must always be greater than v rlo for proper operation of the device. the reference inputs provide a high impedance dynamic load similar to the analog inputs and the effective input impedance for the reference inputs can be calculated in the same manner as it is for the analog input impedance. the only difference in the calculation is that c in for the reference inputs is 10.67pf. therefor, the input impedance range for the reference inputs is from 149k w in a gain of 8 or higher mode to 833k w in the gain of 1 mode. v cm input the voltage at the v cm input is the voltage that the internal analog circuitry is referenced to and should always be tied to the midpoint of the av dd and av ss supplies. this point provides a common mode input voltage for the internal oper- ational ampli?ers and must be driven from a low noise, low impedance source if it is not tied to analog ground. failure to do so will result in degraded hi7190 performance. it is recommended that v cm be tied to analog ground when operating off of av dd = +5v and av ss = -5v supplies. v cm also determines the headroom at the upper and lower ends of the power supplies which is limited by the common mode input range where the internal operational ampli?ers remain in the linear, high gain region of operation. the hi7190 is designed to have a range of av ss +1.8v < v cm < av dd - 1.8v. exceeding this range on the v cm pin will compromise the device performance. transducer burn-out current source the v inhi input of the hi7190 contains a 500na (typ) current source which can be turned on/off via the control register. this current source can be used in checking whether a trans- ducer has burnt-out or become open before attempting to take measurements on that channel. when the current source is turned on an additional offset will be created indicating the presence of a transducer. the current source is controlled by the bo bit (bit 4) in the control register and is disabled on power up. see figure 8 for an applications circuit. table 3. effective input impedance vs gain gain sampling rate (khz) input impedance (m w ) 1 78.125 1.6 2 156.25 0.8 4 312.5 0.4 8, 16, 32, 64, 128 625 0.2 z in = 1/(c in x f s ), fsr bipolar = 2 x v ref /gain fsr unipolar = v ref /gain hi7190
1881 digital section description a block diagram of the digital section of the hi7190 is shown in figure 9. this section includes a low pass decimation ?l- ter, conversion controller, calibration logic, serial interface, and clock generator. digital filtering one advantage of digital ?ltering is that it occurs after the conversion process and can remove noise introduced during the conversion. it can not, however, remove noise present on the analog signal prior to the adc (which an analog ?lter can). one problem with the modulator/digital ?lter combination is that excursions outside the full scale range of the device could cause the modulator and digital ?lter to saturate. this device has headroom built in to the modulator and digital ?l- ter which tolerates signal deviations up to 33% outside of the full scale range of the device. if noise spikes can drive the input signal outside of this extended range, it is recom- mended that an input analog ?lter is used or the overall input signal level is reduced. low pass decimation filter the digital low-pass ?lter is a hogenauer (sinc 3 ) decimating ?lter. this ?lter was chosen because it is a cost effective low pass decimating ?lter that minimizes the need for internal multipliers and extensive storage and is most effective when used with high sampling or oversampling rates. figure 10 shows the frequency characteristics of the ?lter where f c is the -3db frequency of the input signal and f n is the programmed notch frequency. the analog modulator sends a one bit data stream to the ?lter at a rate of that is determined by: f modulator = f osc /128 f modulator = 78.125khz for f osc = 10mhz. the ?lter then converts the serial modulator data into 40-bit words for processing by the hogenauer ?lter. the data is decimated in the ?lter at a rate determined by the code word fp10-fp0 (programed by the user into the control register) and the external clock rate. the equation is: f notch = f osc /(512 x code). the control register has 11 bits that select the ?lter cutoff frequency and the ?rst notch of the ?lter. the output data update rate is equal to the notch frequency. the notch fre- quency sets the nyquist sampling rate of the device while the -3db point of the ?lter determines the frequency spec- trum of interest (f s ). the fp bits have a usable range of 10 through 2047 where 10 yields a 1.953khz nyquist rate. the hogenauer ?lter contains alias components that re?ect around the notch frequency. if the spectrum of the frequency of interest reaches the alias component, the data has been aliased and therefore undersampled. filter characteristics please note: we have recently discovered a performance anomaly with the hi7190. the problem occurs when the digital code for the notch ?lter is programmed within certain frequencies. we believe the error is caused by the calibration logic and the digital notch code not the absolute frequency. the error is seen when the user applies mid-scale (0v input, bipolar mode). with this input, the expected digital output should be mid-scale (800000 h ). instead, there is a small probability, of an erroneous negative full scale (000000 h )output. ref er to t ec hnical brief tb348 f or complete details. the fp10 to fp0 bits programmed into the control register determine the cutoff (or notch) frequency of the digital ?lter. the allowable code range is 00a h . this corresponds to a maximum and minimum cutoff frequency of 1.953khz and 10hz, respectively when operating at a clock frequency of 10mhz. if a 1mhz clock is used then the maximum and min- imum cutoff frequencies become 195.3khz and 1hz, respec- tively. a plot of the (sinx/x) 3 digital ?lter characteristics is shown in figure 10. this ?lter provides greater than 120db of 50hz or 60hz rejection. changing the clock frequency or the programming of the fp bits does not change the shape of the ?lter characteristics, it merely shifts the notch fre- quency. this low pass digital ?lter at the output of the con- v rhi v rlo v inhi v inlo av dd av ss current source hi7190 ratiometric configuration load cell figure 7. burn-out current source circuit modulator output serial i/o sdo sdio sclk cs drd y reset sync osc 2 osc 1 modulator clock digital calibration and control clock generator filter figure 8. digital section block diagram hi7190
1882 verter has an accompanying settling time for step inputs just as a low pass analog ?lter does. new data takes between 3 and 4 conversion periods to settle and update on the serial port with a conversion period t conv being equal to 1/f n . input filtering the digital ?lter does not provide rejection at integer multi- ples of the modulator sampling frequency. this implies that there are frequency bands where noise passes to the output without attenuation. for most cases this is not a problem because the high oversampling rate and noise shaping char- acteristics of the modulator cause this noise to become a small portion of the broadband noise which is ?ltered. how- ever, if an anti-alias ?lter is necessary a single pole rc ?lter is usually suf?cient. if an input ?lter is used the user must be careful that the source impedance of the ?lter is low enough not to cause gain errors in the system. the dc input impedance at the inputs is > 1g w but it is a dynamic load that changes with clock frequency and selected gain. the input sample rate, also dependent upon clock frequency and gain, determines the allotted time for the input capacitor to charge. the addi- tion of external components may cause the charge time of the capacitor to increase beyond the allotted time. the result of the input not settling to the proper value is a system gain error which can be eliminated by system calibration of the hi7190. clocking/oscillators the master clock into the hi7190 can be supplied by either a crystal connected between the osc 1 and osc 2 pins as shown in figure 11a or a cmos compatible clock signal connected to the osc 1 pin as shown in figure 11b. the input sampling frequency, modulator sampling frequency, ?l- ter -3db frequency, output update rate, and calibration time are all directly related to the master clock frequency, f osc . for example, if a 1mhz clock is used instead of a 10mhz clock, what is normally a 10hz conversion rate becomes a 1hz conversion rate. lowering the clock frequency will also lower the amount of current drawn from the power supplies. please note that the hi7190 speci?cations are written for a 10mhz clock only. operational modes the hi7190 contains several operational modes including calibration modes for cancelling offset and gain errors of both internal and external circuitry. a calibration routine should be initiated whenever there is a change in the ambi- ent operating temperature or supply voltage. calibration should also be initiated if there is a change in the gain, ?lter notch, bipolar, or unipolar input range. non-calibrated data can be obtained from the device by writing 000000 to the offset calibration register, 800000 (h) to the positive full scale calibration register, and 800000 (h) to the negative full scale calibration register. this sets the offset correction factor to 0 and both the positive and negative gain slope factors to 1. the hi7190 offers several different modes of self-calibration and system calibration. for calibration to occur, the on-chip microcontroller must convert the modulator output for three different input conditions - zero-scale, positive full scale, and negative full scale. with these readings, the hi7190 can null any offset errors and calculate the gain slope factor for the transfer function of the converter. it is imperative that the zero-scale calibration be performed before either of the gain calibrations. however, the order of the gain calibrations is not important. the calibration modes are user selectable in the control register by using the md bits (md2-md0) as shown in ta b l e 6 . drd y will go low indicating that the calibration is complete and there is valid data at the output. alias band f n f c frequency (hz) amplitude (db) f n f c 2f n 3f n 4f n 0 -20 -40 -60 -80 -100 -120 figure 9. low pass filter frequency characteristics figure 10a. figure 10b. figure 10. oscillator configurations hi7190 osc 1 osc 2 10mhz 16 17 hi7190 osc 1 osc 2 10mhz 16 17 no connection hi7190
1883 conversion mode for conversion mode operation the hi7190 converts the dif- ferential voltage between v inhi and v inlo . from switching into this mode it takes 3 conversion periods (3 x 1/f n ) for drd y to go low and new data to be valid. no calibration coef?cients are generated when operating in conversion mode as data is calibrated using the existing calibration coef?cients. self-calibration mode please note: self-calibration is only valid when operating in a gain of one. in addition, the offset and gain errors are not reduced as with the full system calibration. the self-calibration mode is a three step process that updates the offset calibration register, the positive full scale calibration register, and the negative full scale cali- bration register. in this mode an internal offset calibration is done by disconnecting the external inputs and shorting the inputs of the pgia together. after 3 conversion periods the offset calibration register is updated with the value that corrects any internal offset errors. after the offset calibration is completed the positive and negative full scale calibration registers are updated. the inputs v inhi and v inlo are disconnected and the external reference is applied across the modulator inputs. the hi7190 then takes 3 conversion cycles to sample the data and update the positive full scale calibration register. next the polarity of the reference voltage across the modulator input terminals is reversed and after 3 conversion cycles the negative full scale calibration register is updated. the values stored in the positive and negative full scale calibration registers correct for any internal gain errors in the a/d transfer function. after 3 more conversion cycles the drd y line will activate signaling that the calibration is com- plete and valid data is present in the data output register. system offset calibration mode the system offset calibration mode is a single step process that allows the user to lump offset errors of external circuitry and the internal errors of the hi7190 together and null them out. this mode will convert the external differential signal applied to the v in inputs and then store that value in the off- set calibration register. the user must apply the zero point or offset voltage to the hi7190 analog inputs and allow the signal to settle before selecting this mode. after 4 conver- sion periods the drd y line will activate signaling that the calibration is complete and valid data is present in the data output register. system positive full scale calibration mode the system positive full scale calibration mode is a single step process that allows the user to lump gain errors of external circuitry and the internal errors of the hi7190 together and null them out. this mode will convert the exter- nal differential signal applied to the v in inputs and stores the converted value in the positive full scale calibration regis- ter. the user must apply the +full scale voltage to the hi7190 analog inputs and allow the signal to settle before selecting this mode. after 4 conversion periods the drd y line will activate signaling the calibration is complete and valid data is present in the data output register. system negative full scale calibration mode the system negative full scale calibration mode is a single-step process that allows the user to lump gain errors of external circuitry and the internal errors of the hi7190 together and null them out. this mode will convert the exter- nal differential signal applied to the v in inputs and stores the converted value in the negative full scale calibration regis- ter. the user must apply the -full scale voltage to the hi7190 analog inputs and allow the signal to settle before selecting this mode. after 4 conversion periods the drd y line will activate signaling the calibration is complete and valid data is present in the data output register. system offset/internal gain calibration mode please note: system offset/internal gain is only v alid when operating in a gain of one. in addition, the offset and gain errors are not reduced as with the full system calibra- tion. the system offset/internal gain calibration mode is a single step process that updates the offset calibration register, the positive full scale calibration register, and the negative full scale calibration register. first the external differential signal applied to the v in inputs is converted and that value is stored in the offset calibration register. the user must apply the zero point or offset voltage to the hi7190 analog inputs and allow the signal to settle before selecting this mode. after this is completed the positive and negative full scale calibration registers are updated. the inputs v inhi and v inlo are disconnected and the external reference is switched in. the hi7190 then takes 3 conversion cycles to sample the data and update the positive full scale calibration register. next the polarity of the reference voltage across the v inhi and v inlo terminals is reversed and after 3 conversion cycles the negative full calibration register is updated. the values stored in the positive and negative full scale calibration registers correct for any internal gain errors in the a/d transfer function. after 3 more conversion cycles, the drdy line will activate signaling that the calibration is complete and valid data is present in the data output register. table 4. hi7190 operational modes md2 md1 md0 operational mode 0 0 0 conversion 0 0 1 self calibration (gain of 1 only) 0 1 0 system offset calibration 0 1 1 system positive full scale calibration 1 0 0 system negative full scale calibration 1 0 1 system offset/internal gain calibration (gain of 1 only) 1 1 0 system gain calibration 1 1 1 reserved hi7190
1884 system gain calibration mode the gain calibration mode is a single step process that updates the positive and negative full scale calibration reg- isters. this mode will convert the external differential signal applied to the v in inputs and then store that value in the nega- tive full scale calibration register. then the polarity of the input is reversed internally and another conversion is per- formed. this conversion result is written to the positive full scale calibration register. the user must apply the +full scale voltage to the hi7190 analog inputs and allow the signal to settle before selecting this mode. after 1 more conversion period the drd y line will activate signaling the calibration is complete and valid data is present in the data output register. reserved this mode is not used in the hi7190 and should not be selected. there is no internal detection logic to keep this condition from being selected and care should be taken not to assert this bit combination. offset and span limits there are limits to the amount of offset and gain which can be adjusted out for the hi7190. for both bipolar and unipolar modes the minimum and maximum input spans are 0.2xv ref /gain and 1.2 x v ref /gain respectively. in the unipolar mode the offset plus the span cannot exceed the 1.2 x v ref /gain limit. so, if the span is at its minimum value of 0.2 x v ref /gain, the offset must be less than 1 x v ref /gain. in bipolar mode the span is equidistant around the voltage used for the zero scale point. for this mode the offset plus half the span cannot exceed 1.2 x v ref /gain. if the span is at 0.2 x v ref /gain , then the offset can not be greater than 2 x v ref /gain. serial interface the hi7190 has a ?exible, synchronous serial communication port to allow easy interfacing to many industry standard micro- controllers and microprocessors. the serial i/o is compatible with most synchronous transfer formats, including both the motorola 6805/11 spi and intel 8051 ssr protocols. the serial interface is a ?exible 2-wire or 3-wire hardware interface where the hi7190 can be con?gured to read and write on a single bidirectional line (sdio) or con?gured for writing on sdio and reading on the sdo line. the interface is byte organized with each register byte having a speci?c address and single or multiple byte trans- fers are supported. in addition, the interface allows ?exibility as to the byte and bit access order. that is, the user can specify msb/lsb ?rst bit positioning and can access bytes in ascending/descending order from any byte position. the serial interface allows the user to communicate with 5 registers that control the operation of the device. data output register - a 24-bit, read only register containing the conversion results. control register - a 24-bit, read/write register containing the setup and operating modes of the device. offset calibration register - a 24-bit, read/write register used for calibrating the zero point of the converter or system. positive full scale calibration register - a 24-bit, read/write register used for calibrating the positive full scale point of the converter or system. negative full scale calibration register - a 24-bit, read/write register used for calibrating the negative full scale point of the converter or system. two clock modes are supported. the hi7190 can accept the serial interface clock (sclk) as an input from the system or generate the sclk signal as an output. if the mode pin is logic low the hi7190 is in external clocking mode and the sclk pin is con?gured as an input. in this mode the user supplies the serial interface clock and all interface timing speci?cations are synchronous to this input. if the mode pin is logic high the hi7190 is in self-clocking mode and the sclk pin is con?gured as an output. in self-clocking mode, sclk runs at f sclk = osc 1 /8 and stalls high at byte boundaries. sclk does not have the capability to stall low in this mode. all interface timing speci?cations are synchronous to the sclk output. normal operation in self-clocking mode is as follows (see figure 13): cs is sampled low on falling osc 1 edges. the ?rst sclk transition output is delayed 29 osc 1 cycles from the next rising osc 1 . sclk transitions eight times and then stalls high for 28 osc 1 cycles. after this stall period is com- pleted sclk will again transition eight times and stall high. this sequence will repeat continuously while cs is active. the extra osc 1 cycle required when coming out of the cs inactive state is a one clock cycle latency required to prop- erly sample the cs input. note that the normal stall at byte boundaries is 28 osc 1 cycles thus giving a sclk rising to rising edge stall period of 32 osc 1 cycles. the affects of cs on the i/o are different for self-clocking mode (mode = 1) than for external mode (mode = 0). for external clocking mode cs inactive disables the i/o state machine, effectively freezing the state of the i/o cycle. that is, an i/o cycle can be interrupted using chip select and the hi7190 will continue with that i/o cycle when re-enabled via cs. sclk can continue toggling while cs is inactive. if cs goes inactive during an i/o cycle, it is up to the user to ensure that the state of sclk is identical when reactivating cs as to what it was when cs went inactive. for read opera- tions in external clocking mode, the output will go three-state immediately upon deactivation of cs. for self-clocking mode (mode = 1), the affects of cs are different. if cs transitions high (inactive) during the period when data is being transferred (any non stall time) the hi7190 will complete the data transfer to the byte boundary. that is, once sclk begins the eight transition sequence, it will always complete the eight cycles. if cs remains inactive after the byte has been transferred it will be sampled and sclk will remain stalled high inde?nitely. if cs has returned to active low before the data byte transfer period is completed the hi7190 acts as if cs was active during the entire transfer period. hi7190
1885 it is important to realize that the user can interrupt a data transfer on byte boundaries. that is, if the instruction regis- ter calls for a 3 byte transfer and cs is inactive after only one byte has been transferred, the hi7190, when reactivated, will continue with the remaining two bytes before looking for the next instruction register write cycle. note that the outputs will not go three-state immediately upon cs inactive for read operations in self-clocking mode. in the case of cs going inactive during a read cycle the outputs remain driving until after the last data bit is transferred. in the case of cs inactive during the clock stall time it takes 1 osc 1 cycle plus prop delay (max) for the outputs to be disabled. i/o port pin descriptions the serial i/o port is a bidirectional port which is used to read the data register and read or write the control register and calibration registers. the port contains two data lines, a synchronous clock, and a status ?ag. figure 12 shows a diagram of the serial interface lines. sdo - serial data out. data is read from this line using those protocols with separate lines for transmitting and receiving data. an example of such a standard is the motorola serial peripheral interface (spi) using the 68hc05 and 68hc11 family of microcontrollers, or other similar processors. in the case of using bidirectional data transfer on sdio, sdo does not output data and is set in a high impedance state. sdio - serial data in or out. data is always written to the device on this line. however, this line can be used as a bidi- rectional data line. this is done by properly setting up the control register. bidirectional data transfer on this line can be used with intel standard serial interfaces (ssr, mode 0) in mcs51 and mcs96 family of microcontrollers, or other similar processors. sclk - serial clock. the serial clock pin is used to synchro- nize data to and from the hi7190 and to run the port state machines. in synchronous external clock mode, sclk is con?gured as an input, is supplied by the user, and can run up to a 5mhz rate. in synchronous self clocking mode, sclk is con?gured as an output and runs at osc 1 /8. cs - chip select. this signal is an active low input that allows more than one device on the same serial communica- tion lines. the sdo and sdio will go to a high impedance state when this signal is high. if driven high during any communication cycle, that cycle will be suspended until cs reactivation. chip select can be tied low in systems that maintain control of sclk. drdy - data ready. this is an output status ?ag from the device to signal that the data output register has been updated with the new conversion result. drdy is useful as an edge or level sensitive interrupt signal to a microprocessor or microcontroller. drdy low indicates that new data is available at the data output register. drdy will return high upon completion of a complete data output register read cycle. mode - mode. this input is used to select between synchro- nous self clocking mode (1) or the synchronous external clocking mode (0). when this pin is tied to v dd the serial port is con?gured in the synchronous self clocking mode where the synchronous shift clock (sclk) for the serial port is generated by the hi7190 and has a frequency of osc 1 /8. when the pin is tied to dgnd the serial port is con?gured for the synchronous external clocking mode where the synchro- nous shift clock for the serial port is generated by an external device up to a maximum frequency of 5mhz. programming the serial interface it is useful to think of the hi7190 interface in terms of communication cycles. each communication cycle happens in 2 phases. the ?rst phase of every communication cycle is the writing of an instruction byte. the second phase is the data transfer as described by the instruction byte. it is important to note that phase 2 of the communication cycle can be a single byte or a multi-byte transfer of data. for example, the 3-byte data output register can be read using one multi-byte communication cycle rather than three single-byte communication cycles. it is up to the user to maintain synchronism with respect to data transfers. if the system processor gets lost the only way to recover is to reset the hi7190. figure 14 shows both a 2-wire and a 3-wire data transfer. several formats are available for reading from and writing to the hi7190 registers in both the 2-wire and 3-wire protocols. a portion of these formats is controlled by the cr<2:1> (bd and msb) bits which control the byte direction and bit order of a data transfer respectively. these two bits can be written in any combination but only the two most useful will be dis- cussed here. chip select sdo sdio sclk cs drd y hi7190 device status bidirectional data data out port clock mode clock mode figure 11. hi7190 serial interface osc 1 cs sclk 29 33 37 41 45 89 121 125 figure 12. sclk output in self-clocking mode hi7190
1886 the ?rst combination is to reset both the bd and msb bits (bd = 0, msb = 0). this sets up the interface for descending byte order and msb ?rst format. when this combination is used the user should always write the instruction register such that the starting byte is the most signi?cant byte address. for example, read three bytes of dr starting with the most sig- ni?cant byte. the ?rst byte read will be the most signi?cant in msb to lsb format. the next byte will be the next least signi?- cant (recall descending byte order) again in msb to lsb order. the last byte will be the next lesser signi?cant byte in msb to lsb order. the entire word was read msb to lsb format. the second combination is to set both the bd and msb bits to 1. this sets up the interface for ascending byte order and lsb ?rst format. when this combination is used the user should always write the instruction register such that the starting byte is the least signi?cant byte address. for example, read three bytes of dr starting with the least signi?cant byte. the ?rst byte read will be the least signi?cant in lsb to msb for- mat. the next byte will be the next greater signi?cant (recall ascending byte order) again in lsb to msb order. the last byte will be the next greater signi?cant byte in lsb to msb order. the entire word was read msb to lsb format. after completion of each communication cycle, the hi7190 interface enters a standby mode while waiting to receive a new instruction byte. instruction byte phase the instruction byte phase initiates a data transfer sequence. the processor writes an 8-bit byte (instruction byte) to the instruction register. the instruction byte informs the hi7190 about the data transfer phase activities and includes the following information: - read or write cycle - number of bytes to be transferred - which register and starting byte to be accessed data transfer phase in the data transfer phase, data transfer takes place as set by the instruction register contents. see write operation and read operation sections for detailed descriptions. instruction register the instruction register is an 8-bit register which is used during a communications cycle for setting up read/write operations. r/w - bit 7 of the instruction register determines whether a read or write operation will be done following the instruction byte load. 0 = read, 1 = write. mb1, mb0 - bits 6 and 5 of the instruction register deter- mine the number of bytes that will be accessed following the instruction byte load. see table 5 for the number of bytes to transfer in the transfer cycle. fsc - bit 4 is used to determine whether a positive full scale calibration register i/o transfer (fsc = 0) or a nega- tive full scale calibration register i/o transfer (fsc = 1) is being performed (see table 6). a3, a2, a1, a0 - bits 3 and 2 (a3 and a2) of the instruction register determine which internal register will be accessed while bits 1 and 0 (a1 and a0) determine which byte of that register will be accessed ?rst. see table 6 for the address decode. instruction byte data byte 1 data byte 2 data byte 3 instruction data transfer cycle cs sdio figure 13a. 2-wire, 3-byte read or write transfer instruction byte data byte 1 data byte 2 data byte 3 instruction data transfer cycle cs sdio sdo figure 13b. 3-wire, 3-byte read transfer instruction register msb654321lsb r/w mb1 mb0 fsc a3 a2 a1 a0 table 5. multiple byte access bits mb1 mb0 description 0 0 transfer 1 byte 0 1 transfer 2 bytes 1 0 transfer 3 bytes 1 1 transfer 4 bytes hi7190
1887 write operation data can be written to the control register, offset calibra- tion register, positive full scale calibration register, and the negative full scale calibration register. write opera- tions are done using the sdio, cs and sclk lines only, as all data is written into the hi7190 via the sdio line even when using the 3-wire con?guration. figures 15 and 16 show typical write timing diagrams. the communication cycle is started by asserting the cs line low and starting the clock from its idle state. to assert a write cycle, during the instruction phase of the communication cycle, the instruction byte should be set to a write transfer ( r/w = 1). when writing to the serial port, data is latched into the hi7190 on the rising edge of sclk. data can then be changed on the falling edge of sclk. data can also be changed on the rising edge of sclk due to the 0ns hold time required on the data. this is useful in pipelined applica- tions where the data is latched on the rising edge of the clock. read operation - 3-wire transfer data can be read from the data output register, control register, offset calibration register, positive full scale calibration register, and the negative full scale calibration register. when con?gured in 3-wire transfer mode, read operations are done using the sdio, sdo, cs and sclk lines. all data is read via the sdo line. figures 17 and 18 show typical 3-wire read timing diagrams. the communication cycle is started by asserting the cs line and starting the clock from its idle state. to assert a read cycle, during the instruction phase of the communication cycle, the instruction byte should be set to a read transfer ( r/w = 0). when reading the serial port, data is driven out of the hi7190 on the falling edge of sclk. data can be registered externally on the next rising edge of sclk. read operation - 2-wire transfer data can be read from the data output register, control register, offset calibration register, positive full scale cal- ibration register, and the negative full scale calibration register. when con?gured in two-wire transfer mode, read operations are done using the sdio, cs and sclk lines. all data is read via the sdio line. figures 19 and 20 show typical 2-wire read timing diagrams. the communication cycle is started by asserting the cs line and starting the clock from its idle state. to assert a read cycle, during the instruction phase of the communication cycle, the instruction byte should be set to a read transfer (r/w = 0). when reading the serial port, data is driven out of the hi7190 on the falling edge of sclk. data can be registered externally on the next rising edge of sclk. detailed register descriptions data output register the data output register contains 24 bits of converted data. this register is a read only register. table 6. internal data access decode starting byte fsc a3 a2 a1 a0 description x 0000 data output register, byte 0 x 0001 data output register, byte 1 x 0010 data output register, byte 2 x 0100 control register, byte 0 x 0101 control register, byte 1 x 0110 control register, byte 2 x 1000 offset cal register, byte 0 x 1001 offset cal register, byte 1 x 1010 offset cal register, byte 2 0 1100 positive full scale cal register, byte 0 0 1101 positive full scale cal register, byte 1 0 1110 positive full scale cal register, byte 2 1 1100 negative full scale cal register, byte 0 1 1101 negative full scale cal register, byte 1 1 1110 negative full scale cal register, byte 2 byte 2 msb 22 21 20 19 18 17 16 d23 d22 d21 d20 d19 d18 d17 d16 byte 1 15 14 13 12 11 10 9 8 d15 d14 d13 d12 d11 d10 d9 d8 byte 0 7654321lsb d7 d6 d5 d4 d3 d2 d1 d0 hi7190
1888 ir write phase data transfer phase - two-byte write cs sclk sdio sdo three-state three-state i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 figure 14. data write cycle, sclk idle low ir write phase data transfer phase - two-byte write cs sclk s dio sdo i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 three-state three-state figure 15. data write cycle, sclk idle high data transfer phase - two-byte read cs sclk sdio sdo i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 ir write phase figure 16. data read cycle, 3-wire configuration, sclk idle low ir write phase data transfer phase - two-byte read cs sclk sdio sdo i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 figure 17. data read cycle, 3-wire configuration, sclk idle high three-state three-state ir write phase data transfer phase - two-byte read cs sclk sdio sdo i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 figure 18. data read cycle, 2-wire configuration, sclk idle low hi7190
1889 control register the control register contains 24-bits to control the various sections of the hi7190. this register is a read/write register. dc - bit 23 is the data coding bit used to select between twos complementary and offset binary data coding. when this bit is set (dc = 1) the data in the data output register will be twos complement. when cleared (dc = 0) this data will be offset binary. when operating in the unipolar mode the output data is available in straight binary only (the dc bit is ignored). this bit is cleared after a reset is applied to the part. fp10 through fp0 - bits 22 through 12 are the filter pro- gramming bits that determine the frequency response of the digital ?lter. these bits determine the ?lter cutoff frequency, the position of the ?rst notch and the data rate of the hi7190. the ?rst notch of the ?lter is equal to the decimation rate and can be determined by the formula: f notch = f osc /(512 x code) where code is the decimal equivalent of the value in fp10 through fp0. the values that can be programmed into these bits are 10 to 2047 decimal, which allows a conversion rate range of 9.54hz to 1.953khz when using a 10mhz clock. changing the ?lter notch frequency, as well as the selected gain, impacts resolution. the output data rate (or effective conversion time) for the device is equal to the frequency selected for the ?rst notch to the ?lter. for example, if the ?rst notch of the ?lter is selected at 50hz then a new word is avail- able at a 50hz rate or every 20ms. if the ?rst notch is at 1khz a new word is available every 1ms. the settling-time of the converter to a full scale step input change is between 3 and 4 times the data rate. for example, with the ?rst ?lter notch at 50hz, the worst case settling time to a full scale step input change is 80ms. if the ?rst notch is 1khz, the settling time to a full scale input step is 4ms maximum. the -3db frequency is determined by the programmed ?rst notch frequency according to the relationship: f -3db = 0.262 x f notch . md2 through md0 - bits 11 through 9 are the operational modes of the converter. see table 4 for the operational modes description. after a reset is applied to the part these bits are set to the self calibration mode. b/u - bit 8 is the bipolar/unipolar select bit. when this bit is set the hi7190 is con?gured for bipolar operation. when this bit is reset the part is in unipolar mode. this bit is set after a reset is applied to the part. g2 through g0 - bits 7 through 5 select the gain of the input analog signal. the gain is accomplished through a program- mable gain instrumentation ampli?er that gains up incoming signals from 1 to 8. this is achieved by using a switched capacitor voltage multiplier network preceding the modulator. the higher gains (i.e., 16 to 128) are achieved through a com- bination of a pgia gain of 8 and a digital multiply after the dig- ital ?lter (see table 7). the gain will affect noise and signal to noise ratio of the conversion. these bits are cleared to a gain of 1 (g2, g1, g0 = 000) after a reset is applied to the part. three-state three-state ir write phase data transfer phase - two-byte read cs sclk sdio sdo i0 i1 i2 i3 i4 i5 i6 i7 b0 b1 b2 b3 b4 b5 b6 b7 b8 b9 b10 b11 b12 b13 b14 b15 figure 19. data read cycle, 2-wire configuration, sclk idle high byte 2 msb 22 21 20 19 18 17 16 dc fp10 fp9 fp8 fp7 fp6 fp5 fp4 byte 1 15 14 13 12 11 10 9 8 fp3 fp2 fp1 fp0 md2 md1 md0 b/u byte 0 7654321lsb g2 g1 g0 bo sb bd msb sdl table 7. gain select bits g2 g1 g0 gain gain achieved 0 0 0 1 pgia = 1, filter multiply = 1 0 0 1 2 pgia = 2, filter multiply = 1 0 1 0 4 pgia = 4, filter multiply = 1 0 1 1 8 pgia = 8, filter multiply = 1 1 0 0 16 pgia = 8, filter multiply = 2 1 0 1 32 pgia = 8, filter multiply = 4 1 1 0 64 pgia = 8, filter multiply = 8 1 1 1 128 pgia = 8, filter multiply = 16 hi7190
1890 bo - bit 4 is the transducer burn-out current source enable bit. when this bit is set (bo = 1) the burn-out current source connected to v inhi internally is enabled. this current source can be used to detect the presence of an external connection to v inhi . this bit is cleared after a reset is applied to the part. sb - bit 3 is the standby mode enable bit used to put the hi7190 in a lower power/standby mode. when this bit is set (sb = 1) the ?lter nodes are halted, the drd y line is set high and the modulator clock is disabled. when this bit is cleared the hi7190 begins operation as described by the contents of the control register. for example, if the control register is programmed for self calibration mode and a notch frequency to 10hz, the hi7190 will perform the self calibration before providing the data at the 10hz rate. this bit is cleared after a reset is applied to the part. bd - bit 2 is the byte direction bit used to select the multi-byte access ordering. the bit determines the either ascending or descending order access for the multi-byte registers. when set (bd = 1) the user can access multi-byte registers in ascending byte order and when cleared (bd = 0) the multi- byte registers are accessed in descending byte order. this bit is cleared after a reset is applied to the part. msb - bit 1 is used to select whether a serial data transfer is msb or lsb ?rst. this bit allows the user to change the order that data can be transmitted or received by the hi7190. when this bit is cleared ( msb = 0) the msb is the ?rst bit in a serial data transfer. if set ( msb = 1), the lsb is the ?rst bit trans- ferred in the serial data stream. this bit is cleared after a reset is applied to the part. sdl - bit 0 is the serial data line control bit. this bit selects the transfer protocol of the serial interface. when this bit is cleared (sdl = 0), both read and write data transfers are done using the sdio line. when set (sdl = 1), write transfers are done on the sdio line and read transfers are done on the sdo line. this bit is cleared after a reset is applied to the part. reading the data output register the hi7190 generates an active low interrupt ( drd y) indicat- ing valid conversion results are available for reading. at this time the data output register contains the latest conversion result available from the hi7190. data integrity is maintained at the serial output port but it is possible to miss a conversion result if the data output register is not read within a given period of time. maintaining data integrity means that if a data output register read of conversion n is begun but not ?n- ished before the next conversion (conversion n + 1) is com- plete, the drd y line remains active low and the data being read is not overwritten. in addition to the data output register, the hi7190 has a one conversion result storage buffer. no conversion results will be lost if the following constraints are met. 1) a data output register read cycle is started for a given conversion (conversion x) 1/f n - (128*1/f osc ) after drd y ini- tially goes active low. failure to start the read cycle may result in conversion x + 1 data overwriting conversion x results. for example, with f osc = 10mhz, f n = 2khz, the read cycle must start within 1/2000 - 128(1/10 6 ) = 487 m s after drd y went low. 2) the data output register read cycle for conversion x must be completed within 2(1/f n )-1440(1/f osc ) after drd y initially goes active low. if the read cycle for conversion x is not com- plete within this time the results of conversion x + 1 are lost and results from conversion x + 2 are now stored in the data output word buffer. completing the data output register read cycle inactivates the drd y interrupt. if the one word data output buffer is full when this read is complete this data will be immediately trans- ferred to the data output register and a new drd y interrupt will be issued after the minimum drd y pulse high time is met. writing the control register if data is written to byte 2 and/or byte 1 of the control register the drd y output is taken high and the device re-calibrates if written to a calibration mode. this action is taken because it is assumed that by writing byte 2 or byte 1 that the user either reprogrammed the ?lter or changed modes of the part. how- ever, if a single data byte is written to byte 0, it is assumed that the gain has not been changed. it is up to the user to re-cali- brate the hi7190 after the gain has been changed by this method. it is recommended that the entire control register be written to when changing the selected gain. this ensures that the part is re-calibrated before the drd y signal goes low indi- cating valid data is available. offset calibration register the offset calibration register is a 24-bit register containing the offset correction factor. this register is indeterminate on power-up but will contain a self calibration correction value after a reset has been applied. the offset calibration register holds the value that corrects the ?lter output data to all 0s when the analog input is 0v. byte 2 msb 22 21 20 19 18 17 16 o23 o22 o21 o20 o19 o18 o17 o16 byte 1 15 14 13 12 11 10 9 8 o15 o14 o13 o12 o11 o10 o9 o8 byte 0 7654321lsb o7 o6 o5 o4 o3 o2 o1 o0 hi7190
1891 positive full scale calibration register the positive full scale calibration register is a 24-bit regis- ter containing the positive full scale correction coef?cient. this coef?cient is used to determine the positive gain slope factor. this register is indeterminate on power-up but will contain a self calibration correction coef?cient after a reset has been applied. negative full scale calibration register the negative full scale calibration register is a 24-bit reg- ister containing the negative full scale correction coef?cient. this coef?cient is used to determine the negative gain slope factor. this register is indeterminate on power-up but will contain a self calibration correction coef?cient after a reset has been applied. byte 2 msb 22 21 20 19 18 17 16 p23 p22 p21 p20 p19 p18 p17 p16 byte 1 15 14 13 12 11 10 9 8 p15 p14 p13 p12 p11 p10 p9 p8 byte 0 7654321lsb p7 p6 p5 p4 p3 p2 p1 p0 byte 2 msb 22 21 20 19 18 17 16 n23 n22 n21 n20 n19 n18 n17 n16 byte 1 15 14 13 12 11 10 9 8 n15 n14 n13 n12 n11 n10 n9 n8 byte 0 7654321lsb n7 n6 n5 n4 n3 n2 n1 n0 hi7190
1892 die characteristics die dimensions: 3550 m m x 6340 m m metallization: type: alsicu thickness: metal 2, 16k ? metal 1, 6k ? substrate potential (powered up): av ss passivation: type: sandwich thickness: nitride 8k ? usg 1k ? metallization mask layout hi7190 sclk sdo sdio cs drd y dgnd av ss v rlo v rhi v cm v inlo v inhi av dd mode sync reset agnd dv dd osc 2 osc 1 hi7190
1893 hi7190 dual-in-line plastic packages (pdip) c l e e a c e b e c -b- e1 index 1 2 3 n/2 n area seating base plane plane -c- d1 b1 b e d d1 a a2 l a1 -a- 0.010 (0.25) c a m b s notes: 1. controlling dimensions: inch. in case of conflict between english and metric dimensions, the inch dimensions control. 2. dimensioning and tolerancing per ansi y14.5m - 1982. 3. symbols are defined in the mo series symbol list in section 2.2 of publication no. 95. 4. dimensions a, a1 and l are measured with the package seated in jedec seating plane gauge gs - 3. 5. d, d1, and e1 dimensions do not include mold flash or protrusions. mold flash or protrusions shall not exceed 0.010 inch (0.25mm). 6. e and are measured with the leads constrained to be perpen- dicular to datum . 7. e b and e c are measured at the lead tips with the leads uncon- strained. e c must be zero or greater. 8. b1 maximum dimensions do not include dambar protrusions. dam- bar protrusions shall not exceed 0.010 inch (0.25mm). 9. n is the maximum number of terminal positions. 10. corner leads (1, n, n/2 and n/2 + 1) for e8.3, e16.3, e18.3, e28.3, e42.6 will have a b1 dimension of 0.030 - 0.045 inch (0.76 - 1.14mm). e a -c- e20.3 (jedec ms-001-ad issue d) 20 lead dual-in-line plastic package symbol inches millimeters notes min max min max a - 0.210 - 5.33 4 a1 0.015 - 0.39 - 4 a2 0.115 0.195 2.93 4.95 - b 0.014 0.022 0.356 0.558 - b1 0.045 0.070 1.55 1.77 8 c 0.008 0.014 0.204 0.355 - d 0.980 1.060 24.89 26.9 5 d1 0.005 - 0.13 - 5 e 0.300 0.325 7.62 8.25 6 e1 0.240 0.280 6.10 7.11 5 e 0.100 bsc 2.54 bsc - e a 0.300 bsc 7.62 bsc 6 e b - 0.430 - 10.92 7 l 0.115 0.150 2.93 3.81 4 n20 209 rev. 0 12/93
1894 hi7190 small outline plastic packages (soic) index area e d n 123 -b- 0.25(0.010) c a m b s e -a- l b m -c- a1 a seating plane 0.10(0.004) h x 45 o c h 0.25(0.010) b m m a notes: 1. symbols are defined in the mo series symbol list in section 2.2 of publication number 95. 2. dimensioning and tolerancing per ansi y14.5m - 1982. 3. dimension d does not include mold flash, protrusions or gate burrs. mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. dimension e does not include interlead flash or protrusions. interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 5. the chamfer on the body is optional. if it is not present, a visual index feature must be located within the crosshatched area. 6. l is the length of terminal for soldering to a substrate. 7. n is the number of terminal positions. 8. terminal numbers are shown for reference only. 9. the lead width b, as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch) 10. controlling dimension: millimeter. converted inch dimensions are not necessarily exact. m20.3 (jedec ms-013-ac issue c) 20 lead wide body small outline plastic package symbol inches millimeters notes min max min max a 0.0926 0.1043 2.35 2.65 - a1 0.0040 0.0118 0.10 0.30 - b 0.013 0.0200 0.33 0.51 9 c 0.0091 0.0125 0.23 0.32 - d 0.4961 0.5118 12.60 13.00 3 e 0.2914 0.2992 7.40 7.60 4 e 0.050 bsc 1.27 bsc - h 0.394 0.419 10.00 10.65 - h 0.010 0.029 0.25 0.75 5 l 0.016 0.050 0.40 1.27 6 n20 207 a 0 o 8 o 0 o 8 o - rev. 0 12/93

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