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| www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 12 BIT 4 ANALOG INPUT, 6 MSPS, SIMULTANEOUS SAMPLING ANALOG TO DIGITAL CONVERTER FEATURES D Simultaneous Sampling of 4 Single-Ended Signals or 2 Differential Signals or Combination of Both to program the ADC into the desired mode. The THS1207 consists of four analog inputs, which are sampled simultaneously. These inputs can be selected individually and configured to single-ended or differential-inputs. Internal reference voltages for the ADC (1.5 V and 3.5 V) are provided. An external reference can also be chosen to suit the dc accuracy and temperature drift requirements of the application. The THS1207C is characterized for operation from 0C to 70C, the THS1207I is characterized for operation from -40C to 85C. DA PACKAGE (TOP VIEW) D Signal-to-Noise and Distortion Ratio: D D D D D D D D 68 dB at fI = 2 MHz Differential Nonlinearity Error: 1 LSB Integral Nonlinearity Error: 1.5 LSB Auto-Scan Mode for 2, 3, or 4 Inputs 3-V or 5-V Digital Interface Compatible Low Power: 216 mW Max at 5 V Power Down: 1 mW Max 5-V Analog Single Supply Operation Internal Voltage References . . . 50 PPM/C and 5% Accuracy D Glueless DSP Interface D Parallel C/DSP Interface APPLICATIONS D Radar Applications D Communications D Control Applications D High-Speed DSP Front-End D Automotive Applications DESCRIPTION The THS1207 is a CMOS, low-power, 12-bit, 6 MSPS analog-to-digital converter (ADC). The speed, resolution, bandwidth, and single-supply operation are suited for applications in radar, imaging, high-speed acquisition, and communications. A multistage pipelined architecture with output error correction logic provides for no missing codes over the full operating temperature range. Internal control registers are used D0 D1 D2 D3 D4 D5 BVDD BGND D6 D7 D8 D9 D10/RA0 D11/RA1 CONV_CLK SYNC 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 32 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 AINP AINM BINP BINM REFIN REFOUT REFP REFM AGND AVDD CS0 CS1 WR (R/W) RD DVDD DGND ORDERING INFORMATION PACKAGED DEVICE TA 0C to 70C -40C to 85C TSSOP (DA) THS1207CDA THS1207IDA Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright 2002, Texas Instruments Incorporated THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted(1) UNITS DGND to DVDD Su ly Supply voltage range Analog input voltage range Reference input voltage Digital input voltage range Operating virtual junction temperature range, TJ THS1207C Operating free air temperature range TA free-air range, Storage temperature range, Tstg THS1207I BGND to BVDD AGND to AVDD -0.3 V to 6.5 V -0.3 V to 6.5 V -0.3 V to 6.5 V AGND -0.3 V to AVDD + 1.5 V -0.3 V + AGND to AVDD + 0.3 V -0.3 V to BVDD/DVDD + 0.3 V -40C to 150C 0C to 70C -40C to 85C -65C to 150C Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds 260C (1) Stresses beyond those listed under "absolute maximum ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under "recommended operating conditions" is not implied. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. RECOMMENDED OPERATING CONDITIONS POWER SUPPLY Supply voltage y g AVDD DVDD BVDD ANALOG AND REFERENCE INPUTS Analog input voltage in single-ended configuration Common-mode input voltage VCM in differential configuration External reference voltage,VREFP (optional) External reference voltage, VREFM (optional) Input voltage difference, REFP - REFM DIGITAL INPUTS High-level High level input voltage VIH voltage, Low-level Low level input voltage, VIL voltage Input CONV_CLK frequency CONV_CLK pulse duration, clock high, tw(CONV_CLKH) CONV_CLK pulse duration, clock low, tw(CONV_CLKL) Operating free-air temperature, TA free air temperature BVDD = 3.3 V BVDD = 5.25 V BVDD = 3.3 V BVDD = 5.25 V DVDD = 4.75 V to 5.25 V DVDD = 4.75 V to 5.25 V DVDD = 4.75 V to 5.25 V THS1207CDA THS1207IDA 0.1 80 80 0 -40 83 83 MIN 2 2.6 0.6 0.6 6 5000 5000 70 85 1.4 MIN VREFM 1 MIN 4.75 4.75 3 NOM 2.5 3.5 1.5 2 NOM MAX NOM 5 5 MAX 5.25 5.25 5.25 MAX VREFP 4 AVDD-1.2 UNIT V V V V V UNIT V V V V MHz ns ns C V UNIT 2 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 ELECTRICAL CHARACTERISTICS over recommended operating conditions, AVDD = DVDD = 5 V, BVDD = 3.3 V, VREWF = internal (unless otherwise noted) DIGITAL SPECIFICATIONS PARAMETER Digital inputs IIH IIL High-level input current Low-level input current DVDD = digital inputs Digital input = 0 V -50 -50 5 IOH = -50 A IOL = 50 A CS1 = DGND, BVDD-0.5 0.4 -10 5 30 10 50 50 A A pF V V A pF pF TEST CONDITIONS MIN TYP MAX UNIT Ci Input capacitance Digital outputs VOH VOL IOZ CO CL High-level output voltage Low-level output voltage High-impedance-state output current Output capacitance Load capacitance at databus D0 - D11 BVDD = 3 3 V 5 V 3.3 V, CS0 = DVDD ELECTRICAL CHARACTERISTICS over recommended operating conditions, AVDD = DVDD = 5 V, BVDD = 3.3 V, fs = 6 MSPS, VREF = internal (unless otherwise noted) DC SPECIFICATIONS PARAMETER Resolution Accuracy Integral nonlinearity, INL Differential nonlinearity, DNL After calibration in single-ended mode Offset error Gain error Analog input Input capacitance Input leakage current Internal voltage reference Accuracy, VREFP Accuracy, VREFM Temperature coefficient Reference noise Accuracy, REFOUT Power supply IDDA IDDD IDDB Analog supply current Digital supply current Buffer supply current Power dissipation Power dissipation in power down with conversion clock inactive AVDD = DVDD = 5 V, BVDD =3.3 V AVDD = DVDD = 5 V, BVDD = 3.3 V AVDD = DVDD = 5 V, BVDD = 3.3 V AVDD = DVDD = 5 V, BVDD = 3.3 V AVDD = DVDD = 5 V, BVDD = 3.3 V 36 0.5 1.5 186 40 3 4 216 0.25 mA mA mA mW mW 2.475 3.3 1.4 3.5 1.5 50 100 2.5 2.525 3.7 1.6 V V PPM/C V V VAIN = VREFM to VREFP 15 10 pF A After calibration in differential mode -20 -20 20 20 20 1.5 1 LSB LSB LSB LSB LSB TEST CONDITIONS MIN 12 TYP MAX UNIT Bits 3 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com ELECTRICAL CHARACTERISTICS over recommended operating conditions, VREF = internal, fs = 6 MSPS, fI = 2 MHz at -1 dBFS (unless otherwise noted) AC SPECIFICATIONS, AVDD = DVDD = 5 V, BVDD = 3.3 V, CL < 30 pF PARAMETER SINAD SNR THD ENOB SFDR Signal-to-noise Signal to noise ratio + distortion Signal-to-noise Signal to noise ratio Total harmonic distortion Effective number of bits Spurious free dynamic range TEST CONDITIONS Differential mode Single-ended mode Differential mode Single-ended mode Differential mode Single-ended mode Differential mode Single-ended mode Differential mode Single-ended mode 10.17 10 67 65 MIN 63 62 64 64 TYP 63 64 69 68 -70 -68 10.5 10.3 71 69 -67 -64 MAX UNIT dB dB dB Bits dB Analog Input Full-power bandwidth with a source impedance of 150 in differential configuration. Full-power bandwidth with a source impedance of 150 in single-ended configuration. Small-signal bandwidth with a source impedance of 150 in differential configuration. Small-signal bandwidth with a source impedance of 150 in single-ended configuration. 96 Full scale sinewave, -3 dB sinewave 3 54 96 100 mVpp sinewave, -3 dB sinewave 3 54 MHz MHz TIMING REQUIREMENTS AVDD = DVDD = 5 V, BVDD = 3.3 V, VREF = internal, CL < 30 pF PARAMETER tpipe tsu(CONV_CLKL-READL) tsu(READH-CONV_CLKL) td(CONV_CLKL-SYNCL) td(CONV_CLKL-SYNCH) Latency Setup time, CONV_CLK low before CS valid Setup time, CS invalid to CONV_CLK low Delay time, CONV_CLK low to SYNC low Delay time, CONV_CLK low to SYNC high 10 20 10 10 TEST CONDITIONS MIN TYP 5 MAX UNIT CONV CLK ns ns ns ns 4 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 Terminal Functions TERMINAL NAME AINP AINM BINP BINM AVDD AGND BVDD BGND CONV_CLK CS0 CS1 DGND DVDD D0 - D9 D10/RA0 D11/RA1 REFIN REFP NO. 32 31 30 29 23 24 7 8 15 22 21 17 18 1-6, 9-12 13 14 28 26 I/O I I I I I I I I I I I I I I/O/Z I/O/Z I/O/Z I I DESCRIPTION Analog input, single-ended or positive input of differential channel A Analog input, single-ended or negative input of differential channel A Analog input, single-ended or positive input of differential channel B Analog input, single-ended or negative input of differential channel B Analog supply voltage Analog ground Digital supply voltage for buffer Digital ground for buffer Digital input. This input is the conversion clock input. Chip select input (active low) Chip select input (active high) Digital ground. Ground reference for digital circuitry. Digital supply voltage Digital input, output; D0 = LSB Digital input, output. The data line D10 is also used as an address line (RA0) for the control register. This is required for writing to the control register 0 and control register 1. See Table 7. Digital input, output (D11 = MSB). The data line D11 is also used as an address line (RA1) for the control register. This is required for writing to control register 0 and control register 1. See Table 7. Common-mode reference input for the analog input channels. It is recommended that this pin be connected to the reference output REFOUT. Reference input, requires a bypass capacitor of 10 F to AGND in order to bypass the internal reference voltage. An external reference voltage at this input can be applied. This option can be programmed through control register 0. See Table 8. Reference input, requires a bypass capacitor of 10 F to AGND in order to bypass the internal reference voltage. An external reference voltage at this input can be applied. This option can be programmed through control register 0. See Table 8. Analog fixed reference output voltage of 2.5 V. Sink and source capability of 250 A. The reference output requires a capacitor of 10 F to AGND for filtering and stability. The RD input is used only if the WR input is configured as a write only input. In this case, it is a digital input, active low as a data read select from the processor. See timing section. Synchronization output. This signal indicates in a multichannel operation that data of channel A is brought to the digital output and can therefore be used for synchronization. This input is programmable. It functions as a read-write input R/W and can also be configured as a write-only input WR, which is active low and used as data write select from the processor. In this case, the RD input is used as a read input from the processor. See timing section. REFM 25 I REFOUT RD(1) SYNC WR (R/W)(1) 27 19 16 20 O I O I (1) The start-conditions of RD and WR (R/W) are unknown. The first access to the ADC has to be a write access to initialize the ADC. 5 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com FUNCTIONAL BLOCK DIAGRAM AVDD DVDD REFP 3.5 V VREFP 1.5 V 1.225 V REF 2.5 V REFOUT REFM REFIN AINP S/H Single Ended and/or Differential MUX VREFM AINM S/H + - BVDD 12 Bit Pipeline ADC 12 D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10/RA0 D11/RA1 BGND SYNC AGND DGND BINP S/H Buffers BINM S/H CONV_CLK CS0 CS1 RD WR (R/W) Logic and Control Control Register 6 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION vs SAMPLING FREQUENCY (SINGLE-ENDED) 80 75 THD - Total Harmonic Distortion - dB 70 65 60 55 50 45 40 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS SINAD - Signal-to-Noise and Distortion - dB 70 SIGNAL-TO-NOISE AND DISTORTION vs SAMPLING FREQUENCY (SINGLE-ENDED) AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 65 60 55 50 45 40 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz Figure 1 Figure 2 SPURIOUS FREE DYNAMIC RANGE vs SAMPLING FREQUENCY (SINGLE-ENDED) 90 SFDR - Spurious Free Dynamic Range - dB 85 65 75 70 65 60 55 50 45 40 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 40 0 SNR - Signal-to-Noise - dB 80 70 SIGNAL-TO-NOISE vs SAMPLING FREQUENCY (SINGLE-ENDED) AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 60 55 50 45 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz Figure 3 Figure 4 7 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION vs SAMPLING FREQUENCY (DIFFERENTIAL) 85 SINAD - Signal-to-Noise and Distortion - dB 80 THD - Total Harmonic Distortion - dB 75 70 65 60 55 50 45 40 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 80 75 70 65 60 55 50 45 40 0 SIGNAL-TO-NOISE AND DISTORTION vs SAMPLING FREQUENCY (DIFFERENTIAL) AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz Figure 5 Figure 6 SPURIOUS FREE DYNAMIC RANGE vs SAMPLING FREQUENCY (DIFFERENTIAL) 100 SFDR - Spurious Free Dynamic Range - dB 95 90 SNR - Signal-to-Noise - dB 85 80 75 70 65 60 55 50 45 40 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz 40 0 70 65 60 55 50 45 AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 80 75 SIGNAL-TO-NOISE vs SAMPLING FREQUENCY (DIFFERENTIAL) AVDD = 5 V, DVDD = BVDD = 3 V, fIN = 500 kHz, AIN = -0.5 dB FS 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz Figure 7 Figure 8 8 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION vs INPUT FREQUENCY (SINGLE-ENDED) 85 THD - Total Harmonic Distortion - dB SINAD - Signal-to-Noise and Distortion - dB 80 75 70 65 60 55 50 45 40 0.0 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 80 75 70 65 60 55 50 45 40 0.0 SIGNAL-TO-NOISE AND DISTORTION vs INPUT FREQUENCY (SINGLE-ENDED) AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 0.5 1.0 1.5 2.0 2.5 3.0 0.5 1.0 1.5 2.0 2.5 3.0 fi - Input Frequency - MHz fi - Input Frequency - MHz Figure 9 Figure 10 SPURIOUS FREE DYNAMIC RANGE vs INPUT FREQUENCY (SINGLE-ENDED) 100 SFDR - Spurious Free Dynamic Range - dB 95 90 SNR - Signal-to-Noise - dB 85 80 75 70 65 60 55 50 45 40 0.0 0.5 1.0 1.5 2.0 fi - Input Frequency - MHz 2.5 3.0 40 0.0 70 65 60 55 50 45 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 80 75 SIGNAL-TO-NOISE vs INPUT FREQUENCY (SINGLE-ENDED) AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 0.5 1.0 1.5 2.0 2.5 fi - Input Frequency - MHz 3.0 Figure 11 Figure 12 9 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com TYPICAL CHARACTERISTICS TOTAL HARMONIC DISTORTION vs INPUT FREQUENCY (DIFFERENTIAL) 90 80 70 60 50 40 30 20 0.0 SINAD - Signal-to-Noise and Distortion - dB THD - Total Harmonic Distortion - dB AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 80 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 70 SIGNAL-TO-NOISE AND DISTORTION vs INPUT FREQUENCY (DIFFERENTIAL) 60 50 40 30 0.5 1.0 1.5 2.0 2.5 3.0 3.5 20 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 fi - Input Frequency - MHz fi - Input Frequency - MHz Figure 13 SPURIOUS FREE DYNAMIC RANGE vs INPUT FREQUENCY (DIFFERENTIAL) 90 SFDR - Spurious Free Dynamic Range - dB 80 70 60 50 40 30 20 0.0 SNR - Signal-to-Noise - dB 80 Figure 14 SIGNAL-TO-NOISE vs INPUT FREQUENCY (DIFFERENTIAL) AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 70 60 50 40 30 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 0.5 1.0 1.5 2.0 2.5 3.0 3.5 20 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 fi - Input Frequency - MHz fi - Input Frequency - MHz Figure 15 Figure 16 10 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 TYPICAL CHARACTERISTICS EFFECTIVE NUMBER OF BITS vs SAMPLING FREQUENCY (SINGLE-ENDED) 12 ENOB - Effective Number of Bits - Bits ENOB - Effective Number of Bits - Bits AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 11 12 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 11 EFFECTIVE NUMBER OF BITS vs SAMPLING FREQUENCY (DIFFERENTIAL) 10 10 9 9 8 8 7 7 6 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz 6 0 1 2 3 4 5 6 7 fs - Sampling Frequency - MHz Figure 17 EFFECTIVE NUMBER OF BITS vs INPUT FREQUENCY (SINGLE-ENDED) 12 ENOB - Effective Number of Bits - Bits ENOB - Effective Number of Bits - Bits AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 11 12 Figure 18 EFFECTIVE NUMBER OF BITS vs INPUT FREQUENCY (DIFFERENTIAL) AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 11 10 10 9 9 8 8 7 7 6 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 fi - Input Frequency - MHz 6 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 fi - Input Frequency - MHz Figure 19 Figure 20 11 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com TYPICAL CHARACTERISTICS GAIN vs INPUT FREQUENCY (SINGLE-ENDED) 5 AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS 0 -5 G - Gain - dB -10 -15 -20 -25 -30 0 10 20 30 40 50 60 70 80 90 100 110 120 fi - Input Frequency - MHz Figure 21 FAST FOURIER TRANSFORM (4096 POINTS) (SINGLE-ENDED) vs FREQUENCY 20 0 Magnitude - dB -20 -40 -60 -80 -100 -120 -140 0 500000 1000000 1500000 2000000 2500000 3000000 3500000 f - Frequency - Hz AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS Figure 22 12 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 TYPICAL CHARACTERISTICS FAST FOURIER TRANSFORM (4096 POINTS) (DIFFERENTIAL) vs FREQUENCY 20 0 Magnitude - dB -20 -40 -60 -80 -100 -120 -140 0 500000 1000000 1500000 2000000 2500000 3000000 3500000 f - Frequency - Hz AVDD = 5 V, DVDD = BVDD = 3 V, fs = 6 MHz, AIN = -0.5 dB FS Figure 23 DIFFERENTIAL NONLINEARITY vs ADC CODE 1.0 0.8 0.6 0.4 0.2 -0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0 500 1000 1500 2000 ADC Code 2500 3000 3500 4000 AVDD = 5 V DVDD = BVDD = 3 V fs = 8 MSPS DNL - Differential Nonlinearity - LSB Figure 24 INTEGRAL NONLINEARITY vs ADC CODE INL - Integral Nonlinearity - LSB 1.0 0.8 0.6 0.4 0.2 -0.0 -0.2 -0.4 -0.6 -0.8 -1.0 0 AVDD = 5 V DVDD = BVDD = 3 V fs = 8 MSPS 500 1000 1500 2000 ADC Code 2500 3000 3500 4000 Figure 25 13 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com DETAILED DESCRIPTION Reference Voltage The THS1207 has a built-in reference, which provides the reference voltages for the ADC. VREFP is set to 3.5 V and VREFM is set to 1.5 V. An external reference can also be used through two reference input pins, REFP and REFM, if the reference source is programmed as external. The voltage levels applied to these pins establish the upper and lower limits of the analog inputs to produce a full-scale and zero-scale reading respectively. Analog Inputs The THS1207 consists of 4 analog inputs, which are sampled simultaneously. These inputs can be selected individually and configured as single-ended or differential inputs. The desired analog input channel can be programmed. Converter The THS1207 uses a 12-bit pipelined multistaged architecture, which achieves a high sample rate with low power consumption. The THS1207 distributes the conversion over several smaller ADC sub-blocks, refining the conversion with progressively higher accuracy as the device passes the results from stage to stage. This distributed conversion requires a small fraction of the number of comparators used in a traditional flash ADC. A sample-and-hold amplifier (SHA) within each of the stages permits the first stage to operate on a new input sample while the second through the eighth stages operate on the seven preceding samples. Conversion Clock An external clock signal with a duty cycle of 50% has to be applied to the clock input (CONV_CLK). A new conversion is started with every falling edge of the applied clock signal. The conversion values are available at the output with a latency of 5 clock cycles. SYNC In multichannel mode, the first SYNC signal is delayed by [7+ (# Channels Sampled)] cycles of the CONV_CLK after a SYNC reset. This is due to the latency of the pipeline architecture of the THS1207. Sampling Rate The maximum possible conversion rate per channel is dependent on the selected analog input channels. Table 1 shows the maximum conversion rate in the continuous conversion mode for different combinations. Table 1. Maximum Conversion Rate CHANNEL CONFIGURATION 1 single-ended channel 2 single-ended channels 3 single-ended channels 4 single-ended channels 1 differential channel 2 differential channels 1 single-ended and 1 differential channel 2 single-ended and 1 differential channels NUMBER OF CHANNELS 1 2 3 4 1 2 2 3 MAXIMUM CONVERSION RATE PER CHANNEL 6 MSPS 3 MSPS 2 MSPS 1.5 MSPS 6 MSPS 3 MSPS 3 MSPS 2 MSPS The maximum conversion rate in the continuous conversion mode per channel, fc, is given by: fc + 6 MSPS # channels Conversion During conversion the ADC operates with a free running external clock applied to the input CONV_CLK. With every falling edge of the CONV_CLK signal a new converted value is available to the databus with the corresponding read signal. The THS1207 allows up to four analog input to be selected. The inputs can be configured as two differential channels, four single-ended channels or a combination of differential and single-ended. 14 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 To provide the system with channel information, the THS1207 utilizes an active low SYNC signal. When operated in a multichannel configuration, the SYNC signal is active low when data from channel one is available to the databus. When operated in single-channel mode (single-ended or differential operation) the SYNC signal is disabled. Figure 26 shows the timing of the conversion when one analog input channel is selected. The maximum throughput rate is 6 MSPS in this mode. There is a certain timing relationship required for the read signal with respect to the conversion clock. This can be seen in Figure 26 and in the read and SYNC timing table. A more detailed description of the timing is given in the timing section and signal description of the THS1207. Sample N Channel 1 Sample N+1 Channel 1 Sample N+2 Channel 1 Sample N+3 Channel 1 Sample N+4 Channel 1 Sample N+5 Channel 1 Sample N+6 Channel 1 AIN td(A) tw(CONV_CLKH) tw(CONV_CLKL) CONV_CLK tc tsu(CONV_CLKL-READL) READ td(pipe) tsu(READH-CONV_CLKL) Data N-4 Channel 1 Data N-3 Channel 1 Data N-2 Channel 1 Data N-1 Channel 1 Data N Channel 1 Data N+1 Channel 1 Data N+2 Channel 1 READ is the logical combination from CS0, CS1 and RD Figure 26. Conversion Timing in 1-Channel Operation Figure 27 shows the conversion timing when 2 analog input channels are selected. The maximum throughput rate per channel is 3 MSPS in this mode. The data flow in the bottom of the figure shows in which order the converted data is available to the databus. The signal SYNC is active low when data of channel one is available to the databus. The data of channel one is followed by the data of channel two before channel one is again available and the SYNC signal is active low. Sample N Channel 1, 2 Sample N+1 Channel 1, 2 Sample N+2 Channel 1, 2 Sample N+3 Channel 1, 2 AIN td(A) td(pipe) tw(CONV_CLKH) tw(CONV_CLKL) CONV_CLK tc tsu(CONV_CLKL-READL) READ td(CONV_CLKL-SYNCL) SYNC td(CONV_CLKL-SYNCH) tsu(READH-CONV_CLKL) Data N-2 Channel 1 Data N-2 Channel 2 Data N-1 Channel 1 Data N-1 Channel 2 Data N Channel 1 Data N Channel 2 Data N+1 Channel 1 READ is the logical combination from CS0, CS1 and RD Figure 27. Conversion Timing in 2-Channel Operation 15 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com Figure 28 shows the conversion timing when 3 analog input channels are selected. The maximum throughput rate per channel is 2 MSPS in this mode. The data flow in the bottom of the figure shows in which order the converted data is available to the databus. The signal SYNC is always active low if data of channel one is available to the databus. The data of channel one is followed by the data of channel two and data of channel three before channel one is again available to the data bus and SYNC is active low. Sample N Channel 1, 2, 3 Sample N+1 Channel 1, 2, 3 Sample N+2 Channel 1, 2, 3 AIN td(A) tw(CONV_CLKH) tw(CONV_CLKL) CONV_CLK tc tsu(CONV_CLKL-READL) READ td(CONV_CLKL-SYNCL) SYNC td(CONV_CLKL-SYNCH) tsu(READH-CONV_CLKL) td(pipe) Data N-2 Channel 3 Data N-1 Channel 1 Data N-1 Channel 2 Data N-1 Channel 3 Data N Channel 1 Data N Channel 2 Data N Channel 3 READ is the logical combination from CS0, CS1 and RD Figure 28. Conversion Timing in 3-Channel Operation Figure 29 shows the timing of the conversion mode where 4 analog input channels are selected. The maximum throughput rate per channel is 1.5 MSPS in this mode. The data flow in the bottom of the figure shows in which order the converted data is available to the databus. The signal SYNC is active low when data of channel one is available to the databus. The data of channel one is followed by the data of channel two, data of channel three and data of channel 4 before channel one is again available to the data bus and SYNC is active low. Sample N Channel 1, 2, 3, 4 Sample N+1 Channel 1, 2, 3, 4 AIN td(A) td(pipe) tw(CONV_CLKH) tw(CONV_CLKL) CONV_CLK tc tsu(CONV_CLKL-READL) READ tsu(CONV_CLKL-SYNCL) SYNC tsu(CONV_CLKL-SYNCH) tsu(READH-CONV_CLKL) Data N-1 Channel 1 Data N-1 Channel 2 Data N-1 Channel 3 Data N-1 Channel 4 Data N Channel 1 Data N Channel 2 Data N Channel 3 READ is the logical combination from CS0, CS1 and RD Figure 29. Timing of Continuous Conversion Mode (4-channel operation) 16 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 DIGITAL OUTPUT DATA FORMAT The digital output data format of the THS1207 can either be in binary format or in twos complement format. The following tables list the digital outputs for the analog input voltages. Table 2. Binary Output Format for Single-Ended Configuration SINGLE-ENDED, BINARY OUTPUT ANALOG INPUT VOLTAGE AIN = VREFP AIN = (VREFP + VREFM)/2 AIN = VREFM DIGITAL OUTPUT CODE FFFh 800h 000h Table 3. Twos Complement Output Format for Single-Ended Configuration SINGLE-ENDED, TWOS COMPLEMENT ANALOG INPUT VOLTAGE AIN = VREFP AIN = (VREFP + VREFM)/2 AIN = VREFM DIGITAL OUTPUT CODE 7FFh 000h 800h Table 4. Binary Output Format for Differential Configuration DIFFERENTIAL, BINARY OUTPUT ANALOG INPUT VOLTAGE Vin = AINP - AINM VREF = VREFP - VREFM Vin = VREF Vin = 0 Vin = -VREF FFFh 800h 000h DIGITAL OUTPUT CODE Table 5. Twos Complement Output Format for Differential Configuration DIFFERENTIAL, BINARY OUTPUT ANALOG INPUT VOLTAGE Vin = AINP - AINM VREF = VREFP - VREFM Vin = VREF Vin = 0 Vin = -VREF 7FFh 000h 800h DIGITAL OUTPUT CODE 17 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com ADC CONTROL REGISTER The THS1207 contains two 10-bit wide control registers (CR0, CR1) in order to program the device into the desired mode. The bit definitions of both control registers are shown in Table 6. Table 6. Bit Definitions of Control Register CR0 and CR1 REG CR0 CR1 BIT 9 TEST1 RBACK BIT 8 TEST0 OFFSET BIT 7 SCAN BIN/2's BIT 6 DIFF1 R/W BIT 5 DIFF0 RESERVED BIT 4 CHSEL1 RESERVED BIT 3 CHSEL0 RESERVED BIT 2 PD RESERVED BIT 1 RESERVED SRST BIT 0 VREF RESET Writing to Control Register 0 and Control Register 1 The 10-bit wide control register 0 and control register 1 can be programmed by addressing the desired control register and writing the register value to the ADC. The addressing is performed with the upper data bits D10 and D11, which function in this case as address lines RA0 and RA1. During this write process, the data bits D0 to D9 contain the desired control register value. Table 7 shows the addressing of each control register. Table 7. Control Register Addressing D0 - D9 Desired register value Desired register value Desired register value Desired register value D10/RA0 0 1 0 1 D11/RA1 0 0 1 1 Addressed Control Register Control register 0 Control register 1 Reserved for future Reserved for future Start Use Default Values? Yes Write 0x401 to THS1207 (Set Reset Bit in CR1) No Write 0x401 to THS1207 (Set Reset Bit in CR1) Clear RESET By Writing 0x400 to CR1 Clear RESET By Writing 0x400 to CR1 Write the User Configuration to CR0 Write the User Configuration to CR1 (Must Exclude RESET) Continue Figure 30. THS1207 Configuration Flow 18 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 Control Register 0 (see Table 7) BIT 11 0 BIT 10 0 BIT 9 TEST1 BIT 8 TEST0 BIT 7 SCAN BIT 6 DIFF1 BIT 5 DIFF0 BIT 4 CHSEL1 BIT 3 CHSEL0 BIT 2 PD BIT 1 RESERVED BIT 0 VREF Table 8. Control Register 0 Bit Functions BITS 0 RESET VALUE 0 NAME VREF FUNCTION Vref select: Bit 0 = 0 The internal reference is used Bit 0 = 1 The external reference voltage is used for the ADC RESERVED Power down. Bit 2 = 0 The ADC is active Bit 2 = 1 Power down The reading and writing to and from the digital outputs is possible during power down. 3, 4 5,6 7 8,9 0,0 1,0 0 0,0 CHSEL0, CHSEL1 DIFF0, DIFF1 SCAN TEST0, TEST1 Channel select Bit 3 and bit 4 select the analog input channel of the ADC. Refer to Table 9. Number of differential channels Bit 5 and bit 6 contain information about the number of selected differential channels. Refer to Table 9. Autoscan enable Bit 7 enables or disables the autoscan function of the ADC. Refer to Table 9. Test input enable Bit 8 and bit 9 control the test function of the ADC. Three different test voltages can be measured. This feedback allows the check of all hardware connections and the ADC in its bits. Refer to Table 10 for selection of the three different test voltages. 1 2 0 0 RESERVED PD 19 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com ANALOG INPUT CHANNEL SELECTION The analog input channels of the THS1207 can be selected via bits 3 to 7 of control register 0. One channel (single-ended or differential) is selected via bit 3 and bit 4 of control register 0. Bit 5 controls the selection between single-ended and differential configuration. Bit 6 and bit 7 select the autoscan mode, if more than one input channel is selected. Table 9 shows the possible selections. Table 9. Analog Input Channel Configurations BIT 7 SCAN 0 0 0 0 0 0 1 1 1 1 1 1 0 0 1 1 1 1 1 1 1 1 1 1 BIT 6 DIFF1 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 1 1 1 1 1 1 1 BIT 5 DIFF0 0 0 0 0 1 1 0 0 0 1 1 0 1 1 0 1 1 0 0 0 1 1 1 1 BIT 4 CHSEL1 0 0 1 1 0 0 0 1 1 0 1 0 1 1 0 0 1 0 1 1 0 0 1 1 BIT 3 CHSEL0 0 1 0 1 0 1 1 0 1 1 0 1 0 1 0 0 1 0 0 1 0 1 0 1 DESCRIPTION OF THE SELECTED INPUTS Analog input AINP (single ended) Analog input AINM (single ended) Analog input BINP (single ended) Analog input BINM (single ended) Differential channel (AINP-AINM) Differential channel (BINP-BINM) Autoscan two single ended channels: AINP, AINM, AINP, ... Autoscan three single ended channels: AINP, AINM, BINP, AINP, ... Autoscan four single ended channels: AINP, AINM, BINP, BINM, AINP, ... Autoscan one differential channel and one single ended channel AINP, (BINP-BINM), AINP, (BINP-BINM), ... Autoscan one differential channel and two single ended channel AINP, AINM, (BINP- BINM), AINP, ... Autoscan two differential channels (AINP-AINM), (BINP-BINM), (AINP-AINM), ... Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Reserved Test Mode The test mode of the ADC is selected via bit 8 and bit 9 of control register 0. The different selections are shown in Table 10. Table 10. Test Mode BIT 9 TEST1 0 0 1 1 BIT 8 TEST0 0 1 0 1 OUTPUT RESULT Normal mode VREFP ((VREFM)+(VREFP))/2 VREFM Three different options can be selected. This feature allows support testing of hardware connections between the ADC and the processor. 20 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 Control Register 1 (see Table 7) BIT 11 0 BIT 10 1 BIT 9 RBACK BIT 8 OFFSET BIT 7 BIN/2s BIT 6 R/W BIT 5 RESERVED BIT 4 RESERVED BIT 3 RESERVED BIT 2 RESERVED BIT 1 SRST BIT 0 RESET Table 11. Control Register 1 Bit Functions BITS 0 RESET VALUE 0 NAME RESET Reset Writing a 1 into this bit resets the device and sets the control register 0 and control register 1 to the reset values. To bring the device out of reset, a 0 has to be written into this bit. 1 2, 3 4 5 6 0 0,0 1 1 0 SRST RESERVED RESERVED RESERVED R/W Writing a 1 into this bit resets the sync generator. When running in multichannel mode, this must be set during the configuration cycle. Always write 0 Always write 0 Always write 0 R/W, RD/WR selection Bit 6 of control register 1 controls the function of the inputs RD and WR. When bit 6 in control register 1 is set to 1, WR becomes a R/W input and RD is disabled. From now on a read is signalled with R/W high and a write with R/W as a low signal. If bit 6 in control register 1 is set to 0, the input RD becomes a read input and the input WR becomes a write input. 7 0 BIN/2s Complement select If bit 7 of control register 1 is set to 0, the output value of the ADC is in twos complement. If bit 7 of control register 1 is set to 1, the output value of the ADC is in binary format. Refer to Table 2 through Table 5. 8 0 OFFSET Offset cancellation mode Bit 8 = 0 normal conversion mode Bit 8 = 1 offset calibration mode If a 1 is written into bit 8 of control register 1, the device internally sets the inputs to zero and does a conversion. The conversion result is stored in an offset register and subtracted from all conversions in order to reduce the offset error. 9 0 RBACK Debug mode Bit 9 = 0 normal conversion mode Bit 9 = 1 enable debug mode When bit 9 of control register 1 is set to 1, debug mode is enabled. In this mode, the contents of control register 0 and control register 1 can be read back. The first read after bit 9 is set to 1 contains the value of control register 0. The second read after bit 9 is set to 1 contains the value of control register 1. To bring the device back into normal conversion mode, this bit has to be set back to 0 by writing again to control register 1. FUNCTION 21 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com TIMING AND SIGNAL DESCRIPTION OF THE THS1207 The reading from the THS1207 and writing to the THS1207 is performed by using the chip select inputs (CS0, CS1), the write input WR and the read input RD. The write input is configurable to a combined read/write input (R/W). This is desired in cases where the connected processor consists of a combined read/write output signal (R/W). The two chip select inputs can be used to interface easily to a processor. Reading from the THS1207 takes place by an internal RDint signal, which is generated from the logical combination of the external signals CS0, CS1 and RD (see Figure 6). This signal is then used to strobe out the words and to enable the output buffers. The last external signal (either CS0, CS1 or RD) to become valid makes RDint active while the write input (WR) is inactive. The first of those external signals switching to an inactive state deactivates RDint again. Writing to the THS1207 takes place by an internal WRint signal, which is generated from the logical combination of the external signals CS0, CS1 and WR. This signal strobes the control words into the control registers 0 and 1. The last external signal (either CS0, CS1 or WR) to become valid switches WRint active while the read input (RD) is inactive. The first of those external signals going to its inactive state deactivates WRint again. CS0 CS1 RD Write Enable WR Read Enable Control/Data Registers Data Bits Figure 31. Logical Combination of CS0, CS1, RD, and WR 22 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 Read Timing (using RD, RD-controlled) Figure 32 shows the read-timing behavior when the WR(R/W) input is programmed as a write-input only. The input RD acts as the read-input in this configuration. This timing is called RD-controlled because RD is the last external signal of CS0, CS1, and RD which becomes valid. CS0 CS1 tsu(CS) WR th(CS) tw(RD) 10% ta 90% 10% th RD D(0-9) td(CSDAV) DATA_AV 90% Figure 32. Read Timing Diagram Using RD (RD-controlled) Read Timing Parameter (RD-controlled) PARAMETER tsu(CS) ta td(CSDAV) th th(CS) tw(RD) Setup time, RD low to last CS valid Access time, last CS valid to data valid Delay time, last CS valid to DATA_AV inactive Hold time, first CS invalid to data invalid Hold time, RD change to first CS invalid Pulse duration, RD active 0 5 10 MIN 0 0 12 5 10 TYP MAX UNIT ns ns ns ns ns ns OOO OOO 90% 23 OOOO OOOO THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com Write Timing (using WR, WR-controlled) Figure 33 shows the write-timing behavior when the WR(R/W) input is programmed as a write input WR only. The input RD acts as the read input in this configuration. This timing is called WR-controlled because WR is the last external signal of CS0, CS1, and WR which becomes valid. CS0 CS1 tsu(CS) tw(WR) WR 10% 10% th(CS) RD tsu 90% D(0-9) DATA_AV Figure 33. Write Timing Diagram Using WR (WR-controlled) Write Timing Parameter Using WR (WR-controlled) PARAMETER tsu(CS) tsu th th(CS) tw(WR) Setup time, CS stable to last WR valid Setup time, data valid to first WR invalid Hold time, WR invalid to data invalid Hold time, WR invalid to CS change Pulse duration, WR active 24 OOOO OOOO th 90% MIN 0 5 2 5 10 TYP MAX UNIT ns ns ns ns ns OOOOOOOOOOOOOOOOOOOOO OOOOOOOOOOOOOOOOOOOOO OOOOO OOOOO www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 Read Timing (using R/W, CS0-controlled) Figure 34 shows the read-timing behavior when the WR(R/W) input is programmed as a combined read-write input R/W. The RD input has to be tied to high-level in this configuration. This timing is called CS0-controlled because CS0 is the last external signal of CS0, CS1, and R/W which becomes valid. The reading of the data must be done with a certain timing relative to the conversion clock CONV_CLK, as illustrated in Figure 34. t su(CS0H-CONV_CLKL) t su(CONV_CLKL-CS0L) CONV_CLK 10% tw(CS) CS0 10% 10% 90% 10% CS1 tsu(R/W) R/W th(R/W) 90% 90% RD t a 90% t h 90% D(O-11) Figure 34. Read Timing Diagram Using R/W (CS0-controlled) Read Timing Parameter (CS0-controlled) PARAMETER tsu(CONV_CLKL-CSOL) tsu(CSOH-CONV_CLKL) tsu(R/W) ta th th(R/W) tw(CS) Setup time, CONV_CLK low before CS valid Setup time, CS invalid to CONV_CLK low Setup time, R/W high to last CS valid Access time, last CS valid to data valid Hold time, first CS invalid to data invalid Hold time, first external CS invalid to R/W change Pulse duration, CS active MIN 10 20 0 0 0 5 10 10 5 TYP MAX UNIT ns ns ns ns ns ns ns OOO OOO 25 OOO OOO THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com Write Timing Diagram (using R/W, CS0-controlled) Figure 35 shows the write-timing behavior when the WR(R/W) input is programmed as a combined read-write input R/W. The RD input has to be tied to high-level in this configuration. This timing is called CS0-controlled because CS0 is the last external signal of CS0, CS1, and R/W which becomes valid. The writing to the THS1207 can be performed irrespective of the conversion clock signal CONV_CLK. tw(CS) CS0 90% 10% 10% CS1 tsu(R/W) 10% R/W 10% RD tsu th D(0-11) 90% 90% Figure 35. Write Timing Diagram Using R/W (CS0-controlled) Write Timing Parameter (CS0-controlled) PARAMETER tsu(R/W) tsu th th(R/W) tw(CS) Setup time, R/W stable to last CS valid Setup time, data valid to first CS invalid Hold time, first CS invalid to data invalid Hold time, first CS invalid to R/W change Pulse duration, CS active MIN 0 5 2 5 10 TYP MAX UNIT ns ns ns ns ns 26 OOO OOO th(R/W) OOO OOO www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 ANALOG INPUT CONFIGURATION AND REFERENCE VOLTAGE The THS1207 features four analog input channels. These can be configured for either single-ended or differential operation. Figure 36 shows a simplified model, where a single-ended configuration for channel AINP is selected. The reference voltages for the ADC itself are VREFP and VREFM (either internal or external reference voltages). The analog input voltage range is between VREFM to VREFP. This means that VREFM defines the minimum voltage, and VREFP defines the maximum voltage, which can be applied to the ADC. The internal reference source provides the voltage VREFM of 1.5 V and the voltage VREFP of 3.5 V (see also section reference voltage). The resulting analog input voltage swing of 2 V can be expressed by: V REFM v AINP v V REFP VREFP (1) AINP 12-Bit ADC VREFM Figure 36. Single-Ended Input Stage A differential operation is desired in many applications due to a better signal-to-noise ration. Figure 37 shows a simplified model for the analog inputs AINM and AINP, which are configured for differential operation. The differential operation mode provides in terms of performance benefits over single-ended mode and is therefore recommended for best performance. The THS1207 offers 2 differential analog inputs and in the single-ended mode 4 analog inputs. If the analog input architecture is differential, common mode noise and common mode voltages can be rejected. Additional details for both modes are given below. VREFP AINP + - AINM VADC 12-Bit ADC VREFM Figure 37. Differential Input Stage In comparison to the single-ended configuration it can be seen that the voltage, VADC, which is applied at the input of the ADC is the difference between the input AINP and AINM. The voltage VADC can be calculated as follows: V ADC + ABS(AINP-AINM) (2) The advantage to single-ended operation is that the common-mode voltage V CM + AINM ) AINP 2 (3) can be rejected in the differential configuration, if the following condition for the analog input voltages is true: AGND v AINM, AINP v AV 1VvV CM v4V DD (4) (5) 27 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com SINGLE-ENDED MODE OF OPERATION The THS1207 can be configured for single-ended operation using dc or ac-coupling. In either case, the input of the THS1207 must be driven from an operational amplifier that does not degrade the ADC performance. Because the THS1207 operates from a single supply 5 V, it is necessary to level-shift ground-based bipolar signals to comply with its input requirements. This can be achieved with dc and ac-coupling. DC-COUPLING An operational amplifier can be configured to shift the signal level according to the analog input voltage range of the THS1207. The analog input voltage range of the THS1207 is between 1.5 V and 3.5 V. An operational amplifier can be used as shown in Figure 38. Figure 38 shows an example where the analog input signal in the range between -1 V up to 1 V. This signal is shifted by an operational amplifier to the analog input range of the THS1207 (1.5 V to 3.5 V). The operational amplifier is configured as an inverting amplifier with a gain of -1. The required dc voltage of 1.25 V at the noninverting input is derived from the 2.5-V output reference REFOUT of the THS1207 by using a resistor divider. Therefore, the operational amplifier output voltage is centered at 2.5 V. The 10 F tantalum capacitor is required for bypassing REFOUT. REFIN of the THS1207 must be connected directly to REFOUT in single-ended mode. The use of ratio matched, thin-film resistor networks minimizes gain and offset errors. R1 5V 1V 0V -1 V 1.25 V R1 _ + RS C 3.5 V 2.5 V 1.5 V THS1207 AINP REFIN REFOUT + R2 10 F R2 Figure 38. Level-Shift for DC-Coupled Input DIFFERENTIAL MODE OF OPERATION For the differential mode of operation, a conversion from single-ended to differential is required. A conversion to differential signals can be achieved by using an RF-transformer, which provides a center tap. Best performance is achieved in differential mode. Mini Circuits T4-1 49.9 R 200 R AINM C REFOUT C THS1207 AINP 10 F + Figure 39. Transformer Coupled Input 28 www.ti.com THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 DEFINITIONS OF SPECIFICATIONS AND TERMINOLOGY Integral Nonlinearity Integral nonlinearity refers to the deviation of each individual code from a line drawn from zero through full scale. The point used as zero occurs 1/2 LSB before the first code transition. The full-scale point is defined as level 1/2 LSB beyond the last code transition. The deviation is measured from the center of each particular code to the true straight line between these two points. Differential Nonlinearity An ideal ADC exhibits code transitions that are exactly 1 LSB apart. DNL is the deviation from this ideal value. A differential nonlinearity error of less than 1 LSB ensures no missing codes. Zero Offset The major carry transition should occur when the analog input is at zero volts. Zero error is defined as the deviation of the actual transition from that point. Gain Error The first code transition should occur at an analog value 1/2 LSB above negative full scale. The last transition should occur at an analog value 1 1/2 LSB below the nominal full scale. Gain error is the deviation of the actual difference between first and last code transitions and the ideal difference between first and last code transitions. Signal-to-Noise Ratio + Distortion (SINAD) SINAD is the ratio of the rms value of the measured input signal to the rms sum of all other spectral components below the Nyquist frequency, including harmonics but excluding dc. The value for SINAD is expressed in decibels. Effective Number Of Bits (ENOB) For a sine wave, SINAD can be expressed in terms of the number of bits. Using the following formula, N+ (SINAD * 1.76) 6.02 it is possible to get a measure of performance expressed as N, the effective number of bits. Thus, effective number of bits for a device for sine wave inputs at a given input frequency can be calculated directly from its measured SINAD. Total Harmonic Distortion (THD) THD is the ratio of the rms sum of the first six harmonic components to the rms value of the measured input signal and is expressed as a percentage or in decibels. Spurious Free Dynamic Range (SFDR) SFDR is the difference in dB between the rms amplitude of the input signal and the peak spurious signal. 29 THS1207 SLAS284A - AUGUST 2000 - REVISED DECEMBER 2002 www.ti.com MECHANICAL DATA DA (R-PDSO-G**) 38 PINS SHOWN 0,30 0,19 20 PLASTIC SMALL-OUTLINE PACKAGE 0,65 38 0,13 M 6,20 NOM 8,40 7,80 0,15 NOM Gage Plane 1 A 19 0-8 0,75 0,50 0,25 Seating Plane 1,20 MAX 0,15 0,05 0,10 PINS ** DIM A MAX 28 30 32 38 9,80 11,10 11,10 12,60 A MIN 9,60 10,90 10,90 12,40 4040066/D 11/98 NOTES:A. B. C. D. All linear dimensions are in millimeters. This drawing is subject to change without notice. Body dimensions do not include mold flash or protrusion. Falls within JEDEC MO-153 30 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI's terms and conditions of sale supplied at the time of order acknowledgment. TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI's standard warranty. Testing and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed. TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. To minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards. TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI. Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation. Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Mailing Address: Texas Instruments Post Office Box 655303 Dallas, Texas 75265 Copyright 2002, Texas Instruments Incorporated |
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