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mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 1 of 25 data sheet rev 003 feb/12 features and benefits programmable sensor interface ic with 4 to 20 ma current loop output power supply from 6 to 35v dc external or internal temperature sensor for compensating temperature errors application examples industrial pressure transducers. strain gauges, accelerometers, position sensors, etc. any bridge type sensor with current loop output. ordering code product code temperature code package code op tion code packing form code mlx90323 k df a aa-000 tu mlx90323 k df a aa-000 re legend : temperature code: k for temperature range -40c to +125c package code: df for soic300mil packing form: re for reel, tu for tube ordering example: mlx90323kdf-aaa-000-tu 1 functional diagram 2 general description the ic converts small changes of output voltage of full wheatstone resistive bridge (caused by mechanical stimulus such as pressure, force, torque, light or magnetic field) to large changes o f the ic output current. it removes parasitic dc level (offset) from the output bridge voltage and amplifies this signal certain times (gain). offset and gain are temperature dependant, so the ic allows temperature compensation of bridge parasitic dc shift and sensitivity. temperature can be measured either by internal or external (resistor) temperature sensor. the values of offset and gain and their temperature dependency are gotten during the calibration process and are stored in the eeprom.. the ic has industry standard 4 ? 20 ma current loop output interface and takes power directly from 2-wire signal line. the mlx90323 works properly over wide voltage range (from 6 to 35 v) at the signal line. x 35 gain external temp sensor internal temp sensor inv x2 adc 3.5v 0v temp amp gain gntp [1:0] hardware gain = 70 0.97v/v 0.48v/v 1.24kohm fine gain dac micro- processor 2-bit csgn supply regulator vdd vbp vbn tmp gnd io1 io2 coms flt ofc opa 0v 3.5v dac_offset coarse offset vdd1 fet gain cmo cmn tstb
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 2 of 25 data sheet rev 003 feb/12 table of contents 1 functional diagram .............................. ................................................... ................................................... ...... 1 2 general description ............................. ................................................... ................................................... ....... 1 3 glossary of terms ............................... ................................................... ................................................... ....... 3 4 absolute maximum ratings ........................ ................................................... ................................................... 4 5 pin definitions and descriptions................. ................................................... ................................................... 5 6 general electrical specifications ............... ................................................... ................................................... . 6 7 detailed general description .................... ................................................... ................................................... . 8 7.1 understanding 4-20ma current loop interface ... ................................................... ..................................... 8 7.2 analog features ............................... ................................................... ................................................... ..... 8 7.3 digital features .............................. ................................................... ................................................... ....... 9 7.4 parameters calculation ........................ ................................................... ................................................. 1 0 7.5 communications ................................ ................................................... ................................................... 11 8 temperature compensation ........................ ................................................... ................................................ 13 9 calibration ..................................... ................................................... ................................................... ........... 15 9.1 baseline calibration .......................... ................................................... ................................................... . 15 9.2 temperature calibration ....................... ................................................... ................................................. 1 5 9.3 calibration procedure ......................... ................................................... .................................................. 16 10 eeprom and ram byte definitions ................ ................................................... .......................................... 17 11 unique features ................................ ................................................... ................................................... ..... 22 12 application information ........................ ................................................... ................................................... ... 22 13 standard information regarding manufacturability of melexis products with different soldering proce sses 23 14 esd precautions ................................ ................................................... ................................................... .... 24 15 package information ............................ ................................................... ................................................... .. 24 16 disclaimer ..................................... ................................................... ................................................... .......... 24
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 3 of 25 data sheet rev 003 feb/12 3 glossary of terms cmn current mode negative (supply connection) cmo current output coms communication, serial cr carriage return csgn coarse gain csof coarse offset dacfnew filtered dac value, new dacfold filtered dac value, old dardis dac resistor disable eoc end of conversion flag bit etmi timer interrupt enable etpi enable temperature interrupt fet field effect transistor fg fixed gain flt filter pin gno gain and offset adjusted digitized signal gnof gain, offset gntp temperature gain / offset coarse adjustmen t hs hardware / software limit ifix fixed current output value iinv input signal invert command bit ilim current limit modsel mode select mux multiplexer ofc offset control pll phase locked loop por power on reset rx receive sar successive approximation register stc start a/d conversion tdiff temperature difference text temperature, external tmi timer interrupt tmp temperature signal tpi temperature interrupt tref temperature reference tstb test mode pin tx transmit uart universal asynchronous receiver / transmit ter vbn bridge, positive, input vbp bridge, negative, input v dd supply voltage wcb warn / cold boot wdc watch dog counter
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 4 of 25 data sheet rev 003 feb/12 4 absolute maximum ratings table 1. absolute maximum ratings supply voltage v dd max 6v supply voltage v dd min 4.5v supply voltage (operating), v dd1 max 35v supply current, i dd 3.5ma reverse voltage protection -0.7v power dissipation, p d 71mw operating temperature range, t a -40 to +125 storage temperature range, t s -55 to +150c maximum junction temperature, t j 150c exceeding the absolute maximum ratings may cause pe rmanent damage. exposure to absolute-maximum- rated conditions for extended periods may affect de vice reliability.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 5 of 25 data sheet rev 003 feb/12 5 pin definitions and descriptions table 2. pin description pin signal name description 1,2 nc do not connect 3 tstb test pin for melexis production testing. (in normal application connected to vdd) 4 flt filter pin; allows for connection of a capacitor to the internal analog path. 5 ofc offset control output. provides access to the inter nal programmed offset control voltage for use with external circuitry. (u nconnected when not used) 6,7 vbn,vbp bridge inputs, negative and positive. 8 tmp temperature sensor input. an external temperature s ensor can be used in conjunction with the internal one. the external sen sor can provide a temperature reading at the location of the bridge s ensor. 9 v dd regulated supply voltage. used for internal analog circuitry to ensure accurate and stable signal manipulation. 10 fet regulator fet gate control. for generating a stable supply for the bridge sensor and internal analog circuitry (generates reg ulated voltage for vdd). 11 v dd1 unregulated supply voltage. used for digital circui try and to generate fet output. 12 nc do not connect 13 cmo current output. 14 cmn current negative rail. current return path. 15 gnd power supply return. 16 coms serial communications pin. bi-directional serial co mmunication signal for reading and writing to the eeprom. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 nc nc tstb flt ofc vbn vbp tmp coms gnd cmn cmo vdd1 fet vdd nc
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 6 of 25 data sheet rev 003 feb/12 6 general electrical specifications table 3. mlx90323 electrical specifications dc operating parameters: t a = -40 to 125 o c, v dd1 = 6 to 35v dc (unless otherwise specified). parameter symbol test conditions min typ max units regulator & consumption input voltage range v in v dd1 (regulator connected) 6 35 v supply current i dd @ t a = 100oc 2.1 ma regulated supply voltage v reg 4.5 4.75 5.2 v regulated voltage temperature coefficient -600 uv / o c supply rejection ratio psrr v dd1 > 6v 90 db instrumentation amplifier differential input range vbp-vbn iinv = 0 -2.88 8.38 mv/v (vdd) differential input range vbp-vbn iinv = 1 -8.38 2.88 mv/v (vdd) common mode input range 1/2(vbp+vbn) 38.0 65.0 %vdd common mode rejection ratio cmrr 60 db hardware gain 69 84 v/v coarse offset control range csof[1:0] = 00 -4.37 -3.97 mv/v csof[1:0] = 01 -1.46 -1.09 mv/v csof[1:0] = 10 1.09 1.46 mv/v csof[1:0] = 11 3.97 4.37 mv/v fixed offset control range high 1.71 2.29 mv/v low -2.00 -1.43 mv/v ia chopper frequency 300 khz gain stage coarse gain stage coarse gain (fixed gain = 1023) csgn = 00 1.05 1.17 v/v csgn = 01 1.71 1.89 v/v csgn = 10 2.77 3.06 v/v csgn = 11 4.48 4.95 v/v
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 7 of 25 data sheet rev 003 feb/12 fixed gain control range 0.480 0.970 v/v table 3. mlx90323 electrical specifications (contin ued) output stage fixed gain r sense = 24 ohm 8.4 9.3 ma/v output current cmo pin 27 ma current sense resistor 24 ohms signal path ( general) overall gain current sense res = 24 284 2625 ma/v overall non-linearity -0.25 0.25 % bandwidth (-3db) 39 nf (flt to gnd) 2.8 3.5 4.2 khz temperature sensor & amplifier temperature sensor sensitivity 390 uv/oc temperature sensor output voltage 70 380 mv input voltage range tmp pin gntp[1,0] = 00 207 517 mv @ v dd = 5.0v gntp[1,0] = 01 145 367 mv gntp[1,0] = 10 101 263 mv gntp[1,0] = 11 71 186 mv dac / adc resolution 10 bit on-chip rc oscillator and clock trimmed rc oscillator frequency 86.9 87.8 88.7 khz frequency temperature coefficient 26 hz/oc clock stability with temperature compensation over full temperature range -3 +3 % ratio of f (microcontroller main clock and (rc oscillator) turbo = 0 7 turbo = 1 28 uart & coms pin uart baud rate turbo = 0 2400 baud turbo = 1 9600 baud coms pin input levels low 0.3*v dd v high 0.7*v dd v coms pin output resistance low 100 ohms high 100 kohms
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 8 of 25 data sheet rev 003 feb/12 7 detailed general description 7.1 understanding 4-20ma current loop interface mlx90323 ic is optimized for 4 - 20 ma industry sta ndard current loop interface. the 4 - 20ma current loop shown in figure 1 is a common method of transmittin g sensor information in many industrial application s. transmitting sensor information via a current loop is particularly useful when the information has to be sent to a remote location over long distances. the loop ope ration is straightforward: a sensor?s output voltag e is first converted to a proportional current, with 4ma norma lly representing the sensor?s zero-level output, an d 20ma representing the sensor?s full-scale output. then, a receiver at the remote end converts the 4-20ma c urrent back into a voltage which in turn can be further pr ocessed by a controller module. slp vb inp inm gnd signal line positive sln sensor signal line negative mlx90323 transmission line r e output voltage for further processing current loop power source signal processor / controller 4 ? 20 ma figure 1. current loop interface diagram 7.2 analog features supply regulator a bandgap-stabilized supply-regulator is on-chip wh ile the pass-transistor is external. the bridge-typ e sensor is typically powered by the regulated supply (typic ally 4.75v). oscillator the mlx90323 contains a programmable on-chip rc osc illator. no external components are needed to set the frequency (87.8 khz +/-1%). the mcu-clock is ge nerated by a pll (phase locked loop tuned for 614 k hz or 2.46 mhz) which locks on the basic oscillator. the frequency of the internal clock is stabilized o ver the full temperature range, which is divided in to three regions, each region having a separate digital cloc k setting. all of the clock frequency programming i s done by melexis during final test of the component. the device uses the internal temperature sensor to dete rmine which temperature range setting to use. power-on reset the power-on reset (por) initializes the state of t he digital part after power up. the reset circuitry is completely internal. the chip is completely reset a nd fully operational 3.5 ms from the time the supply crosses 3.5 volts. the por circuitry will issue ano ther por if the supply voltage goes below this thre shold for 1.0 us. temperature sensor the temperature measurement, tpo, is generated from the external or internal temperature sensor. this is converted to a 10-bit number for use in calculating the signal compensation factors. a 2-bit coarse ad justment gntp[1:0] is used for the temperature signal gain & offset adjustment.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 9 of 25 data sheet rev 003 feb/12 7.3 digital features uart the serial link is a potentially full-duplex uart. it is receive-buffered, in that it can receive a se cond byte before a previously received byte has been read fro m the receiving register. however, if the first byt e is not read by the time the reception of the second byte i s completed, the first byte will be lost. the uart' s baud rate depends on the rc-oscillator's frequency and t he "turbo"-bit (see output port). transmitted and received data has the following structure: start bi t = 0, 8 bits of data, stop bit = 1. sending data writing a byte to port 1 automatically starts a tra nsmission sequence. the tx interrupt is set when th e stop- bit of the byte is latched on the serial line. receiving data reception is initialized by a 1 to 0 transition on the serial line (i.e., a start-bit). the baud rate period (i.e., the duration of one bit) is divided into 16 phases. the first six and last seven phases of a bit are n ot used. the decision on the bit-value is then the result of a majority vote of phase 7, 8 and 9 (i.e., the cen ter of the bit). spike synchronization is avoided by de-bouncing on the incoming data and a verification of the start-b it value. the rx interrupt is set when the stop bit is latched in the uart. timer the clock of the timers tmi and tpi is taken direct ly from the main oscillator. the timers are never r eloaded, so the next interrupt will take place 2x oscillator pulses after the first interrupt. watch dog an internal watch dog will reset the whole circuit in case of a software crash. if the watch dog count er is not reset at least once every 26 milliseconds (@ 2.46 m hz main clock), the microcontroller and all the peripherals will be reset. temperature processing temperature reading controls the temperature compen sation. this temperature reading is filtered as designated by the user. the filter adjusts the temp erature reading by factoring in a portion of the pr evious value. this helps to minimize the effect of noise w hen using an external temperature sensor. the filte r equation is: if measured_temp > temp_f(n) then temp_f(n+1) = temp_f(n) + [measured_temp - temp_f( n)] / [2 n_factor ] if measured_temp < temp_f(n), then temp_f(n+1) = temp_f(n) - [measured_ temp - temp_f(n)] [2 n_factor ] temp_f(n+1) = new filtered temperature value temp_f(n) = previous filtered temperature value measured_temp = value from temperature a to d n_factor = filter value set by the use r (four lsb?s of byte 25 of eeprom), range 0-6. the filtered temperature value, temp_f, is stored i n ram bytes 58 and 59. the data is a 10 bit value, left justified in a 16 bit field.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 10 of 25 data sheet rev 003 feb/12 7.4 parameters calculation the parameters of and gn represent, respectively, o ffset correction and span control, while oftci and gntci represent their temperature coefficients (the rmal zero shift and thermal span shift). after rese t, the firmware continuously calculates the offset and gai n dac settings as follows: the eeprom holds parameters gn, of, oftci and gntci, where ?i? is th e gap number and can be 1 < i < 4. the transfer function is described below. gain i out = fg * dac_gain * csgn[1:0] * {vin+dac_offset+csof } * 8.85ma/v fg = hardware gain (~72v/v). part of the hardware d esign, and not changeable csgn = course gain, part of byte 2 in eeprom. csof = coarse offset, part of byte 2 in eeprom. dac_gain (new value) ~ gn[9:0] + [gntci * dt] gn[9:0] = fixed gain, bytes 3 and 17 in eeprom. gntci = gain tc for a given temperature segment i. gntcil and gntcih in eeprom table. dt = temp. change within the appropriate gap how to calculate gain in the first temp. gap?: dac_gain = gn[9:0] - gntc1 * (t1 ? temp_f1) how to calculate gain in the other temp. gaps?: 2nd gap: dac_gain = gn[9:0] + gntc2 * (temp_f2 ? t1) 3rd gap: dac_gain = dac_gain2 + gntc3 * (temp_f3 ? t2) 4th gap: dac_gain = dac_gain3 + gntc4 * (temp_f4 ? t3) where: temp_f = filtered temp (previously described) if gntc1 > 2047 => dac_gain if gntc2,3,4 > 2047 => dac_gain [v/v] gain dac gn _ 48.0 1023 ]0:9[ *) 48.0 97.0( = + ? offset dac_offset (new value) ~ of[9:0]+[oftci* dt] of[9:0] = fixed gain, bytes 4 and 17 in eeprom. oftci = offset for a given temperature segment i. o ftcil and oftcih in eeprom table. dt = temp. change within the appropriate gap. calculation of the offset for a given temperature s egment is performed the same way as for the gain. offset dac of _ 57.1 1023 ]0:9[ *) 57.1 83.1( = ? ? ? [mv/v]
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 11 of 25 data sheet rev 003 feb/12 7.5 communications the mlx90323 firmware transfers a complete byte of data into and from the memory based on a simple command structure. the commands allow data to be re ad and written to and from the eeprom and read from the ram. ram data that can be read includes th e current digitized temperature. the commands are described below. melexis provides setup software fo r programming the mlx90323. uart commands the commands can be divided into three parts: (1) d ownloading of data from the asic, (2) uploading of data to the asic and (3) the reset command. uart configu ration: start bit, 8 data bits, stop bit. all the commands have the same identification bits. the two msb?s of the sent byte indicate the comman d while the last six msb?s designate the desired addr ess. the commands are coded as followed: command start bit bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 stop bit read ram 0 1 1 ad5 ad4 ad3 ad2 ad1 ad0 1 write ram 0 0 0 ad5 ad4 ad3 ad2 ad1 ad0 1 read eeprom 0 1 0 ad5 ad4 ad3 ad2 ad1 ad0 1 write eeprom 0 0 1 ad5 ad4 ad3 ad2 ad1 ad0 1 reset 0 1 0 1 1 1 1 1 1 1 the addresses can include 0-63 for the ram, 0-47 fo r the eeprom, and 63 for the eeprom, reset command (read). downloading command with one byte, data can be downloaded from the asic . the asic will automatically send the value of the desired byte. uploading command writing to the ram or eeprom involves a simple hand shaking protocol in which each byte transmitted is acknowledged by the firmware. the first byte transm itted to the firmware includes both command and address. the firmware acknowledges receipt of the c ommand and address byte by echoing the same information back to the transmitter. this ?echo? al so indicates that the firmware is ready to receive the byte of data to be stored in ram or eeprom. next, the byte of value to be stored is transmitted and, if succes sfully received and stored by the firmware, is acknowledge d by a ?data received signal,? which is two bytes o f value bch. if the ?data received signal? is not observed, it may be assumed that no value has been stored in ram or eeprom. reset command reading the address 63 of the eeprom resets the asi c and generates a received receipt indication. immediately before reset, the asic sends a value of bch to the uart, indicating that the reset has bee n received. eeprom data all user-settable variables are stored in the eepro m within the mlx90323. the eeprom is always re- programmable. changes to data in the eeprom do not take effect until the device is reset via a soft re set or power cycle. 12 bit variables are stored on 1.5 byt es. the 4 msb?s are stored in a separate byte and s hared with the four msb?s of another 12-bit variable.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 12 of 25 data sheet rev 003 feb/12 clock temperature stabilization to provide a stable clock frequency from the intern al clock over the entire operating temperature rang e, three separate clock adjust values are used. shifts in op erating frequency over temperature do not effect th e performance but do, however, cause the communicatio ns baud rate to change. the firmware monitors the internal temperature sens or to determine which of three temperature ranges t he device currently is in. each temperature range has a factory set clock adjust value, clktc1, clktc2, a nd clktc3. the temperature ranges are also factory set . the ctemp1 and ctemp2 values differentiate the th ree ranges. in order for the temperature a to d value t o be scaled consistently with what was used during factory programming, the clkgntp (temperature amplifier gai n) valued is stored. the cadj value stored in byte 1 of the eeprom is used to control the internal clock fr equency while the chip boots. unused bytes there are eight unused bytes in the eeprom address map. these bytes can be used by the user to store information such as a serial number, assembly date code, production line, etc. melexis doesn?t guarant ee that these bytes will be available to the user in future revisions of the firmware. eeprom checksum a checksum test is used to ensure the contents of t he eeprom. the eight bit sum of all of the eeprom addresses should have a remainder of 0ffh when the checksum test is enabled (mode byte). byte 47 is used to make the sum remainder totals 0ffh. if the checksum test fails, the output will be driven to a user defined value, faultval. when the checksum test is enabled, the checksum is verified at initialization of ram after a reset. ram data all the coefficients are compacted in a manner simi lar to that used for the eeprom. they are stored on 12 bits (instead of keeping 16 bits for each coefficie nt). all the measurements are stored on 16 bits. th e user must have access to the ram and the eeprom, while i nterrupt reading of the serial port. therefore, byt es must be kept available for the return address, the a-accu and the b-accu, when an interrupt occurs. th e ram keeps the same structure in the both modes. table 4. examples of fixed point signed numbers decimal value hexadecimal equivalent fixed point signed number equivalent 0 0000h +0.00 1023 3ffh +0.9990234 1024 400h +1.000 2047 7ffh +1.9990234 2048 800h -0.000 3071 0bffh -0.9990234 3072 0c00h -1.000 4095 0fffh -1.9990234 data range various data are arranged as follows: temperature points: 10 bits, 0-03ff in high-low order. gn1: 10 bits, 0-03ff in high-low order. of1: 10 bits, 0-03ff in high-low order. gntci: signed 12 bits (with msb for the sign), [-1.9990234, +1.9990234]. oftci: signed 12 bits (with msb for the sign), [-1.9990234, +1.9990234].
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 13 of 25 data sheet rev 003 feb/12 8 temperature compensation the mlx90323?s temperature compensation algorithm i s piece-wise with up to 4 temperature segments, see figure 2. within each temperature segment (?gap?), the correction is a first order calculation. ther e are separate temperature coefficients for gain and offs et. the first temperature gap is slightly different than the other three. the compensation is based on the temp erature difference between the current temp and the t1 point (the upper end of the gap). the other gaps u se the lower end of the gap to measure the temperat ure difference. for instance in the second gap, the te mperature difference is current temperature minus t 1. this difference has to be accounted for in the compensat ion procedure. parameter temperature temperature compensation of of of of & & & & gn gngn gn t3 t2 t1 0 3ffh i1 i2 i3 i4 gntc4 gntc3 gntc2 gntc1 oftc1 oftc2 oftc3 oftc4 1 gap application's temperature range figure 2. temperature compensation. temperature gaps there are four temperature gaps possible with the mlx90323. the gaps are defined with respect to the filtered digitized temperature value saved in ram locations 58 and 59. the first temperature gap is always bound at the low end by a digitized temperature value of zero. the fourth temperature gap is bound at the high end by a digitized temperature value of 1023 10 (3ff hex ). whenever fewer than four gaps are used, the last gap should have an upper bound of 1023 10 . this is to ensure that if the temperature exceeds the last point it won?t enter into an undefined temperature gap. temperature points the temperature points t1, t2 and t3 are defined by the user to differentiate between the four possible temperature compensation ranges. the low endpoint t0 is defined as the minimum digitized filtered temperature value, zero. this means that the coefficients for the first gap, oftc1 and gntc1, will apply to the signal until the digitized filtered temperature reaches zero. the high endpoint t4 is defined as the maximum digitized filtered temperature value, 1023 10 . this means that the coefficients for the last gap, oftc4 and gntc4 will apply to the signal from the t3 point and up until the digitized filtered temperature reaches its maximum, 1023 10 . when defining these points, the number that is used is simply copied from the ?temp value? box (see ?mlx90323_software_descroption.pdf? ) at the desired temperature (contents of ram locations 58 and 59).
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 14 of 25 data sheet rev 003 feb/12 gntc the gntc values are the gain temperature compensati on values for each of the four temperature gaps, gnct1, gntc2, gntc3, and gntc4. these values are u sed to adjust the signal up or down based on the relative temperature within a particular gap. math ematically this is represented by the following equ ation: dac_gain = csgn * {gn[9:0] + [gntci * ? ti]} where: ? ti = (t1 ? temp_f) for gap 1; ? ti = (temp_f ? t i-1 ) for gaps 2,3,and 4; temp_f = filtered temperature; dac_gain = the digital value that adjusts the gain on the gain amplifier; ti = temperature segment point i = 2, 3, or 4; gntci = gain tc for a given temperature segment i; csgn = course gain; gn[9:0] = fixed gain (doesn?t change with temperat ure). the gntc and oftc values are 12 bit fixed point sig ned numbers (see table 4). that means that the mos t significant bit is a sign bit. the next bit is one or zero (whole number). the remaining 10 bits are to the right of the decimal point. this gives the variable the range of ?1.9990234 to +1.9990234. the table below shows how the fixed point numbers are represented as the binary number progresses from 0 to 4095. oftc the oftc values are the offset temperature compensa tion values for each of the four temperature gaps, ofct1, oftc2, oftc3, and oftc4. these values are u sed to adjust the signal?s offset up or down based on the relative temperature within a particular gap . the offset adjustment is additive from one gap t o the next. that is the offset adjustment for the fourth gap is added to the total offset adjustment of the third gap which is also added to the total offset adjustment of the second gap. mathematically this is represen ted by the following equation: for the first temperature gap: dac_offset = of[9:0] + oftci * (t1 ? temp_f) for the second temperature gap: dac_offset =of[9:0] + oftc2 * (temp_f ? t2) for the third temperature gap: dac_offset = of[9:0] + [oftc2 * (t2-t1)] + oftc3 * (temp_f ? t3) for the fourth temperature gap: dac_offset =of[9:0] + [oftc2 * (t2-t1)] + [oftc3 * (t3 ? t2)] + oftc4 * (temp_f ? t4), where of[9:0] = fixed offset
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 15 of 25 data sheet rev 003 feb/12 9 calibration 9.1 baseline calibration the baseline calibration involves setting the opera ting modes and temperature gain along with the coar se and fixed gain and offset. the operating modes are turbo mode, internal or ext ernal temperature sensor, and checksum test. the checksum test, if used, should be enabled after all other settings are complete. the invert signal bit swaps the differential inputs to the signal path. this has the same effect as s wapping the connections to the vbp and vbn pins of the chip. temperature amplifier gain, gntp, should be set suc h that the analog converter doesn?t under-run or ov er- run at the temperature extremes. when using the in ternal temperature sensor over the full temperature span of the device (-40c to +125c) typically a gntp set ting of 2 will work. when using an external temper ature sensor the voltage on the tmp pin must stay within the ranges as described in the datasheet. the more of the voltage range used the greater the temperature compensation adjustment range will be. the coarse gain and fixed gain should be set before the coarse offset and fixed offset. gain and offs et are inter-related, the offset is multiplied by the gain . it is much easier to program the gain first then offset. it may be necessary to make some minor adjustment to the c oarse offset settings before adjusting the gain. t his is only needed if the output clips at either high end or low end. it is difficult to precisely calculate the offset and gain values. the amplifier circuitry within the ch ip uses resistors implemented in silicon. these re sistors have around a 20% tolerance, thus the gain and offs et will vary from chip to chip. each chip is teste d to provide a gain and offset adjustment capability wit hin a specified range. for calculations a typical v alue can be taken. 9.2 temperature calibration the temperature compensation capability of the mlx9 0323 is piece-wise with first order compensation in each segment (gap). the compensation is based on t he difference between the current digitized filtere d temperature and the appropriate temperature point. the equations have been previously described. the first temperature gap is slightly different than the othe r three. the first gap uses the temperature differ ence between the current temperature and the t1 temperat ure point (the upper end of the temperature gap). the second temperature gap also uses the t1 point for d etermining the temperature differences (the low end of the second gap). the third and fourth gaps also us e the temperature point at the low end of their gap . this means that programming the temperature compensation for the first gap is slightly different than the o ther gaps. the compensation coefficients for the first gap (oftc1 and gntc1) apply to digitized filtered temperature values from t1 down to zero. the fourt h gap coefficients apply to digitized filtered temp erature range from t3 to 1023 (decimal). the temperature points t1 thru t3 should always be in increasing order from t1 to t2 to t3. if the temperature sensor has increasing signal with incre asing temperature then the compensation procedure i s intuitively easy. this is the case with the intern al temperature sensor. if the temperature sensor h as decreasing signal with increasing temperature then the compensation will start at a hotter temperature and go towards cold. the procedure below is written with regard to the filtered digitized temperature not th e real physical temperature.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 16 of 25 data sheet rev 003 feb/12 9.3 calibration procedure 1) set the desired operating mode and number of gap s. it is also helpful to set t2 and t3 to 1023. 2) at the t1 temperature do a baseline calibration, the span then the offset by using csgn[1:0] and gn [9:0] then csof[1:0] and of[9:0]. the t1 temperature is somewhat arbitrary, typically its room temperature. if the temperature sensor goes down with increasing te mperature then the t1 value will be towards the hig h end of the application?s temperature range. update the temp value. copy the digitized temperature re ading to the t1 box. if one temperature gap is desired t hen t1 will be the highest digitized temperature va lue. 3) lower the temperature to the lowest operating te mperature and recalibrate the output using gntc1 and oftc1 only. if the temperature sensor go es down with increasing temperature then raise the temperature to its maximum value and re-calibrate t he output using gntc1 and oftc1. do not change the t1, of, or gn values. 4) raise the temperature until the second temperatu re point, t2. if the temperature sensor goes down with increasing temperature then lower the temperature t o the t2 value. this point may be arbitrary and ca n be based on how far the output has deviated from it's desired value. re-calibrate the sensor by adjusting gntc2 and oftc2 only. 5) update the temp value displayed on the screen. copy the digitized temperature value to the t2 box. this must happen after step 4. 6) repeat steps 4 and 5 for t3 and setting gntc3, o ftc3. t1, t2, and t3 must be in ascending order. 7) for the last temperature gap, raise the temperat ure to the highest operating temperature point and re- calibrate the output using gntc4 and oftc4. there is no t4, it is assumed to be 1023 (the maximum val ue of the digitized filtered temperature). for less than four temperature gaps the last temper ature point should be set to 1023. this means that the last gap extends out to the end of the temperature range.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 17 of 25 data sheet rev 003 feb/12 10 eeprom and ram byte definitions table 5. eeprom byte definitions byte designation note 0 turbo mode, temp selection bit 0: must always be set to ?1? bit 1: (0 = internal temp, 1 = external temp) bit 3: (0 = turbo mode not active, 1 = active) bit 2,4,5,6: must always be set to ?0? bit 7: (0 = eeprom checksum test inactive, 1 = acti ve ) 1 cadj controls system clock during boot. 2 coarse control contents described in table 6. 3 gn1l the eight lsb's of the fixed gain, gn[7:0]. 4 of1l the eight lsb's of fixed offset of[7:0]. 5 gntc1l the eight lsb's of the first gain tc gntc1[7:0]. 6 oftc1l the eight lsb's of the first offset tc oftc1[7:0]. 7 tr1l the eight lsb's of the first temperature point, t1[ 7:0]. 8 gntc2l the eight lsb's of the second gain tc gntc2[7:0]. 9 oftc2l the eight lsb's of the second offset tc oftc2[7:0]. 10 tr2l the eight lsb's of the second temperature point t2[ 7:0]. 11 gntc3l the eight lsb's of the third gain tc gntc3[7:0]. 12 oftc3l the eight lsb's of the third offset tc oftc3[7:0] 13 tr3l the eight lsb's of the third temperature point t3[7 :0]. 14 gntc4l the eight lsb's of the fourth gain tc gntc4[7:0]. 15 oftc4l the eight lsb's of the fourth offset tc oftc4. 16 - reserved
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 18 of 25 data sheet rev 003 feb/12 table 5. eeprom byte definitions (continued) byte designation note upper four bits lower fou r bits 17 gn1[9:8] of1[9:8] two msb's of fixed gain two msb's of fix ed offset gn[9:8]. of[9:8 ] 18 gntc1[11:8] oftc1[11:8] four msb's of first gain tc four msb's of the first offset gntc1[11:8]. tc oftc1[11 :8]. 19 tr1[9:8] gntc2[11:8] two msb's, first temperature four msb's, second gain point t1[9:8] tc gntc2 [11:8] 20 oftc2[11:8] tr2[9:8] four msb's second offset two msb's second tc oftc2[11:8] temperature p oint t2[9:8] 21 gntc3[11:8] oftc3[11:8] four msb's third gain tc four msb's third offset gntc3[11:8] tc oftc3[11 :8] 22 tr3[9:8] gntc4[11:8] two msb's third four msb's f ourth gain tc temperature point t3[9:8] gntc4[11:8] 23 oftc4[11:8] - four msb's fourth offset tc reserved 24 pnb_tnb number of temperature gaps, see table 7 25 n_factor temperature filter coefficient, four lsb's. four ms b's must all be zero. 26 - 31 reserved reserved. 32 clktc1 value of cadj at low temperature (don?t change; fac tory set). 33 clktc2 value of cadj at mid temperature (don?t change; fac tory set). 34 clktc3 value of cadj at high temperature don?t change; fac tory set). 35 ctemp1 first cadj temperature point, eight msb?s of the 10 bit internal temperature value (set at factory; do not change). 36 ctemp2 second cadj temperature point, eight msb?s of the 10 bit internal temperature value (set at factory; do not change). 37-38 not used these bytes are not used and are available to the u ser. 39 clkgntp setting for temperature amplifier for clock tempera ture adjustment temperature reading (factory set, do not change).
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 19 of 25 data sheet rev 003 feb/12 table 5. eeprom byte definitions (continued) byte designation note 40-41 faultval value sent to output if checksum test fails is a 10 bit value. 42-46 not used these bytes are not used and are available to the u ser. 47 checksum eeprom checksum; value needed to make all bytes add to 0ffh. must be set by user if checksum test i s active. table 7. pnb_tnb bit definition maximum number of temperature gaps maximum number of signal gaps fixed gain and fixed offset 5 gaps 2 gaps 3 gaps 3 gaps 2 gaps 4 gaps fixed signal table 6. bit definitions, coarse control , byte 2 bit symbol function 7 iinv invert signal sign. 6 gntp1 gain & offset of temperature amplifier. 5 gntp0 gntp = 0 to 3. 4 csof 1 coarse offset of signal amplifier. 3 csof 0 csof = 0 to 3. 2 - coarse gain of signal amplifier. csgn = 0 to 3. 1 csgn1 0 csgn0
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 20 of 25 data sheet rev 003 feb/12 table 8. ram byte definitions byte functions remarks 0 mode byte 1 gn1l fixed gain number (8lsb). 2 of1l fixed offset number (8lsb). 3 gntc1l first gain tc (8lsb). 4 oftc1l first offset tc (8lsb). 5 tr1l first temperature point. 6 gntc2l second gain tc. 7 oftc2l second offset tc. 8 tr2l second temperature point. 9 gntc3l third gain tc. 10 oftc3l third offset tc. 11 tr3l third temperature point. 12 gntc4l fourth gain tc. 13 oftc4l fourth offset tc. 14 - reserved upper four bits lower fou r bits 15 gn1[9:8] of1[9:8] two msb's of fixed gain two msb's of fixe d offset gn[9:8]. of[9:8] . 16 gntc1 oftc1[11:8] [11:8] four msb's of first gain tc four msb's of the first gntc1[11:8]. offset tc o ftc1[11:8] 17 tr1[9:8] gntc2[11:8] two msb's, first temperature four msb's, second gain point t1[9:8] tc gntc2 [11:8] 18 oftc2[11:8] tr2[9:8] four msb's, second offsettc two msb's, second tem p. oftc2[11:8] point t2[9 :8]
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 21 of 25 data sheet rev 003 feb/12 table 8. ram byte definitions (continued) byte functions remarks 19 gntc3[11:8] oftc3[11:8] four msb's, third gain tc four msb's third of fset gntc3[11:8] tc oftc3[11 :8] 20 tr3[9:8] gntc4[11:8] two msb's, third temperature four msb's, fourth gain point t3[9:8] tc gntc 4[11:8] 21 oftc4[11:8] - four msb's fourth offset tc reserved oftc4[11:8] 22 pnb_tnb same as eeprom. 23 n_factor temperature filter coefficient 4 lsb?s, 4 msb = 0 24 not used 25-26 gn offset ordinate of the current gap. 27-28 of gain ordinate of the current gap. 29 taddress 4 bits for the max. temperature address of the curr ent gap; 4 bits for the min. temperature address of the curr ent gap. 35-36 a_16 16 bits a register. 37-38 b_16 16 bits b register. 39-42 result_32 32 bits result (for 16 bit multiplication). 43-44 tempo1 measured temperature, internal or external, and tem porary variable 1. 45 tempo2 temporary variable 2. 46-47 - reserved 48 coms_backup address saved when command is send. 49 p3_copy port 3 setting copy. 50 adsav1 address saved at interrupt. 51-52 aaccsav a-accumulators saved at interrupt. 53 baccsav b-accumulators saved at interrupt. 54-55 dac_gain dac gain (gn). 56-57 dac_offset dac offset (of). 58-59 temp_f filtered temperature. this is a 10 bit number that is left justified in a 16 bit field. 60-61 - reserved 62-63 adsav2 address saved when call. note: because of space considerations, the measured tempe rature can?t be kept in the ram at all times. if the measured temperature is to be available, the te mperature filter variable, n_factor , must be set to 6.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 22 of 25 data sheet rev 003 feb/12 11 unique features special information the output of the sensor bridge is amplified via of fset and gain amplifiers and then converted to the correct output signal form in one of the output stages. the sensitivity and offset of the analog signal cha in are defined by numbers passed to the dac interfa ces from the microcontroller core (gn[9:0] and of[9:0]) . the wide range of bridge offset and gain is accommodated by means of a 2-bit coarse adjustment dac in the offset adjustment (csof[1:0]), and a similar one in the gain adjustment (csgn[1:0]). the signal path can be directed through the processor for digital processing. programming and setup the mlx90323 needs to have the compensation coeffic ients programmed for a particular bridge sensor to create the sensor system. programming the eeprom in volves some minimal communications interface circuitry, melexis setup software, and a pc. the co mmunications interface circuitry is available in a development board. this circuitry communicates with the pc via a standard rs-232 serial communications port. 12 application information figure 3. typical application schematic vdd1 vdd coms vbp vbn cmo gnd 5k 39 nf flt supply ground 100 nf tmp cmn 75 ohms 24 ohms 100 nf 100 nf depends on stability of the current loop fet
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 23 of 25 data sheet rev 003 feb/12 13 standard information regarding manufacturability of melexis products with different soldering processes our products are classified and qualified regarding soldering technology, solderability and moisture s ensitivity level according to following test methods: reflow soldering smd?s (s urface m ount d evices) ? ipc/jedec j-std-020 moisture/reflow sensitivity classification for nonh ermetic solid state surface mount devices (classification reflow profiles according to table 5-2) ? eia/jedec jesd22-a113 preconditioning of nonhermetic surface mount device s prior to reliability testing (reflow profiles according to table 2) wave soldering smd?s (s urface m ount d evices) and thd?s (t hrough h ole d evices) ? en60749-20 resistance of plastic- encapsulated smd?s to combin ed effect of moisture and soldering heat ? eia/jedec jesd22-b106 and en60749-15 resistance to soldering temperature for through-hol e mounted devices iron soldering thd?s (t hrough h ole d evices) ? en60749-15 resistance to soldering temperature for through-hol e mounted devices solderability smd?s (s urface m ount d evices) and thd?s (t hrough h ole d evices) ? eia/jedec jesd22-b102 and en60749-21 solderability for all soldering technologies deviating from above mentioned standard conditions (regarding peak temperature, temperature gradient, temperature prof ile etc) additional classification and qualificatio n tests have to be agreed upon with melexis. the application of wave soldering for smd?s is allo wed only after consulting melexis regarding assuran ce of adhesive strength between device and board. melexis is contributing to global environmental con servation by promoting lead free solutions. for more information on qualifications of rohs compliant products (rohs = european directive on t he restriction of the use of certain hazardous substances) please vis it the quality page on our website: http://www.melexis.com/quality.aspx
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 24 of 25 data sheet rev 003 feb/12 14 esd precautions electronic semiconductor products are sensitive to electro static discharge (esd). always observe electro static discharge control pro cedures whenever handling semiconductor products. 15 package information 10.65 10.00 notes: 1. all dimensions in millimeters. 2. body dimensions do not include mold flash or protrusion, which are not to exceed 0.15mm. 1.27 0.40 0.32 0.23 0 o to 8 o 7.60 7.40 1.27 0.51 0.33 10.50 10.10 2.65 2.35 0.010 min.
mlx90323 4 ? 20 ma loop sensor interface with signal conditioning and eeprom 3901090323 page 25 of 25 data sheet rev 003 feb/12 16 disclaimer devices sold by melexis are covered by the warranty and patent indemnification provisions appearing in its term of sale. melexis makes no warranty, express, s tatutory, implied, or by description regarding the information set forth herein or regarding the freed om of the described devices from patent infringemen t. melexis reserves the right to change specifications and prices at any time and without notice. therefo re, prior to designing this product into a system, it is nece ssary to check with melexis for current information . this product is intended for use in normal commercial ap plications. applications requiring extended tempera ture range, unusual environmental requirements, or high reliability applications, such as military, medical life- support or life-sustaining equipment are specifical ly not recommended without additional processing by melexis for each application. the information furnished by melexis is believed to be correct and accurate. however, melexis shall no t be liable to recipient or any third party for any dama ges, including but not limited to personal injury, property damage, loss of profits, loss of use, interrupt of business or indirect, special incidental or consequ ential damages, of any kind, in connection with or arising out of the furnishing, performance or use of the t echnical data herein. no obligation or liability to recipien t or any third party shall arise or flow out of mel exis? rendering of technical or other services. ? 2012 melexis nv. all rights reserved. for the latest version of this document, go to our website at www.melexis.com or for additional information contact melexis direc t: europe, africa, asia: america: phone: +32 1367 0495 phone: +1 248 306 5400 e-mail: sales_europe@melexis.com e-mail: sales_usa @melexis.com iso/ts 16949 and iso14001 certified

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