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LTC2990 2990f typical a pplica t ion fea t ures a pplica t ions descrip t ion i 2 c temperature, voltage and current monitor the ltc ? 2990 is used to monitor system temperatures, voltages and currents. through the i 2 c serial interface, the device can be confgured to measure many combi- nations of internal temperature, remote temperature, remote voltage, remote current and internal v cc . the internal 10ppm/c reference minimizes the number of supporting components and area required. selectable address and confgurable functionality give the LTC2990 fexibility to be incorporated in various systems needing temperature, voltage or current data. the LTC2990 fts well in systems needing sub-millivolt voltage resolution, 1% current measurement and 1c temperature accuracy or any combination of the three. temperature total unadjusted error n temperature measurement n supply voltage monitoring n current measurement n remote data acquisition n environmental monitoring n measures voltage, current and temperature n measures two remote diode temperatures n 1c accuracy, 0.06c resolution n 2c internal temperature sensor n 14-bit adc measures voltage/current n 3v to 5.5v supply operating voltage n four selectable addresses n internal 10ppm/c voltage reference n 10-lead msop package v cc v1 LTC2990 t internal r sense 2.5v 5v gnd sda scl adr0 adr1 measures: two supply voltages, supply current, internal and remote temperatures v3 v4 v2 i load t remote 2990 ta01a voltage, current, temperature monitor l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. t amb (c) ?50 tue (c) 25 2990 ta01b 1.0 0 ?25 0 50 ?0.5 ?1.0 0.5 75 100 125 t remote
LTC2990 2990f p in c on f igura t ion a bsolu t e maxi m u m r a t ings (note 1) 1 2 3 4 5 v1 v2 v3 v4 gnd 10 9 8 7 6 v cc adr1 adr0 scl sda top view ms package 10-lead plastic msop t jmax = 125c, ja = 150c/w o r d er i n f or m a t ion lead free finish tape and reel part marking* package description temperature range LTC2990cms#pbf LTC2990cms#trpbf ltdsq 10-lead plastic msop 0c to 70c LTC2990ims#pbf LTC2990ims#trpbf ltdsq 10-lead plastic msop C40c to 85c lead based finish tape and reel part marking* package description temperature range LTC2990cms LTC2990cms#tr ltdsq 10-lead plastic msop 0c to 70c LTC2990ims LTC2990ims#tr ltdsq 10-lead plastic msop C40c to 85c consult ltc marketing for parts specifed with wider operating temperature ranges. *the temperature grade is identifed by a label on the shipping container. contact ltc marketing for parts trimmed to ideality factors other than 1.004. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifcations, go to: http://www.linear.com/tapeandreel/ supply voltage v cc ................................... C0.3v to 6.0v input voltages v1, v2, v3, v4, sda, scl, adr1, adr2 ..................................C0.3v to (v cc + 0.3v) operating temperature range l t c2990c ................................................ 0c to 70c l t c2990i .............................................C40c to 85c storage temperature range .................. C65c to 150c lead temperature (soldering, 10 sec)................... 300c e lec t rical c harac t eris t ics the l denotes the specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc = 3.3v, unless otherwise noted. symbol parameter conditions min typ max units general v cc input supply range l 2.9 5.5 v i cc input supply current during conversion, i 2 c inactive l 1.1 1.8 ma i sd input supply current shutdown mode, i 2 c inactive l 1 5 a v cc(uvl) input supply undervoltage lockout l 1.3 2.1 2.7 v measurement accuracy t int(tue) internal temperature total unadjusted error LTC2990c LTC2990i t amb = C40c to 25c t amb = 25c to 85c l l l l C3 C2 C3 1 1 1 2.5 5 5 1 c c c c t rmt(tue) remote diode temperature total unadjusted error = 1.004 (note 4) l 0.5 1.5 c v cc(tue) v cc voltage total unadjusted error 2.9v v cc 5.5v l 0.1 0.25 % v n(tue) v1 through v4 total unadjusted error 0v v n v cc , v n 4.9v l 0.1 0.25 % v diff(tue) differential voltage total unadjusted error v1 C v2 or v3 C v4 C300mv v d 300mv l 0.2 0.75 % v diff(max) maximum differential voltage l C300 300 mv v diff(cmr) differential voltage common mode range l 0 v cc v v lsb(diff) differential voltage lsb weight 19.42 v v lsb(single-ended) single-ended voltage lsb weight 305.18 v v lsb(temp) temperature lsb weight celsius or kelvin 0.0625 deg t noise temperature noise celsius or kelvin t meas = 46ms (note 2) 0.2 0.05 rms /hz
LTC2990 2990f e lec t rical c harac t eris t ics the l denotes the specifcations which apply over the full operating temperature range, otherwise specifcations are at t a = 25c. v cc = 3.3v, unless otherwise noted. symbol parameter conditions min typ max units res resolution (no missing codes) (note 2) l 14 bits inl integral nonlinearity 2.9v v cc 5.5v, v in(cm) = 1.5v (note 2) single-ended differential l C2 C2 2 2 lsb lsb c in v1 through v4 input sampling capacitance (note 2) 0.35 pf i in(avg) v1 through v4 input average sampling current 0v v n 3v (note 2) 0.6 a i dc_leak(vin) v1 through v4 input leakage current 0v v n v cc l C10 10 na measurement delay t int , t r1 , t r2 per confgured temperature measurement (note 2) l 37 46 55 ms v1, v2, v3, v4 single-ended voltage measurement (note 2) per voltage, two minimum l 1.2 1.5 1.8 ms v1 C v2, v3 C v4 differential voltage measurement (note 2) l 1.2 1.5 1.8 ms v cc v cc measurement (note 2) l 1.2 1.5 1.8 ms max delay mode[4:0] = 11101, t int , t r1 , t r2 , v cc (note 2) l 167 ms v1, v3 output (remote diode mode only) i out output current remote diode mode l 260 350 a v out output voltage l 0 v cc v i 2 c interface v adr(l) adr0, adr1 input low threshold voltage falling l 0.3 ? v cc v v adr(h) adr0, adr1 input high threshold voltage rising l 0.7 ? v cc v v ol1 sda low level maximum voltage i o = C3ma, v cc = 2.9v to 5.5v l 0.4 v v il maximum low level input voltage sda and scl pins l 0.3 ? v cc v v ih minimum high level input voltage sda and scl pins l 0.7 ? v cc v i sdai,scli sda, scl input current 0 < v sda , scl < v cc l 1 a i adr(max) maximum adr0, adr1 input current adr0 or adr1 tied to v cc or gnd l 1 a i 2 c timing (note 2) f scl(max) maximum scl clock frequency 400 khz t low minimum scl low period 1.3 s t high minimum scl high period 600 ns t buf(min) minimum bus free time between stop/ start condition 1.3 s t hd,sta(min) minimum hold time after (repeated) start condition 600 ns t su,sta(min) minimum repeated start condition set-up time 600 ns t su,sto(min) minimum stop condition set-up time 600 ns t hd,dati(min) minimum data hold time input 0 ns t hd,dato(min) minimum data hold time output 300 900 ns t su,dat(min) minimum data set-up time input 100 ns t sp(max) maximum suppressed spike pulse width 50 250 ns c x scl, sda input capacitance 10 pf note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: guaranteed by design and not subject to test. note 3: integral nonlinearity is defned as the deviation of a code from a straight line passing through the actual endpoints of the transfer curve. the deviation is measured from the center of the quantization band. note 4: trimmed to an ideality factor of 1.004 at 25c. remote diode temperature drift (tue) verifed at diode voltages corresponding to the temperature extremes with the LTC2990 at 25c. remote diode temperature drift (tue) guaranteed by characterization over the LTC2990 operating temperature range.
LTC2990 2990f t internal error remote diode error with LTC2990 at 25c, 90c remote diode error with LTC2990 at same temperature as diode typical p er f or m ance c harac t eris t ics supply current vs temperature shutdown current vs temperature measurement delay variation vs t normalized to 3.3v, 25c v cc tue single-ended v x tue differential voltage tue t a = 25c, v cc = 3.3v unless otherwise noted t amb (c) ?50 i cc (a) 2.0 2.5 3.0 25 50 75 100 125 2990 g01 1.5 1.0 ?25 0 150 0.5 0 3.5 v cc = 5v v cc = 3.3v t amb (c) ?50 i cc (a) 1050 1100 1150 25 50 75 100 125 2990 g02 ?25 0 150 1000 950 1200 v cc = 5v v cc = 3.3v t amb (c) ?50 measurement delay variation (%) 1 2 3 25 50 75 100 125 2990 g03 ?25 0 150 0 ?1 4 v cc = 5v v cc = 3.3v t amb (c) ?50 v cc tue (%) 0 0.05 25 50 75 100 125 2990 g04 ?25 0 150 ?0.05 ?0.10 0.10 t amb (c) ?50 v x tue (%) 0 0.05 25 50 75 100 125 2990 g05 ?25 0 150 ?0.05 ?0.10 0.10 t amb (c) ?50 v diff tue (%) 0 0.5 25 50 75 100 125 2990 g06 ?25 0 150 ?0.5 ?1.0 1.0 v cc = 5v v cc = 3.3v bath temperature (c) ?50 LTC2990 t rx error (c) 0.2 0.4 25 50 75 100 125 2990 g08 0 ?0.2 ?25 0 150 ?0.4 ?0.6 0.6 LTC2990 at 25c LTC2990 at 90c t amb (c) ?50 t internal error (deg) 1 2 3 25 50 75 100 125 2990 g07 0 ?1 ?25 0 150 ?2 ?3 4 t amb (c) ?50 LTC2990 t rx error (deg) 0.25 0.50 0.75 25 50 75 100 125 2990 g09 0 ?0.25 ?25 0 150 ?0.50 ?1.00 ?0.75 1.00
LTC2990 2990f typical p er f or m ance c harac t eris t ics single-ended noise single-ended transfer function single-ended inl LTC2990 differential noise differential transfer function differential inl t a = 25c, v cc = 3.3v unless otherwise noted lsbs (305.18v/lsb) ?3 counts 3500 0 2990 g10 2000 1000 ?2 ?1 1 500 0 4000 4800 readings 3000 2500 1500 2 3 v x (v) ?1 4 5 2 4 2990 g11 3 2 ?0 1 3 5 6 1 0 ?1 6 LTC2990 value (v) v cc = 5v v cc = 3.3v lsbs (19.42v/lsb) ?4 counts 300 400 500 800 readings ?1 1 2990 g13 200 100 0 ?3 ?2 0 2 3 v1-v2 (v) ?0.4 LTC2990 v1-v2 (v) 0 0.2 0.4 2990 g14 ?0.2 ?0.4 ?0.2 0 0.2 ?0.3 ?0.1 0.1 0.3 0.4 ?0.1 0.1 ?0.3 0.3 t int noise remote diode noise por thresholds vs temperature (c) ?0.75 ?0.5 0 counts 200 500 1000 readings ?0.25 0.25 0.5 2990 g16 100 400 300 0 0.75 (c) ?0.75 ?0.5 0 counts 200 600 1000 readings 500 ?0.25 0.25 0.5 2990 g17 100 400 300 0 0.75 t amb (c) ?50 threshold (v) 1.8 2.2 150 2990 g18 1.4 1.0 0 50 100 ?25 25 75 125 2.6 1.6 2.0 1.2 2.4 v cc rising v cc falling v x (v) 0 ?1.0 inl (lsbs) ?0.5 0 0.5 1.0 1 2 3 4 2990 g12 5 v cc = 5v v cc = 3.3v v in (v) ?0.4 inl (lsbs) 0 1 0.4 2990 g15 ?1 ?2 ?0.2 0 0.2 2
LTC2990 2990f p in func t ions v1 (pin 1): first monitor input. this pin can be confg- ured as a single-ended input or the positive input for a differential or remote diode temperature measurement (in combination with v2). when confgured for remote diode temperature, this pin will source a current. v2 (pin 2): second monitor input. this pin can be con- fgured as a single-ended input or the negative input for a differential or remote diode temperature measurement (in combination with v1). when confgured for remote diode temperature, this pin will have an internal termination, while the measurement is active. v3 (pin 3): third monitor input. this pin can be confg- ured as a single-ended input or the positive input for a differential or remote diode temperature measurement (in combination with v4). when confgured for remote diode temperature, this pin will source a current. v4 (pin 4): fourth monitor input. this pin can be confg- ured as a single-ended input or the negative input for a differential or remote diode temperature measurement (in combination with v3). when confgured for remote diode temperature, this pin will have an internal termination, while the measurement is active. gnd (pin 5): device circuit ground. connect this pin to a ground plane through a low impedance connection. sda (pin 6): serial bus data input and output. in the transmitter mode (read), the conversion result is output through the sda pin, while in the receiver mode (write), the device confguration bits are input through the sda pin. at data input mode, the pin is high impedance; while at data output mode, it is an open-drain n-channel driver and therefore an external pull-up resistor or current source to v cc is needed. scl (pin 7): serial bus clock input. the LTC2990 can only act as a slave and the scl pin only accepts external serial clock. the LTC2990 does not implement clock stretching. adr0 (pin 8): serial bus address control input. the adr0 pin is an address control bit for the device i 2 c address. adr1 (pin 9): serial bus address control input. the adr1 pin is an address control bit for the device i 2 c address. see table 1. v cc (pin 10): supply voltage input.
LTC2990 2990f func t ional diagra m adc mux mode reference i 2 c undervoltage detector v cc v4 uv internal sensor remote diode sensors 4 v3 3 adr1 2990 fd v2 2 v1 1 control logic 9 adr0 8 sda 6 scl 7 gnd 5 v cc 10 ti m ing diagra m t su, dat t su, sto t su, sta t buf t hd, sta t sp t sp t hd, dato, t hd, dati t hd, sta start condition stop condition repeated start condition start condition 2990 td sdai/sdao scl
LTC2990 2990f o pera t ion the LTC2990 monitors voltage, current, internal and remote temperatures. it can be confgured through an i 2 c interface to measure many combinations of these pa- rameters. single or repeated measurements are possible. remote temperature measurements use a transistor as a temperature sensor, allowing the remote sensor to be a discrete npn (ex. mmbt3904) or an embedded pnp device in a microprocessor or fpga. the internal adc reference minimizes the number of support components required. the functional diagram displays the main components of the device. the input signals are selected with an input mux, controlled by the control logic block. the control logic uses the mode bits in the control register to manage the sequence and types of data acquisition. the control logic also controls the variable current sources during remote temperature acquisition. the order of acquisitions is fxed: t internal , v1, v2, v3, v4 then v cc . the adc performs the necessary conversion(s) and supplies the data to the control logic for further processing in the case of temperature measurements, or routing to the appropri- ate data register for voltage and current measurements. current and temperature measurements, v1 C v2 or v3 C v4, are sampled differentially by the internal adc. the i 2 c interface supplies access to control, status and data registers. the adr1 and adr0 pins select one of four possible i 2 c addresses (see table 1). the undervoltage detector inhibits i 2 c communication below the specifed threshold. during an undervoltage condition, the part is in a reset state, and the data and control registers are placed in the default state of 00h. remote diode measurements are conducted using multiple adc conversions and source currents to compensate for sensor series resistance. during temperature measure- ments, the v2 or v4 terminal of the LTC2990 is terminated with a diode. the LTC2990 is calibrated to yield the correct temperature for a remote diode with an ideality factor of 1.004. see the applications section for compensation of sensor ideality factors other than the factory calibrated value of 1.004. the LTC2990 communicates through an i 2 c serial interface. the serial interface provides access to control, status and data registers. i 2 c defnes a 2-wire open-drain interface supporting multiple slave devices and masters on a single bus. the LTC2990 supports 100kbits/s in the standard mode and up to 400kbit/s in fast mode. the four physical addresses supported are listed in table 1. the i 2 c interface is used to trigger single conversions, or start repeated conversions by writing to a dedicated trigger register. the data registers contain a destructive-read status bit (data valid), which is used in repeated mode to determine if the register s contents have been previously read. this bit is set when the register is updated with new data, and cleared when read. v cc v1 LTC2990 2.5v 2-wire i 2 c interface 5v gnd sda scl adr0 adr1 v3 v4 v2 470pf mmbt3904 r sense 15m i load 2990 f01 0.1f figure 1 is the basic LTC2990 application circuit. figure 1 a pplica t ions i n f or m a t ion power up the v cc pin must exceed the undervoltage (uv) thresh- old of 2.5v to keep the LTC2990 out of power-on reset. power-on reset will clear all of the data registers and the control register. temperature measurements the LTC2990 can measure internal temperature and up to two external diode or transistor sensors. during tem- perature conversion, current is sourced through either the v1 or the v3 pin to forward bias the sensing diode.
LTC2990 2990f a pplica t ions i n f or m a t ion figure 2. recommended pcb layout v1 v2 v3 v4 v cc adr1 adr0 scl sda LTC2990 2990 f02 gnd shield trace npn sensor 470pf 0.1f gnd the change in sensor voltage per degree temperature change is 275v/c, so environmental noise must be kept to a minimum. recommended shielding and pcb trace considerations are illustrated in figure 2. the diode equation: v k t q i i be c s = ? ? ? ? ? ? ? ? ? ln (1) can be solved for t, where t is kelvin degrees, i s is a process dependent factor on the order of 1e-13, is the diode ideality factor, k is boltzmanns constant and q is the electron charge. t v q k in i i be c s = ? ? ? ? ? ? ? ? ? (2) the LTC2990 makes differential measurements of diode voltage to calculate temperature. proprietary techniques allow for cancellation of error due to series resistance. sensor can be considered a temperature scaling factor. the temperature error for a 1% accurate ideality factor error is 1% of the kelvin temperature. thus, at 25c, or 298k, a +1% accurate ideality factor error yields a +2.98 degree error. at 85c or 358k, a +1% error yields a 3.6 degree error. it is possible to scale the measured kelvin or celsius temperature measured using the LTC2990 with a sensor ideality factor other than 1.004, to the correct value. the scaling equations (3) and (4) are simple, and can be implemented with suffcient precision using 16-bit fxed-point math in a microprocessor or microcontroller. factory ideality calibration value: cal = 1.004 actual sensor ideality value: act compensated kelvin temperature: t t k comp act cal k meas _ _ ? = (3) compensated celsius temperature t t c comp act cal c meas _ _ ? C = + ( ) ? ? ? ? ? ? 273 273 (4) a 16-bit unsigned number is capable of representing the ratio act / cal in a range of 0.00003 to 1.99997, by multiplying the fractional ratio by 2 15 . the range of scal- ing encompasses every conceivable target sensor value. the ideality factor scaling granularity yields a worst-case t e mperature error of 0.01 at 125c. multiplying this 16 - bit unsigned number and the measured kelvin (unsigned) temperature represented as a 16-bit number, yields a 32- bit unsigned result. to scale this number back to a 13 - bit temperature (9-bit integer part, and a 4-bit fractional part), divide the number by 2 15 per equation (5). similarly, celsius coded temperature values can be scaled using 16-bit fxed-point arithmetic, using equation (6). in both cases, the scaled result will have a 9-bit integer (d[12:4]) and the 4lsbs (d[3:0]) representing the 4-bit fractional part. to convert the corrected result to decimal, divide the fnal result by 2 4 or 16, as you would the register contents. if ideality factor scaling is implemented in the ideality factor scaling the LTC2990 is factory calibrated for an ideality factor of 1.004, which is typical of the popular mmbt3904 npn transistor. the semiconductor purity and wafer-level pro- cessing limits device-to-device variation, making these devices interchangeable (typically <0.5c) for no additional cost. several manufacturers supply suitable transistors, some recommended sources are listed in table 10. while an ideality factor value of 1.004 is typical of target sen- sors, small deviations can yield signifcant temperature errors. contact ltc marketing for parts trimmed to ideality factors other than 1.004. the ideality factor of the diode
LTC2990 0 2990f a pplica t ions i n f or m a t ion target application, it is benefcial to confgure the LTC2990 for kelvin coded results to limit the number of math opera- tions required in the target processor. t unsigned t k comp act cal k meas _ _ = ( ) ? ? ? ? ? ? 2 2 15 15 (5) t unsigned t c comp act cal c meas _ _ . = ( ) ? ? ? ? ? ? + 2 273 15 115 2 2 273 15 2 4 15 4 ? ? . ? ( ) (6) sampling currents single-ended voltage measurements are directly sampled by the internal adc. the average adc input current is a function of the input applied voltage as follows: i in(avg) = (v in C 1.49) ? 0.17a inputs with source resistance less than 200 will yield full-scale gain errors due to source impedance of <1/2lsb for 14-bit conversions. the nominal conversion time is 1.5ms for single-ended conversions. current measurements the LTC2990 has the ability to perform 14-bit current measurements with the addition of a current sense resis- tor (see figure 3). in order to achieve accurate current sensing a few de- tails must be considered. differential voltage or current measurements are directly sampled by the internal adc. the average adc input current for each leg of the differential input signal during a conversion is (v in C 1.49) ? 0.34a. the maximum source impedance to yield 14-bit results with, 1/2lsb full-scale error is ~50. in order to achieve high accuracy, 4-point, or kelvin connected measurements of the sense resistor differential voltage are necessary. in the case of current measurements, the external sense resistor is typically small, and determined by the full-scale input voltage of the LTC2990. the full-scale differential voltage is 0.300v. the external sense resistance is then a function of the maximum measurable current, or r ext_max = 0.300/i max . for example, if you wanted to measure a current range of 5a, the external shunt resistance would equal 0.300/5 = 60m. there exists a way to improve the sense resistors precision using the LTC2990. the LTC2990 measures both differential voltage and remote temperature. it is therefore, possible to compensate for the absolute resistance tolerance of the sense resistor and the temperature coeffcient of the sense resistor in software. the resistance would be measured by running a calibrated test current through the discrete resistor. the LTC2990 would measure both the differential voltage across this resistor and the resistor temperature. from this measurement, r o and t o in the equation be- low would be known. using the two equations, the host microprocessor could compensate for both the absolute tolerance and the tcr. r t = r o ? [1 + (t C t o )] where: = +3930 ppm/c for copper trace = 2 to ~+200ppm/c for discrete r (7) i = (v1 C v2)/r t (8) figure 3. simplifed current sense schematic v1 v2 LTC2990 0v ? v cc r sense i load 2990 f03
LTC2990 2990f a pplica t ions i n f or m a t ion device confguration the LTC2990 is confgured by writing the control register through the serial interface. refer to table 4 for control register bit defnition. the device is capable of many ap- plication confgurations including voltage, temperature and current measurements. it is possible to confgure the device for single or repeated acquisitions. for repeated acquisitions, only the initial trigger is required and new data is written over the old data. acquisitions are frozen during serial read data transfers to prevent the upper and lower data bytes for a particular measurement from becoming out of sync. internally, both the upper and lower bytes are written at the same instant. since serial data transfer timeout is not implemented, failure to terminate a read operation will yield an indefnitely frozen wait state. the device can also make single measurements, or with one trigger, all of the measurements for the confguration. when the device is confgured for multiple measurements, the order of measurements is fxed. as each new data result is ready, the msb of the corresponding data register is set, and the corresponding status register bit is set. these bits are cleared when the corresponding data register is addressed. the confguration register value at power-up yields the measurement of only the internal temperature sensor, if triggered. the four input pins v1 through v4 will be in a high impedance state, until confgured otherwise, and a measurement triggered. data format the data registers are broken into 8-bit upper and lower bytes. voltage and current conversions are 14-bits. the upper bits in the msb registers provide status on the resulting conversions. these status bits are different for temperature and voltage conversions: temperature: temperature conversions are reported as celsius or kelvin results described in tables 7 and 8, each with 0.0625 degree-weighted lsbs. the format is controlled by the control register, bit 7. all temperature formats, t int , t r1 and t r2 are controlled by this bit. the temperature msb result register most signifcant bit (bit 7) is the data_valid bit, which indicates whether the current register contents have been accessed since the result was written to the register. this bit will be set when new data is written to the register, and cleared when accessed. bit 6 of the register is a sensor-shorted alarm. this bit of the corresponding register will be high if the remote sensor diode differential voltage is below 0.14 v dc . the LTC2990 internal bias circuitry maintains this voltage above this level during normal operating conditions. bit 5 of the register is a sensor open alarm. this bit of the cor- responding register will be high if the remote sensor diode differential voltage is above 1.0v dc . the LTC2990 internal bias circuitry maintains this voltage below this level during normal operating conditions. the two sensor alarms are only valid after a completed conversion indicated by the data_valid bit being high. bit 4 through bit 0 of the msb register are the conversion result bits d[12:8], in twos compliment format. note in kelvin results, the result will always be positive. the lsb register contains temperature result bits d[7:0]. to convert the register contents to temperature, use the following equation: t = d[12:0]/16. see table 9 for conversion value examples. voltage/current: voltage results are reported in two respec- tive registers, an msb and lsb register. the voltage msb result register most signifcant bit (bit 7) is the data_valid bit, which indicates whether the current register contents have been accessed since the result was written to the register. this bit will be set when the register contents are new, and cleared when accessed. bit 6 of the msb register is the sign bit, bits 5 though 0 represent bits d[13:8] of the twos complement conversion result. the lsb register holds conversion bits d[7:0]. the lsb value is different for single-ended voltage measurements v1 through v4, and differential (current measurements) v1 C v2 and v3 C v4. single-ended voltages are limited to positive values in the range 0v to 3.5v. differential voltages can have input values in the range of C0.300v to 0.300v. use the following equations to convert the register values (see table 9 for examples): v single-ended = d[13:0] ? 305.18v v differential = d[13:0] ? 19.42v, if sign = 0 v differential = (d[13:0] +1) ? C19.42v, if sign = 1 current = d[13:0] ? 19.42v /r sense , if sign = 0 current = (d[13:0] +1) ? C19.42v/r sense , if sign = 1,
LTC2990 2990f a pplica t ions i n f or m a t ion where r sense is the current sensing resistor, typically <1. v cc : the LTC2990 measures v cc . to convert the contents of the v cc register to voltage, use the following equation: v cc = 2.5 + d[13:0] ? 305.18v digital interface the LTC2990 communicates with a bus master using a two-wire interface compatible with the i 2 c bus and the smbus, an i 2 c extension for low power devices. the LTC2990 is a read-write slave device and supports smbus bus read byte data and write byte data, read word data and write word data commands. the data formats for these commands are shown in tables 2 though 9. the connected devices can only pull the bus wires low and can never drive the bus high. the bus wires are externally connected to a positive supply voltage via a current source or pull-up resistor. when the bus is free, both lines are high. data on the i 2 c bus can be transferred at rates of up to 100kbit/s in the standard mode and up to 400kbit/s in the fast mode. each device on the i 2 c bus is recognized by a unique address stored in that device and can operate as either a transmitter or receiver, depending on the function of the device. in addition to transmitters and receivers, devices can also be considered as masters or slaves when performing data transfers. a master is the device which initiates a data transfer on the bus and generates the clock signals to permit that transfer. at the same time any device addressed is considered a slave. the LTC2990 can only be addressed as a slave. once ad- dressed, it can receive confguration bits or transmit the last conversion result. therefore the serial clock line scl is an input only and the data line sda is bidirectional. the device supports the standard mode and the fast mode for data transfer speeds up to 400kbit/s. the timing diagram shows the defnition of timing for fast/standard mode devices on the i 2 c bus. the internal state machine cannot update internal data registers during an i 2 c read operation. the state machine pauses until the i 2 c read is complete. it is therefore, important not to leave the LTC2990 in this state for long durations, or increased conversion latency will be experienced. start and stop conditions when the bus is idle, both scl and sda must be high. a bus master signals the beginning of a transmission with a start condition by transitioning sda from high to low while scl is high. when the bus is in use, it stays busy if a repeated start (sr) is generated instead of a stop condition. the repeated start (sr) conditions are func- tionally identical to the start (s). when the master has fnished communicating with the slave, it issues a stop condition by transitioning sda from low to high while scl is high. the bus is then free for another transmission. i 2 c device addressing four distinct bus addresses are confgurable using the adr0-adr1 pins. table 1 shows the correspondence between adr0 and adr1 pin states and addresses. acknowledge the acknowledge signal is used for handshaking between the transmitter and the receiver to indicate that the last byte of data was received. the transmitter always releases the sda line during the acknowledge clock pulse. when the slave is the receiver, it must pull down the sda line so that it remains low during this pulse to acknowledge receipt of the data. if the slave fails to acknowledge by leaving sda high, then the master can abort the transmission by generating a stop condition. when the master is receiving data from the slave, the master must pull down the sda line during the clock pulse to indicate receipt of the data. after the last byte has been received the master will leave the sda line high (not acknowledge) and issue a stop condition to terminate the transmission. write protocol the master begins communication with a start condi- tion followed by the seven bit slave address and the r/w# bit set to zero. the addressed LTC2990 acknowledges the address and then the master sends a command byte which indicates which internal register the master wishes to write. the LTC2990 acknowledges the command byte and then latches the lower four bits of the command byte into its internal register address pointer. the master then
LTC2990 2990f a pplica t ions i n f or m a t ion delivers the data byte and the LTC2990 acknowledges once more and latches the data into its internal register. the transmission is ended when the master sends a stop condition. if the master continues sending a second data byte, as in a write word command, the second data byte will be acknowledged by the LTC2990 and written to the next register in sequence, if this register has write access. read protocol the master begins a read operation with a start condition followed by the seven bit slave address and the r/w# bit set to zero. the addressed LTC2990 acknowledges this and then the master sends a command byte which indicates which internal register the master wishes to read. the LTC2990 acknowledges this and then latches the lower four bits of the command byte into its internal register address pointer. the master then sends a repeated start condition followed by the same seven bit address with the r/w# bit now set to one. the LTC2990 acknowledges and sends the contents of the requested register. the transmission is ended when the master sends a stop condition. the register pointer is automatically incremented after each byte is read. if the master acknowledges the transmitted data byte, as in a read word command, the LTC2990 will send the contents of the next sequential register as the second data byte. the byte following register 0x0f is register 0x00, or the status register. control register the control register (table 3) determines the selected measurement mode of the device. the LTC2990 can be confgured to measure voltages, currents and tempera- tures. these measurements can be single-shot or repeated measurements. temperatures can be set to report in celsius or kelvin temperature scales. the LTC2990 can be confgured to run particular measurements, or all possible measurements per the confguration specifed by the mode bits. the power-on default confguration of the control register is set to 0x00, which translates to a repeated measurement of the internal temperature sensor, when triggered. this mode prevents the application of remote diode test currents on pins v1 and v3, and remote diode terminations on pins v2 and v4 at power-up. status register the status register (table 3) reports the status of a par- ticular conversion result. when new data is written into a particular result register, the corresponding data_valid bit is set. when the register is addressed by the i 2 c inter- face, the status bit (as well as the data_valid bit in the respective register) is cleared. the host can then determine if the current available register data is new or stale. the busy bit, when high, indicates a single-shot conversion is in progress. the busy bit is always high during repeated mode, after the initial conversion is triggered. stop 2990 f04 start address r/w p 98 1-7 1-7 1-7 a6-a0 b7-b0 b7-b0 98 98 s data data ack ack ack figure 4. data transfer over i 2 c or smbus s a a data w# address command a 0 0 b7:b0 0 10011a1:a0 from master to slave xxxxxb3:b0 0 2990 f05 p from slave to master a: acknowledge (low) a#: not acknowledge (high) r: read bit (high) w#: write bit (low) s: start condition p: stop condition figure 5. LTC2990 serial bus write byte protocol
LTC2990 2990f a pplica t ions i n f or m a t ion figure 8. LTC2990 serial bus repeated read byte protocol s a a s w# address command a 0 0 1 0 data b7:b0 0 10011a1:a0 address 10011a1:a0 xxxxxb3:b0 1 2990 f07 pa# r figure 7. LTC2990 serial bus read byte protocol s a a s w# address command a 0 0 1 0 a 0 data b7:b0 0 10011a1:a0 address 10011a1:a0 xxxxxb3:b0 1 2990 f08 pa# data b7:b0 r table 2. LTC2990 register address and contents register address* ? register name read/write description 00h status r indicates busy state, conversion status 01h control r/w controls mode, single/repeat, celsius/kelvin 02h trigger** r/w triggers an conversion 03h n/a unused address 04h t int (msb) r internal temperature msb 05h t int (lsb) r internal temperature lsb 06h v1 (msb) r v1, v1 C v2 or tr1 msb 07h v1 (lsb) r v1, v1 C v2 or tr1 lsb 08h v2 (msb) r v2, v1 C v2 or tr1 msb 09h v2 (lsb) r v2, v1 C v2 or tr1 lsb 0ah v3 (msb) r v3, v3 C v4 or tr2 msb 0bh v3 (lsb) r v3, v3 C v4 or tr2 lsb 0ch v4 (msb) r v4, v3 C v4 or tr2 msb 0dh v4 (lsb) r v4, v3 C v4 or tr2 lsb 0eh v cc (msb) r v cc msb 0fh v cc (lsb) r v cc lsb *register address msbs b7-b4 are ignored. **writing any value triggers a conversion. data returned reading this register address is the status register. ? power-on reset sets all registers to 00h. table 1. i 2 c base address hex i 2 c base address binary i 2 c base address adr1 adr0 98h 1001 100x* 0 0 9ah 1001 101x* 0 1 9ch 1001 110x* 1 0 9eh 1001 111x* 1 1 *x = r/w bit s a a data w# address command a 0 0 b7:b0 data b7:b0 0 10011a1:a0 xxxxxb3:b0 0 0 2990 f06 p a figure 6. LTC2990 serial bus repeated write byte protocol
LTC2990 2990f a pplica t ions i n f or m a t ion table 3. status register bit name operation b7 0 always zero b6 v cc ready 1 = v cc register contains new data, 0 = v cc register read b5 v4 ready 1 = v4 register contains new data, 0 = v4 register read b4 v3, t2, v3 C v4 ready 1 = v3 register contains new data, 0 = v3 register data old b3 v2 ready 1 = v2 register contains new data, 0 = v2 register data old b2 v1, t1, v1 C v2 ready 1 = v1 register contains new data, 0 = v1 register data old b1 t int ready 1 = t int register contains new data, 0 = t int register data old b0 busy* 1= conversion in process, 0 = acquisition cycle complete *in repeat mode, busy = 1 always table 4. control register bit name operation b7 temperature format temperature reported in; celsius = 0, kelvin = 1 b6 repeat/single repeated acquisition = 0, single acquisition = 1 b5 reserved reserved b[4:3] mode [4:3] mode description 0 0 internal temperature only (reset value) 0 1 t1, v1 or v1 C v2 only per mode [2:0] 1 0 t2, v3 or v3 C v4 only per mode [2:0] 1 1 all measurements per mode [2:0] b[2:0] mode [2:0] mode description 0 0 0 v1, v2, t r2 (reset value) 0 0 1 v1 C v2, tr2 0 1 0 v1 C v2, v3, v4 0 1 1 tr1, v3, v4 1 0 0 tr1, v3 C v4 1 0 1 tr1. tr2 1 1 0 v1 C v2, v3 C v4 1 1 1 v1, v2, v3, v4
LTC2990 2990f a pplica t ions i n f or m a t ion table 7. temperature measurement msb data register format bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 dv* ss** so ? d12 d11 d10 d9 d8 *data_valid is set when a new result is written into the register. data_valid is cleared when this register is addressed (read) by the i 2 c interface. **sensor short is high if the voltage measured on v1 is too low during temperature measurements. this signal is always low for t int measurements. ? sensor open is high if the voltage measured on v1 is excessive during temperature measurements. this signal is always low for t int measurements. table 8. temperature measurement lsb data register format bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 d7 d6 d5 d4 d3 d2 d1 d0 table 5. voltage/current measurement msb data register format bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 dv* sign d13 d12 d11 d10 d9 d8 *data valid is set when a new result is written into the register. data valid is cleared when this register is addressed (read) by the i 2 c inteface. table 6. voltage/current measurement lsb data register format bit 7 bit 6 bit 5 bit 4 bit 3 bit 2 bit 1 bit 0 d7 d6 d5 d4 d3 d2 d1 d0
LTC2990 2990f table 9. conversion formats voltage formats sign binary value d[13:0] voltage single-ended lsb = 305.18v 0 11111111111111 >5 0 10110011001101 3.500 0 01111111111111 2.500 0 00000000000000 0.000 1 11110000101001 C0.300 differential lsb = 19.42v 0 11111111111111 >0.318 0 10110011001101 +0.300 0 10000000000000 +0.159 0 00000000000000 0.000 1 10000000000000 C0.159 1 00001110101000 C0.300 1 10000000000000 LTC2990 2990f typical a pplica t ions high voltage/current and temperature monitoring ? + ?ins 0.1f v in 5v to 105v 0.1f 470pf all capacitors 20% voltage, current and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v load reg 6, 7 13.2mvlsb v2(i load ) reg 8, 9 1.223ma/lsb t remote reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb mmbt3904 r in 20 1% i load 0a to 10a r out 4.99k 1% 200k 1% 4.75k 1% 0.1f r sense 1m 1% ?inf v + v ? ltc6102hv out v reg +in v cc v1 LTC2990 2-wire i 2 c interface 5v gnd sda scl adr0 adr1 v3 v4 v2 2990 ta02 0.1f 470pf microprocessor v cc v1 LTC2990 2-wire i 2 c interface gnd sda scl adr0 adr1 v3 v4 v2 2990 ta03 10.0k 1% 10.0k 1% 10.0k 1% 3.3v 30.1k 1% 5v 12v voltage, current and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v1 (+5) reg 6, 7 0.61mvlsb v2(+12) reg 8, 9 1.22mv/lsb t processor reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 0.1f computer voltage and temperature monitoring
LTC2990 2990f typical a pplica t ion s motor protection/regulation v cc v1 LTC2990 load pwr = i ? v 0.1 1% motor control voltage 0v dc to 5v dc 0a to 2.2a 2-wire i 2 c interface 5v gnd 470pf t motor mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta04 motor t internal current and temperature configuration: control register: 0x59 t amb reg 4, 5 0.0625c/lsb i motor reg 6, 7 194a/lsb t motor reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb voltage and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v motor reg 8, 9 305.18vlsb t motor reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 0.1f large motor protection/regulation v cc v1 LTC2990 load pwr = i ? v 0.1 1w, 1% motor control voltage 0v to 40v 0a to 10a 2-wire i 2 c interface 5v 71.5k 1% 71.5k 1% 10.2k 1% 10.2k 1% gnd 470pf t motor mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta05 motor t internal voltage and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v motor reg 8, 9 2.44mvlsb t motor reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb current and temperature configuration: control register: 0x59 t amb reg 4, 5 0.0625c/lsb i motor reg 6, 7 1.56ma/lsb t motor reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 0.1f
LTC2990 0 2990f typical a pplica t ion s fan/air filter/temperature alarm v cc v1 LTC2990 2-wire i 2 c interface 3.3v gnd 470pf 22 0.125w heater nds351an temperature for: heater enable good fan bad fan fan mmbt3904 mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta06 t internal heater enable 2 second pulse control register: 0x5d t amb reg 4, 5 0.0625c/lsb t r1 reg 6, 7 0.0625c/lsb t r2 reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 470pf 3.3v 22 0.125w fan 0.1f v cc v1 LTC2990 battery i and v monitor 15m* charging current 2-wire i 2 c interface 5v gnd 470pf nimh battery v(t) 100% 100% ? ? ? t batt mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta07 t internal *irc lrf3w01r015f current and temperature configuration: control register: 0x59 t amb reg 4, 5 0.0625c/lsb i bat reg 6, 7 1.295ma/lsb t bat reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb voltage and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v bat reg 8, 9 305.18vlsb t bat reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb + t(t) 100% i(t) 0.1f battery monitoring
LTC2990 2990f typical a pplica t ion s wet-bulb psychrometer liquid-level indicator v cc v1 LTC2990 5v c gnd 470pf t dry t wet mmbt3904 mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta08 470pf t internal damp muslin water reservoir control register: 0x5d t amb reg 4, 5 0.0625c/lsb t wet reg 6, 7 0.0625c/lsb t dry reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb $t nds351an fan enable 5v fan fan: sunon kde0504pfb2 0.1f v cc LTC2990 3.3v c gnd sda scl adr0 adr1 v1 v4 v3 v2 470pf 3.3v 470pf t internal control register: 0x5d t amb reg 4, 5 0.0625c/lsb t hi reg 6, 7 0.0625c/lsb t lo reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb nds351an 2290 ta09 heater: 75 0.125w *sensor mmbt3904, diode connected sensor lo* $t = ~2.0c pp, sensor hi ~0.2c pp, sensor lo sensor hi* heater enable 2 second pulse heater enable sensor hi sensor lo 0.1f references: http://en.wikipedia.org/wiki/hygrometer http://en.wikipedia.org/wiki/psychrometrics
LTC2990 2990f typical a pplica t ion s oscillator/reference oven temperature regulation v cc v1 LTC2990 heater pwr = i ?v 0.1 heater voltage 2-wire i 2 c interface 5v gnd 470pf feed forward feed back heater heater construction: 5ft coil of #34 enamel wire ~1.6 at 70c p heater = ~0.4w with t a = 20c heater power = a ? (t set ? t amb ) + b ? (t oven ? t set ) dt 20c ambient styrofoam insulation 70c oven t oven a = 0.004w, b = 0.00005w/deg-s mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta10 t internal current and temperature configuration: control register: 0x59 t amb reg 4, 5 0.0625c/lsb i heater reg 6, 7 269vlsb t heater reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb voltage and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v1, v2 reg 8, 9 305.18vlsb t oven reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 0.1f wind direction/instrumentation v cc v1 LTC2990 3.3v c gnd 470pf mmbt3904 mmbt3904 sda scl adr0 adr1 v3 v4 v2 2990 ta11 470pf 3.3v heater 75 0.125w t internal control register: 0x5d t amb reg 4, 5 0.0625c/lsb t r1 reg 8, 9 0.0625c/lsb t r2 reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb 2n7002 fan enable 2 second pulse 0.1f
LTC2990 2990f information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. p ackage descrip t ion ms package 10-lead plastic msop (reference ltc dwg # 05-08-1661 rev e) msop (ms) 0307 rev e 0.53 p 0.152 (.021 p .006) seating plane 0.18 (.007) 1.10 (.043) max 0.17 ? 0.27 (.007 ? .011) typ 0.86 (.034) ref 0.50 (.0197) bsc 1 2 3 4 5 4.90 p 0.152 (.193 p .006) 0.497 p 0.076 (.0196 p .003) ref 8910 7 6 3.00 p 0.102 (.118 p .004) (note 3) 3.00 p 0.102 (.118 p .004) (note 4) note: 1. dimensions in millimeter/(inch) 2. drawing not to scale 3. dimension does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.152mm (.006") per side 4. dimension does not include interlead flash or protrusions. interlead flash or protrusions shall not exceed 0.152mm (.006") per side 5. lead coplanarity (bottom of leads after forming) shall be 0.102mm (.004") max 0.254 (.010) 0o ? 6o typ detail ?a? detail ?a? gauge plane 5.23 (.206) min 3.20 ? 3.45 (.126 ? .136) 0.889 p 0.127 (.035 p .005) recommended solder pad layout 0.305 p 0.038 (.0120 p .0015) typ 0.50 (.0197) bsc 0.1016 p 0.0508 (.004 p .002)
LTC2990 2990f linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com ? linear technology corporation 2010 lt 0910 ? printed in usa r ela t e d p ar t s typical a pplica t ion part number description comments lm134 constant current source and temperature sensor can be used as linear temperature sensor ltc1392 micropower temperature, power supply and differential voltage monitor complete ambient temperature sensor onboard ltc2487 16-bit, 2-/4-channel delta sigma adc with pga, easy drive ? and i 2 c interface internal temperature sensor ltc6102/ltc6102hv precision zero drift current sense amplifer 5v to 100v, 105v absolute maximum (ltc6102hv) easy drive is a trademark of linear technology corporation. high voltage/current and temperature monitoring ? + ?ins 0.1f v in 5v to 105v 0.1f 470pf all capacitors 20% voltage, current and temperature configuration: control register: 0x58 t amb reg 4, 5 0.0625c/lsb v load reg 6, 7 13.2mvlsb v2(i load ) reg 8, 9 1.223ma/lsb t remote reg a, b 0.0625c/lsb v cc reg e, f 2.5v + 305.18v/lsb mmbt3904 r in 20 1% i load 0a to 10a r out 4.99k 1% 200k 1% 4.75k 1% 0.1f r sense 1m 1% ?inf v + v ? ltc6102hv out v reg +in v cc v1 LTC2990 2-wire i 2 c interface 5v gnd sda scl adr0 adr1 v3 v4 v2 2990 ta02 0.1f

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