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1 typical a pplica t ion fea t ures descrip t ion octal i 2 c voltage, current, and temperature monitor the lt c ? 2991 is used to monitor system temperatures, voltages and currents. through the i 2 c serial interface, the eight monitors can individually measure supply voltages and can be paired for differential measurements of cur - rent sense resistors or temperature sensing transistors. additional measurements include internal temperature and internal v cc . the internal 10ppm reference minimizes the number of supporting components and area required. selectable address and configurable functionality give the ltc2991 flexibility to be incorporated in various systems needing temperature, voltage or current data. the ltc2991 fits well in systems needing submillivolt voltage resolution, 1% current measurement and 1c temperature accuracy or any combination of the three. temperature total unadjusted error a pplica t ions n measures voltage, current, t emperature n measures four remote diode temperatures n 0.7c (typ) accuracy, 0.06c resolution n 1c (typ) internal temperature sensor n series resistance cancellation n 14-bit adc measures voltage/current n pwm temperature output n 3v to 5.5v supply operating voltage n eight selectable addresses n internal 10ppm/c voltage reference n v1 to v8 inputs esd rated to 6kv hbm n 16-lead msop package n temperature measurement n supply voltage monitoring n current measurement n remote data acquisition n environmental monitoring l , lt, ltc, ltm, linear technology and the linear logo are registered trademarks and easy drive is a trademark of linear technology corporation. all other trademarks are the property of their respective owners. v cc 2-wire i 2 c interface v1 ltc2991 t ambient r sense 3.3v 5v 1.2v 2.5v gnd sda scl adr0 adr1 adr2 3.3v i/o 2.5v i/o 1.2v core fpga fpga temperature board temperature v3 v4 v5 v6 v7 v8 pwm to fan v2 2991 ta01a t ambient (c) ?50 t error (c) 0.25 0.50 0.75 25 50 75 100 125 2991 ta01b 0 ?0.50 ?0.25 ?25 0 150 ?0.75 ?1.00 1.00 t remote t internal ltc2991 2991fd for more information www.linear.com/ltc2991
2 p in c on f igura t ion a bsolu t e maxi m u m r a t ings supply voltage (v cc ) ................................ C0 .3v to 6.0v input voltages v1, v2, v3, v4, v5, v6, v7, v8, scl, adr0, adr1, adr2 .............. C 0.3v to (v cc + 0.3v) output voltage pwm .................... C 0.3v to (v cc + 0.3v) output voltage sda ..................................... C 0.3v to 6v operating temperature range lt c2991c ................................................ 0 c to 70c l tc2991i ............................................. C 40c to 85c storage temperature range .................. C 65c to 150c lead temperature (soldering, 10 sec) ms package .......................................................... 3 00c (note 1) 1 2 3 4 5 6 7 8 v1 v2 v3 v4 v5 v6 v7 v8 16 15 14 13 12 11 10 9 v cc adr2 adr1 adr0 pwm scl sda gnd top view ms package 16-lead plastic msop t jmax = 125c, ja = 120c/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 ltc2991cms#pbf ltc2991cms#trpbf 2991 16-lead plastic msop 0c to 70c ltc2991ims#pbf ltc2991ims#trpbf 2991 16-lead plastic msop C40c to 85c consult ltc marketing for parts specified with wider operating temperature ranges. *the temperature grade is identified by a label on the shipping container. consult ltc marketing for information on non-standard lead based finish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ e lec t rical c harac t eris t ics 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 1.5 ma i sd input supply current shutdown mode, i 2 c inactive l 1 6 a v cc(uvl) input supply undervoltage lockout l 1.3 2.0 2.6 v measurement accuracy t internal(tue) internal temperature total unadjusted error 1 3.5 c t rmt(tue) remote diode temperature total unadjusted error = 1.004 l 0.7 1.5 c v cc(tue) v cc voltage total unadjusted error 2.9v 5.5v l 0.05 0.25 % v n(tue) v1 through v8 total unadjusted error 0v 4.9v l 0.05 0.25 % v diff(tue) differential voltage total unadjusted error v1 C v2 ,v3 C v4, v5 C v6, v7 C v8 C300mv v d 300mv l 0.1 0.75 % v diff(max) full-scale differential voltage l C312.5 312.5 mv the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c, v cc = 3.3v, unless otherwise noted. ltc2991 2991fd for more information www.linear.com/ltc2991
3 e lec t rical c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c, v cc = 3.3v, unless otherwise noted. symbol parameter conditions min typ max units v diff(cmr) differential voltage common mode range l 0 v cc v v lsb(diff) differential voltage lsb weight 19.075 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 v lsb(diode_voltage) diode voltage lsb weight includes series resistance ir drop 38.15 v t noise temperature noise celsius or kelvin filter disengaged 0.2 rms t noise temperature noise celsius or kelvin filter engaged 0.07 rms 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 c in v1 through v8 input sampling capacitance (note 2) 0.35 pf i in(avg) v1 through v8 input average sampling current (0 v n 4.9v) (note 2) 0.6 a i dc_leak(vin) v1 through v8 input leakage current (0 v n v cc ) l C10 10 na pwm f pwm pwm period l 0.9 1.2 ms dc pwm duty cycle range l 0 99.8 % scale pwm 0% to 100% pwm temperature range 32 deg measurement delay t internal , t r1 , t r2 , t r3 , t r4 per configured temperature measurement l 37 46 55 ms v1, v2, v3, v4, v5, v6, v7, v8 single-ended voltage measurement l 0.9 1.5 1.8 ms v1 C v2, v3 C v4, v5 C v6, v7 C v8 differential voltage measurement l 0.9 1.5 1.8 ms v cc v cc measurement l 0.9 1.5 1.8 ms max delay mode[4:0] = 11101, t internal , t r1 , t r2 , t r3 , t r4 v cc l 277 ms v1, v3, v5, v7 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) adr input low threshold voltage falling l 0.3 ? v cc v v adr(h) adr 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, adr2 input current adr0, adr1 or adr2 tied to v cc or gnd l 1 a ltc2991 2991fd for more information www.linear.com/ltc2991
4 symbol parameter conditions min typ max units 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 e lec t rical c harac t eris t ics the l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at t a = 25c, v cc = 3.3v, unless otherwise noted. 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 defined 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. ltc2991 2991fd for more information www.linear.com/ltc2991
5 typical p er f or m ance c harac t eris t ics t a = 25c, v cc = 3.3v, unless otherwise noted. t internal error remote diode error with ltc2991 at 25c remote diode error with ltc2991 at same temperature as diode supply current vs temperature shutdown current vs temperature measurement delay variation vs t normalized to 3.3v, 25c v cc tue single-ended vx tue differential voltage tue t amb (c) ?50 i cc (a) 2.0 2.5 3.0 25 50 75 100 125 2991 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 2991 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 2991 g03 ?25 0 150 0 ?1 4 v cc = 5v v cc = 3.3v t amb (c) ?50 v cc tue (%) 0 25 50 75 100 125 2991 g04 ?25 0 150 ?0.25 ?0.50 0.25 t amb (c) ?50 vx tue (%) 0 0.25 25 50 75 100 125 2991 g05 ?25 0 150 ?0.25 ?0.50 0.50 t amb (c) ?50 v diff tue (%) 0 25 50 75 100 125 2991 g06 ?25 0 150 ?0.25 ?0.50 0.25 t amb (c) ?50 error (c) 1.0 1.5 25 50 75 100 125 2991 g07 0.5 0 ?25 0 150 ?0.5 ?1.0 2.0 bath temperature (c) ?50 ltc2991 t rx error (c) 0.2 0.4 25 50 75 100 125 2991 g08 0 ?0.2 ?25 0 150 ?0.4 ?0.6 0.6 t amb (c) ?50 ltc2991 t rx error (deg) 0.25 0.50 0.75 25 50 75 100 125 2991 g09 ?0.25 0 ?25 0 150 ?0.50 ?1.00 ?0.75 1.00 ltc2991 2991fd for more information www.linear.com/ltc2991
6 typical p er f or m ance c harac t eris t ics t a = 25c, v cc = 3.3v, unless otherwise noted. ltc2991 differential noise differential transfer function differential inl t internal noise remote diode noise lsbs (19.075v/lsb) ?4 counts 300 400 500 800 readings ?1 1 2991 g13 200 100 0 ?3 ?2 0 2 3 v1-v2 (v) ?0.4 ltc2991 v1-v2 (v) 0 0.2 0.4 2991 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 v in (v) ?0.4 inl (lsbs) 0 1 0.4 2991 g15 ?1 ?2 ?0.2 0 0.2 2 (c) ?0.75 ?0.5 0 counts 200 500 1000 readings ?0.25 0.25 0.5 2991 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 2991 g17 100 400 300 0 0.75 single-ended transfer function single-ended inl v x (v) ?1 4 5 2 4 2991 g11 3 2 ?0 1 3 5 6 1 0 ?1 6 ltc2991 value (v) v cc = 5v v cc = 3.3v v x (v) 0 ?1.0 inl (lsbs) ?0.5 0 0.5 1.0 1 2 3 4 2991 g12 5 v cc = 5v v cc = 3.3v single-ended noise lsbs (305.18v/lsb) ?3 counts 3500 0 2991 g10 2000 1000 ?2 ?1 1 500 0 4000 4800 readings 3000 2500 1500 2 3 ltc2991 2991fd for more information www.linear.com/ltc2991
7 digital filter step response c parallel (pf) 1 t error (c) 2991 g20 0.4 0.2 0 10 100 1k 10k 100k 1000k 1.2 1.0 0.8 0.6 t error vs c parallel t error vs r series iteration 0 % full-scale 50 80 200 2991 g18 30 20 0 50 100 150 100 40 70 60 10 90 r series () 0 t error (c) 5000 2991 g19 1 0.1 1000 2000 3000 4000 100 10 typical p er f or m ance c harac t eris t ics t a = 25c, v cc = 3.3v, unless otherwise noted. ltc2991 2991fd for more information www.linear.com/ltc2991
8 p in func t ions v1 (pin 1): first monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the positive input for a differential or remote diode temperature measurement (in combination with v2). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will source a current. v2 (pin 2): second monitor input. this pin can be config - ured as a single-ended input (0v to 4.9v) or the negative input for a differential or remote diode temperature mea - surement (in combination with v1). differential common mode range is 0v to v cc , 300mv differential. when configured 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 configured as a single-ended input (0v to 4.9v) or the positive input for a differential or remote diode temperature measurement (in combination with v4). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will source a current. v4 (pin 4): fourth monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the negative input for a differential or remote diode temperature measurement (in combination with v3). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will have an internal termination, while the measurement is active. v5 (pin 5): fifth monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the positive input for a differential or remote diode temperature measurement (in combination with v6). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will source a current. v6 (pin 6): sixth monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the negative input for a differential or remote diode temperature measurement (in combination with v5). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will have an internal termination, while the measurement is active. v7 (pin 7): seventh monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the positive input for a differential or remote diode tempera - ture measurement (in combination with v8). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will source a current. v8 (pin 8): eighth monitor input. this pin can be configured as a single-ended input (0v to 4.9v) or the negative input for a differential or remote diode temperature measurement (in combination with v7). differential common mode range is 0v to v cc , 300mv differential. when configured for remote diode temperature, this pin will have an internal termination, while the measurement is active. gnd (pin 9): device ground. connect this pin through a low impedance connection to system ground. sda (pin 10): 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 configuration 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 11): serial bus clock input of the i 2 c interface. the ltc2991 can only act as a slave and the scl pin only accepts external serial clock. the ltc2991 does not implement clock stretching. pwm (pin 12): pwm output. the pwm pin provides a cmos output level with a duty cycle proportional to the remote diode temperature of the sensor connected to pins v7 and v8. adr0, adr1, adr2 (pins 13, 14, 15): serial bus address control input. the adr pins are address control bits for the device i 2 c address. see table 1. v cc (pin 16): chip power. connect to 2.9v to 5.5v low noise supply. a 0.1f decoupling capacitor to gnd is required for this pin. ltc2991 2991fd for more information www.linear.com/ltc2991
9 func t ional diagra m adc mux mode reference i 2 c undervoltage detector v4 v5 v6 v7 uv remote diode sensors power monitoring r l r sense 4 v3 3 scl 2991 fd v2 2 v1 1 7 6 5 control logic 11 sda 10 pwm 12 adr0 13 adr1 14 adr2 15 gnd 9 v cc 16 v8 8 pulse width detector v cc v cc v cc v cc v cc v cc internal sensor +? +? + ? voltage monitoring 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 2991 td sdai/sdao scl ltc2991 2991fd for more information www.linear.com/ltc2991
10 o pera t ion the ltc2991 monitors voltage, current, internal and remote temperatures. it can be configured through an i 2 c inter - face to measure many combinations of these parameters. single or repeated measurements can be configured. remote temperature measurements use transistors as temperature sensors, 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 functional com - ponents of the device. the input signals are selected with an input mux, controlled by the control logic block. the control logic block uses the mode bits in the control registers to manage the sequence and types of data acquisition. the control logic block also controls the current sour ces during remote temperature acquisition. the order of acquisitions is fixed: v1, v2, v3, v4, v5, v6, v7, v8, t internal then v cc . the adc performs the necessary conversion(s) and supplies the data to the control logic for routing to the ap - propriate data register. the i 2 c interface supplies access to control, status and data registers. the adr2, adr1 and adr0 pins select one of eight possible i 2 c addresses (see table 1). the uvlo inhibits i 2 c communication below the specified 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. the v2, v4, v6 or v8 terminals of the ltc2991 are terminated with a diode if that channel is configured for temperature measurements. it is acceptable to ground these pins, but increased noise may result on the temperature measurements. the ltc2991 is calibrated to yield the correct temperature for a remote diode with an ideality factor of 1.004. see the applications information section for compensation of sensor ideality factors other than the factory calibrated value of 1.004. the ltc2991 communicates through an i 2 c serial in - terface. the serial interface provides access to control, status and data registers. i 2 c defines a 2-wire open-drain interface supporting multiple slave devices and masters on a single bus. the ltc2991 supports 100kbit/s in the standard mode and up to 400kbit/s in fast mode. the eight 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 trig - ger register. the data registers contain a destructive read status bit (data valid), which is used in repeated mode to determine if the registers contents have been previously read. this bit is set when the register is updated with new data, and cleared when read. ltc2991 2991fd for more information www.linear.com/ltc2991
11 the basic ltc2991 application circuit is shown in figure 1. a pplica t ions i n f or m a t ion figure 1. power up the v cc pin must exceed the undervoltage (uv) thresh - old of 2.5v to keep the ltc2991 out of power-on reset. power -on reset will clear all of the data registers and the control registers. t emperature measurements the ltc2991 can measure internal temperature and up to four external diode or transistor sensors. during tem - perature conversion, current is sourced through the v1, v3, v5 or the v7 pin to forward bias the remote sensing diode. the change in sensor voltage per degree temperature change is hundreds of v/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 kt q i i be c s = ? ? ? ? ? ? ? ? ?l n (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 vq ki n i i be c s = ? ? ? ? ? ? ? ?? (2) the ltc2991 makes differential measurements of diode voltage to calculate temperature. proprietary techniques allow for cancellation of error due to series resistance. ideality factor scaling the ltc2991 is calibrated to yield the correct temperature for a remote diode with an ideality factor of 1.004. while this value is typical of target sensors, small deviations can yield significant temperature errors. the ideality factor of the diode sensor can be considered a temperature scaling factor. the temperature error for a 1% accurate ideality fac - tor 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 ltc2991 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 sufficient precision using 16-bit fixed point math in a microprocessor or microcontroller. factory ideality calibration value: cal = 1.004 actual sensor ideality value: act figure 2. recommended pcb layout v cc 2-wire i 2 c interface v1 ltc2991 t ambient r sense 3.3v 5v 1.8v 2.5v gnd sda scl adr0 adr1 adr2 3.3v i/o 2.5v i/o 1.8v core fpga fpga temperature board temperature v3 v4 v5 v6 v7 v8 pwm to fan v2 2991 f01 v1 v2 v3 v4 v5 v6 v7 v8 v cc adr2 adr1 adr0 pwm scl sda gnd ltc2991 2991 f01 gnd shield trace npn sensor 470pf 0.1f ltc2991 2991fd for more information www.linear.com/ltc2991
12 a pplica t ions i n f or m a t ion compensated kelvin temperature: t k _ comp = cal act ? t k _ meas (3) compensated celsius temperature: cc omp act cal cm ea s 273.15 273.15 t t= ?+ _ _ ( ) (4) a 16-bit unsigned number is capable of representing the ratio cal/ act 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 temperature error of 0.01 at +125c. multiplying this 16-bit unsigned number and the measured kelvin (un - signed) temperature represented as a 16-bit number, yields a 32-bit unsigned result. t o 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 . similarly, celsius coded temperature values can be scaled using 16-bit fixed-point arithmetic, using equation (4). in both cases, the scaled result will have a 9-bit integer (d[12:4]) and the four lsbs (d[3:0]) representing the 4-bit fractional part. to convert the corrected result to decimal, divide the final result by 24, or 16, as you would the register contents. if ideality factor scaling is implemented in the target application, it is beneficial to configure the ltc2991 for kelvin coded results to limit the number of math operations required in the target processor. t t (unsigned) kc omp act cal km ea s _ _ = ? ? ? ? ? ? 2 2 15 15 (5) (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 sample = (v in C 1.49v) ? 0.17[a/v] inputs with source resistance less than 500 will yield full-scale gain errors due to source impedance of < ? lsb for 14-bit conversions. the nominal conversion time is 1.5ms for single-ended conversions. current measurements the ltc2991 has the ability to perform 14-bit current measurements with the addition of a current sense resis - tor (see figure 3). t (unsigned) t cc om p act cal cm ea s _ _ = ? ? ? ? ? ? + ( 2 273. 15 ? 2 15 4 ) 2 273 15 2 15 4 ? .? figure 3. simplified current sense schematic in order to achieve 13-bit current sensing a few details must be considered. differential voltage or current mea - surements are directly sampled by the internal adc. the average adc input current for each leg of the differential input signal during a conversion is: i sample = (v in C 1.49v) ? 0.34[a/v] the maximum source impedance to yield 14-bit results with ? lsb full-scale error is ~50. in order to achieve 14-bit accuracy, 4-point, or kelvin connected measurements of the sense resistor differential voltage are necessary. v1 v2 ltc2991 0v ? v cc r sense i load 2991 f03 ltc2991 2991fd for more information www.linear.com/ltc2991
13 a pplica t ions i n f or m a t ion in the case of current measurements, the external sense resistor is typically small, and determined by the full-scale input voltage of the ltc2991. 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 = 0.300v/i max . for example, if you wanted to measure a current range of 5a, the external shunt resistance would equal 0.300v/5a = 60m. there exists a way to improve the sense resistors precision using the ltc2991. the ltc2991 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 coefficient of the sense resistor in software. the resistance would be measured by running a calibrated test current through the discrete resistor. the ltc2991 would measure both the differential voltage across this resistor and the resistor temperature. from this measurement, r o and t o in the following equa - tion 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 = 3930ppm/c for copper trace = 2 to ~200ppm/c for discrete r (7) i = (v1 C v2)/r t (8) device configuration the ltc2991 is configured by writing the channel control registers through the serial interface. refer to tables 5, 6 and 7 for control register bit definition. the device is ca- pable of many application configurations including voltage, temperature and current measurements. it is possible to configure 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 indefinitely frozen wait state. the device can also make single measurements, or with one trigger, all of the measurements for the configuration. when the device is configured for multiple measurements, the order of measurements is fixed. as each new data result is ready, the msb of the corresponding data reg - ister is set, and the corresponding status register bit is set. these bits are cleared when the corresponding data register is addressed. the configuration register value at power -up yields the measurement of the internal tempera - ture sensor and v1 through v8 as single-ended voltages, if triggered. the eight input pins v1 through v8 will be in a high impedance state, until configured otherwise, and a measurement triggered. data format the data registers are broken into 8-bit upper and lower bytes. v oltage and temperature conversions are 13-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 11 and 12, each with 0.0625 degree weighted lsbs. the format is controlled by the control registers. the temperature msb result register most significant 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. the ltc2991 internal bias circuitry maintains this voltage above this level during normal operating conditions. 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 16 for conversion value examples. remote diode voltage is digitized at ~50a of bias current. the adc lsb value during these conversions is typically 38.15v. voltages are only available for the remote diodes, not the internal sensor. this code repeats at a diode volt - age of approximately 0.3125v (see tables 13 and 14). the absolute temperature of the diode can be used to detect whether the diode is operating (0.3125v or 0.3125v). this mode is useful for testing small relative ltc2991 2991fd for more information www.linear.com/ltc2991
14 a pplica t ions i n f or m a t ion changes in temperature using the approximate relation - ship of C2.1mv/c of voltage dependence on temperature. with an lsb weight of 38.15v and a diode temperature relationship of C2.1mv/c this yields ~0.018 degree resolu - tion. for sensor applications involving heaters, the ability to sense small changes in temperature with low noise can yield significant power savings, allowing the heater power to be reduced. table 16 has some conversion result examples for various diode voltages. v oltage/current voltage results are reported in two respective registers, an msb and lsb register. the voltage msb result register most significant 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 v8, and differential (current measurements) v1 C v2 , v3 C v4, v5 C v6 and v7 C v8. single-ended voltages are limited to positive values in the range 0v to 4.9v or v cc + 0.2v, whichever is smaller. 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 16 for examples): v single_ended = d[13:0] ? 305.18v v differential = d[13:0] ? 19.075v, if sign = 0 v differential = (d[13:0] +1) ? C19.075v, if sign = 1 current = d[13:0] ? 19.075v/r sense , if sign = 0 current = (d[13:0] +1) ? C19.075v/r sense , if sign = 1, where r sense is the current sensing resistor, typically < 1. v cc the ltc2991 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). pwm output a 9-bit, 1khz pwm output proportional to temperature v7 is available for controlling fans or heaters. pwm_thresh - old is a 9-bit value with an lsb weighting of one degree kelvin. p wm_threshold is subtracted from v7 and a pulse width proportional to the difference is produced. note that the pwm threshold is split among two regis - ters, with pwm_threshold[8:1] in register 09h[7:0] and p wm_threshold[0] in register 08h[7]. equation 9 shows the registers involved. the p wm frequency is ~1khz. the pwm output can be disabled or inverted with the pwm enable and pwm invert bits is register 08h, respectively. figure 9 illustrates the pwm transfer function. the equa - tion for the duty cycle is: (9) pwm_duty_cycle % ( ) = 100 ? (reg7 C pwm ? 16) 512 where reg7 is bits [12:0] and pwm is pwm threshold bits [8:0] a 50% duty cycle p wm signal would occur, for example, if the pwm threshold was set to 10h (16c) and register 7 contained 200h (32c). if channel 7 is configured for kelvin temperatures, the pwm threshold must also be a kelvin temperature. the registers are twos compliment numbers. when calculating the duty cycle above for celsius temperatures care should be taken to sign extend the register 7 and p wm threshold values. for temperatures below the pwm threshold, the pwm output pin will be a constant logic level 0. for temperatures 32 degrees above figure 9. pwm transfer function reg7[12:4]-pwm_threshold[8:0] pwm dc (%) 50% 16 32 2991 f09 0 0% 99.8% pwm invert = logic 0 ltc2991 2991fd for more information www.linear.com/ltc2991
15 a pplica t ions i n f or m a t ion the pwm threshold, the pwm output pin will be a constant logic level 1. this relationship is opposite if the pwm invert bit is set. if the filter is enabled for the v7/v8 pair, the filtered result is routed to the pwm block; otherwise, the unfiltered version is used. the pwm cmos output drive is intended to be buffered to drive large (>100pf) external capacitances or resistors <10k. a recommended noninverting buffer is a nc7sz125 to increase the drive capability of the pwm signal. digital filter each conversion result can be filtered using an on-chip digital filter. the filter equation is: output[x] = (15 ? (output[x C 1]) + sample[x])/16 where output[x] is the register value when enabled. the filter step response is illustrated in the typical perfor - mance characteristics section. the filter can be seeded by triggering an unfiltered conversion of each configured measurement, then subsequently enabling the filter . this will cause the filter to converge instantaneously to the value of the initial unfiltered sample. the filter can be enabled or disabled for each channel pair and internal temperature measurements. v cc measurements cannot be filtered. digital interface the ltc2991 communicates with a bus master using a 2-wire interface compatible with the i 2 c bus and the smbus, an i 2 c extension for low power devices. the ltc2991 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 3 though 15. 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 ltc2991 can only be addressed as a slave. once ad - dressed, it can receive configuration 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 definition 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 ltc2991 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 finished 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 eight distinct bus addresses are configurable using the adr0, adr1 and adr2 pins. table 1 shows the corre - spondence between adr0, adr1 and adr2 pin states and addresses. there is also one global sync address available at eeh which provides an easy way to synchronize multiple ltc2991s on the same i 2 c bus. this allows write only access to all ltc2991s on the bus for simultaneous triggering. 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 ltc2991 2991fd for more information www.linear.com/ltc2991
16 a pplica t ions i n f or m a t ion 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. after the master has received the last data bit from the slave, the master must pull down the sda line during the next 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 condition followed by the 7-bit slave address and the r w bit set to zero. the addressed ltc2991 acknowledges the address and then the master sends a command byte which indi - cates which internal register the master wishes to write. the l tc2991 acknowledges the command byte and then latches the lower five bits of the command byte into its internal register address pointer. the master then deliv - ers the data byte and the ltc2991 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 l tc2991 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 7-bit slave address and the r w bit set to zero. the addressed ltc2991 acknowledges this and then the master sends a command byte which indicates which internal register the master wishes to read. the ltc2991 acknowledges this and then latches the lower five bits of the command byte into its internal register address pointer. the master then sends a repeated start condi - tion followed by the same seven bit address with the rw bit now set to one. the ltc2991 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 ltc2991 will send the contents of the next sequential register as the second data byte. the byte following register 1fh is register 0h, or the status register. control registers the control registers (tables 5 through 8) determine the selected measurement mode of the device. the ltc2991 can be configured 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 ltc2991 can be configured to run particular measurements, or all possible measure - ments per the configuration specified by the channel enable register (table 4). the power -on default configuration of the control registers is 00h, which translates to a single-ended voltage measurement of the triggered channels. this mode prevents the application of remote diode test currents on pins v1, v3, v5 and v7, and remote diode terminations on pins v2, v4, v6 and v8 at power-up. status register the status registers (tables 3 and 4) report the status of a particular 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. figure 4. data transfer over i 2 c or smbus stop 2991 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 ltc2991 2991fd for more information www.linear.com/ltc2991
17 a pplica t ions i n f or m a t ion table 1. i 2 c base address i 2 c base address adr2 adr1 adr0 90h 0 0 0 92h 0 0 1 94h 0 1 0 96h 0 1 1 98h 1 0 0 9ah 1 0 1 9ch 1 1 0 9eh 1 1 1 eeh global sync address s a a data w# address command a 0 0 b7:b0 0 1001 a2:a0 from master to slave xxxxxb3:b0 0 2991 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 s a a data w# address command a 0 0 b7:b0 data b7:b0 0 1001 a2:a0 xxxxxb3:b0 0 0 2991 f06 p a s a a s w# address command a 0 0 1 0 data b7:b0 0 1001 a2:a0 address 1001 a2:a0 xxxxxb3:b0 1 2991 f07 pa# r s a a s w# address command a 0 0 1 0 a 0 data b7:b0 0 1001 a2:a0 address 1001 a2:a0 xxxxxb3:b0 1 2991 f08 pa# data b7:b0 r figure 5. ltc2991 serial bus write byte protocol figure 6. ltc2991 serial bus repeated write byte protocol figure 7. ltc2991 serial bus read byte protocol figure 8. ltc2991 serial bus repeated read byte protocol ltc2991 2991fd for more information www.linear.com/ltc2991
18 a pplica t ions i n f or m a t ion table 2. ltc2991 register address and contents register address* ? register name read/write description 00h st a tus low r data_valid bits (v1 through v8) 01h ch en, stat. hi, trigger** r/w channel enable , v cc , t internal conv. status, trigger 02h reserved n/a reserved 03h reserved n/a reserved 04h reserved n/a reserved 05h reserved n/a reserved 06h v1, v2 and v3, v4 control r/w v1, v2, v3 and v4 control register 07h v5, v6 and v7, v8 control r/w v5, v6, v7 and v8 control register 08h pwm_threshold(lsb), v cc , t internal control r/w pwm threshold and t internal control register 09h pwm_threshold(msb) r/w pwm threshold 0ah v1(msb) r v1 or t r1 t msb 0bh v1(lsb) r v1 or t r1 t lsb 0ch v2(msb) r v2, v1 C v2, or t r1 voltage msb 0dh v2(lsb) r v2, v1 C v2, or t r1 voltage lsb 0eh v3(msb) r v3, or t r2 t msb 0fh v3(lsb) r v3, or t r2 t lsb 10h v4(msb) r v4, v3 C v4, or t r2 voltage msb 11h v4(lsb) r v4, v3 C v4, or t r2 voltage lsb 12h v5(msb) r v5, or t r3 t msb 13h v5(lsb) r v5, or t r3 t lsb 14h v6(msb) r v6, v5 C v6, or t r3 voltage msb 15h v6(lsb) r v6, v5 C v6, or t r3 voltage lsb 16h v7(msb) r v7, or t r4 t msb 17h v7(lsb) r v7, or t r4 t lsb 18h v8(msb) r v8, v7 C v8, or t r4 voltage msb 19h v8(lsb) r v8, v7 C v8, or t r4 voltage lsb 1ah t internal (msb) r t internal msb 1bh t internal (lsb) r t internal lsb 1ch v cc (msb) r v cc msb 1dh v cc (lsb) r v cc lsb * register address msbs b7 to b5 are ignored. ** writing any value triggers a conversion. ? power-on reset sets all registers to 00h. ltc2991 2991fd for more information www.linear.com/ltc2991
19 a pplica t ions i n f or m a t ion table 3. status low (00h) register bit name operation b7 v8, t4, v7 C v8 ready 1 = v8 register contains new data, 0 = v8 register data old b6 v7, t4, v7 C v8 ready 1 = v7 register contains new data, 0 = v7 register data old b5 v6, t3, v5 C v6 ready 1 = v6 register contains new data, 0 = v6 register data old b4 v5, t3, v5 C v6 ready 1 = v5 register contains new data, 0 = v5 register data old b3 v4, t2, v3 C v4 ready 1 = v4 register contains new data, 0 = v4 register data old b2 v3, t2, v3 C v4 ready 1 = v3 register contains new data, 0 = v3 register data old b1 v2, t1, v1 C v2 ready 1 = v2 register contains new data, 0 = v2 register data old b0 v1, t1, v1 C v2 ready 1 = v1 register contains new data, 0 = v1 register data old table 4. status high, channel enable (01h) register (default 00h) bit name r/w operation b7 v7 and v8, v7 C v8, t r4 enable r/w 1 = v7 and v8, or v7 C v8 or t4 enabled 0 = v7 and v8, or v7 C v8 or t4 disabled (default) b6 v5 and v6, v5 C v6, t r3 enable r/w 1 = v5 and v6, or v5 C v6 or t3 enabled 0 = v5 and v6, or v5 C v6 or t3 disabled (default) b5 v3 and v4, v3 C v4, t r2 enable r/w 1 = v3 and v4, or v3 C v4 or t2 enabled 0 = v3 and v4, or v3 C v4 or t2 disabled (default) b4 v1 and v2, v1 C v2, t r1 enable r/w 1 = v1 and v2, or v1 C v2 or t1 enabled 0 = v1 and v2, or v1 C v2 or t1 disabled (default) b3 t internal v cc enable r/w 1 = t internal and v cc enabled 0 = t internal and v cc disabled (default) b2 busy r 1 = a conversion is in process 0 = sleep mode (default) b1 t internal r 1 = t internal register contains new data 0 = t internal register data old (default) b0 v cc r 1 = v cc register contains new data 0 = v cc register data old (default) table 5. v1, v2 and v3, v4 control (06h) register (default 00h) bit name operation b7 v3, v4 filt 1 = filter enabled, 0 = filter disabled for v3 and v4, v3 C v4 or t2 (default) b6 t r2 kelvin 1 = kelvin, 0 = celsius for t2 (default) b5 v3, v4 temperature 1 = temperature, 0 = voltage (per b4 setting) (default) b4 v3, v4 differential 1 1 = differential (v3 C v4) and v3 single-ended 0 = single-ended voltage (v3 and v4) (default) b3 v1, v2 filt 1 = filter enabled, 0 = filter disabled for v1 and v2, v1 C v2 or t1 (default) b2 t r1 kelvin 1 = kelvin, 0 = celsius for t1 (default) b1 v1, v2 temperature 1 = temperature, 0 = voltage (per b0 setting) (default) b0 v1, v2 differential 1 = differential (v1 C v2) and v1 single-ended 0 = single-ended voltage (v1 and v2) (default) ltc2991 2991fd for more information www.linear.com/ltc2991
20 a pplica t ions i n f or m a t ion table 6. v5, v6 and v7, v8 control (07h) register (default 00h) bit name operation b7 v7, v8 filt 1 = filter enabled, 0 = filter disabled for v7 and v8, v7 C v8 or t4 (default) b6 t r4 kelvin 1 = kelvin, 0 = celsius for t4 (default) b5 v7, v8 temperature 1 = temperature, 0 = voltage (per b4 setting) (default) b4 v7, v8 differential 1 = differential (v7 C v8) and v7 single-ended 0 = single-ended voltage (v7 and v8) (default) b3 v5, v6 filt 1= filter enabled, 0 = filter disabled for v5 and v6, v5 C v6 or t3 (default) b2 t r3 kelvin 1 = kelvin, 0 = celsius for t3 (default) b1 v5, v6 temperature 1 = temperature, 0 = voltage (per b0 setting) (default) b0 v5, v6 differential 1 = differential (v5 C v6) and v5 single-ended 0 = single-ended voltage (v5 and v6) (default) table 7. pwm, v cc and t internal control (08h) register (default 00h) bit name operation b7 pwm[0] pwm threshold least significant bit (default = 0) b6 pwm invert* 1 = pwm inverted, 0 = pwm noninverted (default) b5 pwm enable** 1 = pwm enabled, 0 = pwm disabled (default) b4 repeated acquisition 1 = repeated mode 0 = single shot (default) b3 t internal filt 1 = filter enabled for t internal 0 = filter disabled t internal (default) b2 t internal kelvin 1 = kelvin, 0 = celsius for t internal (default) b1 reserved reserved b0 reserved reserved * noninverted would be an increasing duty cycle for an increasing temperature. ** if disabled and noninverted, the pwm pin will be a logic level 0. if disabled and inverted, the pwm pin will be a logic level 1. table 8. pwm register format (default 00h) bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 d8 d7 d6 d5 d4 d3 d2 d1 note: d0 is located in the msb of pwm, v cc and t internal control (08h) register table 9. voltage/current measurement msb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 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 interface. table 10. voltage/current measurement lsb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 d7 d6 d5 d4 d3 d2 d1 d0 ltc2991 2991fd for more information www.linear.com/ltc2991
21 table 11. temperature measurement msb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 dv* x x 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. x unused table 12. temperature measurement lsb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 d7 d6 d5 d4 d3 d2 d1 d0 table 14. diode voltage measurement lsb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 d7 d6 d5 d4 d3 d2 d1 d0 table 13. diode voltage measurement msb data register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 dv* x x 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. x unused table 15. pwm threshold register format bit7 bit6 bit5 bit4 bit3 bit2 bit1 bit0 d7 d6 d5 d4 d3 d2 d1 d0 d7:d0 = pwm[8:1], bit 0 is located in the pwm, v cc and t int control register (table 7) table 16. conversion formats voltage formats sign binary value d[13:0] voltage single-ended lsb = 305.18v = 2.5/2 13 0 11111111111111 >5 0 10110011001101 3.5000 0 01111111111111 2.5000 0 00000000000000 0.0000 1 11110000101001 C0.3000 differential lsb = 19.075v = 2.5/2 17 0 11110101101111 0.300 0 10000010001111 0.159 0 00000000000000 0.0000 1 01111101110001 C0.159 1 00001010010001 C0.300 v cc = result + 2.5v lsb = 305.18v = 2.5/2 13 0 10110011001101 v cc = 6.0 0 10000000000000 v cc = 5.0 0 00001010001111 v cc = 2.7 a pplica t ions i n f or m a t ion ltc2991 2991fd for more information www.linear.com/ltc2991
22 a pplica t ions i n f or m a t ion table 17. recommended transistors to be used as temperature sensors manufacturer part number package fairchild semiconductor mmbt3904 sot-23 fairchild semiconductor fmmt3904 sot-23 fairchild semiconductor 2n3904 to-92 central semiconductor cmpt3904 sot-23 central semiconductor cet3904e sot-883l diodes, inc. mmbt3904 sot-23 on semiconductor mmbt3904lt1 sot-23 nxp mmbt3904 sot-23 infineon mmbt3904 sc-70 rohm umt3904 sot-23 table 16. conversion formats temperature formats format binary value d[12:0] temperature temperature internal, t r1 through t r4 lsb = 0.0625 degrees celsius 0011111010000 125.0000 celsius 0000110010001 25.0625 celsius 0000110010000 25.0000 celsius 1110110000000 C40.0000 kelvin 1100011100010 398.1250 kelvin 1000100010010 273.1250 kelvin 0111010010010 233.1250 kelvin 0010011010000 77.0000 diode v oltage formats sign binary v alue d[13:0] voltage remote temperature t r1 through t r4 lsb = 38.15v 0 00000000000000 0.0000 0 11111111111111 0.31249 0 00000000000000 0.31252 0 11111111111111 0.62501 0 00000000000000 0.62505 0 10011001100100 0.99999 ltc2991 2991fd for more information www.linear.com/ltc2991
23 high voltage/current and temperature monitoring typical a pplica t ions ? + ?ins 0.1f v in 5v to 105v 0.1f all capacitors 20% other apps voltage, current and temperature configuration: control register: 0x06 0xa0 t ambient reg 1a, 1b: 0.0625c/lsb v load reg 0a, 0b: 13.2mv/lsb v2(i load ) reg 0c, 0d: 1.223ma/lsb t processor reg 0e, 0f: 0.0625c/lsb v cc reg 1c, 1d: 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 ltc2991 2-wire i 2 c interface 5v gnd sda scl adr0 adr1 adr2 v3 v4 v5 to v8 v2 2991 ta02 4 ltc2991 2991fd for more information www.linear.com/ltc2991
24 typical a pplica t ions computer voltage and temperature monitoring motor protection/regulation microprocessor v cc v1 ltc2991 2-wire i 2 c interface gnd sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta03 10k 1% 10k 1% 10k 1% 3.3v 30.1k 1% 5v 12v voltage and temperature configuration control register: 0x06 0x0a t ambient reg 1a, 1b: 0.0625c/lsb v1(+5) reg 0a, 0b: 610v/lsb v2(+12) reg 0c, 0d: 1.22mv/lsb t processor reg 0e, 0f: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb 0.1f other apps v5 to v8 4 v cc v1 ltc2991 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 t motor mmbt3904 sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta04 motor t ambient voltage, current and temperature configuration: control register: 0x06: 0xa1 t ambient reg 1a, 1b: 0.0625c/lsb v motor reg 0a, 0b: 305.18v/lsb i motor reg 0c, 0d: 190.75a/lsb t motor reg 1a, 1b: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb other apps v5 to v8 4 ltc2991 2991fd for more information www.linear.com/ltc2991
25 typical a pplica t ions large motor protection/regulation fan/air filter/temperature alarm v cc v1 ltc2991 load pwr = i ? v 0.01 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 t motor mmbt3904 sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta05 motor t ambient voltage, current and temperature configuration: control register 06: 0xa1 t ambient reg 1a, 1b: 0.0625c/lsb v motor reg 0a, 0b: 2.44mv/lsb i motor reg 0c, 0d: 15.54ma/lsb t motor reg 0e, 0f: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb other apps v5 to v8 4 v cc v1 ltc2991 2-wire i 2 c interface 3.3v gnd 22 0.125w heater nds351an temperature for: heater enable good fan bad fan fan mmbt3904 mmbt3904 sda scl adr0 adr1 v3 v4 v2 2991 ta06 t ambient heater enable 2 second pulse control register 0x06 = 0xaa t ambient reg 1a, 1b: 0.0625c/lsb t fan1 reg 0a, 0b: 0.0625c/lsb t fan2 reg 0c, 0d: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb 3.3v 22 0.125w fan other apps v5 to v8 4 ltc2991 2991fd for more information www.linear.com/ltc2991
26 typical a pplica t ions battery monitoring wet bulb psychrometer references http://en.wikipedia.org/wiki/hygrometer http://en.wikipedia.org/wiki/psychrometrics v cc v1 ltc2991 5v c gnd t dry t wet mmbt3904 mmbt3904 sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta08 470pf t ambient damp muslin water reservoir control register 0x06 = 0xaa t ambient reg 1a, 1b: 0.0625c/lsb t wet reg 0a, 0b: 0.0625c/lsb t dry reg 0c, 0d: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb ?t nds351an fan enable 5v fan fan: sunon kde0504pfb2 other apps v5 to v8 4 v cc v1 ltc2991 battery i and v monitor 0.1* charging current 2-wire i 2 c interface 5v gnd nimh battery v(t) 100% 100% ? ? ? t batt mmbt3904 sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta07 t ambient *irc lrf3w01r015f voltage and temperature configuration: control register: 0xa1 t ambient reg 1a, 1b: 0.0625c/lsb v bat reg 0a, 0b: 305.18v/lsb i bat reg 0c, 0d: 190.75a/lsb t bat reg 0e, 0f: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb + t(t) 100% i(t) other apps v5 to v8 4 ltc2991 2991fd for more information www.linear.com/ltc2991
27 typical a pplica t ions wind direction/instrumentation v cc v1 ltc2991 3.3v c gnd mmbt3904 mmbt3904 sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta10 3.3v heater 75 0.125w t ambient control register 0x06 0xaa t ambient reg 1a, 1b 0.0625c/lsb t r1 reg 0a, 0b 0.0625c/lsb t r2 reg 0e, 0f 0.0625c/lsb v cc reg 1c, 1d 2.5v + 305.18v/lsb 2n7002 heater enable 2 second pulse other apps v5 to v8 4 liquid level indicator v cc ltc2991 3.3v c gnd sda scl adr0 adr1 adr2 v1 v4 v3 v2 3.3v t ambient control register 0x06 = 0xaa t ambient reg 1a, 1b: 0.0625c/lsb t dry reg 0a, 0b: 0.0625c/lsb t wet reg 0c, 0d: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb nds351an 2991 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 other apps v5 to v8 4 ltc2991 2991fd for more information www.linear.com/ltc2991
28 oven control with power monitor remote temperature sensing with extended esd performance v cc 2-wire i 2 c interface v1 ltc2991 t ambient 5v gnd sda scl adr0 adr1 adr2 v3 v4 v5 v6 other applications voltage and current (power) monitor oven t set 70c temperature sensor heater v cc v7 v8 pwm v2 2991 ta11 ? + 100k 1f lt6240 100k 1m v cc 5v voltage, current, temperature and pwm configuration: control register 0x06: 0x01 t ambient reg 1a, 1b 0.0625c/lsb v heater reg 0a, 0b 305v/lsb i heater reg 0c, 0d 19.075v/r heater a/lsb t oven reg 16, 17 0.0625c/lsb v cc reg 1c, 1d 2.5v + 305.18v/lsb 0x07: 0xa0 pwm, t internal , v cc reg: pwm register 0x08: 0x50 0x09: 0x1b v cc ltc2991 3.3v gnd sda scl v1 v2 500 500 2991 ta13 control register 0x06 = 0xaa remote temperature sensor reg ob, ob: 0.0625 c/lsb mmbt3904 > 8kv esd mmbt3904 remote temperature sensor protection device typical a pplica t ions ltc2991 2991fd for more information www.linear.com/ltc2991
29 v cc ltc2991 3.3v gnd sda scl sda scl v1 v2 1, 4 9 10 s0, s1 ltc1393 s2, s3 2, 3 5, 8 6, 7 2991 ta14 ltc2291 remote temperature sensor reg ob, ob: 0.0625 c/lsb ltc2991 control register 0x06 0xaa ltc1393 control byte sensor a = 0x0b ltc1393 control byte sensor b = 0x0a ltc1393 control byte sensor c = 0x0c ltc1393 control byte sensor d = 0x0e ltc1393 wired as a dual cross-point switch mmbt3904 mmbt3904 wire pair 1 remote temperature sensor a remote temperature sensor b mmbt3904 mmbt3904 wire pair 2 remote temperature sensor c remote temperature sensor d quad remote temperature sensing with two wire pairs using one ltc2991 channel typical a pplica t ions ltc2991 2991fd for more information www.linear.com/ltc2991
30 p ackage descrip t ion ms package 16-lead plastic msop (reference ltc dwg # 05-08-1669 rev ?) msop (ms16) 1107 rev ? 0.53 0.152 (.021 .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 16151413121110 1 2 3 4 5 6 7 8 9 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) 0 ? 6 typ detail ?a? detail ?a? gauge plane 5.23 (.206) min 3.20 ? 3.45 (.126 ? .136) 0.889 0.127 (.035 .005) recommended solder pad layout 0.305 0.038 (.0120 .0015) typ 0.50 (.0197) bsc 4.039 0.102 (.159 .004) (note 3) 0.1016 0.0508 (.004 .002) 3.00 0.102 (.118 .004) (note 4) 0.280 0.076 (.011 .003) ref 4.90 0.152 (.193 .006) ms package 16-lead plastic msop (reference ltc dwg # 05-08-1669 rev ?) please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. ltc2991 2991fd for more information www.linear.com/ltc2991
31 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. r evision h is t ory rev date description page number a 10/11 corrected axis label on figure 9 inserted new text in i 2 c device addressing section inserted new row in table 1 revised component values in typical application drawing ta05 14 15 17 25 b 07/13 corrected diode voltage value corrected v differential and current equations 13 14 c 10/13 corrected slave address in figures 5, 6, 7 and 8 17 d 03/14 corrected lsb size to 19.075v/lsb and 190.75a/lsb 6, 24, 26, 28, 32 ltc2991 2991fd for more information www.linear.com/ltc2991
32 ? linear technology corporation 2011 lt 0314 rev d ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax : (408) 434-0507 www.linear.com/ltc2991 r ela t e d p ar t s typical a pplica t ion part number description comments ltc2990 quad i 2 c temperature, voltage and current monitor remote and internal temperatures, 14-bit voltages and current, internal 10ppm/c reference ltc2997 remote/internal temperature sensor temperature to voltage with integrated 1.8v voltage reference, 1c accuracy ltc6102/ltc6102hv precision zero drift current sense amplifier 5v to 100v, 105v absolute maximum (ltc6102hv) ltc1392 micropower temperature, power supply and differential voltage monitor complete ambient temperature sensor onboard ltc2970 dual i 2 c power supply monitor and margining controller integrated reference and on-chip temperature sensor sequence, trim, margin and supervise eight power supplies l tc2977 octal pmbus power supply manager with eeprom integrated reference and on-chip t emperature sensor and fault logging ltc2945 high voltage i 2 c power monitor 0v to 80v range, 12-bit voltage and current. measurement with 0.75% tue i 2 c interface calculates 24-bit power value, stores minimum and maximum values l tc2487 16-bit 2-, 4-channel delta sigma adc with pga, easy drive? and i 2 c interface internal temperature sensor lm134 constant current source and temperature sensor can be used as linear temperature sensor parasitic resistance voltage and current monitoring with temperature compensation v cc v1 2.1k 2.1k ltc2991 inductor with r parasitic r parasitic ~ 4000ppm/c i load buck regulator 2-wire i 2 c interface 5v gnd thermal coupling control register 0x06: 0xa1: t ambient reg 1a, 1b: 0.0625c/lsb v load reg 0a, 0b: 305v/lsb i load reg 0c, 0d: 190.75a/lsb t rparasitic reg 1a, 1b: 0.0625c/lsb v cc reg 1c, 1d: 2.5v + 305.18v/lsb quiet node switching waveform mmbt3904 voltage, current and temperature configuration sda scl adr0 adr1 adr2 v3 v4 v2 2991 ta12 t ambient 1f 1f 1f other apps v5 to v8 4 1f 5v ltc2991 2991fd for more information www.linear.com/ltc2991

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