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Table Of Contents

LTC2991

2991fd

For more information www.linear.com/LTC2991

Typical applicaTion

FeaTures DescripTion

Octal I

C Voltage, Current,

and Temperature Monitor

The LT C

2991 is used to monitor system temperatures,

voltages and currents. Through the I

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

. 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 1°C temperature accuracy

or any combination of the three.

Temperature Total Unadjusted Error

applicaTions

Measures Voltage, Current, Temperature

Measures Four Remote Diode Temperatures

0.7°C (Typ) Accuracy, 0.06°C Resolution

1°C (Typ) Internal Temperature Sensor

Series Resistance Cancellation

14-Bit ADC Measures Voltage/Current

PWM Temperature Output

3V to 5.5V Supply Operating Voltage

Eight Selectable Addresses

Internal 10ppm/°C Voltage Reference

V1 to V8 Inputs ESD Rated to 6kV HBM

16-Lead MSOP Package

Temperature Measurement

Supply Voltage Monitoring

Current Measurement

Remote Data Acquisition

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.

2-WIRE

C INTERFACE

LTC2991

AMBIENT

SENSE

3.3V

1.2V

2.5V

GND

SDA

SCL

ADR0

ADR1

ADR2

3.3V I/O

2.5V I/O

1.2V CORE

FPGA

TEMPERATURE

BOARD

TEMPERATURE

V3 V4

PWM TO FAN

2991 TA01a

AMBIENT

(°C)

–50

ERROR

(°C)

0.25

0.50

0.75

25 50 75 100 125

2991 TA01b

–0.50

–0.25

–25 0 150

–0.75

–1.00

1.00

REMOTE

INTERNAL

Summary of content (32 pages)

PAGE 1
LTC2991 Octal I2C Voltage, Current, and Temperature Monitor Features n n n n n n n n n n n n Description Measures Voltage, Current, Temperature Measures Four Remote Diode Temperatures 0.7°C (Typ) Accuracy, 0.06°C Resolution 1°C (Typ) Internal Temperature Sensor Series Resistance Cancellation 14-Bit ADC Measures Voltage/Current PWM Temperature Output 3V to 5.
PAGE 2
LTC2991 Absolute Maximum Ratings Pin Configuration (Note 1) Supply Voltage (VCC)................................. –0.3V to 6.0V Input Voltages V1, V2, V3, V4, V5, V6, V7, V8, SCL, ADR0, ADR1, ADR2...............–0.3V to (VCC + 0.3V) Output Voltage PWM.....................–0.3V to (VCC + 0.3V) Output Voltage SDA...................................... –0.3V to 6V Operating Temperature Range LTC2991C................................................. 0°C to 70°C LTC2991I........................................
PAGE 3
LTC2991 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C, VCC = 3.3V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN VDIFF(CMR) Differential Voltage Common Mode Range VLSB(DIFF) Differential Voltage LSB Weight 19.075 µV VLSB(SINGLE_ENDED) Single-Ended Voltage LSB Weight 305.18 µV VLSB(TEMP) Temperature LSB Weight Celsius or Kelvin 0.
PAGE 4
LTC2991 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C, VCC = 3.3V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS I2C Timing (Note 2) fSCL(MAX) Maximum SCL Clock Frequency 400 kHz tLOW Minimum SCL Low Period 1.3 µs tHIGH Minimum SCL High Period 600 ns tBUF(MIN) Minimum Bus Free Time Between Stop/Start Condition 1.
PAGE 5
LTC2991 Typical Performance Characteristics Shutdown Current vs Temperature 3.5 TA = 25°C, VCC = 3.3V, unless otherwise noted. 4 1200 VCC = 5V MEASUREMENT DELAY VARIATION (%) VCC = 5V 3.0 1150 2.5 1100 2.0 ICC (µA) ICC (µA) Measurement Delay Variation vs T Normalized to 3.3V, 25°C Supply Current vs Temperature 1.5 1050 VCC = 3.3V 1.0 VCC = 3.3V 1000 0.5 0 –50 –25 0 25 50 75 TAMB (°C) 950 –50 –25 100 125 150 0 25 50 75 TAMB (°C) 2991 G01 3 VCC = 5V 2 1 VCC = 3.
PAGE 6
LTC2991 Typical Performance Characteristics Single-Ended Noise Single-Ended Transfer Function 4800 READINGS 3500 LTC2991 VALUE (V) COUNTS 1.0 5 3000 2500 2000 1500 1000 VCC = 5V 4 0.5 VCC = 3.3V 3 2 1 –3 –2 2 1 0 LSBs (305.18µV/LSB) –1 3 –1 VCC = 5V –1 –0 1 3 2 VX (V) 5 4 –1.0 6 0 1 2 3 VX (V) 4 2991 G11 LTC2991 Differential Noise Differential INL 2 0.4 800 READINGS 5 2991 G12 Differential Transfer Function 0.3 400 1 0.2 300 200 0.
PAGE 7
LTC2991 Typical Performance Characteristics Digital Filter Step Response TA = 25°C, VCC = 3.3V, unless otherwise noted. TERROR vs CPARALLEL TERROR vs RSERIES 100 1.2 100 90 1.0 70 0.8 TERROR (°C) 10 TERROR (°C) % FULL-SCALE 80 60 50 40 0.4 1 30 0.6 20 0.2 10 0 0 50 100 150 200 ITERATION 2991 G18 0.1 0 1000 2000 3000 RSERIES (Ω) 4000 5000 2991 G19 0 1 10 100 1k 10k CPARALLEL (pF) 100k 1000k 2991 G20 2991fd For more information www.linear.
PAGE 8
LTC2991 Pin Functions 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 VCC, ±300mV differential. When configured for remote diode temperature, this pin will source a current. V2 (Pin 2): Second Monitor Input. This pin can be configured as a single-ended input (0V to 4.
PAGE 9
LTC2991 Functional Diagram VCC –+ VOLTAGE MONITORING –+ + – POWER MONITORING 1 3 4 5 RL 6 7 REMOTE DIODE SENSORS VCC VCC VCC VCC 16 MODE 2 RSENSE VCC 8 GND 9 V1 ADR2 V2 CONTROL LOGIC V3 ADR1 I2C ADC V4 ADR0 SCL V5 MUX V6 SDA V7 15 14 13 11 10 UV REFERENCE V8 INTERNAL SENSOR UNDERVOLTAGE DETECTOR VCC PWM PULSE WIDTH DETECTOR 12 2991 FD Timing Diagram SDAI/SDAO tSU, DAT tHD, DATO, tHD, DATI tSU, STA tSP tHD, STA tSP tBUF tSU, STO 2991 TD SCL tHD, STA START CON
PAGE 10
LTC2991 Operation The LTC2991 monitors voltage, current, internal and remote temperatures. It can be configured through an I2C interface 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.
PAGE 11
LTC2991 Applications Information The basic LTC2991 application circuit is shown in Figure 1. 5V 3.3V 2.5V I/O RSENSE 1.8V VCC V1 V2 SCL ADR0 V3 FPGA V4 V5 LTC2991 FPGA TEMPERATURE V6 T= ADR1 ADR2 V7 BOARD TEMPERATURE TAMBIENT V8 PWM GND TO FAN Figure 1. Power Up The VCC pin must exceed the undervoltage (UV) threshold 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.
PAGE 12
LTC2991 Applications Information Sampling Currents Compensated Kelvin temperature: TK _ COMP = ηCAL • TK _ MEAS η ACT (3) Compensated Celsius temperature: TC _ COMP = ηCAL ηACT (T C _ MEAS ISAMPLE = (VIN – 1.49V) • 0.17[µA/V] ) + 273.15 – 273.15 (4) A 16-bit unsigned number is capable of representing the ratio ηCAL/ηACT in a range of 0.00003 to 1.99997, by multiplying the fractional ratio by 215. The range of scaling encompasses every conceivable target sensor value.
PAGE 13
LTC2991 Applications Information 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 REXT_MAX = 0.300V/IMAX. For example, if you wanted to measure a current range of ±5A, the external shunt resistance would equal 0.300V/5A = 60mΩ.
PAGE 14
LTC2991 Applications Information changes in temperature using the approximate relationship of –2.1mV/°C of voltage dependence on temperature. With an LSB weight of 38.15µV and a diode temperature relationship of –2.1mV/°C this yields ~0.018 degree resolution. 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.
PAGE 15
LTC2991 Applications Information 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.
PAGE 16
LTC2991 Applications Information 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.
PAGE 17
LTC2991 Applications Information S ADDRESS W# A COMMAND A DATA A 1001 a2:a0 0 0 XXXXXb3:b0 0 b7:b0 0 FROM MASTER TO SLAVE FROM SLAVE TO MASTER A: ACKNOWLEDGE (LOW) A#: NOT ACKNOWLEDGE (HIGH) P R: READ BIT (HIGH) W#: WRITE BIT (LOW) S: START CONDITION P: STOP CONDITION 2991 F05 Figure 5. LTC2991 Serial Bus Write Byte Protocol S ADDRESS W# A COMMAND A DATA A DATA A 1001 a2:a0 0 0 XXXXXb3:b0 0 b7:b0 0 b7:b0 0 P 2991 F06 Figure 6.
PAGE 18
LTC2991 Applications Information Table 2. LTC2991 Register Address and Contents REGISTER ADDRESS* † REGISTER NAME READ/WRITE 00h STATUS LOW R 01h CH EN, STAT. HI, TRIGGER** R/W CHANNEL ENABLE , VCC, TINTERNAL Conv.
PAGE 19
LTC2991 Applications Information Table 3.
PAGE 20
LTC2991 Applications Information Table 6.
PAGE 21
LTC2991 Applications Information 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 I2C 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 13.
PAGE 22
LTC2991 Applications Information Table 16. Conversion Formats TEMPERATURE FORMATS FORMAT BINARY VALUE D[12:0] TEMPERATURE Temperature Internal, TR1 Through TR4 LSB = 0.0625 Degrees Celsius 0011111010000 125.0000 Celsius 0000110010001 25.0625 Celsius 0000110010000 25.0000 Celsius 1110110000000 –40.0000 Kelvin 1100011100010 398.1250 Kelvin 1000100010010 273.1250 Kelvin 0111010010010 233.1250 Kelvin 0010011010000 77.0000 Sign Binary Value D[13:0] Voltage 0 00000000000000 0.
PAGE 23
LTC2991 Typical Applications High Voltage/Current and Temperature Monitoring RSENSE = 1mΩ 1% ILOAD 0A TO 10A VIN 5V TO 105V RIN 20Ω 1% –INF +IN 0.1µF –INS – + V– V+ VREG OUT 200k 1% 4.75k 1% LTC6102HV ROUT 4.99k 1% 0.1µF 0.1µF 5V VCC 2C 2-WIRE I INTERFACE V1 V2 SDA SCL LTC2991 ADR0 ADR1 ADR2 GND MMBT3904 V3 V4 2991 TA02 V5 TO V8 4 OTHER APPS ALL CAPACITORS ±20% VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION: CONTROL REGISTER: 0x06 0xA0 REG 1A, 1B: 0.0625°C/LSB TAMBIENT REG 0A, 0B: 13.
PAGE 24
LTC2991 Typical Applications Computer Voltage and Temperature Monitoring 12V 5V 3.3V 0.1µF 10k 1% 30.1k 1% 10k 1% 10k 1% VCC V1 2C 2-WIRE I INTERFACE SDA SCL ADR0 ADR1 ADR2 V2 LTC2991 MICROPROCESSOR V3 V4 GND V5 TO V8 2991 TA03 4 OTHER APPS VOLTAGE AND TEMPERATURE CONFIGURATION CONTROL REGISTER: 0x06 0x0A REG 1A, 1B: 0.0625°C/LSB TAMBIENT V1(+5) REG 0A, 0B: 610µV/LSB V2(+12) REG 0C, 0D: 1.22mV/LSB REG 0E, 0F: 0.0625°C/LSB TPROCESSOR REG 1C, 1D: 2.5V + 305.
PAGE 25
LTC2991 Typical Applications Large Motor Protection/Regulation MOTOR CONTROL VOLTAGE 0V TO 40V 0A TO 10A 5V LOADPWR = I • V 0.01Ω 1W, 1% 71.5k 1% 71.5k 1% 10.2k 1% 10.2k 1% TAMBIENT 2-WIRE I2C INTERFACE VCC V1 V2 SDA SCL LTC2991 ADR0 ADR1 ADR2 MMBT3904 V3 V4 MOTOR TMOTOR GND V5 TO V8 2991 TA05 4 OTHER APPS VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION: CONTROL REGISTER 06: 0xA1 REG 1A, 1B: 0.0625°C/LSB TAMBIENT REG 0A, 0B: 2.44mV/LSB VMOTOR REG 0C, 0D: 15.54mA/LSB IMOTOR REG 0E, 0F: 0.
PAGE 26
LTC2991 Typical Applications Battery Monitoring CHARGING CURRENT BATTERY I AND V MONITOR 0.1Ω* 5V 2-WIRE I2C INTERFACE VCC V1 V2 MMBT3904 SDA V3 SCL LTC2991 ADR0 ADR1 V4 ADR2 GND V5 TO V8 ••• T(t) V(t) NiMH BATTERY 100% TBATT I(t) 100% 100% 2991 TA07 *IRC LRF3W01R015F 4 TAMBIENT + OTHER APPS VOLTAGE AND TEMPERATURE CONFIGURATION: CONTROL REGISTER: 0xA1 REG 1A, 1B: 0.0625°C/LSB TAMBIENT REG 0A, 0B: 305.18µV/LSB VBAT REG 0C, 0D: 190.75µA/LSB IBAT REG 0E, 0F: 0.
PAGE 27
LTC2991 Typical Applications Liquid Level Indicator 3.3V SENSOR HI* TAMBIENT 3.3V HEATER ENABLE VCC µC V1 SDA V2 SCL LTC2991 V3 ADR0 ADR1 V4 ADR2 GND V5 TO V8 4 SENSOR LO* SENSOR HI SENSOR LO ∆T = ~2.0°C pp, SENSOR HI ~0.2°C pp, SENSOR LO HEATER ENABLE 2 SECOND PULSE NDS351AN *HEATER: 75Ω 0.125W *SENSOR MMBT3904, DIODE CONNECTED OTHER APPS 2991 TA09 CONTROL REGISTER 0x06 = 0xAA REG 1A, 1B: 0.0625°C/LSB TAMBIENT REG 0A, 0B: 0.0625°C/LSB TDRY REG 0C, 0D: 0.0625°C/LSB TWET REG 1C, 1D: 2.5V + 305.
PAGE 28
LTC2991 Typical Applications Oven Control with Power Monitor VOLTAGE AND CURRENT (POWER) MONITOR 5V VCC V1 V2 SDA I SCL 2-WIRE ADR0 2C INTERFACE OTHER APPLICATIONS V3 LTC2991 ADR1 V4 VCC V5 OVEN TSET 70°C V6 ADR2 V7 TAMBIENT HEATER V8 GND TEMPERATURE SENSOR PWM VCC 5V 100k + VOLTAGE, CURRENT, TEMPERATURE AND PWM CONFIGURATION: CONTROL REGISTER 0x06: 0x01 0x07: 0xA0 PWM, TINTERNAL, VCC REG: 0x08: 0x50 PWM REGISTER 0x09: 0x1B TAMBIENT VHEATER IHEATER TOVEN VCC REG 1A, 1B REG 0A, 0B RE
PAGE 29
LTC2991 Typical Applications QUAD Remote Temperature Sensing with Two Wire Pairs Using One LTC2991 Channel 3.
PAGE 30
LTC2991 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS MS Package Package 16-Lead MSOP 16-Lead Plastic Plastic MSOP (Reference LTC DWG # 05-08-1669 Rev Ø) (Reference LTC DWG # 05-08-1669 Rev Ø) 0.889 ± 0.127 (.035 ± .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 4.039 ± 0.102 (.159 ± .004) (NOTE 3) 0.50 (.0197) BSC 0.305 ± 0.038 (.0120 ± .0015) TYP RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) DETAIL “A” 3.00 ± 0.102 (.
PAGE 31
LTC2991 Revision History REV DATE DESCRIPTION A 10/11 Corrected axis label on Figure 9 PAGE NUMBER 14 Inserted new text in I2C Device Addressing section 15 Inserted new row in Table 1 17 Revised component values in Typical Application drawing TA05 25 Corrected diode voltage value 13 B 07/13 Corrected VDIFFERENTIAL and current equations 14 C 10/13 Corrected slave address in Figures 5, 6, 7 and 8 17 D 03/14 Corrected LSB size to 19.075µV/LSB and 190.
PAGE 32
LTC2991 Typical Application Parasitic Resistance Voltage and Current Monitoring with Temperature Compensation SWITCHING WAVEFORM INDUCTOR WITH RPARASITIC QUIET NODE ILOAD 5V 1µF BUCK REGULATOR 2.1k 2.1k 1µF 1µF THERMAL COUPLING 5V 1µF VCC 2-WIRE I2C INTERFACE V1 VOLTAGE, CURRENT AND TEMPERATURE CONFIGURATION CONTROL REGISTER 0x06: 0xA1: TAMBIENT REG 1A, 1B: 0.0625°C/LSB REG 0A, 0B: 305µV/LSB VLOAD REG 0C, 0D: 190.75µA/LSB ILOAD REG 1A, 1B: 0.0625°C/LSB TRPARASITIC REG 1C, 1D: 2.5V + 305.