LTC2990
Quad I2C Voltage, Current
and Temperature Monitor
FEATURES
DESCRIPTION
Measures Voltage, Current and Temperature
nn Measures Two Remote Diode Temperatures
nn ±0.5°C Accuracy, 0.06°C Resolution (Typ)
nn ±1°C Internal Temperature Sensor (Typ)
nn 14-Bit ADC Measures Voltage/Current
nn 3V to 5.5V Supply Operating Voltage
nn Four Selectable Addresses
nn Internal 10ppm/°C Voltage Reference
nn 10-Lead MSOP Package
nn
The LTC®2990 is used to monitor system temperatures,
voltages and currents. Through the I2C serial interface,
the device can be configured to measure many combinations of internal temperature, remote temperature,
remote voltage, remote current and internal VCC. The
internal 10ppm/°C reference minimizes the number of
supporting components and area required. Selectable
address and configurable functionality give the LTC2990
flexibility to be incorporated in various systems needing
temperature, voltage or current data. The LTC2990 fits
well in systems needing sub-millivolt voltage resolution,
1% current measurement and 1°C temperature accuracy
or any combination of the three.
nn
All registered trademarks and trademarks are the property of their respective owners.
nn
APPLICATIONS
Temperature Measurement
Supply Voltage Monitoring
nn Current Measurement
nn Remote Data Acquisition
nn Environmental Monitoring
TYPICAL APPLICATION
Voltage, Current, Temperature Monitor
Temperature Total Unadjusted Error
RSENSE
2.5V
1.0
ILOAD
5V
SDA
SCL
ADR0
ADR1
V1
0.5
V2
V3
LTC2990
TREMOTE
TUE (°C)
VCC
TREMOTE
0
V4
2990 TA01a
GND
–0.5
TINTERNAL
MEASURES: TWO SUPPLY VOLTAGES,
SUPPLY CURRENT, INTERNAL AND
REMOTE TEMPERATURES
–1.0
–50 –25
0
50
25
TAMB (°C)
75
100
125
2990 TA01b
Rev. F
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1
LTC2990
ABSOLUTE MAXIMUM RATINGS
(Note 1)
PIN CONFIGURATION
Supply Voltage VCC.................................... –0.3V to 6.0V
Input Voltages V1, V2, V3, V4, SDA, SCL,
ADR1, ADR2...................................–0.3V to (VCC + 0.3V)
Operating Temperature Range
LTC2990C................................................. 0°C to 70°C
LTC2990I..............................................–40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec).................... 300°C
TOP VIEW
V1
V2
V3
V4
GND
10
9
8
7
6
1
2
3
4
5
VCC
ADR1
ADR0
SCL
SDA
MS PACKAGE
10-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 150°C/W
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2990CMS#PBF
LTC2990CMS#TRPBF
LTDSQ
10-Lead Plastic MSOP
0°C to 70°C
LTC2990IMS#PBF
LTC2990IMS#TRPBF
LTDSQ
10-Lead Plastic MSOP
–40°C to 85°C
LEAD BASED FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2990CMS
LTC2990CMS#TR
LTDSQ
10-Lead Plastic MSOP
0°C to 70°C
LTC2990IMS
LTC2990IMS#TR
LTDSQ
10-Lead Plastic MSOP
–40°C to 85°C
Consult the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Contact the factory for parts trimmed to ideality factors other than 1.004.
Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.
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
5.5
V
1.1
1.8
mA
General
VCC
Input Supply Range
l
ICC
Input Supply Current
During Conversion, I2C Inactive
ISD
Input Supply Current
Shutdown Mode, I2C Inactive
VCC(UVL)
Input Supply Undervoltage Lockout
l
l
2.9
1
5
µA
2.1
2.7
V
±0.5
±1
±3
±3.5
°C
°C
°C
l
±0.5
±1.5
°C
l
1.3
Measurement Accuracy
TINT(TUE)
Internal Temperature Total Unadjusted
Error
TRMT(TUE)
Remote Diode Temperature Total
Unadjusted Error
VCC(TUE)
VCC Voltage Total Unadjusted Error
l
±0.1
±0.25
%
Vn(TUE)
V1 Through V4 Total Unadjusted Error
l
±0.1
±0.25
%
VDIFF(TUE)
Differential Voltage Total Unadjusted Error –300mV ≤ VD ≤ 300mV
V1 – V2 or V3 – V4
l
±0.2
±0.75
%
VDIFF(MAX)
Maximum Differential Voltage
l
300
mV
2
TAMB = 0°C to 85°C
TAMB = –40°C to 0°C
η = 1.004 (Note 4)
–300
Rev. F
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LTC2990
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
VOFFSET_DIFF
Differential Offset
V1 = V2 = VCC, V3 = V4 = 0V
–12.5
0
12.5
LSB
VOFFSET_SE
Single-Ended Offset
V1, V2, V3, V4 = 0V
–6
0
6
LSB
VDIFF(CMR)
Differential Voltage Common Mode Range
VLSB(DIFF)
Differential Voltage LSB Weight
l
0
VCC
19.42
VLSB(SINGLE-ENDED) Single-Ended Voltage LSB Weight
VLSB(TEMP)
Temperature LSB Weight
Celsius or Kelvin
TNOISE
Temperature Noise
Celsius or Kelvin
TMEAS = 46ms (Note 2)
Res
Resolution (No Missing Codes)
(Note 2)
l
INL
Integral Nonlinearity
2.9V ≤ VCC ≤ 5.5V, VIN(CM) = 1.5V
(Note 2)
Single-Ended
Differential
l
UNITS
V
µV
305.18
µV
0.0625
Deg
0.2
0.05
°RMS
°/√Hz
14
Bits
–2
–2
2
2
LSB
LSB
CIN
V1 Through V4 Input Sampling
Capacitance
(Note 2)
0.35
pF
IIN(AVG)
V1 Through V4 Input Average Sampling
Current
0V ≤ VN ≤ 3V (Note 2)
0.6
µA
IDC_LEAK(VIN)
V1 Through V4 Input Leakage Current
0V ≤ VN ≤ VCC
l
–10
l
37
10
nA
46
55
ms
Measurement Delay
TINT , TR1, TR2
Per Configured Temperature Measurement (Note 2)
V1, V2, V3, V4
Single-Ended Voltage Measurement
(Note 2) Per Voltage, Two Minimum l
1.2
1.5
1.8
ms
V1 – V2, V3 – V4
Differential Voltage Measurement
(Note 2)
l
1.2
1.5
1.8
ms
VCC
VCC Measurement
(Note 2)
l
1.2
1.5
1.8
ms
Max Delay
Mode[4:0] = 11101, TINT , TR1, TR2, VCC
(Note 2)
l
167
ms
Remote Diode Mode
l
350
µA
VCC
V
0.3 • VCC
V
0.4
V
0.3 • VCC
V
V1, V3 Output (Remote Diode Mode Only)
IOUT
Output Current
260
VOUT
Output Voltage
l
VADR(L)
ADR0, ADR1 Input Low Threshold Voltage Falling
l
VADR(H)
ADR0, ADR1 Input High Threshold Voltage Rising
l
VOL1
SDA Low Level Maximum Voltage
IO = –3mA, VCC = 2.9V to 5.5V
l
VIL
Maximum Low Level Input Voltage
SDA and SCL Pins
l
VIH
Minimum High Level Input Voltage
SDA and SCL Pins
l
ISDAI,SCLI
SDA, SCL Input Current
0 < VSDA,SCL < VCC
l
±1
µA
IADR(MAX)
Maximum ADR0, ADR1 Input Current
ADR0 or ADR1 Tied to VCC or GND
l
±1
µA
0
I2C Interface
0.7 • VCC
V
0.7 • VCC
V
I2C Timing (Note 2)
fSCL(MAX)
Maximum SCL Clock Frequency
tLOW
Minimum SCL Low Period
400
1.3
kHz
µs
tHIGH
Minimum SCL High Period
600
ns
tBUF(MIN)
Minimum Bus Free Time Between Stop/
Start Condition
1.3
µs
tHD,STA(MIN)
Minimum Hold Time After (Repeated)
Start Condition
600
ns
Rev. F
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LTC2990
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
tSU,STA(MIN)
Minimum Repeated Start Condition Set-Up
Time
600
ns
tSU,STO(MIN)
Minimum Stop Condition Set-Up Time
600
ns
tHD,DATI(MIN)
Minimum Data Hold Time Input
tHD,DATO(MIN)
Minimum Data Hold Time Output
tSU,DAT(MIN)
Minimum Data Set-Up Time Input
tSP(MAX)
Maximum Suppressed Spike Pulse Width
CX
SCL, SDA Input Capacitance
300
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.
4
MIN
50
TYP
MAX
UNITS
0
ns
900
ns
100
ns
250
ns
10
pF
Note 4: Trimmed to an ideality factor of 1.004 at 25°C. Remote diode
temperature drift (TUE) verified at diode voltages corresponding to
the temperature extremes with the LTC2990 at 25°C. Remote diode
temperature drift (TUE) guaranteed by characterization over the LTC2990
operating temperature range.
Rev. F
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LTC2990
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, VCC = 3.3V unless otherwise noted
1200
3.5
4
MEASUREMENT DELAY VARIATION (%)
VCC = 5V
3.0
1150
VCC = 5V
2.5
1100
2.0
ICC (µA)
ICC (µA)
Measurement Delay Variation
vs T Normalized to 3.3V, 25°C
Supply Current vs Temperature
Shutdown 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)
3
VCC = 5V
2
1
–1
–50 –25
100 125 150
VCC TUE
Single-Ended VX TUE
0.5
VDIFF TUE (%)
0.05
VX TUE (%)
0.05
0
–0.05
25 50 75
TAMB (°C)
100 125 150
–0.10
–50 –25
0
25 50 75
TAMB (°C)
4
LTC2990 TRX ERROR (°C)
TINTERNAL ERROR (DEG)
1
0
–1
0
25 50 75
TAMB (°C)
100 125 150
2990 G07
25 50 75
TAMB (°C)
100 125 150
Remote Diode Error with LTC2990
at 25°C, 90°C
Remote Diode Error with LTC2990
at Same Temperature as Diode
1.00
0.75
LTC2990
AT 25°C
0.2
LTC2990
AT 90°C
0
0.50
0.25
–0.25
–0.2
0
–0.50
–0.4
–2
0
2990 G06
0.4
2
–3
–50 –25
–1.0
–50 –25
100 125 150
0.6
3
VCC = 3.3V
2990 G05
2990 G04
TINTERNAL Error
VCC = 5V
0
–0.5
LTC2990 TRX ERROR (DEG)
VCC TUE (%)
1.0
0
100 125 150
Differential Voltage TUE
0.10
–0.10
–50 –25
25 50 75
TAMB (°C)
2990 G03
0.10
–0.05
0
2990 G02
2990 G01
0
VCC = 3.3V
0
–0.6
–50 –25
–0.75
0
25 50 75 100 125 150
BATH TEMPERATURE (°C)
2990 G08
–1.00
–50 –25
0
25 50 75
TAMB (°C)
100 125 150
2990 G09
Rev. F
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5
LTC2990
TYPICAL PERFORMANCE CHARACTERISTICS
Single-Ended Noise
Single-Ended Transfer Function
4800 READINGS
3500
LTC2990 VALUE (V)
COUNTS
1.0
5
3000
2500
2000
1500
1000
VCC = 5V
4
0.5
VCC = 3.3V
3
2
1
0
VCC = 5V
–0.5
–3
–2
2
1
0
LSBs (305.18µV/LSB)
–1
–1
3
–1
–0
1
3
2
VX (V)
5
4
2990 G10
–1.0
6
0
1
2
3
VX (V)
4
Differential Transfer Function
Differential INL
2
0.4
800 READINGS
5
2990 G12
2990 G11
LTC2990 Differential Noise
500
VCC = 3.3V
0
500
0
Single-Ended INL
6
INL (LSBs)
4000
TA = 25°C, VCC = 3.3V unless otherwise noted
0.3
1
0.2
300
200
0.1
INL (LSBs)
LTC2990 V1-V2 (V)
COUNTS
400
0
–0.1
–1
–0.2
100
0
–0.3
0
–4
–3
0
1
–2 –1
LSBs (19.42µV/LSB)
2
–0.4
–0.4 –0.3 –0.2 –0.1 0 0.1
V1-V2 (V)
3
0.2
0.3
Remote Diode Noise
600
1000 READINGS
POR Thresholds vs Temperature
1000 READINGS
2.4
THRESHOLD (V)
COUNTS
COUNTS
400
300
200
100
1.8
VCC FALLING
1.6
–0.75 –0.5 –0.25
0 0.25
(°C)
0.5
0.75
0
1.2
–0.75 –0.5 –0.25
0 0.25
(°C)
0.5
2990 G16
6
2.0
1.4
100
0
VCC RISING
2.2
200
0.4
2.6
500
400
0.2
2990 G15
2990 G14
TINT Noise
300
0
–0.2
VIN (V)
2990 G13
500
–2
–0.4
0.4
0.75
2990 G17
1.0
–50 –25
0
25 50 75
TAMB (°C)
100 125 150
2990 G18
Rev. F
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LTC2990
PIN FUNCTIONS
V1 (Pin 1): First Monitor Input. This pin can be configured as a single-ended input or the positive input for a
differential or remote diode temperature measurement (in
combination with V2). 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 or the negative input for a
differential or remote diode temperature measurement (in
combination with V1). 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 or the positive input for a
differential or remote diode temperature measurement (in
combination with V4). 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 or the negative input for a
differential or remote diode temperature measurement (in
combination with V3). When configured for remote diode
temperature, this pin will have an internal termination,
while the measurement is active.
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 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 VCC 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 I2C
address. See Table 2.
ADR1 (Pin 9): Serial Bus Address Control Input. The
ADR1 pin is an address control bit for the device I2C
address. See Table 2.
VCC (Pin 10): Supply Voltage Input.
GND (Pin 5): Device Circuit Ground. Connect this pin to a
ground plane through a low impedance connection.
Rev. F
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LTC2990
FUNCTIONAL DIAGRAM
REMOTE
DIODE
SENSORS
VCC 10
MODE
1
2
3
4
V1
GND 5
V2
SCL
CONTROL
LOGIC
V3
MUX
SDA
ADC
I2C
V4
ADR0
ADR1
7
6
8
9
UV
INTERNAL
SENSOR
VCC
UNDERVOLTAGE
DETECTOR
REFERENCE
2990 FD
TIMING DIAGRAM
SDA
tSU, DAT
tHD, DATO,
tHD, DATI
tSU, STA
tSP
tHD, STA
tSP
tBUF
tSU, STO
2990 TD
SCL
tHD, STA
START
CONDITION
8
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Rev. F
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LTC2990
OPERATION
The LTC2990 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 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 fixed: TINTERNAL, V1, V2, V3, V4 then VCC. 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 appropriate data register for voltage and current measurements.
Current and temperature measurements, V1 – V2 or V3
– V4, are sampled differentially by the internal ADC. The
I2C interface supplies access to control, status and data
registers. The ADR1 and ADR0 pins select one of four
possible I2C addresses (see Table 2). The undervoltage
detector inhibits I2C 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. During temperature
measurements, 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 I2C serial interface. The serial interface provides access to control, status and data registers. I2C defines 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 2.
The I2C 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.
APPLICATIONS INFORMATION
Figure 1 is the basic LTC2990 application circuit.
2.5V
5V
RSENSE
15mΩ
ILOAD
0.1µF
2-WIRE
I2C
INTERFACE
VCC
V1
MMBT3904
V2
SDA
SCL LTC2990
ADR0
ADR1
GND
V3
The VCC pin must exceed the undervoltage (UV) threshold 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
470pF
V4
2990 F01
Figure 1.
Power Up
The LTC2990 can measure internal temperature and up
to two external diode or transistor sensors. During temperature conversion, current is sourced through either the
V1 or the V3 pin to forward bias the sensing diode. The
Rev. F
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9
LTC2990
APPLICATIONS INFORMATION
change in sensor voltage per degree temperature change
is 275µV/°C, so environmental noise must be kept to a
minimum. Recommended shielding and PCB trace considerations are illustrated in Figure 2.
The diode equation:
VBE = η •
⎛I ⎞
• ln ⎜ C ⎟
q
⎝ IS ⎠
k•T
(1)
can be solved for T, where T is Kelvin degrees, IS is a
process dependent factor on the order of 1E-13, η is the
diode ideality factor, k is Boltzmann’s constant and q is
the electron charge.
T=
VBE • q
⎛I ⎞
η • k •In ⎜ C ⎟
⎝ IS ⎠
(2)
The LTC2990 makes differential measurements of diode
voltage to calculate temperature. Proprietary techniques
allow for cancellation of error due to series resistance.
0.1µF
GND SHIELD
TRACE
LTC2990
470pF
NPN SENSOR
V1
V2
V3
V4
VCC
ADR1
ADR0
SCL
GND SDA
Table 1. Recommended Transistors to Be Used as Temperature
Sensors
MANUFACTURER
PART NUMBER
PACKAGE
Fairchild Semiconductor
MMBT3904
FMMT3904
SOT-23
SOT-23
Central Semiconductor
CMPT3904
CET3904E
SOT-23
SOT-883L
Diodes, Inc.
MMBT3904
SOT-23
MMBT3904LT1
SOT-23
NXP
MMBT3904
SOT-23
Infineon
MMBT3904
SOT-23
UMT3904
SC-70
On Semiconductor
Rohm
ideality factor of the diode 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 25°C, or 298K, a +1% accurate ideality
factor error yields a +2.98 degree error. At 85°C 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 sufficient
precision using 16-bit fixed-point math in a microprocessor or microcontroller.
Factory Ideality Calibration Value:
ηCAL = 1.004
2990 F02
Actual Sensor Ideality Value:
Figure 2. Recommended PCB Layout
ηACT
Ideality Factor Scaling
Compensated Kelvin Temperature:
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 processing limits device-to-device variation, making these
devices interchangeable (typically
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