LTC2942
Battery Gas Gauge
with Temperature,
Voltage Measurement
FeaTures
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DescripTion
The LTC
®
2942 measures battery charge state, battery
voltage and chip temperature in handheld PC and portable
product applications. Its operating range is perfectly suited
for single-cell Li-Ion batteries. A precision coulomb counter
integrates current through a sense resistor between the
battery’s positive terminal and the load or charger. Battery
voltage and on-chip temperature are measured with an
internal 14-bit No Latency ∆∑™ ADC. The three measured
quantities (charge, voltage and temperature) are stored in
internal registers accessible via the onboard SMBus/I
2
C
interface.
The LTC2942 features programmable high and low thresh-
olds for all three measured quantities. If a programmed
threshold is exceeded, the device communicates an alert
using either the SMBus alert protocol or by setting a flag
in the internal status register.
The LTC2942 requires only a single low value sense resis-
tor to set the measured current range.
L,
LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
No Latency
∆Σ,
ThinSOT and Bat-Track are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Indicates Accumulated Battery Charge and
Discharge
High Accuracy Analog Integration
ADC Measures Battery Voltage and Temperature
Integrated Temperature Sensor
High Side Sense
1% Voltage and Charge Accuracy
±50mV Sense Voltage Range
SMBus/I
2
C Interface
Configurable Alert Output/Charge Complete Input
2.7V to 5.5V Operating Range
Quiescent Current Less than 100µA
Small 6-Pin 2mm × 3mm DFN package
applicaTions
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Low Power Handheld Products
Cellular Phones
MP3 Players
Cameras
GPS
Typical applicaTion
Total Charge Error vs
Differential Sense Voltage
2.0
CHARGER
SENSE
+
LTC2942
AL/CC
SDA
SENSE
–
SCL
GND
LOAD
0.1µF
R
SENSE
100m
1.5
CHARGE ERROR (%)
1.0
0.5
0
–0.5
–1.0
–1.5
–2.0
0.1
1
V
SENSE
(mV)
2942 TA01b
V
SENSE+
= 3.6V
I
2
C/SMBus
TO HOST
+
1-CELL
Li-Ion
2942 TA01a
10
100
2942fa
1
LTC2942
absoluTe maximum raTings
Supply Voltage (SENSE
+
) ............................. –0.3V to 6V
SCL, SDA,
AL/CC
......................................... –0.3V to 6V
SENSE
–
.................................. –0.3V to (V
SENSE+
+ 0.3V)
Operating Ambient Temperature Range
LTC2942C ................................................ 0°C to 70°C
LTC2942I.............................................. –40°C to 85°C
Storage Temperature Range................... –65°C to 150°C
(Notes 1, 2)
pin conFiguraTion
TOP VIEW
SENSE
+
1
GND 2
SCL 3
7
6 SENSE
–
5
AL/CC
4 SDA
DCB PACKAGE
6-LEAD (2mm
×
3mm) PLASTIC DFN
T
JMAX
= 150°C,
θ
JA
= 120°C/W
EXPOSED PAD (PIN 7), DO NOT CONNECT
orDer inFormaTion
Lead Free Finish
TAPE AND REEL (MINI)
LTC2942CDCB#TRMPBF
TAPE AND REEL
LTC2942CDCB#TRPBF
PART MARKING*
LDVN
PACKAGE DESCRIPTION
6-Lead (2mm × 3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
LTC2942IDCB#TRMPBF
LTC2942IDCB#TRPBF
LDVN
6-Lead (2mm × 3mm) Plastic DFN
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container.
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on 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/
elecTrical characTerisTics
SYMBOL
V
SENSE+
I
SUPPLY
PARAMETER
Supply Voltage
Supply Current (Note 3)
CONDITIONS
Power Requirements
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
MIN
2.7
Battery Gas Gauge On, ADC Sleep
Battery Gas Gauge On, ADC Converting Voltage
Shutdown
Shutdown, V
SENSE+
≤ 4.2V
l
l
TYP
MAX
5.5
UNITS
V
µA
µA
µA
µA
µA
V
mV
kΩ
70
300
350
100
350
420
2.5
1
Battery Gas Gauge On, ADC Converting Temperature
l
l
V
UVLO
V
SENSE
R
IDR
Undervoltage Lockout Threshold
Sense Voltage Differential Input
Range
Differential Input Resistance,
Across SENSE
+
and SENSE
–
(Note 8)
V
SENSE+
Falling
V
SENSE+
– V
SENSE–
l
2.5
2.6
2.7
±50
Coulomb Counter
l
400
2942fa
2
LTC2942
elecTrical characTerisTics
SYMBOL
q
LSB
TCE
PARAMETER
Charge LSB (Note 4)
Total Charge Error (Note 5)
CONDITIONS
Prescaler M = 128 (Default), R
SENSE
= 50mΩ
10mV ≤ |V
SENSE
| ≤ 50mV DC
10mV ≤ |V
SENSE
| ≤ 50mV DC, V
SENSE +
≤ 4.2V
1mV ≤ |V
SENSE
| < 50mV DC (Note 8)
Voltage Measurement ADC
Resolution (No Missing Codes)
V
FS
∆V
LSB
TUE
V
Gain
V
OS
INL
t
CONV
Full-Scale Voltage
Quantization Step of 14-Bit
Voltage ADC
Voltage Total Unadjusted Error
l
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
MIN
TYP
0.085
±1
±1.5
±3.5
14
6
366.2
1
1.3
1.3
±1
l
l
MAX
UNITS
mAh
%
%
%
Bits
V
µV
%
%
%
LSB
LSB
ms
Bits
(Note 8)
(Note 6)
l
l
Gain Accuracy
Offset
Integral Nonlinearity
Conversion Time
Resolution (No Missing Code)
(Note 8)
Extrapolated from Measurements at 5.5V and 2.7V
l
±10
±4
15
±1
Temperature Measurement ADC
10
l
T
FS
∆T
LSB
TUE
T
t
CONV
V
ITH
V
OL
I
IN
C
IN
t
PCC
Full-Scale Temperature
Quantization Step of 10-Bit
Temperature ADC
Temperature Total Unadjusted
Error
Conversion Time
Logic Input Threshold,
AL/CC,
SCL, SDA
Low Level Output Voltage,
AL/CC,
I = 3mA
SDA
Input Leakage,
AL/CC,
SCL, SDA
Input Capacitance,
AL/CC,
SCL,
SDA
Minimum Charge Complete (CC)
Pulse Width
Maximum SCL Clock Frequency
Bus Free Time Between STOP/
START
V
IN
= V
SENSE+
/2
(Note 8)
(Note 6)
V
SENSE+
≥ 2.8V (Note 8)
600
0.586
K
K
±5
±3
15
K
K
ms
V
V
µA
pF
µs
l
l
Digital Inputs and Digital Outputs
l
l
l
l
0.3 • V
SENSE+
0.7 • V
SENSE+
0.4
1
10
1
I
2
C Timing Characteristics
f
SCL(MAX)
t
BUF(MIN)
l
l
l
l
l
l
l
400
900
1.3
600
600
600
100
0
kHz
µs
ns
ns
ns
ns
µs
2942fa
t
SU,STA(MIN)
Minimum Repeated START
Set-Up Time
t
HD,STA(MIN)
Minimum Hold Time (Repeated)
START Condition
t
SU,STO(MIN)
Minimum Set-Up Time for STOP
Condition
t
SU,DAT(MIN)
Minimum Data Set-Up
Time Input
t
HD,DATI(MIN)
Minimum Data Hold Time Input
3
LTC2942
elecTrical characTerisTics
SYMBOL
t
HD,DATO
t
OF
PARAMETER
Data Hold Time Output
Data Output Fall Time
(Notes 7, 8)
CONDITIONS
l
l
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
MIN
0.3
20 + 0.1 • C
B
TYP
MAX
0.9
300
UNITS
µs
ns
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:
All currents into pins are positive, all voltages are referenced to
GND unless otherwise specified
Note 3:
I
SUPPLY
= I
SENSE+
+ I
SENSE–
Note 4:
The equivalent charge of an LSB in the accumulated charge
register depends on the value of R
SENSE
and the setting of the internal
prescaling factor M:
q
LSB
=
0.085mAh •
50mΩ M
•
R
SENSE
128
Note 5:
Deviation of q
LSB
from its nominal value.
Note 6:
The quantization step of the 14-bit ADC in voltage mode and
10-bit ADC in temperature mode is not to be mistaken with the LSB of the
combined 16-bit voltage registers (I, J) and 16-bit temperature registers
(M, N).
Note 7:
C
B
= Capacitance of one bus line in pF (10pF ≤ C
B
≤ 400pF). See
Voltage and Temperature Registers section for more information.
Note 8:
Guaranteed by design, not subject to test.
See Choosing R
SENSE
and Choosing Coulomb Counter Prescaler M section
for more information. 1mAh = 3.6C (coulombs).
Timing Diagram
t
of
SDA
t
SU, DAT
t
HD, DATO,
t
HD, DATI
t
SU, STA
t
HD, STA
t
SU, STO
t
BUF
2942 F01
SCL
t
HD, STA
START
CONDITION
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Figure 1. Definition of Timing on I
2
C Bus
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4
LTC2942
Typical perFormance characTerisTics
Total Charge Error vs Differential
Sense Voltage
3
2
CHARGE ERROR (%)
1
0
–1
–2
–3
0.1
CHARGE ERROR (%)
1.00
0.75
CHARGE ERROR (%)
0.50
0.25
0
Total Charge Error
vs Supply Voltage
1.00
0.75
0.50
0.25
0
–0.25
–0.50
–0.75
Total Charge Error vs Temperature
–0.25
–0.50
–0.75
–1.00
2.5
3.0
3.5
V
SENSE
= –50mV
V
SENSE
= –10mV
4.0 4.5
5.0
+
(V)
V
SENSE
5.5
6.0
V
SENSE+
= 2.7V
V
SENSE+
= 4.2V
1
V
SENSE
(mV)
2942 G01
10
100
–1.00
–50
V
SENSE
= –50mV
V
SENSE
= –10mV
–25
25
50
0
TEMPERATURE (°C)
75
100
2942 G03
2942 G02
Supply Current vs Supply Voltage
100
90
80
70
60
50
40
2.5
0
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
I
SHUTDOWN
(µA)
2.0
Shutdown Supply Current
vs Supply Voltage
10
8
TOTAL UNADJUSTED ERROR (mV)
1.5
6
4
2
0
–2
–4
–6
–8
–10
Voltage Measurement ADC
Total Unadjusted Error
T
A
= 85°C
I
SUPPLY
(µA)
1.0
T
A
= –45°C
0.5
T
A
= 25°C
T
A
= –40°C
T
A
= 85°C
2.5
3.0
3.5
4.0 4.5
5.0
+
(V)
V
SENSE
5.5
6.0
T
A
= 25°C
3.0
3.5
4.0 4.5
5.0
V
SENSE+
(V)
5.5
6.0
2.5
3.0
3.5
4.0 4.5
5.0
–
(V)
V
SENSE
5.5
6.0
2942 G04
2942 G05
2942 G06
Voltage Measurement ADC
Integral Nonlinearity
1.0
T
A
= 85°C
0.5
INL (V
LSB
)
TEMPERATURE ERROR (°C)
3
2
1
0
–1
–2
–1.0
2.5
Temperature Error vs Temperature
0
T
A
= –40°C
–0.5
T
A
= 25°C
3.0
3.5
4.0 4.5 5.0
V
SENSE–
(V)
5.5
6.0
–3
–50
–25
0
25
50
TEMPERATURE (°C)
75
100
2942 G08
2942 G07
2942fa
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