FeaTures
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LTC2942-1
1A Battery Gas Gauge with
Internal Sense Resistor and
Temperature/Voltage
Measurement
DescripTion
The LTC
®
2942-1 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 an internal 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
∆Σ™
ADC. The three measured quantities (charge, voltage and
temperature) are stored in internal registers accessible via
the onboard SMBus/I
2
C interface.
The LTC2942-1 features programmable high and low
thresholds for all three measured quantities. If a pro-
grammed threshold is exceeded, the device communicates
an alert using either the SMBus alert protocol or by setting
a flag in the internal status register.
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
SMBus/I
2
C Interface
Integrated 50mΩ High Side Sense Resistor
±1A Sense Current Range
High Accuracy Analog Integration
ADC Measures Battery Voltage and Temperature
Integrated Temperature Sensor
1% Voltage and Charge Accuracy
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
n
n
n
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n
Low Power Handheld Products
Cellular Phones
MP3 Players
Cameras
GPS
Typical applicaTion
Total Charge Error vs Sense Current
1.00
CHARGER
SENSE
+
LTC2942-1
I
2
C/SMBus
TO HOST
AL/CC
SDA
SCL
GND
SENSE
–
V
SENSE+
= 3.6V
LOAD
0.1µF
CHARGE ERROR (%)
0.75
0.50
0.25
0
+
1-CELL
Li-Ion
29421 TA01a
–0.25
–0.50
–0.75
–1.00
1
10
100
|I
SENSE
| (mA)
1000
29421 TA01b
29421f
LTC2942-1
absoluTe maximum raTings
Supply Voltage (SENSE
+
) ............................. –0.3V to 6V
SCL, SDA,
AL/CC
......................................... –0.3V to 6V
Sense Current (into SENSE
–
) ....................................±2A
Operating Ambient Temperature Range
LTC2942-1C ............................................. 0°C to 70°C
LTC2942-1I .......................................... –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
= 160°C/W (Note 9)
EXPOSED PAD (PIN 7): DO NOT CONNECT
orDer inFormaTion
Lead Free Finish
TAPE AND REEL (MINI)
LTC2942IDCB-1#TRMPBF
TAPE AND REEL
LTC2942IDCB-1#TRPBF
PART MARKING*
LDYR
LDYR
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
LTC2942CDCB-1#TRMPBF LTC2942CDCB-1#TRPBF
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
l
TYP
MAX
5.5
UNITS
V
µA
µA
µA
µA
µA
µA
V
A
mΩ
mΩ
mAh
70
l
100
120
400
450
2.5
1
Battery Gas Gauge On, ADC Converting Voltage
Shutdown
Shutdown, V
SENSE+
≤ 4.2V
V
UVLO
I
SENSE–
R
SENSE
R
PP
q
LSB
TCE
Undervoltage Lockout Threshold
Sense Current
Internal Sense Resistance
Pin-to-Pin Resistance from
SENSE
+
to SENSE
–
Charge LSB (Note 4)
Total Charge Error (Note 5)
(Note 8)
Prescaler M = 128 (Default)
0.2A ≤ |I
SENSE–
| ≤ 1A DC
0.2A ≤ |I
SENSE–
| ≤ 1A DC, 0°C to 70°C
0.02A ≤ |I
SENSE–
| ≤ 1A DC (Note 8)
V
SENSE+
Falling
300
350
Battery Gas Gauge On, ADC Converting Temperature
l
l
l
2.5
2.6
2.7
±1
Coulomb Counter
l
50
50
74
0.085
±1
±1.8
l
100
%
%
%
29421f
±2.8
LTC2942-1
elecTrical characTerisTics
SYMBOL
PARAMETER
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
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
(Note 8)
(Note 6)
l
l
MIN
14
TYP
MAX
UNITS
Bits
Voltage Measurement ADC
6
366.2
1
1.3
1.3
±1
l
l
V
µV
%
%
%
LSB
LSB
ms
Bits
Gain Accuracy
Offset
Integral Nonlinearity
Conversion Time
Resolution (No Missing Code)
(Note 8)
(Note 10)
(Note 6)
V
SENSE+
≥ 2.8V (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
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
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)
I
2
C Timing Characteristics
f
SCL(MAX)
t
BUF(MIN)
l
l
l
l
l
l
400
900
1.3
600
600
600
100
kHz
µs
ns
ns
ns
ns
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 Setup Time Input
29421f
LTC2942-1
elecTrical characTerisTics
SYMBOL
t
HD,DATO
t
of
PARAMETER
Data Hold Time Output
Data Output Fall Time
(Notes 7, 8)
CONDITIONS
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
0.3
20 + 0.1 • C
B
TYP
MAX
0
0.9
300
UNITS
µs
µs
ns
t
HD,DATI(MIN)
Minimum Data Hold Time Input
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 setting of the internal prescaling factor M:
q
LSB
=
0.085mAh •
M
128
See Choosing Coulomb Counter Prescaler M section for more information.
1mAh = 3.6C (Coulombs).
Note 5:
Deviation of q
LSB
from its nominal value. Data is for a new device
and does not include long-term sense resistor aging. See the Internal
Sense Resistor section for more information.
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.
Note 9:
Value decreases if exposed pad is soldered to large copper area.
See Power Dissipation section for more information.
Note 10:
Use for scaling of temperature reading only. Do not use part
outside operating temperature range.
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
29421 F01
SCL
t
HD, STA
START
CONDITION
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Figure 1. Definition of Timing on I
2
C Bus
29421f
LTC2942-1
Typical perFormance characTerisTics
Total Charge Error
vs Sense Current
1.00
0.75
CHARGE ERROR (%)
CHARGE ERROR (%)
0.50
0.25
0
1.0
0.8
0.6
CHARGE ERROR (%)
0.4
0.2
0
–0.2
–0.4
–0.6
V
SENSE+
= 2.7V
V
SENSE+
= 4.2V
1
10
100
|I
SENSE
| (mA)
1000
29421 G01
Total Charge Error
vs Supply Voltage
1.00
0.75
0.50
0.25
0
–0.25
–0.50
–0.75
6
Total Charge Error vs Temperature
TEMPERATURE
COMPENSATION
TRIM DEVIATION
+50ppm/K
OPTIMUM
–50ppm/K
–0.25
–0.50
–0.75
–0.8
–1.0
2.5
3
3.5
4
V
SENSE
4.5
–1.00
|I
SENSE
| = 1A
|I
SENSE
| = 200mA
+
(V)
5
5.5
–1.00
–50
|I
SENSE
| = 200mA
–25
50
25
TEMPERATURE (°C)
0
75
100
24921 G03
29421 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
29421 G04
29421 G05
29421 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
–0.5
–1.0
∆R/R
O
(%)
–1.5
–2.0
–2.5
–3.0
Sense Resistor Stability
ACCELERATED LOAD LIFE TEST
DATA SCALED TO T
AMB
= 85°C,
I
SENSE
= 1A CONDITIONS
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
29421 G08
0
10
20
30
kHOURS
40
50
29421 G09
29421 G07
29421f
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