LTC2941-1
1A I
2
C Battery Gas Gauge
with Internal Sense Resistor
FeaTures
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DescripTion
The LTC
®
2941-1 measures battery charge state in battery-
powered 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. The measured
charge is stored in internal registers. An SMBus/I
2
C in-
terface accesses and configures the device.
The LTC2941-1 features programmable high and low
thresholds for accumulated charge. If a threshold is ex-
ceeded, 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 Hot
Swap, 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
1% 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
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Low Power Handheld Products
Cellular Phones
MP3 Player
Cameras
GPS
Typical applicaTion
Total Charge Error vs Sense Current
CHARGER
SENSE
+
LTC2941-1
I
2
C/SMBus
TO HOST
AL/CC
SDA
SCL
GND
SENSE
–
LOAD
0.1µF
CHARGE ERROR (%)
1.00
0.75
0.50
0.25
0
V
SENSE+
= 3.6V
+
1-CELL
Li-Ion
29411 TA01a
–0.25
–0.50
–0.75
–1.00
1
10
100
|I
SENSE
| (mA)
1000
29411 TA01b
29411f
LTC2941-1
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
LTC2941-1C ............................................. 0°C to 70°C
LTC2941-1I .......................................... –40°C to 85°C
Storage Temperature Range..................... –65°C to 150°
(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 8)
EXPOSED PAD (PIN 7): DO NOT CONNECT
orDer inFormaTion
Lead Free Finish
TAPE AND REEL (MINI)
LTC2941IDCB-1#TRMPBF
TAPE AND REEL
LTC2941IDCB-1#TRPBF
PART MARKING*
LFKP
LFKP
PACKAGE DESCRIPTION
6-Lead (2mm
×
3mm) Plastic DFN
TEMPERATURE RANGE
0°C to 70°C
–40°C to 85°C
LTC2941CDCB-1#TRMPBF LTC2941CDCB-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/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Power Requirements
V
SENSE+
Supply Voltage
2.7
5.5
V
I
SUPPLY
Supply Current (Note 3)
Device On
70
100
µA
l
120
µA
l
Shutdown
2.5
µA
Shutdown, V
SENSE+
≤ 4.2V
1
µA
l
V
UVLO
Undervoltage Lockout Threshold
V
SENSE+
Falling
2.5
2.6
2.7
V
Coulomb Counter
l
I
SENSE–
Sense Current
±1
A
R
SENSE
Internal Sense Resistance
50
mΩ
R
PP
Pin-to-Pin Resistance from SENSE
+
to (Note 7)
50
74
100
mΩ
–
SENSE
Charge LSB (Note 4)
Prescaler M = 128 (Default)
0.085
mAh
q
LSB
TCE
Total Charge Error (Note 5)
0.2A ≤ |I
SENSE
| ≤ 1A DC
±1
%
0.2A ≤ |I
SENSE
| ≤ 1A DC, 0°C to 70°C
0.02A ≤ |I
SENSE
| ≤ 1A DC (Note 7)
V
bat
Alert
V
bat
Alert Threshold
V
SENSE–
Falling, B[7:6] = 01, I
SENSE–
= 0A
V
SENSE–
Falling, B[7:6] = 10, I
SENSE–
= 0A
V
SENSE–
Falling, B[7:6] = 11, I
SENSE–
= 0A
l
l
l
l
elecTrical characTerisTics
±1.8
±2.8
2.75
2.85
2.95
2.8
2.9
3
2.85
2.95
3.05
%
%
V
V
V
29411f
LTC2941-1
elecTrical characTerisTics
SYMBOL
PARAMETER
Digital Inputs and Digital Outputs
V
ITH
Logic Input Threshold,
AL/CC,
SCL,
SDA
Low Level Output Voltage,
AL/CC,
SDA
V
OL
I
IN
Input Leakage,
AL/CC,
SCL, SDA
C
IN
Input Capacitance,
AL/CC,
SCL, SDA
t
PCC
Minimum Charge Complete (CC) Pulse
Width
I
2
C Timing Characteristics
f
SCL(MAX)
Maximum SCL Clock Frequency
t
BUF(MIN)
Bus Free Time Between Stop/Start
t
SU,STA(MIN)
Minimum Repeated Start Setup Time
t
HD,STA(MIN)
Minimum Hold Time (Repeated)
Start Condition
t
SU,STO(MIN)
Minimum Setup Time for Stop
Condition
t
SU,DAT(MIN)
Minimum Data Setup Time Input
t
HD,DATI(MIN)
Minimum Data Hold Time Input
t
HD,DATO
Data Hold Time Output
t
of
Data Output Fall Time
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. (Note 2)
CONDITIONS
MIN
l
0.3 • V
SENSE+
TYP
MAX
0.7 • V
SENSE+
0.4
1
10
1
UNITS
V
V
µA
pF
µs
I = 3mA
V
IN
= V
SENSE+
/2
(Note 7)
l
l
l
l
l
l
l
l
l
l
400
900
1.3
600
600
600
100
0
0.9
300
kHz
µs
ns
ns
ns
ns
µs
µs
ns
(Notes 6, 7)
0.3
l
20 + 0.1 • C
B
l
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
registers (C,D) depends on the setting of the internal pre-scaling factor M.
It is calculated by:
M
q
LSB
=
0.085mAh •
128
See Choosing Coulomb Counter Prescaler M section for more information.
1mAh = 3.6A • s = 3.6C (Coulomb), 0.085mAh = 306mC.
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:
C
B
= capacitance of one bus line in pF (10pF ≤ C
B
≤ 400pF).
Note 7:
Guaranteed by design, not subject to test.
Note 8:
Value decreases if exposed pad is soldered to large copper area.
See Power Dissipation section for more information.
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
29411 F01
SCL
t
HD, STA
START
CONDITION
REPEATED START
CONDITION
STOP
CONDITION
START
CONDITION
Figure 1. Definition of Timing on I
2
C Bus
29411f
LTC2941-1
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
29411 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
–1.00
|I
SENSE
| = 1A
|I
SENSE
| = 200mA
4.5
4
V
SENSE+
(V)
5
5.5
–1.00
–50
|I
SENSE
| = 200mA
–25
0
50
25
TEMPERATURE (°C)
75
100
24911 G03
29411 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
0
–0.5
1.5
–1.0
1.0
∆R/R
O
(%)
–1.5
–2.0
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
SENSE+
(V)
5.5
6.0
–2.5
–3.0
Sense Resistor Stability
ACCELERATED LOAD LIFE TEST
DATA SCALED TO T
AMB
= 85°C,
I
SENSE
= 1A CONDITIONS
I
SUPPLY
(µA)
3.0
3.5
4.0 4.5
5.0
V
SENSE+
(V)
5.5
6.0
0
10
20
30
kHOURS
40
50
29411 G06
29411 G04
29411 G05
29411f
LTC2941-1
pin FuncTions
SENSE
+
(Pin 1):
Positive Current Sense Input and Power
Supply. Connect to the load and battery charger output.
V
SENSE+
operating range is 2.7V to 5.5V.
GND (Pin 2):
Device Ground. Connect directly to the nega-
tive battery terminal.
SCL (Pin 3):
Serial Bus Clock Input.
SDA (Pin 4):
Serial Bus Data Input and Output.
AL/CC
(Pin 5):
Alert Output or Charge Complete Input.
Configured either as an SMBus alert output or charge
complete input by control register bits B[2:1]. At power-up,
the pin defaults to alert mode conforming to the SMBus
alert response protocol. It behaves as an open-drain logic
output that pulls to GND when a value in the threshold
registers is exceeded.
When configured as a charge complete input, a high level
at CC sets the value of the accumulated charge (registers
C, D) to FFFFh. Coulomb counting starts when the input
returns to low level.
SENSE
–
(Pin 6):
Negative Current Sense Input. Connect
SENSE
–
to the positive battery terminal. Current from/into
this pin must not exceed 1A in normal operation.
Exposed Pad (Pin 7):
Do Not Connect. Soldering the
exposed pad to adequate electrically isolated copper area
is recommended for best thermal performance.
29411f
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