19-5223; Rev 1; 4/10
Stand-Alone OCV-Based Fuel Gauge
General Description
The DS2786B estimates available capacity for recharge-
able Li-ion (Li+) and Li+ polymer batteries based on the
cell voltage in the open-circuit state following a relax-
ation period. The open-circuit voltage (OCV) is used to
determine relative cell capacity based on a lookup table
stored in the IC. This capability makes accurate capacity
information available immediately after a battery pack is
inserted. During periods of moderate to high rate dis-
charging, which preclude OCV measurements, the
DS2786B uses coulomb counting as a secondary
means of estimating relative capacity.
Remaining capacity is reported in percent, along with
cell voltage, current, and temperature information. Cell
characteristics and application parameters used in the
calculations are stored in on-chip EEPROM.
The DS2786B is intended for use on the host side of
portable devices, though it can also be mounted within a
battery pack. Measurement and estimated capacity data
are accessed through an I
2
C interface. Temperature
data is available from an on-die sensor. Resistance mea-
surements of a pack identification resistor and pack ther-
mistor are supported by ratiometric measurements on
two auxiliary inputs.
The DS2786B comes in a 10-pin, lead-free, TDFN 3mm
x 3mm package with an exposed pad (EP).
Features
♦
Relative Capacity Calculated from Combination
Coulomb Counter and Open-Circuit Cell Voltage
(OCV) Battery Model
♦
Accurate Warning of Low-Battery Conditions
Even on First Cycle (No Learn Cycle Needed)
♦
12-Bit Battery Voltage Measurement
±10mV Accuracy
1.22mV LSB, 0V to 4.5V Input Range
♦
11-Bit Bidirectional Current Measurement
25µV LSB, ±51.2mV Dynamic Range
1.67mA LSB, ±3.4A (R
SNS
= 15mΩ)
♦
Current Accumulation Measurement Resolution
±204.8mVh Range
±13.65Ah (R
SNS
= 15mΩ)
♦
Internal Temperature Measurement
0.125°C LSB, ±3°C Accuracy
♦
Two 11-Bit Auxiliary Input-Voltage Measurements
±8 LSB Accuracy, Ratiometric Inputs Eliminate
Supply Accuracy Issues
♦
V
OUT
Pin Drives Resistive Dividers, Reduces
Current Consumption
♦
2-Wire Interface
♦
Low Power Consumption
Active Current: 50µA (typ), 80µA (max)
Sleep Current: 1µA (typ), 3µA (max)
DS2786B
Applications
3G Multimedia Wireless Handsets
Digital Still Cameras
Digital Audio (MP3) Players
PART
DS2786BG+
Ordering Information
TEMP RANGE
-20°C to +70°C
PIN-PACKAGE
10 TDFN-EP*
DS2786BG+T&R
-20°C to +70°C
10 TDFN-EP*
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed pad.
T&R = Tape and reel.
Operating Diagram
V
OUT
V
IN
SYSTEM
μP
DS2786B
Li+
PROTECTION
CIRCUIT
THERMISTOR
PACKID
AIN0
AIN1
V
SS
SDA
SCL
SNS
I
2
C
INTERFACE
R
SNS
(EEPROM PROGRAMMING TEST POINT NOT SHOWN)
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
Stand-Alone OCV-Based Fuel Gauge
DS2786B
ABSOLUTE MAXIMUM RATINGS
Voltage on All Pins Except V
PROG
Relative to V
SS
...-0.3V to +6V
Voltage on V
PROG
Relative to V
SS
..........................-0.3V to +18V
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-55°C to +125°C
Lead Temperature (soldering, 10s) .................................+300°C
Soldering Temperature (reflow) .......................................+260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
RECOMMENDED DC OPERATING PROCEDURE
(2.5V
≤
V
DD
≤
4.5V, T
A
= -20°C to +70°C.)
PARAMETER
Supply Voltage
Data I/O Pins
Programming Pin
V
IN
, AIN0, AIN1 Pin
SYMBOL
V
DD
SCL, SDA
V
PROG
V
IN
, AIN0,
AIN1
(Note 1)
(Note 1)
(Note 1)
(Note 1)
CONDITIONS
MIN
+2.5
-0.3
-0.3
-0.3
TYP
MAX
+4.5
+4.5
+15.5
V
DD
+
0.3
UNITS
V
V
V
V
DC ELECTRICAL CHARACTERISTICS
(2.5V
≤
V
DD
≤
4.5V, T
A
= -20°C to +70°C, unless otherwise noted.)
PARAMETER
Active Current
Sleep-Mode Current
Current-Measurement Resolution
Current-Measurement
Full-Scale Magnitude
Current-Measurement
Offset Error
Current-Measurement Gain Error
SYMBOL
I
ACTIVE
I
SLEEP
I
LSB
I
FS
I
OERR
I
GERR
V
DD
= 3.6V at +25°C
Timebase Accuracy
t
ERR
T
A
= 0°C to +70°C
T
A
= -20°C to +70°C
Voltage Error
Input Resistance V
IN
, AIN0, AIN1
AIN0, AIN1 Error
V
OUT
Output Drive
V
OUT
Precharge Time
Temperature Error
t
PRE
T
ERR
I
O
= 1mA
13.2
-3
V
GERR
R
IN
V
DD
= V
IN
= 3.6V, T
A
= 0°C to +50°C
T
A
= -20°C to +70°C
(Note 1)
(Note 2)
-50
-1.5
-1
-2
-3
-10
-20
15
-8
V
DD
-
0.5
13.7
14.2
+3
+8
V
DD
= 2.0V, SCL, SDA = V
SS
SCL, SDA = V
SS
CONDITIONS
MIN
TYP
50
0.3
1
25
±51.2
+50
+1.5
+1
+2
+3
+10
+20
mV
M
LSB
V
ms
°C
%
MAX
75
1.0
3
UNITS
μA
μA
μV
mV
μV
% of
reading
2
_______________________________________________________________________________________
Stand-Alone OCV-Based Fuel Gauge
DC ELECTRICAL CHARACTERISTICS (continued)
(2.5V
≤
V
DD
≤
4.5V, T
A
= -20°C to +70°C, unless otherwise noted.)
PARAMETER
Input Logic-High: SCL, SDA
Input Logic-Low: SCL, SDA
Output Logic-Low: SDA
Pulldown Current: SCL, SDA
V
PROG
Pulldown
Input Capacitance: SCL, SDA
Bus Low Timeout
EEPROM Programming Voltage
EEPROM Programming Current
EEPROM Programming Time
EEPROM Copy Endurance
SYMBOL
V
IH
V
IL
V
OL
I
PD
R
VPROG
C
BUS
t
SLEEP
V
PROG
I
PROG
t
PROG
3.1
100
(Note 3)
1.5
14
(Note 1)
(Note 1)
I
OL
= 4mA (Note 1)
V
DD
= 4.2V, V
PIN
= 0.4V
0.2
20
50
2.2
15
2
14
CONDITIONS
MIN
1.4
0.6
0.4
1.0
TYP
MAX
UNITS
V
V
V
μA
k
pF
s
V
mA
ms
Writes
DS2786B
ELECTRICAL CHARACTERISTICS: 2-WIRE INTERFACE
(2.5V
≤
V
DD
≤
4.5V, T
A
= -20°C to +70°C.)
PARAMETER
SCL Clock Frequency
Bus Free Time Between a STOP
and START Condition
Hold Time (Repeated)
START Condition
Low Period of SCL Clock
High Period of SCL Clock
Setup Time for a Repeated
START Condition
Data Hold Time
Data Setup Time
Rise Time of Both SDA and
SCL Signals
Fall Time of Both SDA and
SCL Signals
Setup Time for STOP Condition
Spike Pulse Widths Suppressed
by Input Filter
Capacitive Load for Each Bus Line
SCL, SDA Input Capacitance
SYMBOL
f
SCL
t
BUF
t
HD:STA
t
LOW
t
HIGH
t
SU:STA
t
HD:DAT
t
SU:DAT
t
R
t
F
t
SU:STO
t
SP
C
B
C
BIN
(Note 8)
(Note 9)
(Notes 6, 7)
(Note 6)
(Note 5)
(Note 4)
CONDITIONS
MIN
0
1.3
0.6
1.3
0.6
0.6
0
100
20 +
0.1C
B
20 +
0.1C
B
0.6
0
50
400
60
300
300
0.9
TYP
MAX
400
UNITS
kHz
μs
μs
μs
μs
μs
μs
ns
ns
ns
μs
ns
pF
pF
Note 1:
All voltages are referenced to V
SS
.
Note 2:
Offset specified after autocalibration cycle and Current Offset Bias Register = 00h.
Note 3:
The DS2786B enters the sleep mode 1.5s to 2.2s after (SCL < V
IL
)
and
(SDA < V
IL
).
Note 4:
Timing must be fast enough to prevent the DS2786B from entering sleep mode due to bus low for period > t
SLEEP
.
Note 5:
f
SCL
must meet the minimum clock low time plus the rise/fall times.
_______________________________________________________________________________________
3
Stand-Alone OCV-Based Fuel Gauge
DS2786B
ELECTRICAL CHARACTERISTICS: 2-WIRE INTERFACE (continued)
(2.5V
≤
V
DD
≤
4.5V, T
A
= -20°C to +70°C.)
Note 6:
The maximum t
HD:DAT
has only to be met if the device does not stretch the low period (t
LOW
) of the SCL signal.
Note 7:
This device internally provides a hold time of at least 100ns for the SDA signal (referred to the V
IHMIN
of the SCL signal) to
bridge the undefined region of the falling edge of SCL.
Note 8:
Filters on SDA and SCL suppress noise spikes at the input buffers and delay the sampling instant.
Note 9:
C
B
—total capacitance of one bus line in pF.
SDA
t
F
t
LOW
t
R
t
SU:DAT
t
F
t
HD:STA
t
SP
t
R
t
BUF
SCL
t
HD:STA
S
t
HD:DAT
t
SU:STA
Sr
t
SU:STO
P
S
Figure 1. 2-Wire Bus Timing Diagram
4
_______________________________________________________________________________________
Stand-Alone OCV-Based Fuel Gauge
Pin Configuration
TOP VIEW
DS2786B
AIN1
AIN0
SCL
SDA
SNS
1
2
3
10
9
8
V
DD
V
IN
V
OUT
V
PROG
V
SS
DS2786B
4
5
EP
7
6
TDFN
(3mm x 3mm)
Pin Description
PIN
1
2
3
4
5
6
7
8
9
10
—
NAME
AIN1
AIN0
SCL
SDA
SNS
V
SS
V
PROG
V
OUT
V
IN
V
DD
EP
Auxiliary Voltage Input Number 1
Auxiliary Voltage Input Number 0
Serial Clock Input. Input only 2-wire clock line. Connect this pin to the clock signal of the 2-wire
interface. This pin has a 0.2μA typical pulldown to sense disconnection.
Serial Data Input/Output. Open-drain 2-wire data line. Connect this pin to the clock signal of the 2-
wire interface. This pin has a 0.2μA typical pulldown to sense disconnection.
Current-Sense Input. Connect to the handset side of the sense resistor.
Device Ground. Connect to the battery side of the sense resistor.
EEPROM Programming Voltage Input. Connect to external supply for production programming.
Connect to V
SS
during normal operation.
Voltage Out. Supply for auxiliary input voltage measurement dividers. Connect to high side of
resistor-divider circuits.
Battery Voltage Input. The voltage of the cell pack is measured through this pin.
Power-Supply Input. 2.5V to 4.5V Input Range. Connect to system power through a decoupling
network.
Exposed Pad. Connect to V
SS
.
FUNCTION
_______________________________________________________________________________________
5
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