19-4637; 5/09
DS2786
Stand-Alone OCV-Based
Fuel Gauge
www.maxim-ic.com
GENERAL DESCRIPTION
FEATURES
The DS2786 estimates available capacity for
rechargeable Li-Ion and Li-Ion Polymer batteries
based on the cell voltage in the open-circuit state
following a relaxation 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 discharging,
which preclude OCV measurements, the DS2786
uses coulomb counting as a secondary means of
estimating relative capacity.
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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
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1.22mV LSB, 0V to 4.5V Input Range
11-Bit Bidirectional Current Measurement:
25V LSB, ±51.2mV Dynamic Range
1.67mA LSB, ±3.4A (RSNS = 15m)
Current Accumulation Measurement
Resolution:
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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.
±204.8mVh Range
±13.65Ah (RSNS = 15m)
Internal Temperature Measurement:
0.125°C LSB, ±3°C Accuracy
Two 11-Bit Aux Input Voltage Measurements:
±8 LSB Accuracy, Ratiometric Inputs
Eliminate Supply Accuracy Issues
VOUT Pin Drives Resistive Dividers, Reduces
Current Consumption
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The DS2786 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 I2C interface.
Temperature data is available from an on-die sensor.
Resistance measurements of a pack identification
resistor and pack thermistor are supported by
ratiometric measurements on two auxiliary inputs.
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2-Wire Interface
Low Power Consumption:
Active Current: 50A typ, 80A max
Sleep Current: 1A typ, 3A max
APPLICATIONS
ORDERING INFORMATION
3G Multimedia Wireless Handsets
Digital Still Cameras
PART
TEMP RANGE PIN-PACKAGE
DS2786G+
-20ºC to +70ºC 10 TDFN-EP*
-20ºC to +70ºC 10 TDFN-EP*
Digital Audio (MP3) Players
DS2786G+T&R
+Denotes a lead(Pb)-free/RoHS-compliant package.
T&R = Tape and reel.
TYPICAL OPERATING CIRCUIT
*EP = Exposed pad.
PIN CONFIGURATION
3mm x 3mm TDFN-10
Top View
Commands, Registers, and Modes are capitalized for clarity.
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