BQ27425-G1 Datasheet, PDF (7/32 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated Sense Resistor

bq27425-G1
www.ti.com
SLUSAI6 – NOVEMBER 2011
GENERAL DESCRIPTION
The bq27425 accurately predicts the battery capacity and other operational characteristics of a single LiCoO₂
rechargeable cell. It can be interrogated by a system processor to provide cell information, such as
state-of-charge (SOC).
Information is accessed through a series of commands, called Standard Commands. Further capabilities are
provided by the additional Extended Commands set. Both sets of commands, indicated by the general format
Command( ), are used to read and write information contained within the bq27425 control and status registers,
as well as its data locations. Commands are sent from system to gauge using the bq27425’s I²C serial
communications engine, and can be executed during application development, pack manufacture, or
end-equipment operation.
The key to the bq27425’s high-accuracy gas gauging prediction is Texas Instrument’s proprietary Impedance
Track™ algorithm. This algorithm uses cell measurements, characteristics, and properties to create
state-of-charge predictions that can achieve high accuracy across a wide variety of operating conditions and over
the lifetime of the battery.
The bq27425 measures charge/discharge activity by monitoring the voltage across a small-value integrated
sense resistor (10 mΩ typical) located between the system’s Vss and the battery’s PACK– terminal. When a cell
is attached to the bq27425, cell impedance is computed, based on cell current, cell open-circuit voltage (OCV),
and cell voltage under loading conditions.
The bq27425 utilizes an integrated temperature sensor for estimating cell temperature. Alternatively, the host
processor can provide temperature data for the bq27425.
To minimize power consumption, the bq27425 has several power modes: INITIALIZATION, NORMAL, SLEEP,
and HIBERNATE. The bq27425 passes automatically between these modes, depending upon the occurrence of
specific events, though a system processor can initiate some of these modes directly. More details can be found
in Section Power Modes.
NOTE
FORMATTING CONVENTIONS IN THIS DOCUMENT:
Commands: italics with parentheses and no breaking spaces, e.g.
RemainingCapacity( ).
NVM Data: italics, bold, and breaking spaces, e.g. Design Capacity.
Register bits and flags: brackets and italics, e.g. [TDA]
NVM Data bits: brackets, italics and bold, e.g: [LED1]
Modes and states: ALL CAPITALS, e.g. UNSEALED mode.
Copyright © 2011, Texas Instruments Incorporated
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