BQ27425-G2_14 Datasheet, PDF (7/35 Pages) Texas Instruments – System-Side Impedance Track™ Fuel Gauge With Integrated Sense Resistor

bq27425-G2
www.ti.com
SLUSB23A – OCTOBER 2012 – REVISED FEBRUARY 2013
GENERAL DESCRIPTION
The bq27425 accurately predicts the battery capacity and other operational characteristics of a single Li-based
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, system 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 uses 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, that is,
RemainingCapacity( ).
NVM Data: italics, bold, and breaking spaces, that is, Design Capacity.
Register bits and flags: brackets and italics, that is, [TDA]
NVM Data bits: brackets, italics and bold, that is: [LED1]
Modes and states: ALL CAPITALS, that is, UNSEALED mode.
Copyright © 2012–2013, Texas Instruments Incorporated
Product Folder Links: bq27425-G2
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