BQ28400PWR Datasheet, PDF (13/24 Pages) Texas Instruments – Tablet PC and Netbook 2-Series Cell Li-Ion Battery Gas Gauge and Protection

bq28400
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FEATURE SET
SLUSA61A – OCTOBER 2010 – REVISED DECEMBER 2010
Safety Features
The bq28400 supports a wide range of battery and system protection features that can be configured. The
primary safety features include:
• Cell over/undervoltage protection
• Overcurrent during charge and discharge
• Short circuit
• Overtemperature during charge and discharge
• Device watchdog timer
The secondary safety features used to indicate more serious faults which can be used to control FET state or
blow an in-line fuse to permanently disable the battery pack include:
• Safety overvoltage
• Safety undervoltage
• Safety overcurrent in charge and discharge
• Safety overtemperature in charge and discharge
• Charge, pre-charge, and discharge FET fault
• Cell imbalance detection
Charge Control
The bq28400 charge control features include:
• Reporting charging current needed for constant current charging and charging voltage needed for constant
voltage charging to a smart charger using SMBus communications
• Supports pre-charging/zero-volt charging
• Supports fast charging
• Supports charge inhibit and charge suspend if battery pack temperature is out of temperature range
• Reports charging fault and also indicate charge status via charge and discharge alarms
Gas Gauging
The device uses advanced Compensated End-of-Discharge Voltage (CEDV) technology to measure and
calculate the available charge capacity in battery cells under system use and environmental conditions. The
device accumulates a measure of charge and discharge currents, then compensates the charge current
measurement for temperature and the state-of-charge of the battery. The bq28400 further estimates battery
self-discharge, adjusts the self-discharge estimation for temperature, and then updates internal status registers.
These internal registers are made available to the system host via the two-wire SMBus.
The internal general-purpose SRAM can be powered by the RBI pin of the bq28400 if power is lost. Typically, a
0.1-µF capacitor provides the necessary voltage to the SRAM array during inadvertent momentary power loss.
See the bq28400 technical reference guide for further details.
Lifetime Data Logging
The bq28400 maintains the highest temperature value from the last device reset.
Power Modes
The bq28400 supports three power modes to reduce power consumption:
• In Normal Mode, the device performs measurements, calculations, protection decisions, and data updates in
1-second intervals. Between these intervals, the device is in a reduced power stage.
• In Sleep Mode, the bq28400 performs measurements, calculations, protection decisions and data updates in
longer intervals. Between these intervals, the device is in a reduced power stage.
– A wake function operates so that an exit from Sleep mode occurs when current flow, detection of failure,
Copyright © 2010, Texas Instruments Incorporated
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