FEATURE SET

Primary (1st Level) Safety Features

Secondary (2nd Level) Safety Features

Charge Control Features

Gas Gauging

Authentication

Power Modes

bq20z75

The bq20z75 supports a wide range of battery and system protection features that can easily be configured. The

primary safety features include:

• Cell over/under voltage protection

• Charge and Discharge over current

• Short Circuit

• Charge and Discharge Over temperature

• AFE Watchdog

The secondary safety features of the bq20z75 can be used to indicate more serious faults via the SAFE (pin 7).

This pin can be used to blow an in-line fuse to permanently disable the battery pack from charging or

discharging. The secondary safety protection features include:

• Safety overvoltage

• Safety overcurrent in Charge and Discharge

• Safety overtemperature in Charge and Discharge

• Charge FET and 0 Volt Charge FET fault

• Discharge FET fault

• AFE communication fault

The bq20z75 charge control features include:

• Reports the appropriate charging current needed for constant current charging and the appropriate charging

voltage needed for constant voltage charging to a smart charger using SMBus broadcasts.

• Determines the chemical state of charge of each battery cell using Impedance Track™ and can reduce the

charge difference of the battery cells in fully charged state of the battery pack gradually using cell balancing

algorithm during charging. This prevents fully charged cells from overcharging and causing excessive

degradation and also increases the usable pack energy by preventing premature charge termination

• Supports pre-charging/zero-volt charging

• Support 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.

The bq20z75 uses the Impedance Track™ Technology to measure and calculate the available charge in battery

cells. The achievable accuracy is better than 1% error over the lifetime of the battery and there is no full charge

discharge learning cycle required.

See Theory and Implementation of Impedance Track Battery Fuel-Gauging Algorithm application note (SLUA364)

for further details.

The bq20z75 supports authentication by the host using SHA-1.

The bq20z75 supports 3 different power modes to reduce power consumption:

• In Normal Mode, the bq20z75 performs measurements, calculations, protection decisions and data updates in

1 second intervals. Between these intervals, the bq20z75 is in a reduced power stage.

Copyright © 2007–2008, Texas Instruments Incorporated

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Product Folder Link(s): bq20z75