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FEATURE SET

Primary (1st Level) Safety Features

Secondary (2nd Level) Safety Features

Charge Control Features

Gas Gauging

bq20z90

SLUS778 – JULY 2007

The bq20z90 supports a wide range of battery and system protection features that can easily be configured. The

primary safety features include:

•

Battery cell over/under voltage protection

•

Battery pack over/under voltage protection

•

2 independent charge overcurrent protection

•

3 independent discharge overcurrent protection

•

Short circuit protection

•

Over temperature protection

•

AFE Watchdog

•

Host Watchdog

The secondary safety features of the bq20z90 can be used to indicate more serious faults via the SAFE (pin 10)

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

discharging. The secondary safety features include:

•

Safety over voltage

•

Battery cell imbalance

•

2nd level protection IC input

•

Safety over current

•

Safety over temperature

•

Open thermistor

•

Charge FET and Zero-Volt Charge FET fault

•

Discharge FET fault

•

Fuse blow failure detection

•

AFE Communication error

•

AFE Verification error

•

Internal flash data error

The bq20z90 charge control features include:

•

Report 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.

•

Determine the chemical state of charge of each battery cell using Impedance Track™. Using cell balancing

algorithm, gradually decrease the differences in the cells' state of charge in a fully charged state. This

prevents high cells from overcharging, causing excessive degradation and also increases the usable pack

energy by preventing early charge termination.

•

Support Pre-charging/Zero-volt charging

•

Support Fast charging

•

Support Pulse charging

•

Support Charge Inhibit and Charge Suspend modes

•

Report charging faults and also indicate charging status via charge and discharge alarms.

The bq20z90 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.

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Copyright © 2007, Texas Instruments Incorporated

Product Folder Link(s): bq20z90

Not Recommended for New Designs