BQ20Z90_07 Datasheet, PDF (8/27 Pages) Texas Instruments – SBS 1.1-COMPLIANT GAS GAUGE ENABLED WITH IMPEDANCE TRACK™ TECHNOLOGY FOR USE WITH THE bq29330

bq20z90
SLUS662A – DECEMBER 2005 – REVISED JUNE 2006
FEATURE SET
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Primary (1st Level) Safety Features
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
Secondary (2nd Level) Safety Features
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
Charge Control Features
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.
Gas Gauging
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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