BQ20Z655DBTR-R1 Datasheet, PDF (14/25 Pages) Texas Instruments – SBS 1.1-COMPLIANT GAS GAUGE AND PROTECTION

bq20z655-R1
SLUSAN9 – AUGUST 2011
FEATURE SET
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Primary (1st Level) Safety Features
The bq20z655-R1 supports a wide range of battery and system protection features that can easily be configured.
The primary safety features include:
• Cell over/undervoltage protection
• Charge and discharge overcurrent
• Short Circuit protection
• Charge and discharge overtemperature with independent alarms and thresholds for each thermistor
• AFE Watchdog
Secondary (2nd Level) Safety Features
The secondary safety features of the bq20z655-R1 can be used to indicate more serious faults via the SAFE 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 protection features include:
• Safety overvoltage
• Safety undervoltage
• 2nd level protection IC input
• Safety overcurrent in charge and discharge
• Safety over-temperature in charge and discharge with independent alarms and thresholds for each thermistor
• Charge FET and zero-volt charge FET fault
• Discharge FET fault
• Cell imbalance detection (active and at rest)
• Open thermistor detection
• Fuse blow detection
• AFE communication fault
Charge Control Features
The bq20z655-R1 charge control features include:
• Supports JEITA temperature ranges. Reports charging voltage and charging current according to the active
temperature range.
• Handles more complex charging profiles. Allows for splitting the standard temperature range into two
sub-ranges and allows for varying the charging current according to the cell voltage.
• 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
• 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 bq20z655-R1 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 the Theory and Implementation of Impedance Track Battery Fuel-Gauging Algorithm application note
(SLUA364) for further details.
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