bq20z40-R1

SLUS993A

– DECEMBER 2009 – REVISED MARCH 2011

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FEATURE SET

Primary (1st Level) Safety Features

The bq20z40-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

•

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 bq20z40-R1 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 undervoltage

•

Safety overcurrent in charge and discharge

•

Safety overtemperature in charge and discharge with independent alarms and thresholds for each thermistor

•

Charge FET and 0 Volt Charge FET fault

•

Discharge FET fault

•

Cell imbalance detection (active and at rest)

•

Open thermistor detection

•

AFE communication fault

Charge Control Features

The bq20z40-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 bq20z40-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 Theory and Implementation of Impedance Track Battery Fuel-Gauging Algorithm application note (SLUA364)

for further details.

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Product Folder Link(s) :bq20z40-R1

Not Recommended for New Designs