bq20z45
SLUS800–MARCH 2009 .................................................................................................................................................................................................. www.ti.com
Lifetime Data Logging Features
The bq20z45 offers lifetime data logging, where important measurements are stored for warranty and analysis
purposes. The data monitored include:
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Lifetime maximum temperature
Lifetime minimum temperature
Lifetime maximum battery cell voltage
Lifetime minimum battery cell voltage
Lifetime maximum battery pack voltage
Lifetime minimum battery pack voltage
Lifetime maximum charge current
Lifetime maximum discharge current
Lifetime maximum charge power
Lifetime maximum discharge power
Lifetime maximum average discharge current
Lifetime maximum average discharge power
Lifetime average temperature
Authentication
The bq20z45 supports authentication by the host using SHA-1.
Power Modes
The bq20z45 supports 3 different power modes to reduce power consumption:
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In Normal Mode, the bq20z45 performs measurements, calculations, protection decisions and data updates in
1 second intervals. Between these intervals, the bq20z45 is in a reduced power stage.
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In Sleep Mode, the bq20z45 performs measurements, calculations, protection decisions and data update in
adjustable time intervals. Between these intervals, the bq20z45 is in a reduced power stage. The bq20z45
has a wake function that enables exit from Sleep mode, when current flow or failure is detected.
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In Shutdown Mode the bq20z45 is completely disabled.
CONFIGURATION
Oscillator Function
The bq20z45 fully integrates the system oscillators. Therefore the bq20z45 requires no external components for
this feature.
System Present Operation
The bq20z45 checks the PRES pin periodically (1s). If PRES input is pulled to ground by external system, the
bq20z45 detects this as system present.
BATTERY PARAMETER MEASUREMENTS
The bq20z45 uses an integrating delta-sigma analog-to-digital converter (ADC) for current measurement, and a
second delta-sigma ADC for individual cell and battery voltage, and temperature measurement.
Charge and Discharge Counting
The integrating delta-sigma ADC measures the charge/discharge flow of the battery by measuring the voltage
drop across a small-value sense resistor between the SR1 and SR2 pins. The integrating ADC measures bipolar
signals from -0.25 V to 0.25 V. The bq20z45 detects charge activity when VSR = V(SRP)- V(SRN)is positive and
discharge activity when VSR = V(SRP) - V(SRN) is negative. The bq20z45 continuously integrates the signal over
time, using an internal counter. The fundamental rate of the counter is 0.65 nVh.
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