Datasheet

bq20z75-V180
SLUSA22 –DECEMBER 2009 www.ti.com
Power Modes
The bq20z75-V180 supports 3 different power modes to reduce power consumption:
• In Normal Mode, the bq20z75-V180 performs measurements, calculations, protection decisions and data
updates in 1 second intervals. Between these intervals, the bq20z75-V180 is in a reduced power stage.
• In Sleep Mode, the bq20z75-V180 performs measurements, calculations, protection decisions and data
update in adjustable time intervals. Between these intervals, the bq20z75-V180 is in a reduced power stage.
The bq20z75-V180 has a wake function that enables exit from Sleep mode, when current flow or failure is
detected.
• In Shutdown Mode the bq20z75-V180 is completely disabled.
CONFIGURATION
Oscillator Function
The bq20z75-V180 fully integrates the system oscillators. Therefore the bq20z75-V180 requires no external
components for this feature.
System Present Operation
The bq20z75-V180 checks the PRES pin periodically (1 s). Connect the PRES pin to TOUT with a 100kΩ
resistor. If PRES input is pulled to ground by external system host, the bq20z75-V180 detects this as system
present.
BATTERY PARAMETER MEASUREMENTS
The bq20z75-V180 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 SRP and SRN pins. The integrating ADC measures bipolar
signals from –0.25 V to 0.25 V. The bq20z75-V180 detects charge activity when V
SR
= V
(SRP)
–V
(SRN)
is positive
and discharge activity when V
SR
= V
(SRP)
–V
(SRN)
is negative. The bq20z75-V180 continuously integrates the
signal over time, using an internal counter. The fundamental rate of the counter is 0.65 nVh.
Voltage
The bq20z75-V180 updates the individual series cell voltages at one second intervals. The internal ADC of the
bq20z75-V180 measures the voltage, scales and calibrates it appropriately. This data is also used to calculate
the impedance of the cell for the Impedance Track™ gas-gauging.
Current
The bq20z75-V180 uses the GSRP and GSRN inputs to measure and calculate the battery charge and
discharge current using a 5 mΩ to 20 mΩ typ. sense resistor.
Auto Calibration
The bq20z75-V180 provides an auto-calibration feature to cancel the voltage offset error across GSRN and
GSRP for maximum charge measurement accuracy. The bq20z75-V180 performs auto-calibration when the
SMBus lines stay low continuously for a minimum of 5 s.
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