bq20z60-R1

SLUS991 – DECEMBER 2009

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BATTERY PARAMETER MEASUREMENTS

The bq20z60-R1 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

time, using an internal counter. The fundamental rate of the counter is 0.65nVh.

Voltage

The bq20z60-R1 updates the individual series cell voltages through the bq29330 at one second intervals. The

bq20z60-R1 configures the bq29330 to connect the selected cell, cell offset, or bq29330 VREF to the CELL pin

of the bq29330, which is required to be connected to VIN of the bq20z60-R1. The internal ADC of the

bq20z60-R1 measures the voltage, scales it, and calibrates itself appropriately. This data is also used to

calculate the impedance of the cell for the Impedance Track™ gas-gauging.

Current

The bq20z60-R1 uses the SRP and SRN inputs to measure and calculate the battery charge and discharge

current using a 5m

Ω to 20mΩ typ. sense resistor.

Wake Function

The bq20z60-R1 can exit sleep mode, if enabled, by the presence of a programmable level of current signal

across SRP and SRN.

Auto Calibration

he bq20z60-R1 provides an auto-calibration feature to cancel the voltage offset error across SRP and SRN for

maximum charge measurement accuracy. The bq20z60-R1 performs auto-calibration when the SMBus lines stay

low continuously for a minimum of a programmable amount of time.

Temperature

The bq20z60-R1 has an internal temperature sensor and inputs for 2 external temperature sensors, TS1 and

TS2, used in conjunction with two identical NTC thermistors (default are Semitec 103AT) to sense the battery

environmental temperature. The bq20z60-R1 can be configured to use the internal, or up to 2 external

temperature sensors.

COMMUNICATIONS

The bq20z60-R1 uses SMBus v1.1 with Master Mode and package error checking (PEC) options per the SBS

specification.

SMBus On and Off State

The bq20z60-R1 detects an SMBus off state when SMBC and SMBD are logic-low for

≥ 2 seconds. Clearing this

state requires either SMBC or SMBD to transition high. Within 1ms, the communication bus is available.

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