bq30z554-R1

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SLUSBD4 – OCTOBER 2013

BATTERY PARAMETER MEASUREMENTS

Charge and Discharge Counting

The bq30z554-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 measurements.

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 bq30z554-R1 detects charge activity when VSR = V(SRP) – V(SRN) is positive,

and discharge activity when VSR = V(SRP) – V(SRN) is negative. The bq30z554-R1 continuously integrates the

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

Voltage

The bq30z554-R1 updates the individual series cell voltages at 0.25-s intervals. The internal ADC of the

bq30z554-R1 measures the voltage, and 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 bq30z554-R1 uses the SRP and SRN inputs to measure and calculate the battery charge and discharge

current using a 5-m

Ω to 20-mΩ typ. sense resistor.

Auto Calibration

The bq30z554-R1 provides an auto-calibration feature to cancel the voltage offset error across SRN and SRP for

maximum charge measurement accuracy. The bq30z554-R1 performs auto-calibration when the SMBus lines

stay low continuously for a minimum of 5 s.

Temperature

The bq30z554-R1 has an internal temperature sensor and inputs for four external temperature sensors. All five

temperature sensor options are enabled individually and configured for cell or FET temperature. Two

configurable thermistor models are provided to allow the monitoring of cell temperature in addition to FET

temperature, which may be of a higher temperature type.

CELL BALANCING

The device supports cell balancing by bypassing the current of each cell during charging or at rest. If the device

internal bypass is used, up to 10 mA can be bypassed and multiple cells can be bypassed at the same time.

Higher cell balance current can be achieved by using an external cell balancing circuit. In EXTERNAL CELL

BALANCING mode, only one cell at a time can be balanced.

The cell balancing algorithm determines the amount of charge needed to be bypassed to balance the capacity of

all cells.

Copyright © 2013, Texas Instruments Incorporated

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