Design Parameter

Example

Device Chemistry

li-ion

Design Voltage

4000 mV

Cell Low Voltage

2500 mV

9.2.2 Detailed Design Procedure

9.2.2.1 Changing Design Parameters

For the firmware settings needed for the design requirements, refer to the BQ27Z561-R2 Technical Reference

Manual (SLUUC54).

• To change design capacity, set the data flash value (in mAh) in the Gas Gauging: Design: Design Capacity

register.

software automatically populates the correct chemistry identification. This selection is derived from using the

BQCHEM feature in the tools and choosing the option that matches the device chemistry from the list.

• To set the design voltage, go to Gas Gauging: Design: Design Voltage register.

• To set the Cell Low Voltage or clear the Cell Low Voltage, use Settings: Configuration: Init Voltage Low

Set or Clear. This is used to set the cell voltage level that will set (clear) the [VOLT_LO] bit in the Interrupt

Status register.

• To enable the internal temperature and the external temperature sensors: Set Settings:Configuration:

Temperature Enable: Bit 0 (TSInt) = 1 for the internal sensor; set Bit 1 (TS1) = 1 for the external sensor.

9.2.3 Calibration Process

The calibration of current, voltage, and temperature readings is accessible by writing 0xF081 or 0xF082 to

ManufacturerAccess(). A detailed procedure is included in the BQ27Z561-R2 Technical Reference Manual

(SLUUC54) in the Calibration section. The description allows for calibration of cell voltage measurement offset,

battery voltage, current calibration, coulomb counter offset, PCB offset, CC gain/capacity gain, and temperature

measurement for both internal and external sensors.

9.2.4 Gauging Data Updates

When a battery pack enabled with the BQ27Z561-R2 gas gauge is cycled, the value of FullChargeCapacity()

updates several times, including the onset of charge or discharge, charge termination, temperature delta,

resistance updates during discharge, and relaxation. Figure 9-2 shows actual battery voltage, load current, and

FullChargeCapacity() when some of those updates occur during a single application cycle.

Update points from the plot include:

• Charge termination at 7900 s

• Relaxation at 9900 s

• Resistance update at 11500 s

BQ27Z561-R2

SLUSE22 – SEPTEMBER 2020

www.ti.com

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