8.3.2.1 Coulomb Counter (CC)

The first ADC is an integrating analog-to-digital converter designed specifically for tracking charge and discharge

activity, or coulomb counting, of a rechargeable battery. It features a single-channel differential input that

converts the voltage difference across a sense resistor between the SRP and SRN terminals with a resolution of

3.74 µV.

8.3.2.2 CC Digital Filter

The CC digital filter generates a 16-bit conversion value from the delta-sigma CC front-end. Its FIR filter uses the

HFO clock output. New conversions are available every 1 s.

8.3.2.3 ADC Multiplexer

The ADC multiplexer provides selectable connections to the external pins BAT, BAT_SNS, TS, the internal

temperature sensor, internal reference voltages, internal 1.8-V regulator, and VSS ground reference input. In

addition, the multiplexer can independently enable the TS input connection to the internal thermistor biasing

circuitry, and enables the user to short the multiplexer inputs for test and calibration purposes.

8.3.2.4 Analog-to-Digital Converter (ADC)

The second ADC is a 16-bit delta-sigma converter designed for general-purpose measurements. The ADC

automatically scales the input voltage range during sampling based on channel selection. The converter

resolution is a function of its full-scale range and number of bits, yielding a 38-µV resolution.

8.3.2.5 Internal Temperature Sensor

An internal temperature sensor is available on the BQ27Z561-R1 device to reduce the cost, power, and size of

the external components necessary to measure temperature. It is available for connection to the ADC using the

multiplexer, and is ideal for quickly determining pack temperature under a variety of operating conditions.

8.3.2.6 External Temperature Sensor Support

The TS input is enabled with an internal 18-kΩ (Typ.) linearization pull-up resistor to support the use of a

10-kΩ (25°C) NTC external thermistor, such as the Semitec 103AT-2. The NTC thermistor should be connected

between VSS and the individual TS pin. The analog measurement is then taken via the ADC through its input

multiplexer. If a different thermistor type is required, then changes to configurations may be required.

REG18

ADC

TS

NTC

Figure 8-1. External Thermistor Biasing

BQ27Z561-R1

SLUSDH5B – MARCH 2019 – REVISED DECEMBER 2022

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