8 Detailed Description

8.1 Overview

The BQ27Z561-R2 gas gauge is a fully integrated battery manager that employs flash-based firmware to

provide a complete solution for battery-stack architectures composed of 1-series cells. The BQ27Z561-R2

device interfaces with a host system through an I2C or HDQ protocol. High-performance, integrated analog

peripherals enable support for a sense resistor down to 1 mΩ, and simultaneous current/voltage data conversion

for instant power calculations. The following sections detail all of the major component blocks included as part of

the BQ27Z561-R2 device.

8.2 Functional Block Diagram

REG18

REF1

ADC

MUX

CC

ADC

REF2

HFO

LFO

Internal

temperature

sensor

Test

interface

CC/ADC

digital filter

IO and

interrupt

controller

Timers

COM

engine

Timers

bqBMP

CPU

Program flash

32-kBytes

Data flash

4-kBytes

Data SRAM

2-kBytes

ROM

12-

kBytes

PMInstr

(8 bit)

PMAddr

(16 bit)

BAT_SNS

BAT

CE

SRP

SRN

VSS

TS

GPIO

INT

PULS

SDA/HDQ

SCL

8.3 Feature Description

8.3.1 BQ27Z561-R2 Processor

The BQ27Z561-R2 device uses a custom TI-proprietary processor design that features a Harvard architecture

and operates at frequencies up to 4.2 MHz. Using an adaptive, three-stage instruction pipeline, the BQ27Z561-

R2 processor supports variable instruction lengths of 8, 16, or 24 bits.

8.3.2 Battery Parameter Measurements

The BQ27Z561-R2 device measures cell voltage and current simultaneously, and also measures temperature to

calculate the information related to the following:

Remaining capacity

Full charge capacity

State-of-health

Other gauging parameters.

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 pins with a resolution of

3.74 µV.

www.ti.com

BQ27Z561-R2

SLUSE22B – FEBRUARY 2020 – REVISED NOVEMBER 2022

Copyright © 2022 Texas Instruments Incorporated

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Product Folder Links: BQ27Z561-R2