Texas Instruments BQ26231PW

Overview

BQ26231PW from Texas Instruments is a multifunction, high-accuracy coulometric charge/discharge counter IC for Li-Ion, Li-Pol, and NiMH battery packs. It measures voltage drop across a sense resistor with 12.5 µV resolution, integrates internal temperature sensing and timebase, and communicates via single-wire HDQ interface. It enables precise state-of-charge estimation in portable devices with nonremovable batteries.

For engineers reviewing the BQ26231PW datasheet, BQ26231PW pinout, BQ26231PW application, or BQ26231PW equivalent, this page delivers verified technical context, real-world register behavior, HDQ timing constraints, offset calibration workflow, and self-discharge temperature compensation logic - all critical for battery fuel gauge integration and host controller firmware design.

Technical Context

The BQ26231PW implements a dynamically balanced voltage-to-frequency converter (VFC) to integrate current-sense differential voltage (±200 mV range) into 16-bit counters for charge (CCR), discharge (DCR), and self-discharge (SCR). Its internal temperature sensor (±2°C typical accuracy at 25°C) directly modulates SCR count rate - doubling per +10°C above 25°C - without external components.

It uses a single-wire HDQ interface with asynchronous return-to-one protocol (max 5 kbps), requiring external pullup/pulldown for sleep/wake control. Register backup is maintained via RBI input with <100 nA discharge current when VCC drops below 2.4 V, enabling nonvolatile storage during battery short or deep discharge.

Key Specifications

Pinout & Package

Packaged in an 8-pin TSSOP (PW), the BQ26231PW occupies minimal board area - designed to fit between two AA cells or within prismatic cell width.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar coulometric battery monitoring applications.

Compared with BQ26231PW, BQ26100PW sacrifices temperature-aware self-discharge modeling and register persistence, while BQ27210DRVR adds algorithmic intelligence at the cost of interface compatibility and layout simplicity - making BQ26231PW optimal for cost-sensitive, space-constrained, fixed-battery designs needing robust coulometric accuracy.

Availability

BQ26231PW is available at Aetrix Electronics and suitable for smartphone battery packs, tablet power modules, wearable health monitors, Bluetooth headset batteries, and other portable electronics requiring stable component supply and long-lifecycle support.

Supply support for BQ26231PW includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management technologies, with decades of leadership in battery management ICs.

The BQ26231PW belongs to TI's dedicated battery fuel gauge product line, engineered specifically for low-cost, high-accuracy coulometric monitoring in space-constrained, nonremovable battery applications - prioritizing minimal external components and host firmware simplicity.

FAQ

What is the primary function of the BQ26231PW in a battery management system?

The BQ26231PW serves as a dedicated coulometric charge/discharge counter that accumulates current flow through a sense resistor to compute battery state-of-charge. It does not perform full gas gauging or voltage-based modeling - its role is precise, low-power integration of differential voltage (SR1–SR2) into 16-bit counters (DCR, CCR, SCR), with temperature compensation and HDQ-based host communication. The BQ26231PW relies on an external host controller to interpret register values and manage calibration.

How does the BQ26231PW handle offset voltage calibration, and what is the role of the OFR register?

The BQ26231PW performs internal offset calibration by measuring V(SR1)–V(SR2) under zero-current conditions and storing the result in the 8-bit 2's complement Offset Register (OFR) at address 73h. During normal operation, the host subtracts the OFR value from raw DCR/CCR counts to correct for device-level offset (up to ±500 µV). Calibration is initiated by setting the CAL bit in MODE/WOE (75h); the BQ26231PW latches the result after one hour of stable low-input condition and clears CAL automatically upon completion.

Can the BQ26231PW operate without an external crystal or oscillator?

Yes, the BQ26231PW contains a high-accuracy internal temperature-compensated oscillator that eliminates the need for an external crystal. This integrated timebase drives all timing-critical functions including the discharge/charge time counters (DTC/CTC) and self-discharge count rate (SCR), ensuring consistent operation across –20°C to 70°C without additional components. The oscillator's accuracy is specified at ±3% to ±3% over temperature and supply voltage.

What happens to register data in the BQ26231PW when the main supply (VCC) drops below operating voltage?

When VCC falls below 2.4 V, the BQ26231PW switches to register backup mode powered via the RBI pin. In this mode, internal registers (DCR, CCR, SCR, DTC, CTC, MODE/WOE, TMP/CLR, OFR) retain their values with leakage current <100 nA - enabling nonvolatile storage during battery short, deep discharge, or pack removal. RBI must be connected to a charged capacitor or auxiliary cell; if externally powered, a diode is required to prevent backfeed from VCC.

How does the BQ26231PW determine battery temperature, and how is that used in practice?

The BQ26231PW includes an on-die temperature sensor that reports ambient temperature in eight discrete 10°C steps (e.g., 0h = <0°C, 3h = 20–30°C, 7h = >60°C), with ±2°C typical accuracy at 25°C. This value is read from the TMP/CLR register (74h, bits 7–5) and directly controls the self-discharge count rate (SCR): the count rate doubles every +10°C above 25°C and halves every –10°C below - allowing accurate runtime estimation for batteries in storage without external sensors. The BQ26231PW does not output analog temperature or linearized values.