Texas Instruments BQ78412DDWR

Overview

BQ78412DDWR from Texas Instruments is a standalone Pb-acid battery state-of-charge (SoC) and run-time-to-empty (RTTE) indicator IC for 12-V lead-acid batteries up to 327 Ah. It integrates voltage, current (±320 A peak), and on-chip temperature sensing; performs coulomb counting with ±15-min RTTE accuracy; and drives a 10-LED bar graph for real-time discharge runtime or charge %SoC in UPS systems.

For engineers reviewing the BQ78412DDWR datasheet, BQ78412DDWR pinout, BQ78412DDWR application, or BQ78412DDWR equivalent, key selection considerations include its integrated gas-gauging algorithm for Pb-acid aging compensation, UART/IR programmability of cell models and thresholds, and dual operational modes (active/idle/sleep) with configurable transition currents and sleep timing.

Technical Context

The BQ78412DDWR implements a rate- and temperature-compensated coulomb counting algorithm using a 1-mΩ sense resistor (±160 mV full-scale differential input), internal 12-bit ADC, and firmware-based battery characterization table (64-byte) for discharge-rate derating. It supports both internal oscillator and external 8-MHz crystal for timing accuracy within ±2.5% over –40°C to +85°C.

Gas-gauging operation includes two independent capacity update mechanisms: learned FCC via qualified discharge (no SoC >80% during discharge), and age-based FCC decrement (0.1 Ah per CapDerateL/CapDerateH days). State-of-health (SoH) is determined from either cycle count or FCC degradation, with WARN/REPLACE status outputs configurable via EOLCap and LifeCycles parameters.

Key Specifications

Pinout & Package

Package: DDW - 44-pin TSSOP with exposed thermal pad (bottom side); RoHS-compliant, moisture-sensitive level 3.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar Pb-acid battery monitoring applications.

Compared with BQ34Z100-G1 and MAX17205, the BQ78412DDWR delivers lower-system-cost Pb-acid monitoring through integrated LED/buzzer drivers, autonomous operation, and factory-programmable cell models-without requiring external processing or chemistry adaptation.

Availability

BQ78412DDWR is available at Aetrix Electronics and suitable for uninterruptible power supplies, 12-V Pb-acid battery monitors, and battery warranty data logging equipment requiring stable component supply and long-term lifecycle support.

Supply support for BQ78412DDWR 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 company specializing in analog, embedded processing, and power management technologies, with decades of leadership in battery management ICs.

The BQ78412DDWR belongs to TI's battery fuel gauge product line, designed specifically for cost-sensitive, high-reliability Pb-acid applications in UPS, security systems, and industrial backup power where autonomous runtime estimation and health tracking are essential.

FAQ

What is the maximum battery capacity supported by the BQ78412DDWR?

The BQ78412DDWR supports Pb-acid batteries up to 327 Ah when measured at the 20-hour rate. This capacity range is validated per TI's SLUSAA0 datasheet and accommodates large-format sealed lead-acid (SLA) and valve-regulated (VRLA) batteries commonly used in enterprise UPS systems. The device's coulomb counting and aging algorithms scale accurately across this full range when configured with appropriate sense resistor and cell model parameters.

Does the BQ78412DDWR require an external microcontroller to operate?

No, the BQ78412DDWR operates autonomously without an external microcontroller. It integrates all necessary functions-including voltage/current/temperature measurement, coulomb counting, SoC/RTTE calculation, LED bar graph driving (via SDAT/SCLK), and buzzer control-to deliver complete battery monitoring. Configuration is performed once via UART during manufacturing; runtime operation is fully self-contained, making it ideal for smart battery covers and standalone UPS units.

How does the BQ78412DDWR handle battery aging and capacity fade?

The BQ78412DDWR employs two complementary methods: (1) Learned Capacity-updates full charge capacity (FCC) after qualified discharges, and (2) Age-Based Capacity-decrements FCC by 0.1 Ah at configurable intervals (CapDerateL/CapDerateH days) to model long-term Pb-acid degradation. Both methods run independently and can be enabled simultaneously, ensuring SoC accuracy remains within specification over multi-year deployments in industrial environments.

Can the BQ78412DDWR drive LEDs directly, or does it require external shift registers?

The BQ78412DDWR does not drive LEDs directly but provides serial output signals (SDAT and SCLK) to control external shift registers such as the SN74HC164. This architecture reduces pin count and power consumption while enabling flexible LED count (up to 10 segments) and layout. The IC handles all timing and data formatting; external transistors or drivers may be added for higher-current LED configurations, but the base design uses low-power green/yellow/red LEDs driven via shift-register outputs.

What communication interfaces does the BQ78412DDWR support for configuration and data retrieval?

The BQ78412DDWR supports UART communication at 9600 or 1200 baud with multi-drop capability (default address 0xFF), enabling daisy-chained battery monitoring. It also supports optional infrared (IR) communication via the SD pin and IR transceiver (e.g., GP2W0116YPS), allowing connectorless configuration and warranty data retrieval. All parameter programming-including cell models, thresholds, and display settings-is performed exclusively through this UART/IR interface.