Texas Instruments BQ29400DCT3

Overview

BQ29400DCT3 from Texas Instruments is a BiCMOS secondary overvoltage protection IC for 2-, 3-, or 4-cell Li-ion battery packs, featuring 4.35 V ±25 mV overvoltage detection threshold, <2 µA supply current, programmable delay via external capacitor on CD pin, and open-drain OUT pin for fuse control. It operates across –25°C to 85°C and is used in notebook PCs and portable medical equipment as second-level cell voltage safety guard.

For engineers reviewing the BQ29400DCT3 datasheet, BQ29400DCT3 pinout, BQ29400DCT3 application, or BQ29400DCT3 equivalent, key selection criteria include precise 4.35 V overvoltage trip accuracy, ultra-low ICC (<2 µA), CD-pin-based delay configurability, GND-referenced multi-cell sensing architecture, and compatibility with standard SSOP-8 PCB footprints.

Technical Context

The BQ29400DCT3 implements independent per-cell voltage monitoring using four VCx inputs (VC1–VC4) referenced to GND, comparing each against an internal 4.35 V precision bandgap reference. Detection triggers a 0.2 µA current source charging an external capacitor on CD, with OUT activation at 1.2 V threshold.

It features 300 mV hysteresis to prevent chatter during recovery, supports pulse-charge stable operation, and delivers high ripple rejection without external filtering. The OUT pin drives an external N-channel FET to blow a positive-rail fuse, providing irreversible secondary protection after delay timeout.

Key Specifications

Pinout & Package

Package: SSOP-8 (DCT), 3.0 mm × 4.4 mm, 1.3 mm max height, lead pitch 0.65 mm, RoHS-compliant SNBI finish, MSL Level-1.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar secondary overvoltage protection applications.

Compared with BQ29400DCT3, BQ29400PW offers identical functionality in a larger TSSOP footprint better suited for manual assembly or thermal relief, while BQ29400ADCT3 provides a +50 mV overvoltage threshold for enhanced margin with newer Li-ion variants-neither is pin-compatible without layout revision due to differing package dimensions.

Availability

BQ29400DCT3 is available at Aetrix Electronics and suitable for notebook PC battery packs, portable medical devices, and industrial handheld testers requiring stable component supply, long-term lifecycle support, and traceable sourcing for safety-critical applications.

Supply support for BQ29400DCT3 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 delivering analog and embedded processing solutions, with leadership in power management, signal chain, and high-reliability ICs.

The BQ29400DCT3 belongs to TI's battery protection IC product line, designed specifically to provide robust, low-power secondary overvoltage safeguards for multi-cell Li-ion battery packs in portable and medical applications.

FAQ

What is the overvoltage detection threshold of the BQ29400DCT3?

The BQ29400DCT3 has a fixed overvoltage detection threshold of 4.35 V ±25 mV per cell. This value is factory-trimmed and applies across the full operating temperature range of –25°C to 85°C. The BQ29400DCT3 uses an internal precision bandgap reference to maintain this accuracy without external calibration, making it suitable for safety-critical secondary protection where consistent trip points are mandatory.

How does the BQ29400DCT3 implement programmable delay time?

The BQ29400DCT3 implements programmable delay time using an internal 0.2 µA current source that charges an external capacitor connected to the CD pin. When the CD pin voltage reaches 1.2 V, the OUT pin activates. Delay time is calculated as t_D = (1.2 V × C_DELAY) / 0.2 µA. For example, a 0.22 µF capacitor yields ~1.3 s delay. The BQ29400DCT3 does not require external resistors or clocks-only a single capacitor sets timing.

Can the BQ29400DCT3 be used in a 2-cell Li-ion configuration?

Yes, the BQ29400DCT3 supports 2-cell configurations by connecting VC1, VC2, and VC3 together to the most positive node, VC4 to the midpoint, and GND to the battery negative. The BQ29400DCT3 monitors VC4–GND and VC1–VC4 as virtual cell voltages, maintaining accurate per-cell overvoltage detection without additional components. TI's datasheet explicitly validates this wiring in Figure 7.

What is the maximum supply voltage the BQ29400DCT3 can tolerate on VDD?

The BQ29400DCT3 supports a VDD supply voltage range of 4.0 V to 25 V, with absolute maximum rating of –0.3 V to 28 V. This allows direct connection to the full battery stack voltage in 4-cell configurations (up to ~16.8 V fully charged) plus margin. The BQ29400DCT3 maintains stable operation across this range, enabling single-supply operation without regulators in most pack designs.

Does the BQ29400DCT3 provide reverse polarity or short-circuit protection?

No, the BQ29400DCT3 provides only secondary overvoltage protection and does not include reverse polarity, short-circuit, overcurrent, or overtemperature functions. Its sole role is to detect sustained cell overvoltage and assert the OUT pin to trigger an external fuse. System-level protection must be implemented separately-e.g., using dedicated fuel gauges, current-sense amplifiers, or dedicated protection FET drivers. The BQ29400DCT3 is intentionally focused on one critical fault mode to maximize reliability and minimize quiescent current.