Texas Instruments BQ29400DCT3E6

Overview

BQ29400DCT3E6 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 high-accuracy cell voltage monitoring across VC1–VC4 inputs. It drives an external N-channel FET to blow a fuse during overvoltage events in portable medical equipment.

For engineers reviewing the BQ29400DCT3E6 datasheet, BQ29400DCT3E6 pinout, BQ29400DCT3E6 application, or BQ29400DCT3E6 equivalent, key selection criteria include second-level protection accuracy, ultra-low quiescent current, programmable delay timing, and compatibility with multi-cell series configurations requiring precise per-cell voltage sensing.

Technical Context

The BQ29400DCT3E6 implements precision differential voltage comparison across four sense inputs (VC1–VC4) against an internal reference, triggering protection only when any single cell exceeds 4.35 V ±25 mV. Its internal 0.2 µA current source charges an external capacitor on the CD pin to generate a programmable delay before OUT activation.

Upon overvoltage detection, the OUT pin transitions high (min 1.5 V at –40 µA) to control an external N-channel FET; recovery occurs only after all cells fall below 4.35 V – 300 mV hysteresis. The device operates from 4.0 V to 25 V supply and supports stable operation under pulse charging with high ripple rejection.

Key Specifications

Pinout & Package

Package: SSOP-8 (DCT), 3.0 mm × 3.0 mm body, 1.3 mm max height, 0.65 mm lead pitch, 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 BQ29400PW and BQ29400ADCT3, the BQ29400DCT3E6 offers the lowest-profile SSOP package for space-constrained battery modules and the industry-standard 4.35 V trip point for mainstream Li-ion cells - making it optimal for new designs targeting cost-effective, compact, and globally compliant secondary protection.

Availability

BQ29400DCT3E6 is available at Aetrix Electronics and suitable for portable medical devices, handheld test equipment, and notebook PC battery packs requiring stable component supply and long-term lifecycle support.

Supply support for BQ29400DCT3E6 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 headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and personal electronics markets.

The BQ29400DCT3E6 belongs to TI's battery management IC portfolio, designed specifically to provide robust, low-power, hardware-based secondary protection for multi-cell Li-ion battery packs in safety-critical portable applications.

FAQ

What is the overvoltage detection threshold of the BQ29400DCT3E6?

The BQ29400DCT3E6 has a fixed overvoltage detection threshold of 4.35 V ±25 mV per cell. This value is factory-trimmed and specified over the full operating temperature range of –25°C to +85°C. It applies to any individual cell monitored via VC1–VC4 inputs, and triggers the protection sequence when any one cell exceeds this level. The BQ29400DCT3E6 does not support user-programmable thresholds - alternative variants like BQ29400ADCT3 (4.40 V) or BQ29401DCT3 (4.45 V) must be selected for different trip points.

How does the BQ29400DCT3E6 implement programmable delay timing?

The BQ29400DCT3E6 uses an internal 0.2 µA current source to charge an external capacitor connected to the CD pin. When the voltage at CD reaches 1.2 V (typical), the OUT pin transitions high to activate external protection circuitry. For a 0.22 µF capacitor, the delay is 1.0–2.0 s. The delay time is calculated as t_D = (1.2 V × C_DELAY) / 0.2 µA. Larger capacitors increase delay linearly; smaller values reduce it, enabling precise tuning without firmware involvement.

Can the BQ29400DCT3E6 be used in 2-cell or 3-cell battery configurations?

Yes, the BQ29400DCT3E6 supports 2-, 3-, and 4-cell Li-ion configurations through specific pin interconnections. For 3-cell operation, VC1 and VC2 are shorted together; for 2-cell, VC1, VC2, and VC3 are shorted. These connections are defined in TI's SLUS568C datasheet Figures 6 and 7. The device maintains full per-cell voltage monitoring capability in all modes, and the same 4.35 V threshold applies to each monitored node - ensuring consistent protection regardless of stack size.

What is the function of the OUT pin on the BQ29400DCT3E6?

The OUT pin on the BQ29400DCT3E6 is a push-pull output that transitions from low to high (min 1.5 V at –40 µA) when overvoltage protection is triggered. It is designed to drive the gate of an external N-channel MOSFET placed in the battery's positive rail. When asserted, the FET activates a fuse-blowing circuit or disconnects charging current. After all cells fall below 4.05 V (4.35 V – 300 mV hysteresis), OUT returns low automatically - no reset pin or external command is required.

Does the BQ29400DCT3E6 require external passive components for basic operation?

Yes, the BQ29400DCT3E6 requires at minimum an external capacitor on the CD pin to set delay time and a pull-down resistor on the OUT pin if driving a high-impedance load. TI recommends a 0.22 µF capacitor for standard 1–2 s delay. Optional RC filters (e.g., 100 Ω–1 kΩ + 0.01–0.1 µF) on VC1–VC4 inputs improve noise immunity, and a 0–1 kΩ resistor plus 0.1 µF capacitor on VDD enhances supply stability. No external voltage references or op-amps are needed - all sensing and timing functions are self-contained.