Texas Instruments BQ29401PW

Overview

BQ29401PW from Texas Instruments is a BiCMOS secondary overvoltage protection IC for 2-, 3-, or 4-cell Li-ion battery packs, featuring 4.45 V ±25 mV precision cell voltage detection, <2 µA supply current, programmable delay via external capacitor on CD pin, and open-drain OUT pin capable of driving external N-channel FETs for fuse-blowing in high-reliability portable medical equipment.

For engineers reviewing the BQ29401PW datasheet, BQ29401PW pinout, BQ29401PW application, or BQ29401PW equivalent, this device serves as a dedicated second-level safety monitor in multi-cell battery management systems where accuracy, ultra-low quiescent current, and robust ripple rejection during pulse charging are critical selection criteria.

Technical Context

The BQ29401PW implements independent per-cell voltage monitoring across up to four series-connected Li-ion cells using precision comparator circuitry referenced to an internal bandgap. Each VCx input (VC1–VC4) measures differential voltage between adjacent cell terminals, with detection triggered when any cell exceeds 4.45 V ±25 mV.

Upon overvoltage detection, a 0.2 µA current source charges an external capacitor at the CD pin; when CD reaches 1.2 V, the OUT pin transitions high to activate an external protection FET. The device incorporates 300 mV hysteresis and clamps CD to GND if all cells fall below V(PROTECT) − Vhys before timeout, preserving full delay for subsequent events.

Key Specifications

Pinout & Package

TSSOP-8 (PW) package: 3.0 mm × 4.4 mm body, 0.65 mm lead pitch, 1.2 mm max height, RoHS-compliant NiPdAu lead 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 BQ29401PW, BQ29400PW provides earlier intervention for standard Li-ion, while BQ29405PW defers action for specialized high-voltage cells-both share identical PCB footprint and delay programming, enabling variant-based design reuse without layout change.

Availability

BQ29401PW is available at Aetrix Electronics and suitable for portable medical monitors, industrial handheld testers, and notebook PC battery packs requiring stable component supply with guaranteed long-term sourcing and full lifecycle support.

Supply support for BQ29401PW 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 experience in battery safety ICs and industrial-grade signal conditioning.

The BQ29401PW belongs to TI's bq294xx family of secondary protection ICs, designed specifically to provide hardware-enforced, fail-safe overvoltage monitoring for multi-cell Li-ion battery packs in safety-critical portable applications.

FAQ

What is the exact overvoltage detection threshold of the BQ29401PW?

The BQ29401PW has a nominal overvoltage detection threshold of 4.45 V with a tolerance of ±25 mV across the operating temperature range of –20°C to +85°C. This value is factory-trimmed and specified in the Electrical Characteristics table of the SLUS568C datasheet. It applies to each monitored cell individually-VC1–VC2, VC2–VC3, VC3–VC4, and VC4–GND-and is not adjustable externally. The BQ29401PW maintains this accuracy without calibration or external components.

Can the BQ29401PW be used in a 2-cell Li-ion configuration?

Yes, the BQ29401PW supports 2-cell configurations by connecting VC1, VC2, and VC3 together to the positive terminal of the top cell, VC4 to the junction between the two cells, and GND to the negative terminal of the bottom cell. This wiring is explicitly documented in Figure 7 of the SLUS568C datasheet. The device automatically adapts its internal comparison logic to monitor only the two relevant differential voltages, retaining full accuracy and delay functionality.

How is the delay time calculated for the BQ29401PW?

The delay time t_D1 for the BQ29401PW is calculated using the formula t_D1 = (1.2 V × C_DELAY) / I_CD, where I_CD is the internal current source of 0.2 µA and C_DELAY is the capacitor connected to the CD pin. For example, with a 0.22 µF capacitor, t_D1 = (1.2 × 0.22 µF) / 0.2 µA = 1.32 seconds-matching the typical 1.5 s value in the datasheet's Electrical Characteristics table. The BQ29401PW uses this fixed current source; no external resistor is involved.

Does the BQ29401PW require an external power supply or operate directly from the battery pack?

The BQ29401PW operates directly from the battery pack voltage applied to its VDD pin, with a specified supply range of 4.0 V to 25 V. No external regulator or auxiliary supply is needed. Its ultra-low 2 µA supply current allows it to remain active continuously on the pack-even during storage-without significant self-discharge. The BQ29401PW draws power internally from VDD for all sensing, timing, and output functions, making it ideal for always-on battery safety monitoring.

What happens to the OUT pin of the BQ29401PW after overvoltage protection triggers?

When overvoltage is detected and the CD pin reaches 1.2 V, the BQ29401PW drives its open-drain OUT pin high (to VDD level, typically ~16 V in a 4S pack), enabling an external N-channel FET to blow a fuse or disconnect the charge path. The OUT pin remains high until all monitored cell voltages fall below V(PROTECT) − V_hys (i.e., 4.45 V − 0.3 V = 4.15 V). Once satisfied, OUT returns to high-impedance state, allowing external pull-down or system reset to restore normal operation. This behavior is inherent to the BQ29401PW's internal state machine and requires no external control signals.