Texas Instruments BQ29412PW

Overview

BQ29412PW from Texas Instruments is a secondary overvoltage protection IC for 2-, 3-, or 4-cell Li-ion battery packs, featuring fixed 4.45 V per-cell overvoltage threshold, programmable delay via external capacitor on CD pin, and ultra-low 2 µA supply current. It monitors individual cell voltages (VC1–VC4) and drives an external N-channel FET to blow the fuse upon overvoltage detection - used in notebook computers and portable instrumentation.

For engineers reviewing the BQ29412PW datasheet, BQ29412PW pinout, BQ29412PW application, or BQ29412PW equivalent, key selection criteria include its precise 4.45 V overvoltage trip point, ±80 mV accuracy over –40°C to 110°C, 1–2 s programmable delay with 0.22 µF capacitor, TSSOP-8 (PW) package compatibility, and role as second-level hardware safety guard in multi-cell battery management systems.

Technical Context

The BQ29412PW implements independent voltage monitoring across four sense inputs (VC1–VC4), comparing each against an internal reference to detect any single-cell overvoltage condition. Its precision bandgap-based comparator achieves ±80 mV total overvoltage detection error across full temperature range.

Upon detection, a 0.18 µA current source charges the external CD capacitor; when CD reaches 1.2 V, the open-drain OUT pin pulls high to trigger external FET activation. The device maintains stable operation during pulse charging and rejects supply ripple without false triggering.

Key Specifications

Pinout & Package

TSSOP-8 (PW) package, 3.0 mm × 4.4 mm, 1.2 mm max height, lead pitch 0.65 mm, RoHS-compliant NiPdAu finish, MSL Level-2 (260°C, 1 year).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ29411PW and BQ29413PW, the BQ29412PW provides the industry-standard 4.45 V trip point for mainstream NMC and NCA Li-ion cells, balancing safety margin against usable capacity - making it the default choice for notebook and portable instrumentation designs requiring compliance with JEITA EC-62133.

Availability

BQ29412PW is available at Aetrix Electronics and suitable for notebook computer battery packs, portable medical instrumentation, and industrial test equipment requiring stable component supply with guaranteed long-term sourcing and full traceability.

Supply support for BQ29412PW 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 BQ2941x family was designed specifically for secondary overvoltage protection in multi-cell Li-ion battery packs, providing hardware-redundant safety independent of host controller firmware.

FAQ

What is the exact overvoltage protection threshold of the BQ29412PW?

The BQ29412PW has a fixed overvoltage protection threshold of 4.45 V per cell, specified with ±80 mV accuracy over the full operating temperature range of –40°C to 110°C. This value is laser-trimmed at wafer test and does not require external calibration. The BQ29412PW is part of the bq2941x family where each variant has a unique factory-set threshold - BQ29412PW is specifically designated for 4.45 V operation.

How is the delay time configured on the BQ29412PW?

The BQ29412PW uses an external capacitor connected to the CD pin to set overvoltage detection delay. With a 0.22 µF capacitor, the delay is 1–2 seconds, calculated as t_D = (1.2 V × C_DELAY) / 0.18 µA. The CD pin sources a precise 0.18 µA current to charge the capacitor; no external resistor is needed. The BQ29412PW's delay remains stable across temperature and supply voltage variations due to its internally regulated current source.

Which battery configurations does the BQ29412PW support?

The BQ29412PW supports 2-, 3-, and 4-cell Li-ion battery configurations. In 4S mode, VC1–VC4 connect to each cell junction; in 3S, VC1 and VC2 are shorted; in 2S, VC1, VC2, and VC3 are shorted. All configurations use the same BQ29412PW device and pinout - no configuration pins or firmware are required. The BQ29412PW's flexible sensing architecture eliminates need for multiple SKUs per cell count.

What is the function of the OUT pin on the BQ29412PW?

The OUT pin on the BQ29412PW is an open-drain output that transitions high (pulls toward VDD) when any monitored cell exceeds 4.45 V. It is designed to drive the gate of an external N-channel MOSFET, which in turn activates a fuse-blowing circuit in the battery pack's positive rail. The BQ29412PW does not provide current limiting or latching - the external FET and fuse implement irreversible shutdown. OUT remains high until all cells fall below (4.45 V – 320 mV hysteresis).

Is the BQ29412PW pin-compatible with other devices in the bq2941x family?

Yes, the BQ29412PW is fully pin-compatible with all members of the bq2941x family including BQ29410PW, BQ29411PW, BQ29413PW, BQ29414PW, and BQ29415PW. All share identical TSSOP-8 (PW) package, pin assignment, electrical interface, and functional behavior - differing only in factory-programmed overvoltage threshold. This allows design reuse and simplified inventory management across battery voltage variants while maintaining the same BQ29412PW footprint and layout.