Texas Instruments BQ29209DRBT

Overview

BQ29209DRBT from Texas Instruments is a secondary overvoltage protection IC for 2-series Li-ion battery packs, providing ±25-mV overvoltage detection accuracy (0°C to 60°C), 4.30-V fixed OVP threshold, and automatic cell imbalance correction with ±30-mV enable/0-mV disable thresholds. It operates from 4 V to 10 V supply, consumes <3 µA typical quiescent current below protection, and supports internal balancing up to 15 mA - used in netbook computers and power tools for redundant cell safety.

For engineers reviewing the BQ29209DRBT datasheet, BQ29209DRBT pinout, BQ29209DRBT application, or BQ29209DRBT equivalent, key selection criteria include its 8-pin VSON (DRB) package, external capacitor-controlled delay timing (9 s/µF nominal), CB_EN–controlled balancing activation, and dual-cell voltage monitoring via VC1 and VC2 inputs with independent balancing paths.

Technical Context

The BQ29209DRBT implements a precision analog comparator architecture that continuously monitors VC1–GND (bottom cell) and VC2–VC1 (top cell) against a factory-trimmed 4.30-V reference. Upon overvoltage detection, it initiates a programmable delay using an external capacitor on CD before asserting high-level output on OUT.

Cell balancing is enabled by pulling CB_EN low, activating internal MOSFET switches (RCB1/RCB2) to discharge the higher-voltage cell until voltage difference falls within ±0 mV hysteresis; balancing resumes if mismatch exceeds ±30 mV. The device supports both internal balancing (up to 15 mA) and external balancing via VC1_CB and discrete FETs.

Key Specifications

Pinout & Package

8-pin VSON (DRB) package with exposed thermal pad (PWR PAD) requiring solder connection to PCB ground plane for thermal and electrical integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BQ29209DRBT, BQ29200DRBT offers identical functionality at a higher OVP threshold, while BD14000GUL integrates switching drivers but omits programmable balancing - making BQ29209DRBT the sole option for systems requiring adjustable, low-power, auto-hysteresis cell equalization in a minimal 3×3 mm footprint.

Availability

BQ29209DRBT is available at Aetrix Electronics and suitable for netbook computers, power tools, and portable instrumentation requiring stable component supply with guaranteed long-term lifecycle support.

Supply support for BQ29209DRBT 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 battery management system expertise.

The bq2920x product line delivers secondary overvoltage protection with integrated cell balancing for 2-series Li-ion battery packs - designed specifically for safety-critical, space-constrained portable and industrial energy storage applications.

FAQ

What is the exact overvoltage protection threshold of the BQ29209DRBT?

The BQ29209DRBT has a fixed overvoltage protection (OVP) threshold of 4.30 V per cell, factory-programmed and specified with ±25 mV accuracy over 0°C to 60°C. This value is distinct from the BQ29200DRBT (4.35 V) and applies independently to both VC1–GND and VC2–VC1 measurements. The BQ29209DRBT does not support user-adjustable thresholds.

How does the BQ29209DRBT initiate and terminate cell balancing?

The BQ29209DRBT initiates cell balancing when the voltage difference between VC2–VC1 and VC1–GND exceeds ±30 mV (nominally), provided CB_EN is pulled low. Balancing terminates when the difference falls within ±0 mV hysteresis. The BQ29209DRBT uses internal MOSFET switches (RCB1/RCB2) to discharge the higher-voltage cell, and balancing resumes automatically if imbalance reappears.

Can the BQ29209DRBT be used without external balancing components?

Yes, the BQ29209DRBT operates fully functional with only essential passives: CD capacitor for delay timing, RVD/CVD for VDD filtering, and CIN for VCx filtering. Internal balancing (up to 15 mA) requires only CB_EN control and proper PCB layout; no external RCB resistors are needed unless higher balancing current is required via external FETs.

What is the role of the PWR PAD terminal on the BQ29209DRBT DRB package?

The PWR PAD on the BQ29209DRBT is an exposed thermal pad electrically connected to GND. It must be soldered to a PCB copper pour tied to system ground to ensure proper thermal dissipation and electrical stability. Leaving it unconnected degrades thermal performance and may cause functional instability under sustained balancing load.

Does the BQ29209DRBT support Customer Test Mode (CTM), and how is it activated?

Yes, the BQ29209DRBT supports Customer Test Mode (CTM) to reduce overvoltage delay for production testing. CTM is activated by setting VDD ≈ 9.5 V higher than VC2 (e.g., VC2 = 7.6 V, VDD = 17.1 V), which switches the delay scale factor from 9 s/µF to ~0.08 s/µF. The BQ29209DRBT exits CTM only upon full power cycle - not by voltage adjustment alone.