Texas Instruments BQ24735RGRR

Overview

BQ24735RGRR from Texas Instruments is a 1- to 4-cell Li⁺ SMBus charge controller with integrated N-FET drivers for hybrid power path management. It enables adapter + battery concurrent power delivery to support Intel® CPU Turbo Boost mode, features ±0.5% charge voltage accuracy up to 19.2 V, ±3% charge current accuracy up to 8.128 A, and operates across 4.5–24 V adapter input range.

For engineers reviewing the BQ24735RGRR datasheet, BQ24735RGRR pinout, BQ24735RGRR application, or BQ24735RGRR equivalent, key selection criteria include SMBus-programmable input/charge current limits, dual N-FET driver architecture for automatic AC/battery source selection, turbo boost discharge capability, and integrated safety protections including OVP, OCP, and thermal shutdown.

Technical Context

The BQ24735RGRR implements a synchronous buck converter with programmable switching frequencies (615/750/885 kHz) controlled via SMBus ChargeOption() register. It uses two independent charge pumps to drive ACFET/RBFET (adapter path) and BATFET (battery path), enabling seamless system power source arbitration without external logic.

Its dual-current-sense architecture supports independent regulation of adapter input current (via ACN/ACP) and battery charge current (via SRP/SRN), both amplified at 20× with ±2% accuracy. Real-time ILIM pin control allows hardware-based current limiting alongside SMBus DAC settings, with priority given to the lower of the two limits.

Key Specifications

Pinout & Package

VQFN-20 (RGR) package, 3.5 mm × 3.5 mm, 0.5 mm pitch, with exposed PowerPAD™ thermal pad soldered to PCB ground plane for enhanced thermal dissipation (R_θJA = 46.8°C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar hybrid power path management applications.

Compared with BQ24735RGRR, BQ24725ARGRR omits battery-to-system discharge and dual-pump architecture, limiting its use to basic charging-only topologies, while BQ24780SRGRR extends functionality with USB PD support and higher current capability but increases BOM and layout overhead.

Availability

BQ24735RGRR is available at Aetrix Electronics and suitable for portable computing, industrial handheld terminals, and medical portable equipment requiring stable component supply, long-term lifecycle support, and guaranteed traceable sourcing.

Supply support for BQ24735RGRR 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 ICs, with decades of expertise in battery charging and power path solutions.

The BQ24735RGRR belongs to TI's bqSwitcher™ family of SMBus-controlled battery chargers designed specifically for high-efficiency, multi-source power management in space-constrained mobile computing platforms.

FAQ

What is the primary function of the BQ24735RGRR in a notebook power architecture?

The BQ24735RGRR serves as a hybrid power path manager that simultaneously regulates battery charging from an AC adapter while enabling battery discharge into the system bus during CPU Turbo Boost events. It replaces discrete charger + OR-ing controller combinations with integrated N-FET drivers, SMBus control, and safety circuitry - all in a single 3.5 mm × 3.5 mm VQFN package. This architecture ensures uninterrupted system operation even when adapter power is insufficient for peak loads.

Does the BQ24735RGRR support battery-to-system power delivery, and how is it activated?

Yes, the BQ24735RGRR supports battery-to-system power delivery through its BATFET driver (BATDRV pin) and integrated turbo boost mode. Activation occurs automatically when system load exceeds adapter capability - detected via real-time comparison of input current limit and system demand. The device then turns on BATFET while modulating ACFET/RBFET to inject battery energy into the system rail, all without host intervention. This behavior is enabled by default and requires no SMBus command.

How does the BQ24735RGRR handle adapter detection and what pins are involved?

The BQ24735RGRR uses the ACDET pin as its primary adapter detection input, where a resistor divider sets a threshold between 2.4 V and 3.15 V. When ACDET exceeds 0.6 V and VCC is above UVLO (3.5–4.0 V), the internal REGN LDO activates and the ACOK open-drain output pulls high (with external 10-kΩ pullup) to signal valid adapter presence. The ACOK assertion also requires VCC to be at least 275 mV above SRN - ensuring reliable detection even during battery-only operation or weak adapter conditions.

What are the accuracy specifications for charge voltage and current regulation in the BQ24735RGRR?

The BQ24735RGRR delivers ±0.5% charge voltage accuracy across its full 1.024–19.2 V range, verified at multiple setpoints including 16.8 V (4S), 12.592 V (3S), and 8.4 V (2S). For charge current, it achieves ±3% accuracy up to 8.128 A using a 10-mΩ sense resistor, with tighter tolerance maintained across the full 0.128–8.128 A range. Input current regulation matches this performance at ±3% up to 8.064 A, enabling precise power budgeting between adapter and battery paths.

Can the BQ24735RGRR operate with different Li⁺ cell counts, and how is configuration managed?

Yes, the BQ24735RGRR natively supports 1S, 2S, 3S, and 4S Li⁺ battery configurations without hardware changes. Cell count is configured entirely via SMBus registers - specifically the ChargeVoltage() command, which accepts 16-bit values corresponding to target voltages from 1.024 V to 19.2 V in 12.5-mV steps. The device automatically scales its OVP, depletion, and safety thresholds proportionally to the programmed voltage, eliminating manual resistor adjustments or board variants for different pack configurations.