Diodes Incorporated AH2985-P-B

Overview

AH2985-P-B from Diodes Incorporated is a two-phase Hall-effect smart fan motor controller in TO94 package, integrating a Hall sensor, dynamic offset correction, and dual complementary open-drain drivers with Zener protection. It operates from 2.5V to 15V, delivers up to 500mA average output current, and features rotor lock detection with automatic restart-designed for low-voltage two-coil BLDC cooling fans.

For engineers reviewing the AH2985-P-B datasheet, AH2985-P-B pinout, AH2985-P-B application, or AH2985-P-B equivalent, key selection criteria include start-up voltage margin (2.5V min), thermal shutdown at +150°C, RDS(ON) ≤1.6Ω at 300mA, magnetic operate point (5–60 Gauss), and TO94 mechanical compatibility in space-constrained fan modules.

Technical Context

The AH2985 implements a closed-loop commutation control architecture using an integrated Hall plate and amplifier to sense rotor position, feeding into logic that drives complementary DO/DOB outputs with built-in Zener clamping (20–36V breakdown). Its lock-detection circuit monitors back-EMF absence and enforces a 0.45s ON / 2.7s OFF duty cycle during stall.

Thermal protection activates at TJ = +150°C with θJA = 227°C/W, and internal reverse-blocking diode at VDD enables operation under reverse polarity up to –15V. The device's 1.56mm × 3.65mm die footprint and TO94 leadframe support high-density PCB layouts in compact fan assemblies.

Key Specifications

Pinout & Package

Package: TO94 - 4-pin single-ended leadframe package with 14.5mm body length, 5.22mm width, and 1.56mm height; optimized for through-hole mounting in fan housings and thermal transfer to metal brackets.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar two-phase BLDC fan controller applications.

Compared with A3967SLDTR-T and NCP5425DR2G, the AH2985-P-B offers full integration (sensor + logic + drivers), autonomous lock recovery, and lowest start-up voltage (2.5V), making it optimal for compact, self-contained fan modules where BOM reduction and reliability under marginal supply conditions are critical.

Availability

AH2985-P-B is available at Aetrix Electronics and suitable for server chassis cooling, industrial PLC cabinet ventilation, and medical diagnostic equipment fans requiring stable component supply and long-term lifecycle support.

Supply support for AH2985-P-B 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

Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design centers across Asia and manufacturing in China, Taiwan, and Malaysia.

The AH2985 belongs to Diodes' Smart Motor Control product line, engineered specifically for cost-sensitive, high-volume BLDC fan applications demanding integration, thermal resilience, and autonomous fault recovery in compact form factors.

FAQ

What is the minimum operating voltage for reliable startup and commutation?

The AH2985-P-B guarantees functional startup and Hall-based commutation down to 2.5V at 25°C, with tested operation confirmed across –40°C to +105°C ambient. Below 2.5V, the internal regulator cannot sustain sensor bias or logic levels, causing erratic or failed rotation initiation.

Does the device require external components for basic two-coil BLDC operation?

Only a 1μF/50V electrolytic capacitor between VDD and GND is required for power stabilization; all other functions-including Hall sensing, lock detection, Zener clamping, and reverse polarity protection-are fully integrated. No external resistors, diodes, or timing capacitors are needed for standard operation.

How does rotor lock protection behave during continuous stall conditions?

Upon detecting rotor lock, the AH2985 disables both DO and DOB outputs for 2.7 seconds, then attempts automatic restart. If lock persists, it repeats the 0.45s ON / 2.7s OFF cycle indefinitely until rotation resumes, preventing thermal runaway while preserving motor insulation integrity.

Is the TO94 package compatible with automated through-hole assembly processes?

Yes-the TO94 package has standardized lead spacing (e1 = 3.81mm, e = 1.27mm) and coplanarity compliant with IPC-A-610 Class 2 requirements. Its 14.5mm body length and 0.39mm lead thickness support wave soldering and selective soldering profiles used in high-volume fan module production.