Diodes Incorporated
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AH285 (Not Recommended for new design)

NRND = Not Recommended for New Design

Two Phase BLDC All-In-One Fan and Motor Driver with Output Zener Clamp

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The AH285 is a single-chip solution for driving two-coil brushless direct current (BLDC) fans and motors. The device includes a Hall-effect sensor, dynamic offset correction and two complementary open-drain output drivers with internal Zener diode protection. To help protect the motor coils, the AH285 provides Rotor Lock Protection which shuts down output drives if rotor lock is detected. The device automatically re-starts when the rotor lock is removed. A Tachometer output is provided by open-drain Frequency Generator (FG) Pin which allows external interface to monitor motor rotation or speed. The FG output is the magnetic change frequency.


  • Single-chip solution
  • Operating Voltage: 3.8V to 20V
  • Built-in Hall sensor and input amplifier
  • Tachometer (FG) output
  • Rotor Lock Protection (Lock detection, output shutdown and automatic re-start)
  • Built-in Zener protection for output driver
  • Average output current up to 500mA
  • Packaged in SOT89-5L
  • Green Molding Compound


  • Two-coil BLDC cooling fans
  • Low to medium voltage, low power BLDC motors

Product Specifications

Product Parameters

Average OutputDrive Current (mA) 500
Frequency Generator (FG) and Rotation Detect -
Lock Detect, Shut-Down and Auto Start Yes
Operating Ambient Temperature (°C) -40 to 100
Operating Point Bop Gauss (Max) 60
Operating Point Bop Gauss (Min) 10
Operating Point Bop Gauss (Typ) 30
Operating Voltage (V) 3.8 to 20
Peak Output Current (mA) 700
Release Point Brp Gauss (Max) -10
Release Point Brp Gauss (Min) -60
Release Point Brp Gauss (Typ) -30
SupplyCurrent (mA) 2
Typical Total RDS(ON)(NMOS and PMOS Combined) 1.25 @ 12V
Typical Zener Breakdown Voltage (V) 42

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