US90A / US91A

24V Hall IC Fan Driver

Features and Benefits

• Low cost
• High sensitivity Hall Sensor
• Locked rotor protection and auto-restart
• Power-efficient CMOS and power MOSFETs
• Built-in output protection clamping diode
• Integrated tachometer (US90A) or alarm (US91A) signal output
• 2-coil fan driver with FG/RD output in 4-pin VK / VA and 8-pin narrow SOIC packages (all RoHS Compliant)

Application Examples

• 12V/24V fans
• Peak current up to 500mA

General Description

The US90A/91A is a one-chip solution for driving two-coil brushless DC cooling fans.

Based on the advanced Melexis CMOS process, the IC contains a Hall-effect sensor, dynamic offset correction and low side output drivers.

Frequency Generator or Rotation Detection is available. The open-drain output makes the connectivity with any external interface such as hardware monitoring or Super I/O IC easier.

These features are combined with the Melexis patented no-VDD design to fit the IC in small 4-pin VK and VA package. The device is also delivered in DC package for automatic assembly.

Absolute Maximum Ratings

Exceeding the absolute maximum ratings may cause permanent damage. Exposure to absolute-maximumrated conditions for extended periods may affect device reliability.

Functional Diagram

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