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
Ordering Information
Part No.
US90A
US90A
US90A
US91A
US91A
US91A
Temperature Code
E (-40° to 85°
C
C)
E (-40° to 85°
C
C)
E (-40° to 85°
C
C)
E (-40° to 85°
C
C)
E (-40° to 85°
C
C)
E (-40° to 85°
C
C)
Package Code
VK (4-pin TO-92)
DC (8-pin narrow SOIC)
VA (4-pin TO-92 flat)
VK (4-pin TO-92)
DC (8-pin narrow SOIC)
VA (4-pin TO-92 flat)
1 Functional Diagram
2 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-V
DD
design to fit the IC in small 4-pin
VK and VA package.
The device is also delivered in DC package for
automatic assembly.
390109026302
Rev 002
Page 1 of 12
Data Sheet
Apr/07
MELEXIS [ Melexis Microelectronic Systems ]
