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AH5795

SINGLE PHASE HALL EFFECT LATCH SMART FAN MOTOR CONTROLLER

Diodes Incorporated. 

AH5795

SINGLE PHASE HALL EFFECT LATCH SMART

FAN MOTOR CONTROLLER

Application Note

DC Supply voltage speed control

Motor speed can be controlled by varying the Vdd supply voltage while PWM pin is tied to Vdd pin.

For example, with 5V nominal motor, changing supply voltage between 5V to 1.8V, speed can be reduced from 100% to 36%

typically.

PWM speed control

Motor speed can also be adjusted by applying a PWM speed control signal into the PWM pin while keeping the Vdd pin at

nominal motor voltage. The motor speed is proportional to the PWM signal duty. For example, with 5V nominal motor, Vdd

pin is maintained at 5V typical while varying the PWM control signal duty to adjust the motor speed linearly. Figure below

shows the output O1 and O2 in relation to PWM speed control signal at PWM pin.

Frequency of PWM speed control signal can be between 15Hz to 50kHz. Recommended typical PWM signal frequency is

25kHz to keep switching frequency away from audible band. If PWM signal level at PWM pin stays low for longer than 65ms

typical, the outputs are disabled.

Depending on the motor design and its inertia, minimum start-up PWM duty required can be typically between 30% - 40%

while minimum running PWM duty can be down to 20%-25% typical. If voltage at Vdd is lower than the nominal motor

voltage, both start-up PWM duty and minimum running PWM duty required will be higher.

AH5795

Document number: DS35277 Rev. 1 - 2

7 of 13

www.diodes.com

August 2011

© Diodes Incorporated

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