# Set PWM Frequency on LM63 !?



## MMos (Feb 23, 2005)

The problem: my Fan makes 'clicking' sounds.

First thing that came into my mind: It's because the LM63 has digital Fan control (PWM).
I ran some test to verify my thoughts.

1. I unplugged the fan from the card and connected it, to my powersupply, using a pot.
result : Fan doesn't generate any clicking sounds at all.

2. I connected a "Papst" fan to the fan-connector on my ATI Card.
result: Clicking sounds ! (Less then the stock cooler but still there).

3. I built a filter (100uF+2x7Ohm+2x4.7uh) and put the filter between the ATI Fan-out and the Fan.
result: much less clicking sounds but still there 

I took a look at the LM63 Datasheet and saw that it is possible to change it's PWM frequency.
I downloaded National's Sensor Eval 1.1 but it couldn't connect to the ATI LM63 (wrong address?)

I realy would like to change the PWM frequency on my LM63, but i dont know how to do it 
Is it possible to connect Sensor Eval to the ATI LM63 ?
Is it possible to built a "change PWM option" for ATI Tool ?

I had a similar problem with a Intel-Motherboard before. But there i could change the PWM frequency with Speedfan . I changed the PWM frequency from ~10KHz to ~20Khz and that helped alot! What i found out , if the PWM freq. is to low there are much clicking sounds, if the PWM freq. is to high the Fan start to "sing / hum"


----------

