Hi All.
I'm a software developer with little exposure to hardware and electronics, and the project I'm involved in requires me to produce a PWM output from a general port on an MCU. The technique was fairly simple, i used a programmable counter array that has a PWM mode. All good so far.
But now.
The guy I work with, the EE, told me that the output frequency is incorrect, he wants it at 25Khz. I used the system clock as the source for the PCA (22.1 MHz). the PCA is 8 bits, so my frequency would be around 86khz. I can change a pre-scale for the PCA clock source to change the frequency to 21.6 KHz, 28.8 Khz... And that's the closest i can get to 25KHz without writing the whole damn PWM routine in software... which i ended up doing to fit the requirements.
Now, the EE is unable to provide an explanation for me. So could someone in plain english explain why PWM frequency is important? We're controlling a SanAce 80 GV (Sanyo) 12V Fan.
I'm reading elsewhere that PWM frequency is only important "as long as you're fast enough", but what does that mean? The spec for the Sanyo fan has an example where they discuss 25Khz PWM, but i suspect it's only an example - not a specification, and I'm not sure my coworker understands that.
Thanks for any clarification
Edit: Here's a link to the datasheet **broken link removed**
I'm a software developer with little exposure to hardware and electronics, and the project I'm involved in requires me to produce a PWM output from a general port on an MCU. The technique was fairly simple, i used a programmable counter array that has a PWM mode. All good so far.
But now.
The guy I work with, the EE, told me that the output frequency is incorrect, he wants it at 25Khz. I used the system clock as the source for the PCA (22.1 MHz). the PCA is 8 bits, so my frequency would be around 86khz. I can change a pre-scale for the PCA clock source to change the frequency to 21.6 KHz, 28.8 Khz... And that's the closest i can get to 25KHz without writing the whole damn PWM routine in software... which i ended up doing to fit the requirements.
Now, the EE is unable to provide an explanation for me. So could someone in plain english explain why PWM frequency is important? We're controlling a SanAce 80 GV (Sanyo) 12V Fan.
I'm reading elsewhere that PWM frequency is only important "as long as you're fast enough", but what does that mean? The spec for the Sanyo fan has an example where they discuss 25Khz PWM, but i suspect it's only an example - not a specification, and I'm not sure my coworker understands that.
Thanks for any clarification
Edit: Here's a link to the datasheet **broken link removed**
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