Ringing noise in PWM Outputs STM32F4

lortiz · ‎2016-10-13

Posted on October 13, 2016 at 17:02

Hi,

I�m using the STM32F4 Discovery TIMER3 with channel 1 and channel 3 in mode pwm output.

I realised that when I�m use the module timer, I get ringing noise in the rising edge and falling edge of the PWM, and also in the VDD. Also I watched in an osciloscope that this noise adds in the others channels of the timer too.

Is there a solution to eliminate that noise?

I used my code and the example code for the discovery (official).

Thanks for advance.

Leonardo

#stm32f4-pwm-output-noise

Tesla DeLorean · ‎2016-10-13

Posted on October 13, 2016 at 17:22

If you are generating 50Hz PWM signals don't set the pin driver slew rate to 25-100 MHz? Pick something that is appropriate to the speed and loading you have.

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mark239955_stm1 · ‎2016-10-13

Posted on October 14, 2016 at 05:36

What clive said.

Also, you could try adding a small series resistor and cap to ground to damp the ringing a little. Something in the range 47-220R and 10-100pF might do it.

lortiz · ‎2016-10-14

Posted on October 14, 2016 at 21:37

First at all, thanks Clive1.

I forgot to mention that the frequency of the PWM is 500 KHz and the pin driver with slew rate to 25 to 100 MHz in Pull-up mode.

The PWM output controls a H bridge (DRV592A) with an LC output

filter.

I think the probe of the oscilloscope is adding the noise.