Eduardo Dias Vilela

Noise at PWM

Discussion created by Eduardo Dias Vilela on Oct 14, 2009
Latest reply on Nov 11, 2009 by Daniel Lundin

Hi guys,

I´m doing a PWM to DC level converter, and I make the  RC filter, and it is good. BUT, the problem is that the edges of the PWM wave generate in others pins of output, a relative high noise (400mV pp). Its continue to occur after I configure the Port P Reduced Drive Register.Before this configuration, the noisewas 850mV pp!!! It´s normal?How can I cancel this noise?  Just for info: my PWM output is connectet to base of NPN transistor, by 2K2 resistor. The frequence of PWM is 100KHz, but the noise, is not associated at the frequency, is vary with the rise and fall times of the PWM signal. 

The intention is to generate a DC lever to use in a external comparator.  ...

If somebody can help me, please... give me a ligth!


Eduardo Vilela