> My PWM is at 5kHz.  I discovered that the current readings were not
> averages, because the A/D acquisition time is much faster that the PWM
> frequency, so the current sense readings were sometimes coming back as
> maximum, and sometimes as zero !  It is obviously catching either the
> low or high state of the PWM output.  Only occasionally were they
> coming back somewhere in between - obviously when the A/D acquisition
> happened to catch the PWM on a rising or falling edge.

If the PWM and A/D are done in the same chip, then synch the A/D
sample to the PWM on cycle. Even so, low pass filter plus software
averaging are almost mandatory.

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Brent Brown, Electronic Design Solutions
16 English Street, Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/txt: 025 334 069
eMail:  brent.brown@clear.net.nz

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