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What is PWM Resolution?

Started by Cap'n Ahab August 23, 2006
I have been experimenting with PWM on a PIC 16F877A.  Initially, I used
an example program that came with my development board & tweeking the
values to see what effect they had on the trace of my oscilloscope.

Having done that, I am now attempting to get a waveform to my
specifications.  I am having a little difficulty in understanding the
Microchip datasheets (or maybe it is just general ignorance!).  I just
cannot fathom out what is meant by PWM Resolution.

I am a novice to electronics, but I understand that, say, a 10-bit A/D
converter would give you a reading of 0-1023 or an 8-bit one a reading
between 0-255, but the datasheet gives a formula to work out the
*Maximum PWM Resolution* in bits.  I don't fully understand why that is
a variable.

ATM, I am guessing that the higher the frequency of the PWM the less
resolution you have available to specify the duty cycle. So with a low
frequency PWM, you could have 10-bits of resolution i.e. the duty cycle
could be 1/1024 of the period.  A much higher frequency, may only allow
you to have 3-bit resolution i.e. 1/8 of the period.

Am I on the right track?


Thx in advance,

Cap'n Ahab

Cap'n Ahab wrote:

> ATM, I am guessing that the higher the frequency of the PWM the less > resolution you have available to specify the duty cycle. So with a low > frequency PWM, you could have 10-bits of resolution i.e. the duty cycle > could be 1/1024 of the period. A much higher frequency, may only allow > you to have 3-bit resolution i.e. 1/8 of the period. > > Am I on the right track?
Yes.