[volt-nuts] PWM voltage divider

John Devereux john at devereux.me.uk
Wed Jan 8 08:56:20 EST 2014

"Ulrich Bangert" <df6jb at ulrich-bangert.de> writes:

>> -----Ursprungliche Nachricht-----
>> Von: volt-nuts-bounces at febo.com 
>> [mailto:volt-nuts-bounces at febo.com] Im Auftrag von Jan Fredriksson
>> Gesendet: Mittwoch, 8. Januar 2014 09:25
>> An: volt-nuts at febo.com
>> Betreff: [volt-nuts] PWM voltage divider
>> I'm thinking of using a PWM divider for voltage generation of 
>> adjustable DC voltages from a voltage reference.
>> Does anyone have any pointers to circuits, solutions, 
>> topologies, error analysis etc. for such solutions?
>> Jan
> Jan,
> with standard PWM generated from a microcontroller the repetition rates of
> the signal may get VERY slow with higher resolutions, making it difficult to
> make a pure DC signal from. You should consider to use a Sigma-Delta DAC
> which is very easy to program in a microcontroller. I have used AVR Megas
> with software Sigma Delta DACs and precision analogue multiplexers to switch
> between the reference and GND up to 20 bits of resolution. Worked fine!
> Best regards
> Ulrich

Another approach is to combine a "coarse" and "fine" PWM (as Fluke do in
their calibrators I think).


John Devereux

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