[time-nuts] V standards

Poul-Henning Kamp phk at phk.freebsd.dk
Tue Dec 2 08:47:26 UTC 2008


In message <58C70987-017E-44ED-BF07-D578679C03C2 at hughes.net>, Richard Moore wri
tes:

>> If you are controlling this with a microcontroller, there is an  
>> alternative
>> you should consider:
>>
>> Use only a single DAC and then PWM modulate its output, followed
>> by a low-pass filter.
>
>Poul, how do I PWM a DAC that is itself a PWM device? This question  
>is prompted by the DAC I'm using in Bert Zauhar's FLL GPSDO, which is  
>a dithered 10-bit DAC in a PIC chip that results in 14-bit  
>resolution. I'd like to have a simple way to get 2 to 4 extra bits of  
>resolution out of this. Can you recommend some design resources to do  
>this?

I would simply cummutate the DAC output with a PWM controlled fet or
CMOS switch.

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
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