> Would a PIC12F675 using internal osc with code to control the PWM and
AD's, with a linear or log pot as input, or with the PIC using it's A/D pin
as input.  The PIC code would be minimal, and certainly offset if the volume
produced is high.
Would that work?
>

No hardware PWM I think. And cost is rather high compared with alternatives.
Using Digikey as a guide (there MAY be cheaper but DK is easy to get
comparison prices from). 12F675 is about $US1.35/1000s

The tiny11 (also no hardware PWM) is $0.25 or less in that quantity! The
question as to suitability of low frequency PWM is the only issue.

_____________________________

> ATTiny13 would seem a good fit - internal RC osc, on-chip ADC,  internal
RC at up to 9.6MHZ
you could get about 0.1uS PWM resolution in software, so about 0.2%
resolution at 20KHz
>

A nice processor, but again, price is too high. About $US0.75/1000s
And still no hardware PWM AFAIK.
My PWM spec of at least 6 bits of resolution at 20 Khz means a PWM bit
changes at 1/(20,000 x 2^16) = 0.78 uS
At 20 Mhz you probably get about 15 MIPS (even though Atmel say 20 MIPS at
20 Mhz. If this sat in a tight loop doing nothing but PWm you would probably
make it. 15MIPs * .78uS = ~ 12 instructions per PWM bit! Not really enough
to run interupts. Reading an A2D in there would get tough. I've little doubt
that Scott D could coax out the magic needed, but it still costs more than
the analogue solution and does the PWM and nothing else.

______________________

Someone offlist suggested the Philips LPC901 8051 variant at under $US1 -
and it has got hardware PWM. No A2D. Sigma Delta would work.
________________________

At present the tiny15 at about $US1.20/1000's with A2Ds and hadware PWM is
attractive
I have a solutuion working with ease with a tiny26 at $US1.30/1000s. Big
brother to the 15 at about $US0.10 more.
_____________

The HIP 4080 addresses the FET driving aspect but is dearish compared to
other laternatives and doesn't seem to address the analog to PWM aspect
(maybe I missed something there).

____________

I'm going to have to try a 4060 version "just to see". And read the LPC901
spec sheet more closely

        http://www.acqura.com/datasheets.asp?ID=499



        RM

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