[sdiy] as3340 PW/tuning issue

[ColinMuirDorward]

OK I found the answer to this in the TH vco maximus thread at muffs.
User chrissugar reports " So as a conclusion the goal is to have on pin3 as
close as possible to -5V and the PWM to tune error will not manifest
itself."

On Wed, Dec 18, 2019 at 2:44 PM ColinMuirDorward <colindorward at gmail.com>
wrote:

> Thanks Jay and Dave.
> I found some muffs threads. In one of them, alfa (presumably alfa rpar
> spokesperson) chimed in to say that the issue would be corrected in future
> versions.
> Dave, you added a -5v regulator, is that to power the 3340, or as a
> reference voltage somewhere, or both? I know the datasheet suggests
> powering from -5v to reduce self heating, but did not mention effect on pwm.
> Colin
>
> On Wed, Dec 18, 2019 at 4:58 PM Jay Schwichtenberg <jschwich53 at comcast.net>
> wrote:
>
>> Colin,
>>
>> There has been a lot of talk and info on this in Muff Wigglers. Go there
>> and do a search.
>>
>> Seems that the different (manufactures) 3340s behave differently and from
>> what I've seen the AS3340 is the worst. There are things that can be done
>> to minimize the problem, that's been documented on Muff's.
>>
>> Jay S.
>> On 12/18/2019 10:31 AM, ColinMuirDorward wrote:
>>
>> Hi folks,
>>
>> Was there ever a conclusive investigation of the PW/pitch interaction on
>> the as3340 chip? What I mean is that when you adjust the pw, you get some
>> detuning as well.
>>
>> I've never been sure if this was a bug in my circuit or the chip itself.
>> Also not sure if the other 3340 versions exhibit the same behavior. I asked
>> someone to test on their ms101 if that issue was evident, and they said "no
>> detune".
>>
>> I know that I'm not the only one experiencing this since alfa rpar sells
>> a module "for circuits where requirements on influence of PWM signal on
>> frequency are strict <http://www.alfarzpp.lv/eng/sc/AS3340-HYB.php> "
>>
>> Any thoughts welcome.
>>
>> Cheers,
>> Colin
>>
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>
>
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