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Re: is there a model or subckt for the PWM chip SG3524?


Gandolf
 

Hi RainbowSally!

Wow, you weren't kidding. OMIGOD, you should have seen the circuit I came up with while you were redoing the first one...somehow I got the notion in my head I needed to use peak detecting op amp circuits to define the top and bottom of the sawtooth, so I had both positive and negative peak detectors feeding a potentiometer going to a comparator....

....your circuit was a marvel of sophisticated elegance, I can't thank you enough.

I would post my new version of your re-do, but...I'm still waiting for LTspice to find an operating point LOL!!!

I'm going to bed now. If, in the morning, it gave an error (time-step error most likely; I think that's when it can't converge?), I'll post it asking for help getting it to run, and we can talk about design at the same time.

However, if it does finally run, then I have no reason to post it here; it would be off-topic to discuss the design elements (I've added a new section you haven't seen yet that's the point of the 1st circuit) - so am wondering where you'd like to continue the discussion...electronics_101? funwithtransistors? (both yahoo groups).

Very Best, with gratitude for your help, Maturin..errr, Gandolf LOL

--- In LTspice@..., rainbowsally <rainbowsally@...> wrote:

Hi Gandolf.

First pass, yer parts count has just gone way way WAY down.

Check your folder for the "rs-01" mods. I left the holes where the old
parts were and added jumpers to show where the new connections go... if
this still works for you.

Check your original file and verify that the wave forms in/out for the
opamp are identical. There is nothing really loading that source so the
opamp (buffer) is unnecessary as currently implemented.

Note: There's an NE555.asc file in the examples folder. It shows that
the CV is 5K to Vcc and 10K to Gnd. You don't need a resistor on the
control voltage output. Just the cap. And if you were attempting to
pull it down, use a much smaller resistor to do that, but chances are
you want to stay with the default.

:-)

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