MOTM

although I still dont know what Ill use this module for, Im all for adding as
many options, including led's : )  as possible./
Jim

jhaible@... wrote:

> > On the VC Pulse Divider from Serge, there is an output called 'STEPPED'.
> I'm
> > am pretty sure
> > how they did it (not seeing the circuit).
>
> I thought I was pretty sure how they did it, too, but I may me wrong:
> I thought they used a charge pump like that NS app note for the
> LM3900. I mean they might have used a counter, but seeing Serge's
> general fondness of the 3900, I'd be surprised if he would not have
> done it with that single chip. (Anybody knows for sure ?)
>
> And yes, bringing out the ramp would be useful. (I have not done it
> on my version, but I wished I had.)
>
> JH.
>
> >
> > The output is a stair-cased, positive-going sawtooth. The sawtooth is
> > generated by a 5-bit
> > counter, that is *clocked* by the input pulses and *reset* by the
> > divide-by-N pulse.
> > The output counter bits feed a 5-bit DAC.
> >
> > So, here are some interesting things about this sawtooth:
> >
> > a) for a fixed frequency in, the *amplitude* is inversly proportional to
> the
> > divide ratio. Think
> > about it: the longer you count, the higher the amplitude.
> >
> > b) of course, for a fixed input frequency, the *output* frequency is
> > proportional to the divide
> > ratio. If you input 4Khz and divide by 8, you get out a 500Hz sawtooth
> with
> > 8 steps. Assuming
> > a -5V to +5V output scaling (like all the other signal generators), we
> have
> > 10V/32 steps = 312mv/step. So for 8 steps = -5V to -2.5V sawtooth.
> >
> > For straining the brain more: this acts as a low-pass filter! Since the
> > divide ratio is a control
> > voltage, then if the input is fixed (say 2Khz) then as the divisor is
> swept
> > from 32 to 1 the
> > amplitude AND frequency change. But, the amplitude drops off at higher
> > frequency outputs
> > since the counter is reset faster and faster.
> >
> > Of course, if you fix the divide ratio and sweep the input, the amplitude
> of
> > the sawtooth is *constant*
> > at the divide ratio X 312mv.
> >
> > Will add $15 to the cost of the module. Discuss!
> >
> > Paul S.
> >
> >
> >
> >
> >
> >
>