On Sun, 7 Mar 2010 18:04:29 -0000, alan.b.pearce said:
> > I'm looking for a single supply voltage to frequency converter.
> 
> What is wrong with the oscillator section of a CD4046 PLL chip?

I'd forgotten about the CD4046, it's great chip. The biggest problem is
the performance over temperature.

+- 12% frequency stability over 50 degree C range with 5 volt supply.
It's three times better at 10 volts, but the chip itself wasn't really
designed for remote instrumentation.

I need to think about using a PIC or other small micro. VFC chips are
nice and simple, but they pretty much all require a trimpot for
calibration, and NPO caps. If I use a micro I can get one with a bandgap
reference and use a crystal for frequency accuracy and then I won't need
to trim it. But each one will require programming.

Thanks everyone for all the good input.

Cheerful regards,

Bob

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