Re: Replacing crystal with external clock signal

"PeteS" <PeterSmith1954@xxxxxxxxxxxxxx> writes:

Florian wrote:
I have a chip that wants a specific low-frequency (38k) clock crystal,
which are somewhat hard to find and pricy. I could synthesize a 38k
clock signal, but the chip is not designed to accept an external clock -
it wants that 38k crystal and a 10pF series capacitor between two pins.

Would it be possible to trick the crystal driver into syncing to an
external clock by proper attenuation and filtering? What sort of
voltages would be present in a running oscillator like this? Am I
likely to damage the chip by experimenting?

What device are you using?

These devices usually use an oscillator across the pins of 'XTAL1',
'XTAL2' or some such. In the documentation it usually specifies which
pin is the output of the amplifier and which is the input. You should
be able to drive the input side without problems from an external clock
at the appropriate levels, but what they are depend on the device.

The chip is a BA1404 FM transmitter. I found a data*** at
<http://www.radiochips.com/images/ba1404v2.pdf> but I can't tell from that
which pin is the input. Am I likely to fry the output if I try to drive
that?

Any guesses as to the voltages to start experimenting with? I'm planning to
run the chip at 1.5V.

Thanks for your help!
.

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