Lpc2000

From: "Tom Walsh" <tom@...>
> While looking at the schematic for the Keil MCB2130, I noticed that they
> put a 560K resistor in series with the 32KHz crystal.  This seems odd,
> the only reason I can see for a series resistance is to lower the
> current through a crystal circuit.
>
> Anyone see this?   From what I can tell from the LCP2138 manual, only
> load capacitors are called for to pull the crystal on frequency.
> AFAICT, my 32KHz crystal is running fine on my board without the series
> resistor.

A deja vu, see the archives of this group...

The max power into a 32kHz Xtal is very limited, the resistor lowers the
actual power. I've had Xtals literallly break in a 5V CMOS oscillator when
that resistor was missing. And they were $10 in those days...

BTW: the series resistor must be between the output of the oscillator buffer
in the chip and the C-Xtal-C network, not in series with the XTAL itself! A
drawing error in the diagram, I'm sure.

The extra heating caused may cause the Xtal to drift, too.

Arie de Muynck