| ??? 01/17/08 16:04 Read: times |
#149650 - 470k series resistance needed Responding to: ???'s previous message |
If the manufacturer of quartz doesn't recommend a scheme, try the following:
If you take a 12pF crystal then you should use smaller burden caps. Connect a 470kOhm series resistor from output of built-in Pierce oscillator to quartz. Use a burden cap at this terminal of about 22pF to GND. Connect the other terminal of quartz to input of oscillator. Connect at this terminal a burden cap of 10pF to GND. The sense of the high series resistor is not only to heavily reduce the drive level of quartz, but also to add enough phase shift to allow the Pierce oscillator to work properly. Have also a look at here http://www.8052.com/forum/read.phtml?id=79811 Kai |
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