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ADAU144x XTALI and XTALO Pins

SigmaDSP & SigmaStudio db10 Jan 10, 2013 00:00 1 replies Original on forum ↗
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db10 Question
Jan 10, 2013 00:00

On the ADAU144x evaluation board, there are jumpers that allow very several different clock input choices for the XTALI pin. The evaluation board essentially disconnects the XTALI pin allowing the selection of different clock sources, but in all cases, the capacitance and crystal network still are "hanging" off of the XTALO pin.

For a design that uses a local oscillator running at 24.576 MHz driving the XTALI pin (not using a crystal) is there any recommended configuration for the XTALO pin? A 22pF capacitor to ground? Other?

Thanks

ADIApproved Reply
Jan 10, 2013 00:00

Internal to those two pins is a ring oscillator that will only drive the output if a crystal is connected. The XTALO pin will sit idly if it is left floating. So, you can simply leave the XTALO pin floating in a design where MCLK is supplied externally.