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Design >> Analog Design >> Supply noise filtering in crystal oscillators
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Message started by Murat H. Eskiyerli on Mar 8^th, 2011, 7:04am

Title: Supply noise filtering in crystal oscillators
Post by Murat H. Eskiyerli on Mar 8^th, 2011, 7:04am

Hi All,

I am designing a crystal oscillator in 28nm CMOS using 1.8V thick-oxide devices. It is a simple Pierce oscillator type design. The circuit is mostly done, but I need to meet the specs with certain supply noise injection, i.e. 200mVpp at 100Hz, 10kHz, and 1MHz. Are there any pointers or ideas about how to go about designing a supply filter for such a circuit? Any help would be greatly appreciated.

Murat Eskiyerli

Title: Re: Supply noise filtering in crystal oscillators
Post by loose-electron on Mar 14^th, 2011, 1:58pm

Determine your transfer function from the power supply to the output.

I suspect you will find that the dominant component of the transfer function comes from the power supply to the output amplifier.

The crystal has such a high Q that little or no OOB will pass thru it directly.

With that you can determine your PSRR needs.

Title: Re: Supply noise filtering in crystal oscillators
Post by Murat H. Eskiyerli on Mar 18^th, 2011, 5:56am

Thanks for your help.

Murat