Comparator for oscillator

borges · 14th April 2011, 08:35 PM

I'm considering various MCLK sources (XO, TCXO, OCXO), and see that the output drives are not that strong. "CMOS" clock edges are sloppy, and "clipped-sine" probably sloppier.

I'd like to put a comparator close to the DAC and route the XO output quasi-differentially there. That is, one phase is lo-pass filtered XO output, the other is actual XO output.

Any recommendations on a comparator which could do that with minimal added phase noise? This far I've trusted the XO output, so I don't have a lot of circuit ideas.

Perhaps it's destiny that this one dropped into my mailbox 10 seconds ago: High Performance Buffers - Cypress Semiconductor Looks neat but not really for 5V single-ended outputs.

Børge

lakeside · 16th April 2011, 04:44 PM

Perhaps the AD8561.

AD8561 | Ultrafast 7 ns Single Supply Comparator | Comparators | Amplifiers and Comparators | Analog Devices

borges · 17th April 2011, 02:53 PM

Thanks Lakeside.

The tricky thing is that I have to mux between one clock for the 44.1 domain and one for the 48 domain. The input capacitance of the mux (in pass mode) is often at least as much as the stated load capacitance of the XO.

So I'm trying to come up with something which can act as a clock buffer and multiplexer at the time. Tricky business considering noise and load capacitance.

Borge

14th April 2011, 08:35 PM	#1
borges diyAudio Member Join Date: Dec 2003 Location: Oslo, Norway	Comparator for oscillator I'm considering various MCLK sources (XO, TCXO, OCXO), and see that the output drives are not that strong. "CMOS" clock edges are sloppy, and "clipped-sine" probably sloppier. I'd like to put a comparator close to the DAC and route the XO output quasi-differentially there. That is, one phase is lo-pass filtered XO output, the other is actual XO output. Any recommendations on a comparator which could do that with minimal added phase noise? This far I've trusted the XO output, so I don't have a lot of circuit ideas. Perhaps it's destiny that this one dropped into my mailbox 10 seconds ago: High Performance Buffers - Cypress Semiconductor Looks neat but not really for 5V single-ended outputs. Børge

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16th April 2011, 04:44 PM	#2
lakeside diyAudio Member Join Date: Jul 2008 Location: Northeast Wisconsin	Perhaps the AD8561. AD8561 \| Ultrafast 7 ns Single Supply Comparator \| Comparators \| Amplifiers and Comparators \| Analog Devices

17th April 2011, 02:53 PM	#3
borges diyAudio Member Join Date: Dec 2003 Location: Oslo, Norway	Thanks Lakeside. The tricky thing is that I have to mux between one clock for the 44.1 domain and one for the 48 domain. The input capacitance of the mux (in pass mode) is often at least as much as the stated load capacitance of the XO. So I'm trying to come up with something which can act as a clock buffer and multiplexer at the time. Tricky business considering noise and load capacitance. Borge

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