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Old 9th March 2006, 03:56 PM   #1
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Location: Calgary, Alberta
Default CS4398 filtering?

I am interested in using the CS4398 for a DAC. The question I have is about filtering. The datasheet indicates that there is on-chip analog bandpass filtering, 10Hz to 20kHz. However, it also recommends LP filtering be implemented in the external output stage and makes reference to a 20kHz LP filter and shows an example of such an output stage in the datasheet.

So, my question is, is the external filter absolutely necessary, or can it be safely implemented without?
The whole problem with the world is that fools and fanatics are always so certain of themselves, and wiser people so full of doubts. Bertrand Russell
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Old 12th May 2006, 07:58 AM   #2
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Yes, iit is useful to set the filter cutoff frequency about 44 kHz, but not lower because of the phase response.
If you do not use filter, the amplifier next may oscillate, warm, etc.
Prefer passiv filter design, maybe LRC...

CS4398 is amongst the best chips today.
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Old 29th December 2006, 10:39 PM   #3
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I'm looking examples using the CS4398. I have found the datasheet and the evaluation board but nothing else.

Do you have something for me?
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Old 1st January 2007, 10:10 PM   #4
jcx is offline jcx  United States
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gives internal details and refs for several high end dacs

CS4398 is a Voltage Output DAC with an integrated Sw-C filter/charge-V converter output

the clock frequency controlling the Sw-C filter will have feed through components in the output V, especially at high signal slew rates. these MHz? frequency components require analog filtering, preferably passive before they reach the input transistors of any subsequent op amps or power amps

the on chip digital filter will be fairly steep and have a corner freq ~ 0.4xfs(check data sheet), your analog low pass filter should be higher than this
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