CS4398 filtering?

leadbelly · 9th March 2006, 03:56 PM

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?

tarcuper · 12th May 2006, 07:58 AM

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.

Antonytls · 29th December 2006, 10:39 PM

Hello,

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?

jcx · 1st January 2007, 10:10 PM

http://www.iet.ntnu.no/~ivarlo/files...t_audiodac.pdf

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

9th March 2006, 03:56 PM	#1
leadbelly diyAudio Member Join Date: Dec 2002 Location: Calgary, Alberta	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? __________________ Aerodynamics are for people who can't build engines. Enzo Ferrari

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12th May 2006, 07:58 AM	#2
tarcuper diyAudio Member Join Date: May 2005 Location: Budapest	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.

29th December 2006, 10:39 PM	#3
Antonytls diyAudio Member Join Date: Mar 2004 Location: Toulouse	Hello, 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?

1st January 2007, 10:10 PM	#4
jcx diyAudio Member Join Date: Feb 2003 Location: ..	http://www.iet.ntnu.no/~ivarlo/files...t_audiodac.pdf 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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