PCM2902 power supply

jmar · 7th January 2006, 02:29 PM

I have a few basic questions about this chip as I'm a bit confused on a few issues.

(1) Can anyone explain the Vccp1I -- Vccp2I -- VccxI pins? What are these all about? Are they just points in the regulator that need some noise suppresion with caps?

(2)I want to use an external regulator and from what I've read it's advisable to supply Vccc with an outboard 3.3v regulator...BUT what does that mean for the Vbus pin?

It shows this pin as the 5v input for the internal regulator and now I'm really mixed up.

Do you leave the (USB) Vbus open and supply your own +5v ?
Do you leave the pin open completely so the internal regulator won't function?

And what about Vddd? Is that also 3.3v or 5v ?

The data sheet is really hard to decipher (for me anyway).

Thanks kindly for any help on this.

dsavitsk · 7th January 2006, 06:01 PM

You might get some ideas by tracing the board here http://www.ecp.cc/usb-spdif.html

7th January 2006, 02:29 PM	#1
jmar diyAudio Member Join Date: Jan 2004 Location: Indiana	PCM2902 power supply I have a few basic questions about this chip as I'm a bit confused on a few issues. (1) Can anyone explain the Vccp1I -- Vccp2I -- VccxI pins? What are these all about? Are they just points in the regulator that need some noise suppresion with caps? (2)I want to use an external regulator and from what I've read it's advisable to supply Vccc with an outboard 3.3v regulator...BUT what does that mean for the Vbus pin? It shows this pin as the 5v input for the internal regulator and now I'm really mixed up. Do you leave the (USB) Vbus open and supply your own +5v ? Do you leave the pin open completely so the internal regulator won't function? And what about Vddd? Is that also 3.3v or 5v ? The data sheet is really hard to decipher (for me anyway). Thanks kindly for any help on this.

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7th January 2006, 06:01 PM	#2
dsavitsk diyAudio Member Join Date: Jan 2005 Location: Chicago	You might get some ideas by tracing the board here http://www.ecp.cc/usb-spdif.html

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