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-   -   PCM2707 Schematic Review (http://www.diyaudio.com/forums/digital-source/89134-pcm2707-schematic-review.html)

bacworth 27th October 2006 11:12 AM

PCM2707 Schematic Review
 
2 Attachment(s)
Any ideas on what is wrong with the attached schematic. Fundamentally I intend on using the i2s interface, but as part of testing I have applied 5v to Vccr and ran Voutr into a opamp without sucess.

thanks

Alien8 27th October 2006 11:33 AM

Quote:

I have applied 5v to Vccr
you may want to check the datasheet...
your pcm2707 is dead :eek:

bacworth 27th October 2006 11:45 AM

The usb receiver still detects it under xp when I attach and disconnect it. According to the datatsheet Vccr should be 3.3v if self powered is this correct???

Add: I just changed it over (on the same channel) to 3.3v and still no previal.

cheers...

Alien8 27th October 2006 01:35 PM

check datasheet p29

I assume that is more or less what you've built.

Several pins have to be connected to a 3.3V supply in order for it to work. If you exceed 5V for these pins, you are very likely to destroy it.

A

bacworth 28th October 2006 04:21 AM

anyone???

dsavitsk 28th October 2006 04:27 AM

How are you powering it? I've not tried the analog out, but you can see a working schematic at http://www.ecp.cc/NOS-USB-DAC.html and some notes on powering it under the VR3 section at http://www.ecp.cc/HPDAC.html

-d

bacworth 28th October 2006 04:36 AM

self powered using LP2950CZ3.3 (datasheet link here ) for 3.3v, I will take a look at the notes... cheers

bacworth 28th October 2006 04:44 AM

Not 100% sure on this, but should SSPND be connected to 3.3v. I just noticed mine isn't and the HPDAC is? According to the datashet SSPND is an output.

fluckscapacitor 5th May 2007 07:38 PM

Quote:

Originally posted by bacworth
Not 100% sure on this, but should SSPND be connected to 3.3v. I just noticed mine isn't and the HPDAC is? According to the datashet SSPND is an output.

I know this is an old thread....but I too am scratching my head as to why every PCM270X schematic I see has SSPND connected to 3.3V. I have yet to build a device based on this chip yet, but it looks like the purpose of SSPND pin is just a flag, indicating suspend mode, that can then be used for whatever purpose (an LED, disabling/enabling other parts of the circuit, etc)

My guess is that someone misinterpreted this pin to cause the PCM270X to suspend when put LOW. And then about 20 people decided to copy this rather than reading the datasheet.

dsavitsk 5th May 2007 08:04 PM

You are correct. This is a harmless bug in the hpdac and it is noted in the instructions. I don't remember why I did this in the first place, but I think it was just a misreading of the datasheet.


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