Dear all,
I'm having some problems with a prototype based on the PCM2707 in bus powered mode. Descriptor is programmed through SPI for 250mA max, etc and the chip is configured for I2S output while using the built-in headphone amplifier connected to a set headphones. The design is based on a combination of the reference designs depicted in figures 33 and 34 in the datasheet.
Symptoms are that the board works flawlessly for about 30 - 60 minutes, then suddenly and unexpectedly, !SSPND goes low and playback stops as a direct result. After waiting a while the board again works perfectly for another short period of time, however much shorter. The longer I wait before re-attempting, the longer the board works. Also sometimes immediately replacing the crystal helps, but not always.
NOTE: USB audio is continuously fed so the bus is not going idle or anything like that.
Of apparent reasons, I suspect this may have something to do with the oscillator circuit. Turns out that the oscillator (12.000Mhz crystal) often (not always it seems) stops in conjunction with !SSPND going low. My questions are as follows:
1) Is the PCM2707 system clock derived from the 96Mhz PLL based on the 12.000Mhz crystal?
2) Depending on q1, does the PCM2707 stop the oscillator as a result of going into suspended mode?
3) What other reasons (see above) could cause !SSPND to suddenly go low?
Also, I wonder what's wrong with this link to the PCM2707 EVM - I get a HTTP 404 error when trying to reference it:
http://www.ti.com/litv/pdf/sleu116
Please advice. Thank you.
