Help needed with PCM2706

appleby · 14th March 2007, 06:42 PM

Hi,

I built the circuit at page 29 of PCM2706 datasheet:

focus.ti.com/lit/ds/symlink/pcm2707.pdf

It doesn't work. When I connect the USB cable to PC (Windows XP) it says "UNKNOWN DEVICE".
I also notice that the 12 MHz crystal oscillator doesn't work (I use CMAC HC49 12.000).
I don't know what to do.

Thanks for your help

dddac · 14th March 2007, 08:41 PM

If the oscilator does not work, the device will NOT be recognized by Windows, so fix that first ....

doede

gfiandy · 14th March 2007, 08:50 PM

Have you pulled the suspend pin high, if not the circuit will not start up. Also check the circuit arround the clock oscillator to make sure it has not got any shorts and is wired correctly the oscillator should start even if the part is not running correctly. Also check the power supply is good and is getting to all the power pins.

Regards,
Andrew

appleby · 15th March 2007, 01:28 PM

Thanks for suggestions!

I check the circuit and it seems to be ok.

I pulled up the suspend pin too, but I obtain the same Windows message.

I will do more attempts and I'll see.

Thank You all!

jaycee · 15th March 2007, 02:03 PM

See my own PCM2607 design here

I think that the PCM2606 has to have a programmed serial EEPROM connected to it, containing the USB identification data. The PCM2607 does not.

Check the chip is generating 3.3v on the VDD pin. Note how the USB D+ line needs to be pulled up with this 3.3v. I am assuming you are using bus-powered here.

edit: Hey, I just noticed I didn't pull *SSPND high! Whoops, oh well, my circuit still works.... it is probably internally pulled up.

appleby · 15th March 2007, 06:54 PM

I think that PCM2706 works without the EEPROM too.

I make some measurement and I think my problem is that the oscillator doesn't start.
I measured 3.3 V on pin 13 (XTO) and 1.8 V on pin 12 (XTI) but I didn't see any oscillation.

Thanks for replies.

jaycee · 16th March 2007, 04:04 AM

I would say that you need to mess about with the values of C1 and C2. The data sheet for your xtal should recommend values for these.

14th March 2007, 06:42 PM	#1
appleby diyAudio Member Join Date: Jan 2007 Location: Piacenza	Help needed with PCM2706 Hi, I built the circuit at page 29 of PCM2706 datasheet: focus.ti.com/lit/ds/symlink/pcm2707.pdf It doesn't work. When I connect the USB cable to PC (Windows XP) it says "UNKNOWN DEVICE". I also notice that the 12 MHz crystal oscillator doesn't work (I use CMAC HC49 12.000). I don't know what to do. Thanks for your help

14th March 2007, 08:41 PM	#2
dddac diyAudio Member Join Date: Jul 2003 Location: Wiesbaden	If the oscilator does not work, the device will NOT be recognized by Windows, so fix that first .... doede __________________ www.dddac.de Happy listening and building

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14th March 2007, 08:50 PM	#3
gfiandy Audio Engineer diyAudio Member Join Date: Jul 2003 Location: Cambridge UK	Have you pulled the suspend pin high, if not the circuit will not start up. Also check the circuit arround the clock oscillator to make sure it has not got any shorts and is wired correctly the oscillator should start even if the part is not running correctly. Also check the power supply is good and is getting to all the power pins. Regards, Andrew

15th March 2007, 01:28 PM	#4
appleby diyAudio Member Join Date: Jan 2007 Location: Piacenza	Thanks for suggestions! I check the circuit and it seems to be ok. I pulled up the suspend pin too, but I obtain the same Windows message. I will do more attempts and I'll see. Thank You all!

15th March 2007, 02:03 PM	#5
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	See my own PCM2607 design here I think that the PCM2606 has to have a programmed serial EEPROM connected to it, containing the USB identification data. The PCM2607 does not. Check the chip is generating 3.3v on the VDD pin. Note how the USB D+ line needs to be pulled up with this 3.3v. I am assuming you are using bus-powered here. edit: Hey, I just noticed I didn't pull *SSPND high! Whoops, oh well, my circuit still works.... it is probably internally pulled up.

15th March 2007, 06:54 PM	#6
appleby diyAudio Member Join Date: Jan 2007 Location: Piacenza	I think that PCM2706 works without the EEPROM too. I make some measurement and I think my problem is that the oscillator doesn't start. I measured 3.3 V on pin 13 (XTO) and 1.8 V on pin 12 (XTI) but I didn't see any oscillation. Thanks for replies.

16th March 2007, 04:04 AM	#7
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	I would say that you need to mess about with the values of C1 and C2. The data sheet for your xtal should recommend values for these.

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