What is killing my pcm2707

blacky77 · 23rd January 2011, 03:21 PM

Hello,

I want to build a NOS DAC similar to Doedes Project on dddac.de. My Problem is that the circuit is working - but after repowering, I suddently get no more answers on the USB bus and the chip PCM2707 seems to be dead.
I replaced the 2707 and it worked again. After repowering, the chip again is dead.

I assume some problems in the voltage supply or so. Anyone has an idea?

Attached are the power supply and the dac circuit.

singa · 24th January 2011, 02:22 AM

Hi, Check usb and other wiring /connections to 2707 are they correct?
Singa

SoNic_real_one · 03:21 AM

1. Use a wire instead of the L3, L5 inductance...
2. Also, check into "(3) D+ pull-up must not be activated (HIGH: 3.3V) while the device is detached from USB or power supply is not applied on VDD and VCCx. VBUS of USB (5V) can be used to detect USB power status"

blacky77 · 24th January 2011, 05:19 AM

Quote:

Originally Posted by SoNic_real_one

1. Use a wire instead of the L3, L5 inductance...
2. Also, check into "(3) D+ pull-up must not be activated (HIGH: 3.3V) while the device is detached from USB or power supply is not applied on VDD and VCCx. VBUS of USB (5V) can be used to detect USB power status"

Ah, that is the and gate some people have in the circuit. Ok - i'll try that. two more pcm 2707 left...

Does anyone exactly the reason why this is needed?

thanks

theAnonymous1 · 24th January 2011, 06:05 AM

The gate it to prevent PC HOST detection when the IC is powered off.

analog_sa · 24th January 2011, 08:06 AM

Is anything connected to the dac? There may be some unequalised ground potential between the PC and whatever follows the 2707...

blacky77 · 24th January 2011, 07:35 PM

Until now, there is nothing behind the DAC. A capacitor...

SoNic_real_one · 24th January 2011, 10:05 PM

I am thinking that those inductances would make some kind of self-induced spikes. I don't see the need for them on the ground path - if you want you can add one on the digital +5V supply.

blacky77 · 30th January 2011, 08:01 PM

Ok. Problem solved everything is working now with the third chip. In the end, the inductors in the USB path where the problem. In addition I found out that I did not connect the I2S right, so do not rely on the schematic posted above.

--Thanks for support.

24th January 2011, 03:19 AM	#3
SoNic_real_one diyAudio Member Join Date: Jan 2008 Location: Virginia	1. Use a wire instead of the L3, L5 inductance... 2. Also, check into "(3) D+ pull-up must not be activated (HIGH: 3.3V) while the device is detached from USB or power supply is not applied on VDD and VCCx. VBUS of USB (5V) can be used to detect USB power status" Last edited by SoNic_real_one; 24th January 2011 at 03:21 AM.

24th January 2011, 06:05 AM	#5
theAnonymous1 diyAudio Member Join Date: Feb 2004 Location: Anonymityville	The gate it to prevent PC HOST detection when the IC is powered off. __________________ "If you don't like funerals don't kick sand in Ninja's face." - Ninja

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24th January 2011, 02:22 AM	#2
singa diyAudio Member Join Date: Apr 2004 Location: near	Hi, Check usb and other wiring /connections to 2707 are they correct? Singa

24th January 2011, 08:06 AM	#6
analog_sa diyAudio Member Join Date: Aug 2002 Location: Sofia	Is anything connected to the dac? There may be some unequalised ground potential between the PC and whatever follows the 2707...

24th January 2011, 07:35 PM	#7
blacky77 diyAudio Member Join Date: Jan 2011	Until now, there is nothing behind the DAC. A capacitor...

24th January 2011, 10:05 PM	#8
SoNic_real_one diyAudio Member Join Date: Jan 2008 Location: Virginia	I am thinking that those inductances would make some kind of self-induced spikes. I don't see the need for them on the ground path - if you want you can add one on the digital +5V supply.

30th January 2011, 08:01 PM	#9
blacky77 diyAudio Member Join Date: Jan 2011	Ok. Problem solved everything is working now with the third chip. In the end, the inductors in the USB path where the problem. In addition I found out that I did not connect the I2S right, so do not rely on the schematic posted above. --Thanks for support.

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