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Old 29th February 2012, 06:22 PM   #11
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Join Date: Feb 2012
SoNic_real_one, thank you, a lot!
This is REALLY helpful for my project. I have so much concern about routing, spending hours copying the schematic is frustuating.
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Old 29th February 2012, 08:56 PM   #12
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Location: Virginia
You're welcome. I don't see too many polite people on forums anymore
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Old 1st March 2012, 02:02 PM   #13
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Hey again,

Maybe I should start another thread, but since it is about the same datasheet I go on here.
I'm now wondering about powering and grounds. Maybe you've seen it coming .
Page 25 and 26, opamps are powered by 5v, and wired to ground. I believe this is a "mistake". Opamps process analog signals, so they have to be wired to AGND. And their positive inputs are biaised to AVdd/2, so they must be powered by AVdd, which is 3.3v, not 5v. Am I right?
This is what TI did page 26 of this application note:

Isolating analog and digital sections now:
I use an arduino mega, so power supply is regulated.The arduino provides me with 5v and 3.3v power supplies. 5v is my digital supply, and 3.3v the analog one.
I think I will only use one ferrite bead, placed between the two grounds. DGND will be directly wired to power supply ground, and will physically be close to it (to prevent high frequencies currents from returning into the analog part). AGND will be isolated by the ferrite bead.
What do you think?

Knowing that what I'm designing is an audio effect. So this is NOT hifi. And it will be my first pcb design with more than 10 components. So I'm not looking for perfection.

Sorry for english mistakes, everyone noticed I'm not a native ;+).

Last edited by nirv4nh4ck; 1st March 2012 at 02:29 PM. Reason: wrong smiley
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Old 3rd March 2012, 05:21 PM   #14
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AGND is the same as GND. Bias is provided by VCOM (DAC output) or 2.5V (in the ADC input schematic), and is power by 5V. Is not a perfect, but is a easy arrangement.

Last edited by SoNic_real_one; 3rd March 2012 at 05:26 PM.
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Old 3rd March 2012, 07:40 PM   #15
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Join Date: Jan 2010
Originally Posted by nirv4nh4ck View Post
And their positive inputs are biaised to AVdd/2, so they must be powered by AVdd, which is 3.3v, not 5v. Am I right?
The text says the maximum differential signal is 4V, so the op amps cannot be powered from 3V3. 5V is correct for AVdd, with 2.5V common mode.
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