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Old 13th October 2008, 09:34 PM   #21
borges is offline borges  Norway
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Default Re: S/PDIF to SPORT receiver PCB

Iain,

I just saw your original post. Just a small comment: I used to work as a chip designer, and it did happen from time to time that we used multiple pins for the same internal power. The way we designed things, each power domian was routed in a (once broken) ring just inside the bond pads. From the internal parts we threw in a wire out to the power ring. And from the power rings we would add connections to bond pads here and there, for example in each corner or at other regular intervals.

Separate regulation for separate power domains is great. But separate regulation for two pins on the same power domain could potentially send some destructive current down one pin and up the other.

Quote:
Originally posted by Iain McNeill
A few of my pet must-haves: individual regulators for every IC power pin. (If the chip designer bothered to give us multiple pins, we shouldn't tie them together)

Cheers,
Borge
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Old 14th October 2008, 02:41 AM   #22
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Thanks for that piece of inside information, Borges. You're right, connecting two regulators together inside an IC is probably not a good thing to do! It pays to read the datasheet eh? The first layout I came up with on the CS8416 had link resistors where I could easily evaluate the benefit of separate supplies. As the design grew to SRC4392, there were too many compromises to justify linking all the power rails. I'll have to build up the supplies one at a time with wire links to evaluate.

Would you say (from your IC experience) that if the pins have the identical name (mnemonic) then they are internally connected but if they have different names then they are different power domains?

Seems like a good convention but a few exceptions would destroy the rule.
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Old 14th October 2008, 06:52 PM   #23
borges is offline borges  Norway
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Quote:
Originally posted by Iain McNeill
Would you say (from your IC experience) that if the pins have the identical name (mnemonic) then they are internally connected but if they have different names then they are different power domains?
Well, given pins "VDDx1", "VDDx2", "VDDy1", "VDDy2", I would join all the x's at one regulator, and all the y's at another.

My personal little hangup is star power. The picture shows one regulator powering multiple opamps that handle related (same-audio-channel) audio data. The layout on the picture minimizes common-impedance noise on the PCB. The output impedance of the regulator will still transform current going to one sink to a voltage drop seen by all sinks. But board will not!

When datasheets say "connect the power pins x and y" I some times make a small power plane beneath the chip. And with multiple chips like that I often use a common regulator and a star. In my present DAC I have one row of regulators for L and one for R.

Remember that with the star, the resistance in the tracks and the local decoupling set up one lowpass filter per IC. So I rarely make those tracks super-narrow.


Cheers,
Borge
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Old 22nd October 2008, 02:27 PM   #24
SteB is offline SteB  England
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This Ti chip looks very straight forward to use as receiver for spdif for i2s output, will this circuit work as it is here as an s/pdif reciever with my tda1543 dac board?
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Old 23rd October 2008, 05:32 AM   #25
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unfortunately, the SRC4392 resets into a powered down state. You need a controller to write it's registers over either I2C or SPI.

You also need a master clock but if you're doing a DAC then you probably got a good one of those
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Old 31st October 2008, 02:21 AM   #26
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Ahh that brief moment of exhilaration just after you solder the last component and before you plug it in.
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Old 31st October 2008, 09:13 AM   #27
borges is offline borges  Norway
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Quote:
Ahh that brief moment of exhilaration just after you solder the last component and before you plug it in.
Yeah, and the dilemma of which music to put on first.

Board looks good. Just a tip: use some strips / glue / other mech. assembly to keep the connectors in place. I've torn too many connector pins when disconnecting and reconnecting prototype boards.


Good luck!


Borge
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Old 5th November 2008, 05:01 AM   #28
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Haven't had much time to debug but there seems to be a flaw in my strategy. Not wanting to do a register-by-register write setup, I tried to DMA the whole 0x33 bytes of registers in one block. Several of the registers are read-only so I'm not sure this is allowed (datasheet doesn't say you can't)

Anyway, the SPI isn't working yet.

P.S. thanks for the tip Borges - I'll follow your advice. I was wondering if that ever happened.
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Old 5th November 2008, 09:45 AM   #29
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Default Src & Dma

  I've tried DMA in my DAC4392 module and it works flawlessly... but I've spend few days write the code for it so, I can confirm DMA mode for the control registers (I didn't try to read the other pages but it should work). BTW, I'm using SRC4392 in SPI mode because it's easier for me.
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Old 5th November 2008, 02:44 PM   #30
borges is offline borges  Norway
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Default Re: Src & Dma

Quote:
Originally posted by Lucifix
  I've tried DMA in my DAC4392 module and it works flawlessly... but I've spend few days write the code for it so, I can confirm DMA mode for the control registers (I didn't try to read the other pages but it should work). BTW, I'm using SRC4392 in SPI mode because it's easier for me.

Lucifix,

are you able to read out all the config of the SRC4392 using SPI? I'm considering using this chip on a board which is IO limited. I'll have a full SPI available with one CSN pin and only one additional IO pin.

I see that the PLL lock is available on a pin. But I was hoping not to waste IO on it if it's available on SPI. And I don't want to add a separate MCU to monitor stuff on the board. Insted I'm planning to use the SRC4392 GPO pins to turn various stuff on and off (control I2S multiplexer since the board will also bridge to a CD drive).


Regards,
Borge
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