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Old 7th April 2004, 11:03 AM   #1
guido is offline guido  Netherlands
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Lightbulb TDA1541 info

Hi,

I am mailing with someone who seems to know all the ins and outs of the TDA1541(A). Discussing DEM reclocking and other things, guess you know who it is now.

According to this source, the powersupply pins are used for:

quote "-5 = analog AND digital supply"
quote "+5 = analog AND digital supply"

As you can see -15 is not known to me yet (for now i guess it is analog, but i need confirmation).

For the -5 and +5, they need to be decoupled to ground. Since a voltage difference between agnd and dgnd appears on the output of a DAC, my guess would be to decouple to dgnd direct. The currents through the trace between dgnd and agnd from the decoupling would then be from the analog side. I would think they are less harmfull as digital currents.

quote "More important than decoupling to gnd is that -5 and +5 are decoupled to each other"

I'm not shure it is enough to have '+5 cap gnd cap -5 ' or that one extra cap is better. This creates some kind of triangle.
opinions ?

quote "the DEM decouple caps should go to analog ground" as expected.

There are more "quotes" expected to follow, on the -15 and interesting stuff on driving the i2s inputs! I will post if i have all the information Gimme a few days!

Regards,
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Old 7th April 2004, 07:57 PM   #2
Pedja is offline Pedja  Serbia
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Default Re: TDA1541 info

Hi Guido,

Quote:
Originally posted by guido
According to this source, the powersupply pins are used for:
quote "-5 = analog AND digital supply"
quote "+5 = analog AND digital supply"
Both -5V and +5V are the digital supplies and this conclusion can be made from the fact you set the mode using +5V and 5V (and gnd).

But I would not be surprised if the analog part partially uses +5V.

As about the claim for -5V I would like to know more about your source.

Quote:
As you can see -15 is not known to me yet (for now i guess it is analog, but i need confirmation).
The -15V is surely the analog supply and simple measurement of voltages on the decoup pins will tell you why.

Quote:
quote "More important than decoupling to gnd is that -5 and +5 are decoupled to each other"
And it is because...?

Pedja
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Old 7th April 2004, 08:03 PM   #3
Bricolo is offline Bricolo  France
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Since the DAC has an ouput voltage compliance fo 25mV (plus and minus, I think), this means that the analog stage has a positive and a negative supply

so the 5V seems to be shared between digital and analog, as Guido said
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Old 8th April 2004, 04:12 AM   #4
TDA1540 is offline TDA1540  Netherlands
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IIRC there is a capacitor between -15 and +5 in the 472.
and sometimes there are resistors between +5 and I2S signals(wsbd,clbd)

TDA
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Old 8th April 2004, 08:36 AM   #5
Bricolo is offline Bricolo  France
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Quote:
Originally posted by TDA1540
sometimes there are resistors between +5 and I2S signals(wsbd,clbd)

TDA

I got those too in my player, I wonder what they are for.
The value is 5k I think


BTW, what does IIRC mean?
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Old 8th April 2004, 09:46 AM   #6
ZERS is offline ZERS  France
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And moreover, how do you link AGND and DGND ?

With a wire ?
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Old 8th April 2004, 09:57 AM   #7
Bricolo is offline Bricolo  France
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Quote:
Originally posted by ZERS
And moreover, how do you link AGND and DGND ?

With a wire ?

yes, or better: on the groundplane

see here:
http://www.tentlabs.com/Info/Article...decoupling.pdf
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Old 8th April 2004, 11:18 AM   #8
ZERS is offline ZERS  France
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does it mean that a slot shouldn't be placed beetwen the AGND plane and the DGND plane ?
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Old 8th April 2004, 11:18 AM   #9
Bricolo is offline Bricolo  France
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what do you mean by a slot? Separating them?

So, no!


But Guido Tent's text is one way to build a DAC. Not the only way.
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Old 8th April 2004, 11:42 AM   #10
ZERS is offline ZERS  France
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Quote:
Originally posted by Bricolo
what do you mean by a slot? Separating them?
that's exactly what I meant.


Quote:
Originally posted by Bricolo
So, no!
Ok.
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