TDA1541A I2S voltage level

[matlerbru]

Hello, i have searched a bit around for answers, and most of the time i get directed to this page, but without the right answer. Therefore i'll write a post myself.

I am making a DAC based on a TDA1541A, for a complete pre-amplifier. I want to use optical s/pdif as digital inputs. For this i am using a CS8422 reciever, to control inputs, and convert the s/pdif to i2s. Datasheet: https://docs-emea.rs-online.com/webdocs/0ee4/0900766b80ee4e5f.pdf

Datsheet for TDA1541A: http://www.lampizator.eu/lampizator/LINKS AND DOWNLOADS/DATAMINING/tda 1541A.pdf

The CS8422 uses a supply of 3.3 V, and the i2s signal will also be 3.3 V.
The TDA1541A used +-5 V for the digital circuitry, and i am not sure if it is able to read the 3.3 V input signals.

Can anyone answer this?

If it is not the case, is it possible to use a one way level shifter, using transistors? I suppose it will be, as the i2s is one way only (as far as i understand).

I hope someone can help

 

[Ben Mah]

It should work.

Page 6 of the TDA1541a datasheet specifies Inputs Ilow and Ihigh as 0.8V and 2.0V respectively.

In fact, one tweak for the TDA1541a is to attenuate the input signal voltage.

 

[3lite]

There won't be an issues. In fact, TTL level of any DAC will do fine with 3,3V on its digital inputs (anything above 2,0V is considered as HIGH).

 

[matlerbru]

Wow. I do not know how i was unable to see that. Quite unimpressive actually.

What would the advantage be, if i chose to attenuate the signals?

 

[Ben Mah]

Thorsten Loesch's take on I2S attenuation:

http://www.diyaudio.com/forums/digi...a-dac-i2s-bus-architecture-3.html#post2110417

Post #30:

Hi,


Well, first, the Attenuators have a clear function. The internal logic of the TDA1541 is bipolar differential current steering, very much like ECL type Logic, just not following any specific ECL standard.

If you drive the Inputs with a full TTL signal the DAC will work, but the logic circuits will saturate and there will be noise leakage into the IC substrate.

So attenuators are desirable. As you will be driving many TDA1541 in parallele buffering the bus with maybe a suitable fanout system is likely a good idea.

I have tried ecdesigns I2S attenuators and DEM reclocking recently and can attest that they work rather well for the comparable simplicity.

As they are easily retrofittable to anything that had a SAA7220 in place which was removed to make space for Non-Os on a small Veroboard that takes the place of the SAA7220 they constitute an easy and extremely worthwhile upgrade for most TDA1541 based CD-Players and should be included in any new design.

Around 5 Years ago I worked on the same problems for a commercial design with the TDA1541. The circuits used there are by far more complex to implement, but they perform a little better. However getting them to work correctly required careful temperature compensation and complex power supply arrangements (and no, I am not at liberty to disclose the solutions arrived at).

Ciao T