ADAU1452 SPDIFIN pin voltage level(s)

philipj451 Question

Mar 8, 2023 00:00

Hi,

can anyone point me to where there is a specification for the acceptable voltage levels on the SPDIFIN pin of an ADAU1452 DSP device?

The only thing I can find in the data-sheet is on page 11 where it says "Digital input pins except SPDIFIN, which is not a standard digital input." and it can be infered from the ADAU144X_evalboard_schematic_rC.pdf where an SPDIF input socket is connected directly (via a blocking capacitor) to the relevant pin of the ADAU1442 device.

Thanks for any help

regards

Philip

Audio Signal Processors

adau1452

spdif

hardware

adau1442

SigmaDSP Audio Processors

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Harishgowtham Reply

Mar 8, 2023 00:00

Hello Philip,

If you want to design a SPDIF RX circuit, then you can refer to the circuit below from the ADAU1452 eval board manual.

I have measured the voltage at the SPDIF RX pin of the eval board which is 3.36V max for logic HIGH and 0V min for logic LOW.

The HIGH is 3.36V because, Acc to the datasheet of PLR135/T10 (the Rx SPDIF connector that we used in our eval board), 0.3V will be added to the Vcc that is 3.3V. so, the HIGH is 3.36V.

So, you can follow the design given in the Eval board manual for a reliable circuit like above which we have been using for a long time.

Regards,

Harish

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philipj451 Reply

Mar 8, 2023 00:00

Hi Harish, thanks for the reply but what I really want is to see Analog Devices' published spec. for this input pin and what minimum voltage range it will respond to. As mentioned I have seen on the schematic of a Demo Board that they have simply taken a SPDIF signal to this pin via a blocking capacitor but, as a designer, I have to create documents that confirm that I have verified that the circuit will work "under all circumstances" for the job it is designed for.

The published specification for S/PDIF is "0.5–0.6 V peak to peak into 75 ohms" so I need to match this to Analog Devices specification for the chip. I hope this helps explain why I am being so pedantic...

Regards

Philip

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Harishgowtham Reply

Mar 9, 2023 00:00

Hello Philip,

Ok I see that.

The ADAU1452 datasheet says that, "The S/PDIF receiver input is a comparator that is centered at IOVDD/2 and requires an input signal level of at least 200 mV p-p to operate properly"

You can see that it is documented in the page no 82 of the datasheet.

Does this answer your question?

Regards,

Harish

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