SN74CBTLV3257: For spdif

Jeff YANG

Mastermind 7825 points

Part Number: SN74CBTLV3257

Hi Sir,

Does SN74CBTLV3257 suitable for audio spdif switch?

My customer using Neperia 74CBTLV3257 meet some distortion issue, I have apply TI part for test,

But still want to check it can use in this application or have better suggestion.

Thanks!

Jeff

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 316690 points

There will not be much difference.

What voltage and frequencies does this signal have? What kind of distortion? Can you show an oscilloscope trace?

0 Jeff YANG over 2 years ago in reply to Clemens Ladisch

Mastermind 7825 points

Hi Clemens,

please see below waveform and schematic. Seems maximum voltage ~4V out of specfication?

CH1:Input

CH2:output

Thanks!

Jeff

0 Jeff YANG over 2 years ago in reply to Jeff YANG

Mastermind 7825 points

Hi Clemens,

BTW, they want using this switch to swap TX/RX. thanks!

Jeff

0 Clemens Ladisch over 2 years ago in reply to Jeff YANG

Guru 316690 points

These look live 3.3 V signals.

Both waveforms show transmission line effects, but those are caused not by the switch but by improper termination, i.e., impedance mismatches between driver, trace, and receiver.

0 Jeff YANG over 2 years ago in reply to Clemens Ladisch

Mastermind 7825 points

Hi Clemens,

Got it, do you have idea how to fix this issue?

Adjust layout? or any other ways?

Thanks!

Jeff

+1 Clemens Ladisch over 2 years ago in reply to Jeff YANG

Guru 316690 points

Add proper termination. The easiest way to do this is probably source termination, i.e., add a series resistor at the driver that, together with the driver's output impedance, increases the total impedance to the same as the characteristic impedance of the trace.

0 Jeff YANG over 2 years ago in reply to Clemens Ladisch

Mastermind 7825 points

Hi Clemens,

Got it, thanks your support.

Jeff

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SN74CBTLV3257: For spdif