Output design considerations for the DIT4096

Clay Shoup

Other Parts Discussed in Thread: PCM4201, DIT4096

Customer has design with DIT4096 using the recommended circuit from the data sheet; i.e. tranformer coupled to RCA connector. When they connect to a SPDIF chip it does not recognize the communication. The output pulses have a lot of noise and seems to drifts. When they change the output design to match the circuit in the PCM4201 EVM it appears to be working; output coupled via a resistor divider network.

The transformer coupled design would seem to be a good idea to avoid ground loops and provide isolation. Any suggestions as to why the transformer coupled design did not work. Also, I would like a little G2 on why you would choose one method over the other.

Thks,

Clay

over 13 years ago

0 Don Dapkus over 13 years ago

TI__Guru**** 189399 points

Hi, Clay,

My apps engineer supporting this product is OOO this week. He will get back with you next week.

Sorry for the delay...

-d2

0 Clay Shoup over 13 years ago in reply to Don Dapkus

Intellectual 410 points

Meeting with customer again tomorrow. Do we have any information that I can respond to their question?

0 Don Dapkus over 13 years ago in reply to Clay Shoup

TI__Guru**** 189399 points

Hi, Clay,

Unfortunately, no. My apps guy is still on the road.

Are they using one of the transformers mentioned in the data sheet? Or is it a different brand/part number?

-d2

0 Clay Shoup over 13 years ago in reply to Don Dapkus

Intellectual 410 points

Don,

They are using a Pulse transformer - T6027NL - http://datasheet.octopart.com/T6027NL-Pulse-datasheet-8637824.pdf

versus the Scientific Conversion SC982-04 mentioned in the DIT4092 data sheet - http://www.scientificonversion.com/catalog.html

A little difficult to compare as the SC site does not provide an actual data sheet and I am not transformer expert.

0 Don Dapkus over 13 years ago in reply to Clay Shoup

TI__Guru**** 189399 points

Clay,

I'm just noodling around here; I'm not a transformer expert, either...

It looks like the Pulse transformer is optimized for voice-band applications. The freq needed for the DIT4092 needs to be in the MHz range. I wonder if the transformer is corrupting the signal since it does not appear (to me) to be specified for high freq operation.

-d2

0 Clay Shoup over 13 years ago in reply to Don Dapkus

Intellectual 410 points

Don,

I did notice the response of the pulse is detailed up to 20KHz and I am not sure of the freq. generated by the customer but most likely over 20KHz I will discuss with them.

0 Clay Shoup over 13 years ago in reply to Clay Shoup

Intellectual 410 points

Don,

Trying to verify whether I have a transformer that is equivilent to the SC982-04 transformer listed in the DIT4096 data sheet but I can not locate a data sheet for the SC982. Does TI have this data sheet in their data base?

0 Don Dapkus over 13 years ago in reply to Clay Shoup

TI__Guru**** 189399 points

Hi, Clay,

No, but let me follow-up with them to see if I can get it.

I will ask for some samples, and if they give 'em to me, I'll ship one to you so your customer can test it.

-d2

0 Don Dapkus over 13 years ago in reply to Don Dapkus

TI__Guru**** 189399 points

Hi, Clay,

I understand you're working with Greg A on this, so I will close this thread. He has the info you need, but it is proprietary, so we can't post it here.

We both called Scientific Conversation, and spoke to a very friendly and knowledgeable gentleman. We just called the number listed on their web site, and he sent us specs and offered to send us free samples to test out.

-d2

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Output design considerations for the DIT4096