DAC908: Suggested Transformer

Russell Wetherley1

Expert 4255 points

Part Number: DAC908

Hello E2E,

Any guidance on specing a transformer for this? I'm driving a single ended 75 Ohm load.

Let me know what additional information you may need.

Russell

over 5 years ago

0 Brian2001 over 5 years ago

TI__Intellectual 2750 points

Hello Russell,
I have sent your question over to an engineer that is familiar with DAC908
Unfortunately he is out today, so you should hear something back tomorrow or Friday.
Regards,
Brian

0 Russell Wetherley1 over 5 years ago in reply to Brian2001

TI__Expert 4255 points

Thanks Brian! Look forward to seeing you suggestion.

Russell

0 jim s over 5 years ago in reply to Brian2001

TI__Guru* 91947 points

Russell,

Per the data sheet, the best distortion performance is typically achieved with the maximum full-scale output signal limited to approximately 0.5V. This is the case for a 50 Ohm doubly-terminated load (25 Ohms per leg) and a 20mA full-scale output current. So with a 75 Ohm load, to achieve this, you will need to connect a 37.5 Ohm resistor on each DAC output leg of the DAC to ground and select a 1:1 ratio transformer that meets the frequency requirement of your system.

Regards,

Jim

0 Russell Wetherley1 over 5 years ago in reply to jim s

TI__Expert 4255 points

Thanks Jim,
Unfortunately, my customer and I are both woefully uneducated with magnetics. Would a pulse transformer work in this application if we got one without chokes? We don't really have any stringent noise requirements. The DAC is really overkill for what we need which is just to generate a tri-level sync pulse (wikipedia link at bottom). Would the below work? What am I looking for other than a flat response at my frequency of interest?

www.digikey.com/.../5285775

en.wikipedia.org/.../Tri-level_sync

Thanks for the help!

Russell

0 jim s over 5 years ago in reply to Russell Wetherley1

TI__Guru* 91947 points

Russell,

I have never used one of these pulse transformers. I would suggest you have the customer order an EVM and attempt to replace the on-board transformer with this one and give it a try. If they need help with doing this modification, let us know, as we have technicians that may be able to do this for them.

Regards,

Jim

0 Glenn Austin31 over 5 years ago in reply to jim s

Prodigy 60 points

What is the Part number of the DAC908EVM onboard transformer?

0 jim s over 5 years ago in reply to Glenn Austin31

TI__Guru* 91947 points

Glenn,

The transformer is a Mini-circuits T1-1T-KK81.

Regards,

Jim

0 Glenn Austin31 over 5 years ago in reply to jim s

Prodigy 60 points

Thanks for the information

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DAC908: Suggested Transformer