EVAL-CN0540. VOCM

TSTEngineer

on Dec 16, 2022

Category: Hardware

Product Number: CN0540

I´m working in a PCB design based on EVB CN0540. CN0540 Schematic show two options to obtain VOCM_REF; 1 - Is using VOCM, 2 - Is using VOCM_ADC. As the schematic shows, in CN0540 EVB is chosen VOCM option by default on the board (selected with a 0R resistor).

VOCM comes from

VOCM_ADC Comes from

I´m trying to simplify my design as much as possible so I would like to know if it would be posible to select only de second option (Obtain VOCM_REF from VOCM_ADC) and not use the first option (Obtain VOCM_REF from VOCM), erasing VOCM section in my design.

I need to know if my proposal would work properly or if there could be any problem with it.

MY PROPOSAL

Thank you very much.

0 JCCillion

on Dec 18, 2022 4:49 AM
Hi TSTEngineer ,

I will move this thread to the proper forum. I hope someone from the community can help you in your query.

Regards,

JC
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0 TSTEngineer
on Dec 19, 2022 7:42 AM in reply to JCCillion
thank you very much JCCillion. I didn´t know what was the properly forum to ask this kind of problem. Anyway, Could anyone help me with this question, please? Thank you
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0 rogueC

on Dec 19, 2022 8:22 AM in reply to TSTEngineer
Hi TSTEngineer ,

It is possible to use only VOCM_ADC from the AD7768-1 and remove the need for the reference buffer. We have a tested setup that does this. It is, however, still necessary to have the external 4.096V reference from the ADR4540 and the buffer which uses the same ADA4807-2.

Best Regards,

Nikko
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0 TSTEngineer
on Dec 19, 2022 11:23 AM in reply to rogueC
Thank you very much for your quick answer. Perfect, but could you explain me why is necessary to use the reference buffer for the AD4540? I need to know why, because I have to safe the most space possible into my board design. Also I read in the AD7768 datasheet that RF+ and REF - have interna reference buffers, Could we use these internal buffers instead of de ADA4807-2 Buffer? If not, please explain me why. Thank You.
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