ADC32RF54: ADC32RF54

Yuval Minster

Part Number: ADC32RF54
Other Parts Discussed in Thread: LMH5401,

HI,

I have few questions about this device:

1. How do you recommend to drive the ADC. My signal is from DC up to 400MHz.

2. I saw that in the EVM scheme you put before the CM pin of the LMH5401 device a OPA376A. Why did you put it ( I never saw it in other devices). Is it must ?

Thanks,

Yuval

over 2 years ago

0 Rob Reeder over 2 years ago

TI__Mastermind 31190 points

Hi Yuval,

Yes, you can use the LMH5401 to drive the ADC32RF54.

The OPA is used to help drive the VCM from the ADC to the LMH. This is critical when DC coupling between the amp and ADC.

If you have the schematic, then I would recommend using this, its a proven solution.

Regards,

Rob

0 Yuval Minster over 2 years ago in reply to Rob Reeder

Intellectual 800 points

Hi,

Can you please explain more about the DC coupling. We use DC coupling between the LMH out to the ADC. Why it is critical to use the OPA ?

Thanks,

Yuval

0 Rob Reeder over 1 year ago in reply to Yuval Minster

TI__Mastermind 31190 points

https://www.analog.com/en/technical-articles/designing-high-speed-analog-signal-chains.html

https://www.electronicdesign.com/technologies/analog/article/21798912/achieve-cm-convergence-between-amps-and-adcs

Hi Yuval,

Here are a couple of good articles that explain why the common mode voltage is critical between the output of the amplifier to the input of the ADC.

The OPA provides a buffer for this VCM from the ADC to drive the input of the amplifier's VOCM pin. Any slight differences can cause errors in your signal fullscale expectations.

Regards,

Rob

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ADC32RF54: ADC32RF54