ADS4145: Schematics Snippet for Feedback

Viktor Boepple

Part Number: ADS4145
Other Parts Discussed in Thread: TPS796

I want to use the fast TI ADC IC ADS4145 in a future project. For that I want to design a application PCB with this IC in combination with a FPGA and a µC.
I want to share a snippet of this schematics (ADC part) for feedback:

Note: Analog and digital power comes from the same power supply IC. Nevertheless, analog and digital signals are layed out with enough space between them for proper signal integrity.
Would this circuit work?

Thank you very much in advance.

over 1 year ago

0 Rob Reeder over 1 year ago

TI__Mastermind 41000 points

Hi Viktor,

Can you please provide a cleaner screenshot of the schematic?

Its fuzzy on this side in order to review properly.

On the power supplies, did you separate the analog and digital supplies with separate ferrite beads at the very least?

Regards,

Rob

0 Viktor Boepple over 1 year ago

Prodigy 40 points

Hi Rob,

sorry for the bad quality of the last screenshot. I hope this one is better.

For Power Supply I´ve used your TPS796. This IC switches (I believe) far under 1MHz, so how would a ferrite bead help here?

Thank you very much.

0 Viktor Boepple over 1 year ago in reply to Viktor Boepple

Prodigy 40 points

In other words. I didn´t use a ferrite bead.

0 Rob Reeder over 1 year ago in reply to Viktor Boepple

TI__Mastermind 41000 points

Hi Viktor,

If you don't care about spurious or noise below 1MHz, then this might not be an issue.

I would still be prudent and breakout each power supply with a ferrite bead and bulk decoupling at the point where the LDO connects to the power plane (see example snapshot below) on the board, then use more localized decoupling at or very near the ADC/DUT.

Thanks,

Rob

0 Viktor Boepple over 1 year ago in reply to Rob Reeder

Prodigy 40 points

Hi Rob,

thank you very much for your input. I have bulk decoupling caps in my power supply design and near ADC. I can also try a ferrite bead.
But beside that, do you see other issues in the ADC schematic?

Thank you,
VIktor.

0 Chase W over 1 year ago in reply to Viktor Boepple

TI__Mastermind 23830 points

Viktor,

I have taken a look at your schematic and only found one concern. The CLK input is AC coupled LVDS however there is no 100 termination prior to the series capacitors. Ensure that the correct termination prior to AC coupling is followed as suggested by the CLK generator. Other than that everything looks fine.

Thanks, Chase

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ADS4145: Schematics Snippet for Feedback