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ADC12D1800RFIU PWB layout issues with multiple ADCs

Randy Mummert
Prodigy 95 points
Other Parts Discussed in Thread: ADC12D1800RF

I'm performing my PWB layout where I'm using 2 ADC12D1800RF devices.

I need advice as to the power plane routing when 2 devices are used. I have a single 1V9 power source for both ADCs. From the data sheet I see specific guidelines for the different power planes on page 53. The planes on my design are routed as peninsulas for VTC, VA, VE and VDR as the guide specifies. When there are two ADCs should each plane for each peninsula be routed across both devices? That is should VTC be a shared plane or strip across each ADC or should VTC connect to 1V9 between each ADC and at each end? The same question for each voltage plane VA, VE and VDR

Should VDR be a peninsula plane? It's not clear from the data sheet if it's common with 1V9.

Thank in advance,

Randy

  • 0
    TI__Mastermind 44680 points

    Hi Randy

    All of the ADC power nets should be derived from this single 1.9V supply including VDR. This is how our reference board is designed and ensures all supplies ramp up and down together.

    I would recommend separating the 1.9V feeds to the two ADCs just to provide some additional isolation between converters. We have never seen the need to isolate the nets within an ADC, but have not run 2 ADCs from a common regulator.

    From those 2 feeds, split off peninsulas to each different ADC power net. You may need to do this on two separate power layers to get all of the different nets in. You can review the PCB layout in the ADC12D1800RFRB design package for an example: http://www.ti.com/litv/zip/snac040

    I hope this is helpful.

    Jim B

  • 0 in reply to Jim Brinkhurst1
    Prodigy 95 points

    Jim,

    thanks for the guidance. I will separate the peninsulas on each ADC and perform the power connections on different layers for each ADC.

    Randy