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TRF7970A NFC transceiver ground plane

Politeknik
Prodigy 75 points
Other Parts Discussed in Thread: TPS61222, TRF7970A

Solid ground plane vs. split ground plane, has always been a question which leads to endless discussions. Actually, I have read many documents, been through the pros and cons of each of the strategies, and still can not say that I have found the most reliable answer.

I am working on a TRF7970A NFC transceiver (which includes TRF7970A, MSP430, TPS61222, ...) and itself is a subsystem of a bigger module (consists of -at least - a GHz RF transceiver). Here is my question: In a 2-layer PCB design, should we have ground islands or follow the solid ground rules? In case the former idea would be more appropriate, does the ground island include the TRF7970A only, or the whole NFC transceiver subsystem?

Thanks alot, in advance!

Best Regards,
Politeknik

  • 0
    TI__Guru* 91086 points
    There should be a common ground plane for the digital and analog sections. The multiple ground sections or “islands” should have vias that tie the different sections of the planes together.

    the complete layout guidelines which apply to the TRF79xx family are here ==> www.ti.com/.../sloa139.pdf
  • 0 in reply to Josh Wyatt
    Prodigy 75 points
    Thank you very much for your quick reply.

    Actually, I have read the aforementioned document. On page 5, section 9, it says: "If the system implementation is complex (i.e. RFID reader module is a subsystem of a greater system with other modules (Bluetooth, WiFi, microprocessors and clocks), special considerations should be taken to ensure that there isn’t any noise coupling into the supply lines". That's why I asked the question.

    So, you mean one solid ground for the whole TRF7970A NFC transceiver? How about the GHz RF transceiver ground (separated / unified)?
  • 0 in reply to Politeknik
    TI__Guru* 91086 points

    i would consider them to be subsystems and therefore independent modules. It may be easier for you to consider this way - that way maybe you don't have a ground loop anywhere to be a free antenna. (which is not a good thing - hope that is 100% understood :))

    in the past i have laid it out like this for co-located transceivers - for example here what i have attached - these are 10x size PDFs of TRF79xxA  and PAN1315 designs i did some time back. follow what the BT layouts say for the IC you are using and should should be OK.

    hope they help you get a good design going - i also like the combo of these two technologies!!!

    10x_size_NFC_Module.pdf

    10x_size_BT_Module.pdf