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CC2642R: Hardware Board Design / Help

SPEEDBIRD
Intellectual 721 points

Part Number: CC2642R

Hey!

I do have three more favors/ questions.

1.  Do the oscillators have to be very close to the CC2642R or can I put it on the bottom side and connect it with vias?

2. The GND from the CC2642R pad I connected with vias to the GND on the Bottom plane is that ok (My vias are probably already to big)?

3. Can you please have a short glance at my Board, especially when it comes to the antenna and oscillators?

Thanks!!!

Everything is done with TI chips, because support counts and thats what keeps me and others as a customers or future customers with TI!

Kind regards,

SPEEDBIRD

(GND Plane not visible but there. But the area around the antenna is still GND Plane free)

  • 0
    TI__Guru**** 317180 points
    1) Yes. Long traces could pick up noise and noise on the xtal lines means noise on the output RF signal. I would advice to have the xtal on the same side as the chip.
    2) Follow the reference design here. It's difficult to see the vias to ground from the picture.
    3) It looks like you use an IPC. Note that the routing distance from the chip to the IPC is important, follow the ref design here.

    Is this a or 4 layer board?
  • 0 in reply to TER
    Intellectual 721 points
    First Thank you!

    No its a 2 layer board, so the reference isn‘t the ideal solution if I‘m correct.

    Since it‘s a prototype I really hope the antenna will work, even if its not Ideal layed out like the reference design of the Antenna manufacturer.

    Will some vias on the side of the board help because of the electrical field?
  • 0 in reply to SPEEDBIRD
    Genius 3790 points

    - If possible go with 4 Layer Board.

     - As TER suggested, try to keep the crystals in the same Layer. I believe 32.768KHz crystal can be placed on the bottom but make sure that trace length should as minimum as possible. Double check with TER once.

    - Keep RF trace minimum as possible & maintain impedance matched.

    - I don't see a good design over here. Once you're done with PCB. try cross-checking with TER.

    - Check your routing of 48MHz crystal It doesn't seem right. 

    - Make sure you have optional JTAG connection Header/ on the custom Board. It looks like you have.

  • 0 in reply to Lakshminarayana
    Intellectual 721 points

    - Thank you, the 48MHz crystal was connected wrong you saved me a lot of trouble! :-)
    - RF trace is close to minimum and is what the Antenna Chip provider recommends, but I still need to add the vias on the edges. I also made the RF trace on the bottom layer clear of any other traces.
    - About the 4 layers, the PCB Layout consideration guide from TI says, that when having a different amount of layers, you must re-design the filter balun. That's it. Therefor I got a Bandpass for Bluetooth and didn't make my own / use the reference design Balun.
    - Why don't you see a good design here (once I correct the crystal and get the ground planes matched)?

    I'm alway happy for tips and corrections!

  • 0 in reply to SPEEDBIRD
    Genius 3790 points

    I recommended you 4 Layer because it'll make a good RF layout and better shielding near the RF. 

    what you mean by this:  "I also made the RF trace on the bottom layer clear of any other traces".

    Proper shielding has to be done on the RF if not you might face a range issue.

    As TER told, follow the ref design.

    Have you matched RF trace width to 50Ohm impedance?

    Once you're completely done with PCB, double check  (like All are routed properly) and then send the Gerber to TER by private message/ on the forum and cross-check and then go for the manufacturing.

    -Lakshminarayana.

  • 0 in reply to TER
    Genius 3790 points
    Hi TER,
    One quick question about the crystal placement(32.768KHz).
    Is it okay to place the 32K crystals on the bottom side of board and making sure that trace length is as minimum as possible?
  • 0 in reply to Lakshminarayana
    TI__Guru**** 317180 points
    Placing the xtal on the other side increase the risk for potential issues. We always recommend placing the xtal on the same side as the chip.
  • 0 in reply to TER
    TI__Guru**** 317180 points
    SPEEDBIRD: As Lakshminarayana suggested, send me the schematic/ layout for a quick review when done
  • 0 in reply to TER
    Genius 3790 points

    Yeah I agree.

    The 24/48 MHz crystal will be placed on the same side of the chip. But what about 32KHz since this is used only at the time of sleep modes?

  • 0 in reply to SPEEDBIRD
    Genius 3790 points
    Any progress on this?
  • 0 in reply to Lakshminarayana
    Intellectual 721 points

    Sorry for the long time not answering, I actually did not get any notifications that you replied :/. I found a few mistakes and in general completely overhauled the whole PCB. I changed it to 4 Layers and also rerouted a lot. 

  • 0 in reply to TER
    Intellectual 721 points

    Would it be somehow possible for me to write you a message, the forum does not give me the option to write you a message. I can send one to Lakshminarayana, but not to you.

  • 0 in reply to SPEEDBIRD
    TI__Guru**** 317180 points

    I should be possible now, I had to accept the friend request.