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3TX BQ500212A Design

MENGKEONG FONG
Prodigy 230 points
Other Parts Discussed in Thread: BQ500212A

Dear Sir,

       We are doing 3TX BQ500212A  at one pcba design

BQ500212A got AGND & DGND.How to do was better for EMI and performance for this pcba

1.BQ500212A 1st  BQ500212A 2nd BQ500212A 3rd AGND connect together

    BQ500212A 1st  BQ500212A 2nd BQ500212A 3rd DGND connect together

    AGND ==>0R===>DGND

2.BQ500212A 1st  AGND1 0R to DGND1

    BQ500212A 2nd  AGND2 0R to DGND2

     BQ500212A 3rd  AGND3 0R to DGND3

6266.WIS TX SCH VER0.1.pdf

  • 0
    TI__Guru 65836 points

    The EMI noise will probably originate from the switching circuit.  Good layout should be used to avoid problems in this area.  Also noise can be caused by bq500xxx 32MHz Osc. Care should be taken with the 3.3V input filter capacitors. 

    Digital 3.3V is V33D, Pin 33 and the return is pin 32.  Filter capacitors on the EVM are C19 & C1.

    Low Noise Analog 3.3V is V33A, Pin 34 and return is pin 36.  Filter capacitors on the EVM are C3 & C5.

    If the trace to the capacitors is long or has vias the high freq filtering will be degraded and cause noise problems.

     

  • 0 in reply to Bill Johns
    TI__Expert 6550 points

    Hello Bill,

    Is it possible to use this part in 2 layer PCB design versus 4 layer in the EVM?

    Thank you,

    Natallia

  • 0 in reply to Natallia Holubeva1
    TI__Guru 65836 points

    I do not recommend a 2 layer PCB design.  Due to grounding and noise performance is poor.  A number of two layer designs have been tried by all have had problems.

  • 0 in reply to Bill Johns
    Prodigy 30 points

    Hi, this is Po,

    Can you explain the problems you encountered with 2 layer board setup? Does it effect the QI standard communication between the RX TX? Will if pass FCC or CE?

  • 0 in reply to Pohan Huang
    TI__Guru 65836 points

    Noise on the COMM + / - signal and RX cannot communicate with TX.  Does not function.

  • 0 in reply to Bill Johns
    Prodigy 30 points

    Hi Bill, 

    Some other question that I had was 

    1.  The recommended stack up for a four layer board, the evm uses 2oz copper, what about the substrate height? 

    2.  For comm+  and  comm-  are they differential pairs? On the Gerbers for the EVM they don't look like they are routed as differential pairs, and if the are what should be the controlled impedance,  90 ohms?

    3. How do you bond the ferrite to PCB? I notice in the app note mentioned that the ferrite should have a one way back to ground, I thought the ferrite should suffice. And is it possible to have the ferrite over the bottom of the PCB with the component side facing down to reduce the size of the final product? 

    Thanks,

    Po

  • 0 in reply to Pohan Huang
    Prodigy 30 points

    Hi Bill, 

    Some other question that I had was 

    1.  The recommended stack up for a four layer board, the evm uses 2oz copper, what about the substrate height? 

    2.  For comm+  and  comm-  are they differential pairs? On the Gerbers for the EVM they don't look like they are routed as differential pairs, and if the are what should be the controlled impedance,  90 ohms?

    3. How do you bond the ferrite to PCB? I notice in the app note mentioned that the ferrite should have a one way back to ground, I thought the ferrite should suffice. And is it possible to have the ferrite over the bottom of the PCB with the component side facing down to reduce the size of the final product? 

    Thanks,

    Po