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LM3478: Layout Review

Jenny Lu69
Expert 1810 points
Part Number: LM3478

Dear TI'ers,

Customer wants to review the layout whether there is problem or not.

Could you please check for attached file and give me any comment ?

Thank you and best regards

Jenny

  • 0
    TI__Guru* 78400 points
    We are going to review it and get back to you. Can yo usend me an email at youhao.xi@ti.com and tell me the following info:

    (1) customer name, and location
    (2) applications of this design
    (3) project schedule
    (4) business volumes in the next few years
    (5) contact info of the designer engineer

    Thanks,
    Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI
  • 0 in reply to Youhao Xi
    TI__Guru* 78400 points
    Hi Jenny,
    My comments about your layout:
    (1) Current sense signal should come from the sense resistor R5 pad for a cleaner sense signal. The source pad of MOSFET Q1 is noisy, though electrically it is connected to R5, but PCB trace may have additional voltage drops from where R1 picks up the signa to R5. Recommend to draw a separate (small) trace from R5 to R1.
    (2) Input ceramic C6 and electrolytic capacitor C5 should switch their positions, and place C6 next to the inductor.
    (3) Critical current path is the AC current loop that flows through Q1, R5, C8//C7, D1 and back to Q1 Drain. These components shoudl be placed as closely to miniize the physical loop size of this ac current. You can move D1 down a little and leave room for C7 and C8 to get closer to Q1 and R5.
    (4) R6 shoud be connected directly to Vout + port, not from the middle of C7 and C8 pads.

    Please also refor to the layout guide provided in teh LM3478 datasheet. Hope these help.

    Best Regards,
    Youhao Xi, System and Applications Engineering, APP-BMC-BCS, TI