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LM3478: Design review request

Yasar Maheen Seenath
Prodigy 80 points
Part Number: LM3478

Hello,

Please help to review the design attached herewith with below mentioned power controllers.

LM3478MM/NOPB

TPS61236PRWLR
TPS62865RQYR

schematic_for_review_ti_LM3478.pdf

  • 0
    TI__Mastermind 20560 points

    Hi Yasar,

    I performed a review of the LM3478 schematic.
    There are two point I would like to address:

    1. The input is stated to be 5V. Is there a min and max value given, or is it always 5V?
    I ask this question because there will be a very high duty cycle for Vin lower than 5V.

    2. On the output side are two time 100uF caps. Electrolytic or Polymere caps often have higher ESR and therefore are not ideal for filtering the output voltage ripple.
    I would recommend to put at least one ceramic with low ESR to reduce the switching noise and create a cleaner output signal.

    Best regards,
    Niklas

  • 0 in reply to Niklas Schwarz
    Prodigy 80 points

    Hi Niklas,

    Thanks for your support.

    1. The input is stated to be 5V. Is there a min and max value given, or is it always 5V?
    I ask this question because there will be a very high duty cycle for Vin lower than 5V.

    We can consider the range as 4.9V to 5.1V, as we are generating 5V out from a boost controller from battery input of 3.7V.

    2. On the output side are two time 100uF caps. Electrolytic or Polymere caps often have higher ESR and therefore are not ideal for filtering the output voltage ripple.
    I would recommend to put at least one ceramic with low ESR to reduce the switching noise and create a cleaner output signal.

    Please note that, the output capacitors are placed based on the WEWBDesign8-LM3478MMNOPB.pdfBench simulation recommendation(attaching the same for your reference).

    Will include 100uF caramic cap.

    Can you please help to review the remaining power circuitry also available in the previous schematics?

    TPS61236PRWLR
    TPS62865RQYR

  • 0 in reply to Yasar Maheen Seenath
    TI__Mastermind 20560 points

    Hi Yasar,

    Thanks for the update.
    This input voltage range is fine.

    I assumed the 100uF caps were high ESR electrolytic caps. If this is a 100uF ceramic cap, I have no concerns.
    The Webench recommendations should be good here.

    For review of the other two parts, could you set up separate threads for each part?
    They are not part of my product line and getting in contact with the according device experts would take longer that creating a new thread that gets assigned automatically.

    Sorry for this inconvenience.

    Thanks and best regards,
    Niklas