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LM51561H-Q1: Schematic review

CHO SR
Expert 2915 points
Part Number: LM51561H-Q1
Other Parts Discussed in Thread: LM51561H, LM5156H

Hi

Please review the customer's schematic

1. In the case of EVM, Out Put GND is to be Isolated. Is there any problem with the schematic layout?

2. In case of D1, it is designated as a guide to set it to 150V or higher, but 10A was designed for the design of public parts. Is there any problem?

LM51561H-Q1 schematic.pdf

  • 0
    TI__Expert 7450 points

    Hi,

    Thanks for your interest in LM5156H.

    1. No problem. The EVM has isolated output because it's a Flyback topology. The schematic here is a SEPIC topology.

    2. We need to know the input, output voltage and output current to decide the selection of the diode.

    Thanks,

    Yinsong

  • 0 in reply to Yinsong Cai1
    Expert 2915 points

    Hi Yinsong,

    Thank you for your reply.

    Sorry, there was no indication on the schematic.

    - Input Voltage : 9V ~16.9V

    - Output Voltage : 12V

    - Output Current : 3A

  • 0 in reply to CHO SR
    TI__Expert 7450 points

    Thank you for the information.

    The 10A current rating is OK. The voltage stress on the diode is 16.9+12=29V. Normally a 50V or 60V diode should be enough unless there is some special concern.

    Thanks,

    Yinsong

  • 0 in reply to Yinsong Cai1
    Expert 2915 points

    Attached is a new schematic.LM51561H-Q1 schematic_201022.pdf

    Additional questions.

    1.In WBDesign, AGND and PGND are shorted.
       Isn't it necessary to connect using a separate Y-cap?
       If you don't need it, is there any problem with AGND without a separate GND connection?

    2. Customers want advice on selecting power inductors.

        Specifications shown in WBDesign for L-value selection are as follows.

    TDK Coil is being selected, please recommend it.

    b82477d6.pdf

  • 0 in reply to CHO SR
    TI__Expert 7450 points

    Hi,

    1. Y cap is used cut high frequency noise in transformer. For noise reduction in PGND and AGND, please make sure to separate them in the PCB design with a single point connection.

    2. The 3.9uH one might be a little overkill based on Webench recommendation. But it should be fine.

    Please let me know if they have any questions.

    Thanks,

    Yinsong