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LM63625-Q1: 24V to 5V regulation

Nout
Prodigy 40 points
Part Number: LM63625-Q1

I'm trying to use the LM63625-Q1 in a new design to regulate the 24V battery input down to 5V. Unfortunately, when raising VIN above 20V, the regulator releases the magic smoke. With a VIN of 20V or less, I do get a 5V output. The regulator is configured with a switching frequency of 400kHz for maximum efficiency. I'm pretty sure I followed the application note correctly, is there something wrong with my schematic?

  • 0
    TI__Mastermind 27045 points

    Hi Daniel,

    How about Pin2,13,16 and 17? 

    Can you also upload the PCB layout for checking?

    B R

    Andy

  • 0 in reply to Andy Chen
    Prodigy 40 points

    Pin 2 is connected to pin 1, pin 13 to pin 12, and pins 16 and 17 to ground. Here's the PCB layout:

  • 0 in reply to Nout
    TI__Mastermind 27045 points

    Hi Tristan,

    The external component placement looks good.

    Do you pour ground plan on the top layer? how to connect output C205 GND to input C201 GND?  you may need to place a short thick jump wire to connect these two GND node.

    If you have current probe, please try to float L201, solder L201 terminal 1# to board, measure inductor current on wire which connect L201 terminal 2 to Cout,  also test SW node waveform at same time to see if any abnormal operation by increasing Vin up to 24V.

  • 0 in reply to Andy Chen
    Prodigy 40 points

    Hi Andy,

    Thank you for your answer. The top and bottom layer both have a ground plane. It is true that the path from C205 GND to C201 GND is a bit long, so I've added several vias to my layout and temporarily soldered a thick wire. And good news is, so far I haven't blown up the regulator. Here's a capture of SW with Vin at 24V, which as far as I can tell looks good:

    Note that this was without a load (although I previously didn't need a load either to get it to fail).

    Unfortunately I ended up blowing it up anyway while trying to probe CBOOT (shorted to VCC ..), so I'll have to wait for new ones to arrive. I'll update this thread once further testing is done.