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TPS56637: cannot work stably with 24V-in 5V-out at light load

Cun Lee
Intellectual 310 points
Part Number: TPS56637

Hi TI

I got the samples around Jan 2019.

and now I have 5 boards to test them. But the chip seems not work well on my boards.

the Input is 24V, the output is 5V and the current is about 50ma for light load test.

1. when I plug in the 24V, I can see the 5V output sometimes, and it cannot output for the other times.   the pass rate is about 20%.

2. in failure case, I just can re-plug many times to get one pass result in some fail results.

3. in ok case, the output can be continue if I keep the input 24V power on.

the schematic is below, SYS_POWER is 24V, VBUS_UTC is 5V.

I have tried to remove R1015/R1019, C1015/R1023, or change another IND L1001, but no changes for this issue.

  • Former Member
    0 Former Member

    Hi Cun,

    Could you please double check the top mark? 

    There is a fast power on issue if the top mark is X56637. When the slew rate of Vin is too fast, the X56637 version device may not start up successfully. 

    We have a new silicon version which fixed this issue available now. You can request samples from TI store now or I can ship the final version silicon to you.

    And I want to remind that this is a pre-RTM device and the final silicon will be RTM at the beginning of October.

    Let me know if anything else I can help, thanks very much.

    BRs,

    Bruce

  • 0 in reply to Former Member
    Intellectual 310 points
    Hi Bruce,
    I appreciate for your reply.
    I will check the top mark and apply new sample.
    But if there is some work around with the current x56637 for this issue? so that I can continue my testing till the new sample arrived?

    Thanks
  • 0 in reply to Cun Lee
    Intellectual 310 points
    Hi Bruce,
    whether the chip can back to work with follow action?

    1. wait the input 24V ready
    2. disable the chip by EN pin tie to GND
    3. enable the chip by EN pin floating
  • Former Member
    0 Former Member in reply to Cun Lee
    Hi Cun,

    Yes, this method should be able to power on the device.
    Or first disable the chip by EN pin tie to GND, then plug in the 24V power supply, and finally enable the chip by EN pin floating.

    BRs,
    Bruce