This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TLV760: Why TLV760 shutdown 1ms and then recover ?

Part Number: TLV760
Other Parts Discussed in Thread: TLV767

Hi team, 

My customer use TLV76050DBZT to translate 17V to 5V, and 5V just power for 1pcs AMC1305. Below is their SCH.

But at sometimes,  TLV760 output shutdown 1ms and then recover. We test the input voltage 17V is stable. So it is output problme.

We guest it have over current or over temp shutdown, Due to AMC1305 current is small, so it should not over current.

Do you think it is  over temp shutdown or other issue?

Thanks!

  • Hi Eggsy, 

    With a Rja = 275C/W and a voltage conversion from 17V to 5V, the part's junction temperature could hit 150C thermal shutdown temperature with a DC current of 37mA at 25C ambient. But during the startup, with a 10uF capacitor, the in-rush current could hit shoot up very high (>1A possible) and this is too fast for the internal current limit loop to respond and the thermal shutdown could be tripped in this process. To confirm this is indeed happening on the customer's board, we would need the scope-shoot that shows the Vin, Vout, and the current flowing into the Vin pin (in-rush) during startup. 

    The required output cap for TLV767 is higher than 0.1uF, if 10uF could be reduced to 1uF, this will possibly help to lower the chance for the undesired power-off with a much lower in-rush during startup. Do you think this is something your customer is willing to try? 

    Regards, 
    Jason

  • Hi Jason,

    As you said, "with a 10uF capacitor, the in-rush current could hit shoot up very high (>1A possible) and this is too fast for the internal current limit loop to respond and the thermal shutdown could be tripped in this process", do you mean the root cause is overcurrent or thermal shutdown? 

    Because the customer's board in the bottom and it is hard for them to test again.

    If the root issue is overcurrent, changing Cap from 10uF  to 1uF, it can solved, right ?

    Thanks!

  • Hi Jason,

    Could you see the C59 and C51 in the above SCH? They are 0.1uF. 

    Do you think if it work when we just remove C48 and C56? 

    Thanks!

  • Hi Eggsy,

    We would need a detailed waveform to confirm the issue. Based on the schematic provided, and the description of the problem, I would suspect the shutdown may be caused by the overheat, and in this application, the overheat is mostly likely happening during the startup. 

    C59 and C51 seem to be the decoupling capacitor at the load side, for the LDO, it will need local capacitors for stability which means only the capacitors very close to the output pin of the LDO can be counted. They try to replace the 10uF capacitors at the output to maybe 1uF and retest. 

    Regards, 
    Jason

  • Hi Jason,

    Customer feedback they change C48 and C56 from 10uF to 1uf or 0.1uf. But both value solutions can't deal with issue.

    Customer also feedback after power up,  it will shutdown soon, and recover and waiting for 1s, shutdown again and recover.

    It should not  overheat because when power up, the board is not hot. Do you have any suggestions?

    And sometimes, after power up 10min, it shutdown. 

  • Hi Eggsy, 

    We would need some more scope-shoots to comment further on the possible issues. Once the LDO is up and running, if the EN and VIN are stable, the thermal shutdown could be the only thing that could potentially shut down the output assuming the LDO is not being damaged. 

    Regards, 
    Jason