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TPS54335A: Information on the EN pin

Richard McClelland
Prodigy 10 points
Part Number: TPS54335A

Tool/software:

I have been using the EN pin for Under voltage detection using the calculations from the Data sheet. This circuit has worked for many builds over some time, but recently the circuit is failing by not starting up. I looked at the EN pin and I can see a noise on the pin related to the switch frequency. Replacing the Converter with alternate sourced and batch device fixes the problem, as does taking the external resistors off the under voltage detection divider (which have been checked for the correct value).

1) Is the EN pin used internally for any other fault detection reset hence the visible noise?

2) Is it possible that there has been a batch issue?

3) Is there a way to check for fake IC?

  • 0
    TI__Mastermind 27256 points

    Hi Richard

    The EN voltage is detected to enable/disable the circuit, when VEN is < the enable threshold, the device shut down. 

    Can you please share the schematic and layout image of your circuit? And can you measure the waveform of the EN ,Vout and SW? 

    There should be no problem if you purchased from ti.com or authorized distributor.

    Thanks and best regards.

  • 0 in reply to Richard McClelland
    TI__Mastermind 27256 points

    Hi Richard

    Can you please also share the layout image?

    Thank you

  • +1 in reply to Gui He
    Prodigy 10 points

    I was hoping for an answer to these questions

    1) Is the EN pin used internally for any other fault detection reset hence the visible noise?

    2) Is it possible that there has been a batch issue?

    3) Is there a way to check for fake IC?

    Not a deep dive into my design (which has been working without issue until now.

  • 0 in reply to Richard McClelland
    TI__Mastermind 27256 points

    Hi Richard

    1) Is the EN pin used internally for any other fault detection reset hence the visible noise?

    EN is used for UVLO detection as specified in the datasheet. when VEN is >the enable threshold, the IC enables , otherwise the IC disables. If the EN is floating, the device is enabled. No other fault detection. 

    2) Is it possible that there has been a batch issue?

    I haven't seen EN issue about this case before. You can do a ABA test and replace it on a EVM and see if can reproduce the problem. If yes, there might be some issue with the IC.

    3) Is there a way to check for fake IC?

    We can guarantee the ICs that are purchased from authorized distributor. For others, we don't have a way to check that.

    Thanks and best regards.