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TPS799-Q1: TPS799-Q1 unexpected output in EN low

Atsushi Yamauchi
Genius 4810 points
Part Number: TPS799-Q1

I would like to confirm the cause of the unexpected output in EN low for TPS799-Q1.

I attached the waveform.

The conditon is VIN = 3.3V, EN = 2.7V, input capacitor 4.7uF and output capacitor 2.2uF.

The output voltage in EN low was about 0.5V.

When input voltage was 2.7V, there was not output voltage.

What is the cause of it ?

Is it correct operation?

Best regards,

Atsushi Yamauchi 

  • 0
    TI__Guru 55940 points
    Hi Atsushi,

    Could you share what is the Channel 1 signal? When Channel 1 starts up there appears to be a disturbance on Channel 4 (the LDO Vout). Could there be a bias on the output of the LDO? One way to check would be to isolate the LDO from the load.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Genius 4810 points

    Dear Ryan-san,

    I have confirmed them.

    Channel 1 is the waveform of the customer's system power supply. So, this is not direct impact to TPS79918-Q1.  

    TPS79918-Q1 got the supply from other DCDC converter.

    And there are not any biases on the output. The output keeps to isolate from load.

    Could you please advise this to me?

    Best regards,

    Atsushi Yamauchi

  • 0 in reply to Atsushi Yamauchi
    TI__Guru 55940 points
    Hi Atsushi-san,

    I have not been able to replicate your issue. Without further data I can only suggest that you once again check for the most likely sources of a biased output which are leakage paths at the load.

    Very Respectfully,
    Ryan