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TPS2662: Recovery delay from reverse blocking for TPS26625

Ken Henderson
Intellectual 670 points
Part Number: TPS2662

Hello,

I am using the TPS26625 with 5V on the input and then connecting 19V on the output. The part reverse blocks the output voltage correctly, but then has a delay of several hundred milliseconds to recover before supplying 5V on the output.

Here is the circuit used:

Occasionally the TPS26625 recovers immediately and the 5V is on the output (red = VOUT, blue = /FLT pin):

But most of the tests show a delay for the TPS26625 to recover from reverse blocking, here it is 442ms but can vary from about 100-500ms:

Removing Cdvdt also has the same result as shown above, but the rising edge on VOUT from 0-5V is faster.

I also checked a TPS26600 and that works correctly every time (red = VOUT, blue = VIN 5V):

What is causing the TPS26625 to have this recovery delay?

Thanks, Ken

  • 0
    TI__Expert 8630 points

     

    Hello Ken,

     

    TPS2662 recovers from reverse conduction when voltage across IN to OUT goes above VFWDTH threshold. As the output voltage is 19V and IN voltage is 5V in your testcase, the device stays in reverse blocking condition. A load resistor ~10k can be connected between OUT and GND to discharge the output cap quickly and bring the device out of reverse blocking condition.

  • 0 in reply to Lokesh Ghulyani
    Intellectual 670 points

    Hi Lokesh,

    Thanks for your reply. Sorry, perhaps it was not so clear from my waveforms. The OUT voltage is dropping to 0V before the TPS26625 recovers while the IN voltage is at a constant 5V, so VFWDTH has been met at least 400ms before the device turns back on. This waveform shows IN (blue) at 5V and OUT (red) dropping from 19V to zero at 545ms before recovering to 5V:

    Here is another test with a 10ohm load connected on the output. IN = 5V, OUT is connected to a 10V supply and then the supply is turned off. The TPS26625 still takes 222ms to recover.

    Any advice on what is happening would be appreciated.

    Thanks, Ken

  • 0 in reply to Ken Henderson
    TI__Expert 8630 points

    Hello Ken,

    Was the output going negative when Power supply was turned-off on Output?

    Can you also probe FLT pin with above waveform when 10-Ohm Load was connected on OUT to discharge the output?

  • 0 in reply to Lokesh Ghulyani
    Intellectual 670 points

    Hello Lokesh,

    Here is the output falling edge when the 10V power supply on the output is turned off, and with the 10R load on the output (red = VOUT, blue = /FLT). VOUT does not go negative. It is just the 10R load discharging the power supply output in a few milliseconds.

    And here is the /FLT signal during the whole recovery time. It stays low until the TPS26625 recovers from reverse blocking:

    And here is VOUT and RTN signal. RTN remains at 0V for whole time:

    I hope this sheds some light.

    Thanks, Ken

  • 0 in reply to Ken Henderson
    TI__Expert 5575 points

    Hello Ken

    We are looking into this.  I will try to replicate this behavior at our end. I will get back to you in couple of days.

    Thanks & Regards

    Abhijeet 

  • 0 in reply to Abhijeet Godbole
    Intellectual 670 points

    Thanks Abhijeet,

    Let me know if you need any more tests at my end.

    Best regards, Ken

  • 0 in reply to Ken Henderson
    TI__Expert 5575 points

    Hi Ken

    In order to test this condition on EVM, I would like to understand your application use conditions in more detail. I can connect with you over email ID provided in your profile to discuss this further.

    If that works for you then we can close this thread and discuss application specific details over email.

    Thanks & Regards

    Abhijeet

  • 0 in reply to Abhijeet Godbole
    Intellectual 670 points

    Hi Abhijeet,

    That works for me. Please contact me by email

    Thanks, Ken