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TPS709: No Power (3.3V at Vout ?

Simon Noel
Prodigy 120 points
Part Number: TPS709
Other Parts Discussed in Thread: TPS706

Hi Guys,

I have a lot of fail on the TPS70933DRVR, there is no 3.3V out, it seem HI Z at the output.

The Vin is 3.66V and the current at 3.3Vout is 20mA

Cap at Vin is 1uF and Cap at Vout is 2uF.

The EN pin is floating

Let us know if you have an idea please or there a better part with same footprint for this application..?

Thanks again!

Regards

  • 0
    Prodigy 120 points

    There is the sch and PCB...!

  • 0 in reply to Simon Noel
    TI__Guru 55940 points
    Hi Simon,

    Thanks for the schematic and layout. I do not see anything on either that would explain your issue. You mention that you have a lot of boards that did not show an output voltage after Vin was applied, have you had any boards startup in the past? If you replace the TPS709 with another unit does the output rise?

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    TI__Guru 55940 points
    Hi Simon,

    One additional question:

    Are you able to apply 3.3 V to EN from an external supply while debugging? If you can, does the LDO output turn on?

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 120 points
    Yes, apply 3.3 V to EN from an external supply and nothing !!

    Thanks!
  • 0 in reply to Simon Noel
    TI__Guru 55940 points
    Hi Simon,

    Thank you for the extra data point. TPS709 should operate with your stated application and definitely should have started up when you applied 3.3 V to EN. I am curious if you were to use a TPS709 from another lot if it would successfully startup. You can sample some TPS70933DRVR devices and/or an EVM in order to see if the issue follows the part or if it follows the board.

    www.ti.com/.../samplebuy

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 120 points

    Hi Ryan,

    Use a TPS709 from another lot if it would successfully startup?  No, It the first 2K buy.

    If I replace the TPS70933 on the PCB board it work well.

    We have 3.6Vin and we need 3.3Vout it to drive a GPS L70 Quectel or Telit 

    Do you have a better part for this application same footprint?

    Thanks again!

  • 0 in reply to Simon Noel
    TI__Guru 55940 points
    Hi Simon,

    I do not see any reason why TPS709 would not work for your application especially as replacing the LDO with another TPS709 did work; however, TPS706 is a pin to pin replacement that should also work for your application.

    Was the replacement TPS709 from the same shipment or did you follow my suggestion and sample some additional TPS709s so that it was from a separate shipment? If the replacement was from the same shipment, it is possible that an unintentional leakage path was on the EN pin of the TPS709 such as residual flux. The internal pullup on enable is relatively week and could have been overcome by residual flux. If the replacement was from a different shipment, I would encourage you to contact your TI authorized distributor about pursuing a return:
    www.ti.com/.../customer-returns.html

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 120 points
    Hi Ryan,

    Was the replacement TPS709 from the same shipment?
    YES, I have 2.5K populated, I remove one of the other good board and resolder to the defect board for my test.

    It is possible that an unintentional leakage path was on the EN pin of the TPS709 such as residual flux?
    No even apply 3.3 V to EN from an external supply and nothing !!

    I well check where we buy the parts...

    Thanks!
  • 0 in reply to Simon Noel
    Prodigy 120 points

    Hi Ryan,

    We have done several tests on other parts and the problem seems to be the link inside the LDO.

    We have 2500 populated PCBs with this component series...

    What would be the next step to follow to remedy the situation?

    Thanks again!

    Regards

  • 0 in reply to Simon Noel
    TI__Guru 55940 points
    Hi Simon,

    At this time, the quickest method to remedy the situation that I can see is for you to follow the customer return procedure as noted here:
    www.ti.com/.../customer-returns.html

    The above website provides links to the forms and procedures to process a return. One thing to note is that you will need to involve whichever TI authorized distributor you used to purchase the devices as part of the return process.

    Very Respectfully,
    Ryan
  • 0 in reply to Ryan Eslinger
    Prodigy 120 points

    Hi Ryan,

    Ok We will go in this way!

    Thaks again!