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TPS7A19: PG goes low and the LDO output shutsdown

Fawaz Malik
Prodigy 70 points
Part Number: TPS7A19

I am using TPS7A19 to generate 18V

The current coming out of the regulator is 20mA  and the input voltage supply is 24V. 

The temperature on the LDO is not more than 40C. The input power supply is stable and the circuit is identical to the eval board except for the feedback resistors. The eval board functions without any issues but all other ICs that I have bought from digikey show this strange behavior. It looks like a manufacturing or fake component issue.

Please share thoughts if anything similar or in this direction is known about this component.  

The output voltage works fine for 40-50seconds and then the Power Good  output goes low and the output voltage follows it and also goes to low.

As shown in the diagram below:

PG (power good) in Red goes to low and the output 18V in blue also goes low.

  • 0
    TI__Mastermind 43610 points

    HI Fawaz,

    Without more details it is difficult to say what is going on. If the IC is indeed around 40C, we are nowhere near thermal shutdown. Can you clarify 'except for the feedback resistors'? Since the EVM worked for your application, is it possible to order free samples from ti.com and repeat your tests?

    If not you have a sales contact to submit the example IC's for failure analysis?

    Regards,

  • 0 in reply to JCHK
    Prodigy 70 points

    Hello John,

    By feedback resistors i mean the feedback resistor combination to generate the 18V output. I have now also changed the eval board in order to use the same resistor combination it works as well. 

    I do not have any sales contact. If you can provide some information, i would like to initiate a contact.

    I would like to order some samples so that I can test them and be sure that I have the correct components from TI.  I will order free samples. 

    What details would you like to know, I would be happy to provide you that. Following is the snippet of my circuit.

  • 0 in reply to Fawaz Malik
    TI__Mastermind 43610 points

    HI Fawaz,

    If you can let me know what company you are with and where you are located, I can try to get you in contact with your local sales for support.

    Also, what is the trace on channel 1?

    In the mean time, please order free samples from TI to test in your circuitry.

    Regards,

  • 0 in reply to JCHK
    Prodigy 70 points

    Hello John,

    I have sent you an email with company details.

    Channel 1 is the sensor analog signal in our application. It is unrelated to the LDO. I took a scope picture with channel 1 active and therefore it is part of the picture. The analog circuit needs 18V to function and therefore, as 18V signal goes low the analog signal also goes low.

  • 0 in reply to Fawaz Malik
    TI__Mastermind 43610 points

    Hi Fawaz,

    Thanks for the clarification.

    Our local sales should be in contact with you shortly.

    Were you able to order samples?

    Regards,

  • 0 in reply to JCHK
    Prodigy 70 points

    Hello John,

    Thanks for your support. No,  I have not been able to order sample yet. As I need to create a case t request sample access. Somehow, it is complicated to order samples, although it did not use to be like that. 

    I you could expedite the process i would highly appreciate it. I have ordered ICs from Digi key again, and also additional eval boards so that i can replace the LDO IC from the functional eval board and test it on my circuit. I have tried attaching the eval board output to my circuit and it works perfectly as well.

    So, my problem is really limited to the LDO IC that I have on my board. It is working differently than the one on Eval board.

    Thank you.

  • 0 in reply to Fawaz Malik
    TI__Mastermind 43610 points

    Hi Fawaz,

    You should receive samples in the next few days.

    Regards,

  • 0 in reply to JCHK
    Prodigy 70 points

    Hello John,

    Thank you for your outstanding support. We have found out that the soldering contact of the Enable pin was intermittent and this was the reason for the strange behavior. The LDO works fine now and exactly as expected. Once we have corrected the soldering on the Enable pin we don't see any strange behavior anymore.

  • 0 in reply to Fawaz Malik
    TI__Mastermind 43610 points

    Hi Fawaz,

    Happy to hear it!

    Thank you,

    John