• State Resolved
  • Locked Locked
  • Replies 9 replies
  • Subscribers 62 subscribers
  • Views 2852 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS65150: VIN drop issue

Patrick Chen
Mastermind 8875 points
Part Number: TPS65150

Hello,

            While VIN is above UVLO, SW start switching and it cause Vin(VCC3) drop as below waveform. Could timing of SW be tuned to solve this issue?  or any other method to improvement. Thank you.

BR

Patrick

  • 0
    TI__Guru 58225 points
    Hello Patrick,

    Maybe you try the following:
    1. Pull the REF pin to GND until the input voltage reaches a higher value (I need to check this in the lab, but this should work in theory.)
    2. Increase the capacitors connected to VIN to reduce the drop.
    3. Insert series resistors (like 2.2 ohms) in series to DRVN and DRVP.
    The later 2 solutions are most probable not helping too much.

    Best regards,
    Brigitte
  • 0 in reply to Brigitte
    Mastermind 8875 points
    Hello Brigitte

    Customer already test item 2 &3. But Vin still have drop issue. How about item 1 testing? Or any suggestion for this issue? Thank you.

    1. Pull the REF pin to GND until the input voltage reaches a higher value (I need to check this in the lab, but this should work in theory.)
    2. Increase the capacitors connected to VIN to reduce the drop.
    3. Insert series resistors (like 2.2 ohms) in series to DRVN and DRVP.

    BR
    Patrick
  • 0 in reply to Patrick Chen
    TI__Guru 58225 points
    Hello Patrick,

    The tests in the lab showed that not the REF pin shall be pulled to GND to delay the startup, but the COMP pin. So the customer could delay the startup of TPS65150 by pulling the COMP pin to GND. Due to the fact that this pin is sensitive (it guarantees the stability of the boost converter), a low leakage path should be used for this pull-down.

    Best regards,
    Brigitte
  • 0 in reply to Brigitte
    Mastermind 8875 points
    Hello Brigitte,

    Could I know what value pull down resistor more suitable? If pull down for COMP pin, has any effect for stability? Thank you.

    BR
    Patrick
  • 0 in reply to Patrick Chen
    TI__Expert 8010 points
    Hello Patrick,

    The tests in the lab were done using a small resistor (100 Ohm) in series with a transistor that is pulled low during the delay. After the delay has passed and the converter needs to start the COMP pin should not be loaded anymore (except from the compensation network) as this highly effects the stability behavior.

    Best Regards.
    Ilona
  • 0 in reply to Ilona
    Mastermind 8875 points

    Hello Ilona

                 Customer change PR12 100 ohm. PC17 not changed. Is the stability of COMP pin ok for it? Thank you. 

    BR
    Patrick

  • 0 in reply to Patrick Chen
    TI__Guru 58225 points
    Hello Patrick,

    This is absolutely not allowed. The converter stability will change dramatically if you do this. Please revert the value back to the 33 kohm the customer had before.

    The circuit that Ilona describes needs to be connected to the COMP pin directly not as the resistor above.

    COMP pin - transistor - 100 ohm - GND for a delay
    and in parallel
    COMP pin - resistor - capacitor - GND for stability

    Best regards,
    Brigitte
  • 0 in reply to Brigitte
    Mastermind 8875 points
    Hello Brigitte/Ilona,

    Could you help provide draft schematics could improve the issue and have good stability that Ilona test to us? We can test also. Thank you.


    BR
    Patrick
  • 0 in reply to Patrick Chen
    TI__Expert 8010 points

    Hello Patrick,

    As Brigitte mentioned the transistor needs to be connected in parallel to the compensation - network, see figure below. You must make sure that the transistor is turned off as soon as the boost converter is in regulation.

    Best Regards.

    Ilona