• State TI Thinks Resolved
  • Locked Locked
  • Replies 4 replies
  • Answers 1 answer
  • Subscribers 63 subscribers
  • Views 146 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.

TPS40211-Q1: Cannot start at low input voltage

Jeff Yun
Intellectual 2735 points
Part Number: TPS40211-Q1

Hi, Team

My customer is using our TPS40211-Q1 as a buck-boost controller.

His usage is: the input voltage range is 9~32V, and the output voltage is constant voltage 27V.

The customer engineer gradually reduced the input voltage from 32V to 9V, and found that when the voltage was reduced to 16V, the TPS40211-Q1 could not start (BP Pin had no output).

When the input voltage increases by 16.5V, the device can start to work normally.

May I ask what could be the cause of this failure?

Thank you for your support and look forward to your reply!

  • 0
    TI__Genius 11215 points

    Hello, 

    Thanks for reaching out. What topology is the customer using (Flyback or SEPIC)? What is the maximum load current required in this system? It might be that the device is hitting current limit as the input voltage is decreasing. Could you please provide the schematic and the scope shot of ISNS, GDRV, SS and the output voltage? We're looking forward to hearing from you soon. 

    Kind regards,
    EM

  • 0 in reply to EM
    TI__Intellectual 2735 points

    Hi, EM

    The topology that customer uses is Sepic, constant current mode. The constant output current is 1.5A, output voltage is about 27V.

    The customer suspects that the chip's internal LDO triggers the protection and causes the chip to shut down. At present, a 4.7K resistor is connected in series between Vin and BP, and the chip can work normally when Vin=16V.
    What could be the reason for this fault?

    And I will synchronously ask customer for the test waveform of the relevant Pins.

  • 0 in reply to Jeff Yun
    TI__Guru 59755 points

    Hello Jeff,

    What type of load is connected to the output? Is it possible that he is using a constant current load that is already drawing 1.5A as soon as the voltage rises a little? If yes, please ask the customer to change to a constant resistance load instead. A converter that needs to boost the input voltage to a higher output voltage needs a lot more input current than output current and especially during startup, this might cause issues if the load is already applied.

    Best regards,
    Brigitte

  • 0 in reply to Brigitte
    TI__Mastermind 46421 points

    Hi Jeff,

    as we have not received an additional information, I assume this issue is solved and I am closing the thread.
    If there is still something open, just reply to open it again or open a new thread.

    Best regards,
    Stefan