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TPS23750: TPS23750

user6219301
Prodigy 60 points
Part Number: TPS23750

I have a project use TPS23750 and found some issues. . Attached is the schematic diagram. I use 23750 to generate 5V voltage for my system. But now the output is only about 2V. Which change I can do for this issue?

Thanks

  • 0
    Prodigy 60 points

    I add 30V voltage to vdd-vss, and the output is normal about 5V. But the input current is about 115mA, and our 5V load only needs 50mA . The inductance and capacitance at the load end will heat up. Vgate switches one group every 500ms. When vdd-vss is increased to 35-40v, it will crash. The current drops to 30 ma.

  • 0 in reply to user6219301
    TI__Mastermind 40100 points

    Hi User,

    The secondary has a 33uH inductance. Typically for flyback it is only in the 100nH range. The 33uH is probably making this converter unstable.

    I might be good to order the TPS23750 Flyback EVM and compare your solution since the EVM is working solution.

  • 0 in reply to Darwin Fernandez
    Prodigy 60 points

    Hello:

              we have change 33uH to 4.7uH, but it's not work normally. The output is 2V, also  delete the two 330uF capacitor and get the same result. 

                                                                                                            Thanks               

  • 0
    Prodigy 60 points

    UVLO THRESHOLDS PACKAGE(2) TA MARKING TYPE LOW HIGH TSSOP-20 PowerPAD™ Standard 30.5 V 39.3 V 

    How to understand the UVLO of 23750 is 39.3V and the POE supply VDD-VSS is DC 48V? 48V>39.3V the IC can not support this system

  • 0 in reply to user6219301
    TI__Mastermind 21320 points

    Hello,

    4.7uH is still much larger than the 100nH range. Please change it to 100nH range.

    As for the UVLO,  the input voltage is between 42-57 volts typically. The rising UVLO threshold for the standard is 39.0V. That means the IC is going to try to turn on at a voltage greater than or equal to 39V. This supports the PoE standard input range of 42-57. 

    The UVLO falling threshold is 30.5V. When VDD_RTN reaches 30.5V, the IC will shut off. Until that point, the IC is still trying to be powered. So if there is a 48V input the IC will be powered. Then when it is removed, the IC will continue to switch until the VDD_RTN voltage drops across 30.5V. 

    If this post answers your question, please indicate so by marking this thread as resolved. Thank you.

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments