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PMP20588: Output Voltage issue

Naresh K
Intellectual 510 points
Part Number: PMP20588
Other Parts Discussed in Thread: TL431, TLV431

I am using PMP20588 Fully Autonomous Single Port Type 2 (30W) PoE PSE Reference Design without any changes in the schematic and BOM.  While testing the board i can see output voltage as 23VDC instead of 54VDC.

Please help me to get the required output voltage(54VDC). Do i need to make any changes in the schematic?

www.ti.com/.../PMP20588

Regards

Naresh

  • 0
    TI__Genius 15655 points
    Hi Naresh,

    We are notifying the team developed this board and they will get back to you ASAP. Thanks.

    Best regards,
    Penny
  • 0
    TI__Intellectual 2350 points

    No changes are required for the circuit to function.

    Resitors R21/R25/R26 set the output voltage.  Check that these values are correct.  Check that R14 and R17 are zero ohms.  These resistors are only used for testing the control loop.  Check that D13 is installed correctly.

    Where are you measuring the 23V?  Is it a DC value or pulsating?  When power is applied at J1 there should be a continuous 54VDC at R4.

    To obtain PoE power at J2 a valid PD load needs to be applied that can pass the Detect and Class cycles.  It also needs to provide the minimum MPS load of 10mA.

    If none of these suggestions resolve your issue and you don't have the correct voltage at R4, please attach a waveform of the output at R4, the voltage at U2-4 and the voltage at U1-4.

    Thanks,

    David

  • 0 in reply to David Strasser
    Intellectual 510 points

    Hi David,

    Thanks for the reply.

    We are using R21= 75K Ohm, R25 = 4.42K and R26 = 20K Ohm.And  D13 also correctly installed but still i can see 24V DC output at R4 resistor.  You can see attached wave forms  at R4, U1-4 and U2-4.

  • 0 in reply to Naresh K
    TI__Intellectual 2350 points
    Do you have a TLV431 installed for U3 instead of a TL431? The TLV reference is 1.24V versus 2.495V for the TL. This would set the output to a little less than half.
  • 0 in reply to David Strasser
    Intellectual 510 points

    Thank you David,

    The issue is clear now. We got the output 54VDC. Thanks for your support

    regards

    Naresh