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Original question:

TPS23753A: PD off after start

TPS23753A: POE chip damaged

user6062940
Intellectual 610 points
Part Number: TPS23753A

Hi TI ,

I have encountered some problems in the test. I look forward to your help.

The same model, TPS23753A chip and adapter at the same time power.The default is POE first.The circuit design is shown in the attached picture 2. The only difference from the reference circuit is that a diode D is added to the POE output terminal.

During the actual production test, 4 POE chips were damaged in more than 80 units.For the reason of damage, our preliminary judgment is that the voltage value of the adapter input is higher than the output voltage of the POE, resulting in abnormal operation of the POE. 

1) if the hypothesis is true and the adapter voltage is higher than the POE voltage, what is the reason for the chip damage?

2) in addition, what is the maximum output voltage of TPS23753A?In what range is the output voltage recommended for conventional electronic applications?

  • 0
    TI__Mastermind 21320 points

    Hello,

    The situation you are describing sounds like the diode is backwards and back-driving power to the primary side. 

    Can you describe the damage and provide a schematic, showing the part(s) and pin(s) that get damaged? I cannot tell you the source of the damage if I do not know the nature of the damage. 

    the TPS23753A is a type 1 PD, which means it is rated for 13W applications. The IC is a PoE PD and a PWM controller. The DC-DC design is what sets the power limit and the output voltage. In an ideal world any output voltage can be chosen based on the DC-DC. Practically we typically see 3.3V-24V (most typically 5V or 12V). 

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    Intellectual 610 points

    The schematic diagram is as follows： 2783.原理图.pdf

  • 0 in reply to user6062940
    TI__Mastermind 21320 points

    Hello, 

    So what damages exactly?

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    TI__Mastermind 21320 points

    Additionally, it appears your adapter is 12V but the PoE DCDC output is either 5V or 3.3V depending on the transformer used. So the adapter is certainly higher than the PoE. 

    In the end you are trying to Diode-OR two voltages that will never be close to equal. Depending on the power source of the adapter it could be backdriving the DCDC. It is strange that it only happens on 4 out of 80 devices. On the 4 that damaged, was both output diodes installed correctly?

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments 

  • 0 in reply to Michael Pahl
    TI__Mastermind 21320 points

    Hello,

    I have not heard from this post in over a week. I am going to close it, but feel free to post here when you have answers to the questions above. 

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments