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WEBENCH® Tools/TPS2373: PD controller TPS2373-4 damaged

Steven Kang
Prodigy 40 points
Part Number: TPS2373
Other Parts Discussed in Thread: TPS23861

Tool/software: WEBENCH® Design Tools

Dear sir.
When PoE_PSE output voltage higher AC/DC adapter,
Step 1: plugged in PSE first.
Step 2:then an AC/DC adapter plugged in later.
In step2, Why PSE still power on and supply voltage to PD?

Step 3: AC/DC adapter unplugged.
It damaged PD controller TPS2373-4RGW.
We damaged 3 Viking(project name) units in this scenario.
Please help to provide the solution.

Adapter ORing: Viking unit is option 2.
Option 2 applies power between the TPS2373 PoE section and the power circuit
APD pin voltage is 3.2V when AC/DC adapter plugged in, in Viking unit.

TPS2373 specification:
When a voltage of more than about 1.65 V is applied on the APD pin relative to RTN, the
TPS2373 does the following:
• Internal pass MOSFET is turned off

PSE TPS23881EVM and PD TPS2373-4 EVM are also have this issue.

Thanks!
Inventec Appliances Corp.
Steven Kang

  • 0
    TI__Expert 3700 points

    Hi Steven, 

    Thank you for your question. The PoE applications engineering team is currently out of the office but will respond to this post on Monday, 9/28. 

    Best Regards,

    Brett Colteaux

    PoE Product Marketing Engineer

  • 0
    TI__Mastermind 21320 points

    Hello Steven,

    Can you provide a schematic?

    If the PSE is still powering the PD but APD is above 1.65V, then the part might be damaged. 

    Can you confirm this is the case? 

    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
    Prodigy 40 points
    Dear Michael,
    Thanks for your reply!
    Attached schematic.
    1.AC/DC adapter is 54VDC, supply to P7 connector of Connector board DVT_SCHEMATIC-1.pdf
    2. U4306 via 6 pin cable to connected J7 of U4306
    3. PD or AC/DC adapter output to system and DVT_SCHEMATIC1_ PSE_TPS23861.pdf
    4. ADP pin voltage is ~1.7V. 
       Even we change R3550 from 7.5Kohm to 15Kohm, then APD pin voltage change to ~3.2VDVT_SCHEMATIC1_ PSE_TPS23861.pdf
    It may damaged PD controller TPS2373-4 when  AC/DC adapter unplugged.. 
    Thanks!
    Inventec Appliances Corp.
    Steven Kang

    DVT_Schematic_PD_TPS2373-4.pdfConnector board DVT_SCHEMATIC-1.pdf

  • 0 in reply to Steven Kang
    TI__Mastermind 21320 points

    Hello Steven,

    Thank you for the schematic. We are currently working with your Field Applications Engineer on this issue. We will continue to escalate this issue through email. Thank you!

    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
    Prodigy 40 points

    Dear Michael
    Thanks for you and Jim Tsai / FAE!
    To suggest remove AMPS_CTL external resister to disable PSE power delivery while adapter in.

    The other question,
    page 7 of specification, The APD voltage threshold: 1.38V ~ 1.82V
    page 17, When a voltage of more than about 1.65 V is applied on the APD pin relative to RTN,
    1.65V is under 1.82V.

    When Auxiliary power detected, which APD voltage is correct?
    Between voltage threshold range 1.38V ~ 1.82V, or higher then 1.82V ?

    In our system,
    When APD pin resistors divider are 237K ohm and 7.5K ohm from adapter 54VDC.
    Is it guaranteed that the PD actually turns off when the power adapter is connected and APD voltage ~1.66V?

    Thanks!
    Inventec Appliances Corp.
    Steven Kang

  • 0 in reply to Steven Kang
    TI__Mastermind 21320 points

    Hello Steven,

    That is exactly the point I making. There is some variance on what the actual value of APD is required - 1.38V-1.82V. 

    1.66V is the typical value, but for mass production I would increase this value. The absolute maximum is 6V, so my suggestion is to raise APD to 2V to ensure all parts go above threshold without damage. 

    Did you not experience any more damage after removing the AMPS_CTL resistor?

    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
    Prodigy 40 points

    Dear Michael,

    Thanks for your help!

    After removing the AMPS_CTL resistor,

    We still testing PSE and adapter plugged/unplugged on product.