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about LM5073

ACGUY
Guru 11170 points

Hello E2E,

The customer is using the LM5073. We know that the LM5073 is discontinued.
The LM5073 detects Elecom PoE hubs, but not Netgear hubs.
Both hubs have a Vin of 1.5V or higher when connected.
Elecom: 7.25V
Netgear: 5.75V
We are being asked to improve by our customers. Can this be solved with H/W?

Regards,
ACGUY

  • 0
    TI__Mastermind 21320 points

    Hello,

    If one PSE works and the other doesn't..

    Can you show a waveform of Vin - VEE during a full PoE handshake and power up, for both PSE's?

    Also, Vin typical range for PoE is 37-57Vin. Can you clarify what you mean by Vin of 7.25V and 5.75V?

    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
    Guru 11170 points

    Hi,

    Thank you for response. I got waveform from customer, I want to do send it you on private message. Can I apply a friendship?

    Regards,
    ACGUY

  • 0 in reply to ACGUY
    TI__Mastermind 21320 points

    Yes you can or you can post it here. 

    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
    Guru 11170 points

    Hi,

    I got the information is confidential. There for, I can't post it here. I will post in private message.

    >> Can you clarify what you mean by Vin of 7.25V and 5.75V?
    By the datasheet, when Vin rise up to more than 1.5V the LM5073 has Vin detection status. If the handshake between the LM5073 and the HUB is successful, the HUB should output a classification pulse. However, NetGear HUB does not output a classification pulse with the LM5073.

    Regards,
    ACGUY

  • 0 in reply to ACGUY
    TI__Mastermind 21320 points

    Hello, 

    I understand now, so it is failing detection. There is a detection resistor integrated into the LM5073. You could put a resistor in parallel (between VIn and VEE) to increase/decrease the detection resistance. I would try the range 24K-27.5K (combined). 

    As an incentive to swtich parts in future projects, all of our new IC's do not integrate this resistor so it is easily adjustable for this exact reason. 

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

     

    Regards, 

     

    Michael P.

    Applications Engineer

    Texas Instruments