• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Subscribers 62 subscribers
  • Views 617 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS23754: We can't boot up system via TPS23754.

Rich Kuo
Prodigy 40 points
Part Number: TPS23754

Hi,

We are Barco limited in Taiwan New Taipei City and we're facing a question that need your support. We design TPS23754PWPR-1 for POE application on our system, but it can't properly boot up. Here are schematic, waveform and another MP project's normal boot up waveform and reference EVM data for your reference in advance. Please check and get feedback, hope to see your response as soon as possible, many thnaks!

Rich.

Gulden Graak POE normal start up waveform.rarWGA-910 abnormal start up waveform.rarRK3399_BOX_REF _ 23.POE PD+_TPS23754-1.pdfTPS23754EVM.pdf

  • 0
    TI__Mastermind 40100 points
    Hi Rich,

    It's nice to meet you! What is the use of R444 and C411. I don't believe any of our designs use this. Can you try removing this? Otherwise, I don't see an issue with the schematic. It might be that what's currently on the board is not populated with right value or connection. Can you double check this? Thanks!
  • 0 in reply to Darwin Fernandez
    Prodigy 40 points

    Hi Darwin, 

    Thanks for the update!

    1>We've removed R444 and C411, but system still can't boot up properly via TPS23754.  

    2>We found Q4 is hot even if we disconnect D8507 and its temperature is around 58 degree. 

    3>As you mentioned, we're checking components which is different with original design. Do you have experiences that which components are really sensitive and not recommend to switch? Maybe you can provide your 

    thoughts for quickly debugging. 

    Rich. 

  • 0 in reply to Rich Kuo
    TI__Mastermind 40100 points

    Hi Rich,

    Any particular reason for D21, the BAS21 is used? It has 8x the reverse recovery time from the BAS16.

    Also if the FET is getting hot, you may want to look for shorts on the board. Also it would be good to check if R9257 is the correct value.

    Hopefully the D3 circuit isn't pulling much current? Can you remove this as well?

    Thanks!

  • 0 in reply to Darwin Fernandez
    Prodigy 40 points

    Hi Darwin,

    Thanks for the update! 

    Q1>Any particular reason for D21, the BAS21 is used? It has 8x the reverse recovery time from the BAS16.

    A1>Frankly speaking, we follow our another internal project Gulden Graak's design and we found this difference. However, when we switch BAS21 to BAS16, still can't boot up properly, but on Gulden Graak there is no boot up issue via POE. So I thought this is not key issue. 

    Q2>Also if the FET is getting hot, you may want to look for shorts on the board. Also it would be good to check if R9257 is the correct value.

    A2>Yes, we measured R9257's value and it fits on design. 

    Q3>Hopefully the D3 circuit isn't pulling much current? Can you remove this as well?

    A3>This design is connected to a P-CH MOSFET and the main purpose is to on/off MOSFET once both adapter and POE plug at same time. POE's priority is higher than adapter. 

    Finally, we've figured out root cause is Q13(CYStech: MTE1K0P15KN3). It's alternative part and we thought some basic parameters are identical with original design, so we agreed JDM parter to change. It seems we missed something is really important. Can you point out which is key for this? Please refer to attachment. 

    By the way, in order to avoid design mistakes again, we remove R444 and C411 as your suggestion. 

    One more question, can you recommend us alternative part of Q13 base on your experience? 

    Rich.

  • 0 in reply to Rich Kuo
    TI__Mastermind 40100 points

    Hi Rich,

    Thanks for the update! The alternative FET has more than 3x the turn ON and OFF characteristics.

    If an alternative is needed. I recommend FDMC2523P which we've used in the past.