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Original question:

LM5155: Possible alternatives to replace LM5155

LM5155: Controller can be paired with TPS2373 for PoE bt

Ryan Wang
Prodigy 90 points
Part Number: LM5155
Other Parts Discussed in Thread: UCC2897A, LM5020, LM5022, LM5001,

Hello there:

Currently we are using TPS2323 paired with LM5155 for a PoE bt power design. Due to the component shortage problem of LM5155, I am wondering what are the alternative options to replace with LM5155. Right now I think LM5155/5156/5157/5158 are possible options, and on the evaluation board TI uses UCC2897A as a controller. I am looking for more options, thank you so much in advance!

  • 0
    TI__Guru 74300 points

    Hi Ryan,

    Thank you for reaching out.  Just let you know that we are applications engineering team, and delivery issues are handled by TI sales team.  Please reach out to TI sales personnel in your region.   

    Regarding other options, you may consider LM5022 and LM5020 controllers, as both has been used as the dc-dc stage in PoE, and maybe LM5001 converter (integrated FET) if it fits your operating conditions. 

    Thanks,

    Youhao 

  • 0 in reply to Youhao Xi
    Prodigy 90 points

    Hello Youhao:

    Thanks for getting back to me. Currently we are using LM5155 as a flyback controller design, so if we try to switch to LM5020 (since the stock availability is looking ok) would it require a lot of peripheral circuit design changes? What kind of potential issues that you can foresee since this is an old part? 

  • +1 in reply to Ryan Wang
    TI__Guru 74300 points

    Hi Ryan,

    You need to change some components around the IC including but the power circuit except for the current sense resistor can remain the same.  Namely the Cin, Cout, MOSFET, Flyback transformer and rectifier diodes, and also the operating frequency, can be the same.  The reason for the current sense resistor change is owing to the different operating voltage of the LM5020.  Its cycle by cycle peak limit is about 0.5V while the LM5155's about 100mV. 

    If you are using the hiccup mode with the LM51551, then it is not implemented if the old parts. However, like said, one targeted applications of the LM5020 and LM5022 is PoE when they were released.

    Thanks,

    Youhao