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LMG3522R030: LMG3522R030/LMG3422R030 Drain current vs RθJC

Kevin Vogel
Prodigy 10 points
Part Number: LMG3522R030
Other Parts Discussed in Thread: LMG3422R030,

Tool/software:

Hello,

according to the datasheets, LMG3522R030 and LMG3422R030 have the following values:

LMG3522R030 (Top-side cooled):
ID(RMS) 38A
Tj max 150°C
RθJC(top) 0.28 K/W

LMG3422R030 (Bottom-side cooled):
ID(RMS) 40A
Tj max 150°C
RθJC(bot) 0.55 K/W

How is it possible for the LMG3422R030 to drive more current with a higher thermal resistance?
Shouldn't it be the other way around?

Kind regards
Kevin Vogel

  • 0
    TI__Prodigy 330 points

    Hi Kevin, The information on the datasheet is correct. LMG3522R030 and LMG3422R030 use slightly different dies and have different wire bond structure in internal design in addition to the thermal design difference. Hence the small change in the current rating.

    Thanks,

    Subhransu 

  • 0 in reply to Subhransu Satpathy
    Prodigy 10 points

    Hi Subhransu,

    thanks for your reply.

    So if we assume that both components have the same heatsink and we neglect the higher thermal resistance due to the necessary thermal vias for the LMG3422R030. Then the LMG3522R030 has a lower recommended current rating, although the junction temperature rises only half as much. (Rds,on is the same for both components)

    That sounds completely absurd to me. What am I missing?

    Kind regards
    Kevin

  • +1 in reply to Kevin Vogel
    TI__Prodigy 330 points

    Hi Kevin,

    The recommended current ratings of TI GaN devices on datasheet are based on long term reliability analysis. Since the two have different internal designs, they have different (but very close) recommended current rating based on reliability study. But in your case, if you are only considering the losses and thermal design of package, you can push more current for the same temperature rise through LMG3522R030 than LMG3422R030. 

    I hope this answers your question.

    Thanks,

    Subhransu