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LM2734-Q1: And LM2734 non-Q do NOT create in Webench above 61C with normal design inputs of 10-15Vin, 5Vo, 1A.....Webench bug or very sad family of parts ?

Glenn Stern
Prodigy 10 points
Part Number: LM2734-Q1
Other Parts Discussed in Thread: LM2734

I tried to create 10-15Vin, 5Vout, 1A design in Webench for LM2734XQMKX/NOPB and also the non-Q version.  Webench will NOT create the design above 61C, yet the datasheets clearly show temperatures up to 125C.  I need to know ASAP if this is a Webench bug with this family, or is this family really incapable of at least 85C ???

If the family is incapable of 85C, I need to pick another family ASAP.  Please help !!!

As an additional note:  When I use 60C as the temp, it does create in Webench, BUT it recommends a completely different source of voltage for Vboost....when the datasheet clearly says my design parameters mean the best option is to develop Vboost from Vout, since I am less than 5.5V.  I feel that's the design method for Vboost Webench should create with, since having a completely different PS for Vboost is a ridiculous suggestion.

  • 0
    TI__Expert 7860 points

    Hello Glenn,

    The LM2734XQ should work under these temperature conditions as the junction temperature is rated at a max of 150C and recommended operating max of 125C. 

    You are correct in sourcing Vboost from the Vout node as this is recommended in the datasheet for output voltages between 2.5 - 5.5V. Reference schematic from the datasheet given below:

    WEBENCH gave the same error when I tried inputting your requirements. I will look into this to see if there is some violation preventing it from running correctly.

    Thanks,

    Joseph

  • 0
    TI__Expert 7860 points

    Hello Glenn,

    I wanted to provide an update. The reason it won't let you simulate over 61C (ambient temperature) is that the junction temperature of the device is limited to 125C and it hits this limit at TA = 61C. It seems to be the limitation of the device.

    My recommendation would be to look into the TPS62153A-Q1RGT family. I simulated it in Webench with your requirements and had no problems running the design at 100C. It is a higher efficiency efficiency with comparable BOM costs and lower BOM count.

    Let me know if this helps.

    Thanks,

    Joseph

  • 0 in reply to Joseph Conrad
    Prodigy 10 points

    Thanks for the fast update !  Unfortunately my production schedule needs 30k this year, and TPS62153A-Q1RGT doesn't have that available at TI or the channels.  I realize it must be a limitation of the LM2734 package, but it's a shame TI designed a part whose title is 1A capability, but then doesn't even "create" at 70C....the basic min requirement for any design on Earth.  I don't actually need 1A, and was able to create at 0.7A using 10-14VDCin, and 85C ambient.  So I might still use the part.