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LM25066IA: Won't start vs high current loads

Part Number: LM25066IA
Other Parts Discussed in Thread: LM25066, PMBUSMGRGUI-SW

Hi All ,

A csutomer at a bringup phase claims the following :

"Using the LM25066IA Hot Swap controller that is following an LM5140 20A/12V buck :

Looks like that the LM25066iA  shuts down when we switch on a 20A load. 

If we start with a 5A we can go higher to 20A and even up to 25A of Ccurrent limit set point."

When they have tried to use a lab supply and ramp in the same way @ 20A load it seems that our devices gets into an unknown state when it fails to start.

What can be a reason for this inablity to start in front of these 20A (using an electronic load)  ?

This thread needs an urgent support

Best regards ,



  • Hi Again ,

    The updates are :

    1. In constant resistor mode of the EL the LM25066 can start @ 20A . it does not help the customer.

    2. There is a strange uncontrolled timing of the INRUSH which is 500uSEC quite constant does not matter which load the device is seeing.

    The expectation was that there would be some current limit during as period of initial time until the output caps are loaded enough and only then there should be a release under current limit of the current sense resistor for the rest of the life of this power cycle.

    Apparently this does not seem to work with the LM25066iA and there is a constant ramp up timing which is too past towards 12V on the output. The Gate of the FET is not being controlled properly.

    3. There is a missing SW GUI for this part that 5 month ago should have been fixed on the TI WebSite - PMBUSMGRGUI-SW

    Br ,


  • Arik

    Working via email on this.  Perform requested items and we can go through your results on Monday afternoon Dallas time. Visit for design tool, tutorials, app notes, and PI Commander GUI for the EVM.