LMZ14201: Unusual behavior of power supply

Hello

Can you apply 24V directly and see what result you get.

Does the device regulate otherwise??

Is the input current the only thing you notice that is odd ??

Thanks

Probably is best to include power supply schematic. When  we apply 24VDC on a virgin PCBA the efuse TPS26621 blows up. After the power sequencing is applied as described in the initial message, there is no problem appying 24VDC directly, even after the board is powerdown for days. Thanks for your help.

Hello

You can try to remove the LMZ module and power up with 25V to see if the Efuse trips.

If not, then separate the LMZ from the Efuse and power up the LMZ directly from a power supply and see what happens.

Thanks

Hello 

         On a board that had eFuse failure I bypass power directly to the LMZ14201. It behaves normally. This will point to the eFuse, although I have checked before there was no voltage drop in between, but  I will check that again.

Thanks

Hello

Ok; let us know if you need any more help.

Thanks

I have taken data from 3 boards. Same PCB artwork and same parts.

It is not apparent that the eFuse does not work.

Do you have any other suggestions? Thanks10208_Power_Supply_data.xlsx

Hello

Is the output voltage of the module steady and regulating??

What kind of load are you using?  Rload or Eload ??

Thanks

Thanks for the reply

The input and output of the LMZ14201 have the same amount of ripple in the 18 to 23 VIN range. It is low.

The load I'm using is the actual circuit but it is in a steady state.

On the TPS26621 the OVP pin is well below the trip threshold 0.63V at 23VIN.

Hello

You could try to disconnect the load and test with a resistor load to be sure you have a constant load.

Thanks

Hi

I disconnected the circuit load and place a 60ohm resistor across the 3.8V output.

This is a similar load

The results on the current are very similar, a soon as VIN goes above 20V the current increases as well.

Thanks

Hello

I will ask our module team to look at this and get back to you as soon as possible.

Thanks

Thanks for the update

Hello

I possible, try to hold a scope probe on top of the package in order to 

detect the internal switching node.

This may give us more clues.

Thanks