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LM5145: Unit current limits due to transient condition on input

Jeff Coletti
Expert 8755 points
Part Number: LM5145

Hi Support Team

Working on a design with the LM5145 at a customer. They have the unit in a non standard configuration where the main power can be either a 57 volt supply or a 48-42 volt battery.  they also us an LDO to power the LM5145 at a lower voltage because the LM5145 was getting hot.

The supply output is 48volts. Typical current is 2A peak is 4A.

They problem they are seeing is that when they switch to battery, all is good and as the battery drops the supply puts out approx. VIN.

The problem is that when main power returns, the LM5145 current limit trips. They have the current limit set to 12 amps!. Setting the Ilim to 15 amps seems to solve the issue but they would like too better understand what is happening.

Thanks

Jeff Coletti

  • 0
    TI__Genius 11040 points
    Hi Jeff,

    Can you share the schematic and layout?

    Also, can you clarify the input voltages? My understanding is that typically the LM5145 is powered by the 57V supply or 48-42 Volt battery. When the input voltage drops below 42V, an LDO powers the LM5145 device. When the device enters current limit, is the LM5145 is transitioning input power supplies from the LDO to the battery?

    Thank you,
    Katelyn Wiggenhorn
  • 0
    TI__Guru 73602 points

    Hi Jeff,
     
     I recommend completing the LM5145 quickstart file (available by download from the product folder), so we can review the compensation values, etc. What is the input dv/dt during the voltage step?
     
    Regards,
    Tim

  • 0 in reply to Timothy Hegarty
    TI__Genius 11040 points
    Hi Jeff,

    Since this thread is being continued through e-mail, I am going to close this thread. Please continue to let us know if you have any additional questions via e-mail.

    Best Regards,
    Katelyn