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LP2951: Lp2951csd

Jan Emkjaer
Prodigy 20 points
Part Number: LP2951

Hi

I have a high power 5V SMPS running, witch I wold like to power off at light load. 

At light load I have a LP2951 running parallel, 

Questions:

  1.  Can lp2951 handle back biasing
  2.  Do I have to place a diode in series with LP2951 output
  3. Other problems

In advance thanks

  • 0
    TI__Genius 14245 points

    Hi Jan,

    LP2951 does not have reverse current protection so it cannot handle Vout being higher than Vin by more than 300mV. So if Vou>Vin+300mV current could flow from Vout to Vin, in this case you will need a diode to block to the current, this diode could be placed either on the output (between Cout and the load) or on the input (between the source and Cin) either will work to protect the device from reverse current. 

    As for other potential issues just make sure that the SMPS has a voltage setpoint higher than the LDO that way when you are delivering high power all that power is supplied by the SMPS. 

  • 0 in reply to Kyle Van Renterghem
    Prodigy 20 points

    Hi Kyle

    Thanks for the fast reply.

    Thre will be input voltage on LP2951 all the time.

    Vin on LP2951 is 10-28V but with a low current the output is connected to a High current 5Vdc SMPS.

    The intension is to gain efficiency in standby by shutting down SMPS

    I will set the output from LP2951 to 4.8V, and the 5Vdc SMPS to 5.06V

  • 0 in reply to Jan Emkjaer
    TI__Genius 14245 points

    Hi Jan,

    Your plan sounds good. In the case that there will always be an input voltage above 5V then you shouldn't need the diode in series, however just be verify that your startup and shutdown sequences don't result in unintended behavior which could cause Vout>Vin.