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LM5005 wide range application

David Jennings
Prodigy 60 points
Other Parts Discussed in Thread: LM5005

Using LM5005 in a high volume consumer product, could not contact TI support. Energy Star (low current out) to 1.2A.  Can this switcher be adjusted to maintain regulation for light (3mA) to higher current (1.2A) loads?  Also need to review reliability in higher temperature environments (up to 145F).  Prefer to discuss with FAE or apps engineer.

  • 0
    TI__Mastermind 49351 points

    Hi 

    There is no problem to regulate output at 1.2A load. (Please refer design example in the datasheet)

     At 3mA light load, you may need an external circuit which supports PRE pin function. (Please refer Boost pin section in the datasheet) . PRE helps to charge Boost capacitor at light load, but at some conditions, an additional help from external circuit may be required. 

     LM5005's maximum operating junction temperature is 125 degreeC. From 63 degreeC ambient, 62 degreeC temperature rise is allowed. 

    Regards,

  • 0 in reply to EricLee
    Prodigy 60 points

    We have working boards that perform well at 1.25A and the LM5005 does function light loads of 3mA or even no load, but of course goes into the hiccup mode. We do have pins 17,18 and 19 connected together per the data sheet.  This application is for very high volume with production scheduled for late September 2014.  Reliability curves would be appreciated (temperature) and details of "and external circuit may be required".  Some interaction to determine if this is the best choice for our application would be appreciated.

  • 0 in reply to David Jennings
    TI__Intellectual 1435 points

    David,

    Eric Lee has been out of the office for the past several days.   Are you making progress with your design?  The LM5005 is a good choice for wide Vin DC-DC in the 1A-2A load range. 

  • 0 in reply to David Pace
    TI__Mastermind 49351 points

    Hi 

    In case that LM5005's pre-charge switching is not enough strong, please connect a PNP transistor (Base to PRE, Emitter to SW, Collector to ground) and  a 10k ohm resistor from Base to Emitter. The additional PNP transistor will help LM5005's pre-charge switching. You might be able to see an hiccup operation at noload if the pre-charge switching is not enough strong. 

    Regards,