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LM338: High current 15-A output configuration on Datasheet

Leandro Hernandez
Prodigy 20 points
Part Number: LM338
Other Parts Discussed in Thread: LM1084,

I am an electrical engineering student and I am conducting some research for a high current output voltage regulator with a high voltage differential. Regarding the System example of Fig. 30 on the LM338 Datasheet that can provide 15A. I was wondering if i can get a high current output if my input Voltage is 25 volts with an output voltage of 5V or 12V since I am actually trying to get this design on a PCB for a school project.. I was previously using an LM1084 which can provide 5A but at a high voltage differential I only get an output of 0.3 A. when going from 25V to 5V which is not enough for the system that will be connected to it.

Any an all help is appreciated, As I am currently still learning I appreciate your patience. 

  • 0
    TI__Mastermind 23361 points

    Hi Leandro, 

    I am happy to give you some suggestions for your project. 

    1. At high current and big Vin and Vout difference, thermal performance will be challenging. Please read through the following chapter to know the limitation on thermals. The parameters mentioned in the following chapters are different for each device and package and they can be found in datasheet. 

    2. Once you understand the limitation of thermals, you can start to think how you can improve the thermal for higher current output. There are different ways to do it. Instead of having a output voltage of 5V or 12V from 25V, can you setup a few voltage stages in between by using multiple LDOs? Can you also try to parallel multiple LDOs to increase the output current?  There are applications notes you can find online about how to do parallel LDOs. 

    3. When you are dealing with thermals, can you do better PCB layout to have better heat dissipation? Maybe increasing the size of metal for heat dissipation? Can you create more vias on the PCB to improve heat dissipation? 

    Since this is your project, those are the suggestions I can quickly think of that may give you some ideas on what to research and hopefully they are helpful.  

    Regards, 
    Jason Song