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LMR14050-Q1: How many value of the resistance that can be set ?

Went Cao
Genius 5550 points
Part Number: LMR14050-Q1
Other Parts Discussed in Thread: LMR14030

Dear  all

      As below schematic, if I change the value of the R9 resistance from 0Ω to 10Ω, the ring of uprush would be lower, as below oscillogram.

      My question is that how much the maximum value of R9 resistance will be set ? I am worry that big value will affect chip operation

     

  • 0
    TI__Mastermind 34875 points

    Hi Went,

    Is the application for 18V to 5.5V @ Fsw=1.9MHz?  what's the minimum input voltage and maximum load current?

    R9=10ohm should be Ok for this conversion if Vin>9V, but you still need to estimate chip junction temp by checking chip case top temperature at lowest Vin and highest load current. 

  • 0 in reply to Andy Chen
    Genius 5550 points

    Dear Andy

            SW=1.9MHz，input voltage is 6V-32V，output is 5V，maximum load current is 3A;

            Could you share me how maximum value of R9 resistance can be set at this application ?  Thanks a lot.

  • 0 in reply to Went Cao
    TI__Mastermind 34875 points

    Hi Went,

    Because of limitation of Ton-min and Toff-min, the minimum Vin is about 8.5V if you want to keep fixed Fsw=1.9MHz, otherwise switching freq will drop if Vin below 8V.

    Vin<=32V is Ok for 5V output at 1.9MHz.

     I suggest to use R9 <=10ohm in this application. you may use LMR14030 which is more suitable for load<3A.