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TPS92520-Q1: Consult about the Rcs value limit

zhiyuan zhang
Intellectual 620 points
Part Number: TPS92520-Q1

Hello expert:

    To improve the output current accuracy in low current application(0.1A for example). I want to increase the Rcs value(R1303) and what is the limit? Is 1.5R OK?  Then will much higher than the Rdc of the power inductor as 0.2R and is this an issue? 

    

  • 0
    TI__Mastermind 18955 points

    Hello Zhiyuan,

    What is your max current criteria for the channel?  That generally sets the max current sense resistor value.  

    -fhoude

  • 0 in reply to fhoude
    Intellectual 620 points

    Hello expert,

        My maximum output current is 133mA, we want to use 1.3R current sense resistor to ensure the 5% accuracy when output 100mA.

       Beside limiting the max output current, is there any other issue if we use a current sense resistor up to 1.5R?

  • 0 in reply to zhiyuan zhang
    TI__Mastermind 18955 points

    I haven't tested this at such light loads but it should work.  Normally people opt for linears at this light a load.  Just curious what requirements are forcing you to take this path?  It seems like an expensive solution that is overkill.  We can take this offline if you need privacy.  

    -fhoude

  • 0 in reply to fhoude
    Intellectual 620 points

    Hello fhoude,

        The PCB design is frozen and can not be change. So we need to study the possibility to using this device to drive a light load as 100mA and keep high output current accuracy. Let's come back to the question, could you pls double confirm whether current sense resistor up to 1.5R is OK for the application where max current needed is only133mA?

  • 0 in reply to zhiyuan zhang
    TI__Mastermind 18955 points

    Hello Zhiyuan,

    I tested out the circuit and it seems to be operating fine within this application design.  It should work fine in general.  I would like to understand why you would use this part for a 133mA output when you could use a linear instead if you changed the design.  I did verify that the accuracy was better than +/-4% at full scale, in other words at 134.6mA given a Rcs of 1.3 ohms.  Let me know if you have questions.

    -fhoude