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  1. #1
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    Current sense resistor selection in a DCDC power supply

    Hi, all,

    Would anyone be able to advice the disadvantages of using a too small sense resistor in a DCDC power supply? Or any useful online reading?
    I was using a reference circuit from LT as below,
    http://cds.linear.com/docs/en/demo-b.../1317ahsch.pdf

    Everything remains almost the same except the sense resistor RCS1 was reduced to 3mOhm instead of 5mOhm.
    Recently there are some field returns that having the output 2.2uF/100V ceramic capacitors (i was using 4 per) burnt.
    I am not sure whether this reduce of value will result in a poor load regulation.
    Could anyone shed some light on this?
    Thanks.

    Dyu

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  2. #2
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    Re: Current sense resistor selection in a DCDC power supply

    The reduced sense resistance needs more current through it, in order to develop the same voltage as previously. Your schematic shows that a component (LT1952EGN-1, U1 pin 10) detects that voltage. (This sort of feedback method is common, although I have no hands-on experience with a LT1952EGN-1.)

    As a general principle, it adjusts operation so that it matches a reference voltage. Therefore in order to create the greater current, components are forced to work harder.

    It might reduce the burden if you reduce the reference voltage. This assumes the IC is able to detect the reduced voltages.



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