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LM5146: LM5146-Q1 RILIM Resistance Tolerance Selection

Jongmin Lee
Prodigy 30 points
Part Number: LM5146

I have one question.

When choosing a tolerance for a RILIM resistor, what tolerance do you recommend?

1% or 0.5% or 0.1%?

The Over Current Protection Limit also changes by about 9% depending on the IRDSO current (180uA ~ 220uA) of LM5146.

Of course, using a precise resistor will reduce OCP Tolerance, but since it is related to the amount of product configuration,

I would like to know the tolerance recommended by TI engineers.

Also, when designing a circuit, what percentage of OCP is usually designed? +-10% or 15%?

 

  • 0
    TI__Mastermind 22299 points

    Hi Jongmin,

    The MOSFET RDSON will probably vary quite a bit.

    We do have a temperature coefficient on the RILIM current, but that is based on IC temperatures, which can differ somewhat from the MOSFET temperature.

    For better tolerance a current sense resistor would be better.

    The current sense resistors I've used are 1%, the RILIM is probably also 1% as well. 0.5% might be OK but I think 0.1% might increase cost too much.

    Since this is valley current limiting, the inductor valley current is set by the resistors, and the peak current can be higher.

    The valley current limit can be 10-15% above the maximum output current sure. It's really up to you.

    Hope this helps,

    -Orlando