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LMP8646: changing gain on the fly

Paul Antunes
Intellectual 2550 points
Part Number: LMP8646

Dear current sensing team,

I have suggested my customer to adopt LMP8646 + external DCDC converter for charging a supercap. This is an alternative solution to competitor # LTC3642.

My contact likes the idea and he would know if we can change gain value (Rg) on the fly. At start up, he wants to limit charge current at min value in order to power up system first (power source budget is very limited). Then, he wants to adjust current limit high for charging super cap.

Questions:

Is it possible to change gain on the fly ? if so what are recommendations?

Can we connect any TI dc/dc converter with LMP8646 as long as we follow design procedure like AN-2218 ?

thanks

Paul

  • 0
    TI__Mastermind 31165 points
    Hey Paul,

    I cannot find any designs where the gain setting resistor RG is variable, but I could see this being possible depending on which way customer chooses to vary the resistance whether this is with two resistors in parallel and a switch or using a digital poteniometer. Customer just needs to ensure that the current going through RG circuit (Vsense/5kOhm, typically) is within the current limitations of the variable RG circuit.

    As for your second question, any switching of linear regulator could be used in this design as long as it has a feedback or adjust pin.

    Sincerely,
    Peter Iliya
    Current Sensing Applications