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Why is the current ringing in this resistor in this LTspice simulation?

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treez

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Hello,
Why is the current ringing at several MHz in the resistor (R7) connected to the LTC6101 current monitor?

This doesn't happen in the similarly connected LTC6102 circuit (as shown). Also, in spite of the ringing, the actual output of the LTC6101 circuit seems OK.

Please find LTspice simulation and schematic attached.
 

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ArticCynda

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At which frequency are you running the simulation? If the frequency is too high then a portion of the current will be reflected by impedance mismatches, causing ringing effects.
 
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treez

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Thanks, the sim isnt running at a frequency as such, its just putting a dc current through the sense resistor, the ltc6101 cct rings, the ltc6102 cct doesnt, -which is strange because surely they are exactly the same cct?
 

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The LTC6101 model is apparently instabble with larger Rin values due insufficient compensation of the feedback amplifier. No idea if the effect occurs with the real IC.
 
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