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I am building a step down converter using LTC3892. It will have 12V output sourcing 50A in each of two interleaved phases.
Problem is that LTC3892 has fixed current limit value at 75mV. This means that for 50A current limit, I would need a current sense resistor of 1.5mOhm which is a bit odd value.
I wonder whether I could use a 2mOhm resistor and then use a resistor divider to reduce the signal voltage from 100mV to 75mV? Has anyone had any experience with such method?
Maybe you could, but I suggest simply connecting Ilim to change the limit voltage to 100mV which happens to be the same ratio as 1.5:2, then no additional parts required.
Edit: Since you have the version without the configurable limit, you could try dividing it however you are in unknown territory in some ways. Suggest leaving the 1n cap across the 3m ohm resistor and dividing the resistor with something like 1\$\Omega\$/4.99\$\Omega\$, with the 1 ohms at the Vout side. You might consider a few pF across the sense inputs, but it's probably not necessary. 1% is overkill, but Samsung ones cost 33 cents for 10 so it won't break the bank. The higher you go in resistance for the divider the further you are away from the designers' concept so unforseen problems may occur.
If you have sufficient 2 mOhm resistors, simply parallel 4 of them and place these in series with two more in parallel. That will give you 1.5 mOhm.
