Hi,
I designed this circuit for measuring current flows through output. It'll be up to 30Amps so I choosed 0.01Ohm resistor (R6) to minimalize power losses. TLV2401 amplified 12 times the voltage on resistor and the output is conected to MSP430G2452. What're your opinions? I'm affraid the output voltage of TLV2401 will oscilate too and measurement will be inaccurate.
I choosed TLV2401 mainly due to the low consumption.
It's a part of my bachelor's thesis, thanks for all your ideas!
Dalibor
Dalibor,
First, the close-loop gain of your configuration is 11 rather than 12, G=1+(110k/11k). Second, with the maximum shunt current of 30A through your 0.01ohm R6 shunt resistor, this would result in the 0.3V at the positive input terminal and thus: 11*0.3V=3.3V at the output of TLV2401. Since no linear op amp has output capable of reaching its supply voltage, using 3.3V supply voltage will result in the output of TLV2401 being trioded (non-linear) before reaching desirable 3.3V; looking at the graph of the output voltage vs output current and the table of the output voltage below, and assuming MSP430 draws virtually no current, the output of TLV2401 may swing no closer than 100mV under ~27uA load (3.3V/121k) - therefore, you need to either increase the supply voltage to at least 3.4V or lower the gain to be able accurately measure the max shunt current.
The same is true on the low side where the TLV2401 output is capable of getting only within 180mV of the negative rail (see PDS table below) - this means that the output will be stuck around 180mV above the ground until the shunt current gets above 1.64A (180mV/11/0.01ohm).
