Tool/software:
Hello team,
I set up a differential scaling design by TLV171-Q1 in LTSpice, is for to monitor system current. but the result is not equal to caculation.
And however I changed RADC value, the output voltage is about 362mV
Hello,
The way this is set up, your expected output voltage is 2.3mV, as is there is about 2mA of current through your shunt resistor. This means a voltage drop of about 100uV across your shunt resistor (RADC). 24 times this gives you an ideal output voltage of 2.352mV. However, this is outside the linear range of the output of this amplifier. If you want to accurately sense this level of current, you will need more gain (and definitely a more precise amplifier). Increasing your shunt value will help only to a point. I'm not sure why the output voltage is stuck at ~300mV in LTspice, however, we only build and verify our models for functionality in TINA-TI and PSpice for TI. Unfortunately we do not have visibility into LTspice and cannot debug in LTspice as this is not our software.
Best,
Jerry
Hello,
Well there is about 960uA flowing into the amplifier inputs, as the inputs are not much higher impedance than the load resistance.
You can increase all your diff amp resistors by a factor of 5 to drop the current into the amplifier inputs by a factor of 5.
For the linear output range, there are two output "limits." There is the swing from rail, which is how close to either rail the amplifier can drive the output when the input is overdriven. This is the output trying to drive high or low as hard as possible. There is a second range that is the area of most linearity. The AOL spec shows the output range where the AOL is highest. For the TLV171 this is 350mV from either rail.
Best,
Jerry
