Hi All,
I am having some trouble with setting the offset voltage for the INA170. this is what i have done...
So as stated the V+ pin is connected to +5v. This is also the input for the charge pump.
the ground for the INA170 is -5v from the output of the charge pump. I have done this as I want the output voltage from the ina170 to be between -5v and +5v so i can read it with the range another tool can read over with the best resolution possible.
the vref is set to the ground of the system (ground of the charge pump) 0v that is
Rl and Ros are both 50k to give a gain of 50. and an offset voltage of (Vref / Ros) * Rl which should give an offset of 0v.
I see an output voltage from the INA170 of around -5 v when no current is flowing. I was expecting to see 0V (Vref)
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another way to think about this...
consider the -5v as ground from the charge pump
then the vref is +5v and the power to the INA170 is +10v
using this i should get a voltage offset of (vref / Ros) * Rl or (5/50) * 50 = +5v, again half way between ground and the ina170 power voltage. but i see it as close to ground(in this example)
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Any help you can offer would be greatly appreciated.
Many thanks
Liam