Other Parts Discussed in Thread: OPA277
Good day all.
Now I use OPA2277(2CH PKG) power supply source for sensor.
Sensor equivalent circuit is as about 1k ohm pure resistor. (no capacitor exists.)
It is connected between high side and low side. High side output - 1kohm - Low side output.
Other conditions
Power supply
Positive +9V(Generated by SW regulator)
Negative -9V (Generated by charge pump IC)
Input reference voltage +3.3V (Stable and common for both channels)
Gain high side X2 (High side output=6.6V)
low side X(-1) (Low side output=-3.3V) Total sensor power is 9.9V.
Problem
Under this conditions, negative power supply current is unstable.
By simulation and calculation, negative power current is just only less than 20mA, but it increases to about 100mA by periodically and unstable.
And when we changed output load from 1kohm to 10kohm to reduce output current, negative power source current will be stable.
Is there any possible reason that causes above phenomenon?
Please teach me any hint to solve this issue.
Regards.