the application is a bit odd. it is to control an oxygen sensor is a car, basically i need to source enough charge such that the catylitic reaction in the oxygen sensor is at steady state.
The amount of charge i need to pump in to reach that steady state is proportional to the amount of oxygen left over from internal combustion. it is this amount of oxygen that i am intersted in measureing. Most designs use voltage source pushing current through a small resistor to supply the current needed, and then use A/D to find to voltage drop across the resistor to find the steady state current.
But I would like to do away with using A/Ds, if i had a way to use PWM to control a charge pump or current source that would make things alot simplier.
I need something that I can control percisely to do the following:
supply: -4ma to +4ma
the voltage range of operation would be between -5V to 5V.
I am a bit stuck in finding something, I can explain things in more detail if needed but basically I need a PWM controlled current source/charge pump, even a voltage controlled current source/chrage pump is okay, My only requirement is that the resolution and percision need to be high and it should not be very complex.
Regards
Alan To
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