Hello friends.
There's a circuit I'm trying to build but it seems it would require enough opamps to function to justify just using an MCU instead.
I want to measure the voltage differential across two different resistors in series and ensure they are sharing equal voltage regardless of their resistance differences.
I also need to reach this voltage equalization through the use of a lowside current source.
So in essence I want to tell the MCU to keep X volts across both resistors and have it adjust the current source until that point is reached.

I'm assuming I would have 3 internal ADCs measure the voltage across the 2 resistors in series and use a filter at the PWM output to feed the positive input of an opamp based variable current source.
Then write code to tell the MCU to sweep its output until both of the feedback inputs equal the desired voltage.

Any advice? I haven't built my own MCU circuit before and I'm a little rusty on code. I just want the cheapest part for the job.
Thanks.

 

What kind of voltages are we talking about?

 

Hello friends.
There's a circuit I'm trying to build but it seems it would require enough opamps to function to justify just using an MCU instead.
I want to measure the voltage differential across two different resistors in series and ensure they are sharing equal voltage regardless of their resistance differences.
I also need to reach this voltage equalization through the use of a lowside current source.
So in essence I want to tell the MCU to keep X volts across both resistors and have it adjust the current source until that point is reached.

I'm assuming I would have 3 internal ADCs measure the voltage across the 2 resistors in series and use a filter at the PWM output to feed the positive input of an opamp based variable current source.
Then write code to tell the MCU to sweep its output until both of the feedback inputs equal the desired voltage.

Any advice? I haven't built my own MCU circuit before and I'm a little rusty on code. I just want the cheapest part for the job.
Thanks.

https://www.microchip.com/ParamChartSearch/Chart.aspx?branchID=30048

 

What kind of voltages are we talking about?

I'll be using a -15v supply to power the current source. I want the voltages across the resistors to be under 0v and typically only a few volts between them.
Now that I think of it I will probably have to have the output filter of the MCU feed into a P channel fet so I can reach the negative voltages required to bias the current source.

 

two different resistors in series and ensure they are sharing equal voltage regardless of their resistance differences.

If the two resistors have different values and they are in series then the voltages across them will not be equal.

 

Oh crap you're right haha. I guess my analog skills have gotten rusty too. I will have to rethink my strategy. Thanks.