I have a solenoid with 0-0.8mA current range driven using PWM. The coil resistance is 14ohms and inductance is 14mH. I am using an FPGA to do the closed loop current control, Servoing at 24K. The feedback current is read through a 1 ohm sense resistor. Required pwm resolution is 12bit.
Does anyone have enough experience to help me determine if this is a good configuration??
I'm probably missing a piece, but usually, the constant current driving is done with an OpAmp. FPGA could provide a setpoint for the OpAmp via PWM. Is that what you were planning to do? Are you planning to run your servo loop at the rate of 24kHz?
I have a feeling that a good PWM frequency would be a multiple of the servo rate (20kHz, 40, 60 etc).
Correct me if I'm wrong, but if you want 12-bit resolution with 20kHz frequency, 80MHz clock.
You're probably right about aliasing (although 24kHz will have some aliasing too). I was thinking that PWM generator and servo engine were synchronized.