I have a 12V DC input to a circuit. There is a 660uF Aluminum cap on the input.
The 12 volt source is not in my control and can come from anywhere. So it could be a noisy source or a high current clean source.
I am wondering if it's worth it to put an inductor in series with the input to limit inrush current? Or even if it's worth limiting the inrush current in this specific case at all?
I know that there are ICL devices and MOSFET devices that can limit the rise time and they are made for this.
One device is the TI TPS22810DBVR. And is pretty cheap in volume.
But, I already have a cheap 4.7uH inductor that can handle my 2Amp max draw from my circuit. And i'm hoping I can use this for 2 reasons:
1) Limit inrush current
2) Help clean up the 12V input.
I have done some simulations.
Cap: 660uF with 130mOhms ESR
Inductor: 4.7uH with 37mOhm resistance.
12V DC input with 1V/uS rise time. (Just guessing on that one since I don't have control over what the source is.
This gives a peak current of 62Amps. Now I may not have control over the 12V input source, but i'm pretty sure it's not going to be from a source that can output 62Amps. Maybe a 12Amp source that can handle 12Amps peak loads for a short time.
So since the peak current allowed (theoretically) is 62Amp, but is limited by the source, I would say there is no point in putting the 4.7uH inductor in there because is still going to allow the same peak current of 12Amps whether it's there or not. Is this a good answer for my questions?
It should still help clean up the 12V input though right? A cutoff frequency of around 2857.6Hz. Maybe get rid of switching noise if it's a SMPS.
Please let me know your thoughts and experience with this situation. I could put a bigger inductor in there, but I am very limited on PCB space.