capacitordecoupling-capacitor
The circuit is not important, my quesiton is for example, for C3, while using an electrolytic capacitor(I assume for a 100uF, electrolytic is the most common one); which side should be connected to the + terminal of the capacitor? Right or left? Why?
Thanks.
All digital ICs should have decoupling caps between their power and ground pins. These should be ceramic and physically as close as possible to the IC. You want to minimize the loop length from power pin to cap to ground pin thru the IC and back to the power pin.
Decoupling caps deal with short term current spikes the IC draws. They must therefore be high frequency. Large capacitance is not necessary, and since large capacitors usually have poor high frequency response, they are worse. A 100µF electrolytic cap is pretty useless for decoupling. 1µF to 100nF ceramic is good.
As for the cap on the motor, the idea is good but I think 100nF is too large. That could cause excessive or unnecessary current to flow in the H bridge every time it switches. If you're only reversing motor direction occasionally, then this isn't a big deal. If you're using the H bridge to modulate the apparent motor drive with PWM, then you should lower the cap. Something like 1nF should still cut down the noise the motor is making while not getting in the way of switching.
The designers did a perfect job in the pin assignment:
Each of the power pins is right next to a ground pin; you can't get better than that! All you have to do is place the caps on each of the pin pairs, as close as possible to the pins.
Best Answer
The pictures below can help understanding the problem. Voltages and voltage drops are visualized by vertical bars (in red) with corresponding lengths, and currents - by loops (in green) with corresponding thicknesses.
After the power supply is turned on, the output decoupling capacitor C2 is charged by the current IL flowing along the loop E+ -> Rc -> C2 -> RL -> E-. Similarly, the input decoupling capacitor C1 is charged by the current IG flowing along the loop E+ -> RB -> C1 -> EIN -> E-.
C1 and C2 retain their charges (voltages) during the positive half-wave...
... and during the negative half-wave:
These pictures are combined in the more sophisticated picture below: