Recently, I have stated that in switched-mode power supplies, you should use capacitors with a low equivalent series resistance due to a switched-mode power supply causing high ripple currents to such capacitors. Now, what about motor controllers? The decoupling capacitors to motor controllers are rather similar to those used in power supplies. I’ll put in my recommendation: you should also use low equivalent series resistance decoupling capacitors for a motor controller, especially if you are using PWM motor speed control. That will for sure cause high ripple currents, and you don’t want to have decoupling capacitors that heat up and wear down if you don’t have to.
So yes, that I’m updating my L293D schematics with the corresponding changes.
Previously I’ve discussed the possibility of using a discrete components MOSFET motor controller circuit. It’s actually not a bad idea considering the switching controllers with external MOSFETs. If you want to drive higher current loads, the external components are required. So, simply for the sake of operating with through-hole components at lower voltages, it’s justifiable.
Of course, another option is still yet to use adapters and modern surface-mount MOSFET motor controllers. Saves you board space, for sure.
Okay, but the main thing to beware of when using your own discrete MOSFET controllers. Thermal shutdown… it’s built-in to many motor control ICs. Under voltage… that can damage the MOSFETs. Under-voltage protection is pretty easy to build. Thermal shutdown, that may be a bit more challenging to do right when building your own. One thing to note, though, is that discrete MOSFETs have pretty good heat dissipation built-in to them, they have those metal heat sinks sticking out of their tops and that makes it real easy to get a fairly good heat dissipation in place. It could be that your design may not ever need thermal shutdown.
There are also classes of motor control ICs designed along same principles of switched-mode power supplies, terminology is key… “controller” is the keyword for when the MOSFETs or BJT transistors that control the power directly to the motor are external. If the word “driver” is used that means these are integrated into the same package.
Here is some great information how protection circuits while using discrete MOSFETs. You can put temperature fuses on MOSFETs to protect from overheating, and there are also some other nifty tricks of resistor, diode, and capacitor placement.
20200309/DuckDuckGo mosfet under voltage protection
20200309/https://www.homemade-circuits.com/mosfet-protection-basics-explained-is/