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High current circuits causes voltage drop due to wire/trace resistance.
In addition, fast switching high current circuits also have a lot of
electromagnetic feedback due to inductance. This is especially
the case for motors because motors are high inductance devices.
Even non-inductive high current circuits can cause problems. This is
especially the case when the following conditions are met:
- The current is switched periodically. For example, a pulse
width modulated heater element that draws a lot of current.
- The current is switched on and off. Again, like a pulse width
modulated heater element.
- The current draw is enough to change the supply voltage.
When all of these conditions are met, the supply will see sharp
changes of voltages (like a digital square wave). This is a problem
for the voltage regulator because a voltage regulator cannot
regulate the output voltage when the input voltage has a sharp