High Current Circuits

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 change.