Constant Current — Fixed-Current Pulse Mode

Constant current mode makes the set value an absolute ceiling. Drive a load with a voltage source and the current is whatever the load and that voltage produce — if the load turns out lower-impedance than expected, current follows it up. Fix the current instead, and that value is the most the load will ever see, regardless of what the load actually is.

Loads with a capacitive component raise a separate problem. Driven from a voltage source, the rising edge of the pulse can push current through the capacitive component to very high values for a brief moment — tens of nanoseconds — followed by ringing in the current waveform, a direct consequence of the capacitor's behavior at fast rise times. Driven as a current-controlled pulse instead, neither the spike nor the oscillation occurs — current tracks the set value straight through the rise edge. For some applications, eliminating these transients matters as much as holding the steady-state current itself.