INTRODUCTION
The Inrush Current Reduction Module (ICRM) prevents damage to a protected voltage regulator during power-up
by limiting inrush current to a safe level. Without inrush protection, the inrush current is limited only by the level of
the power source impedance. The lower the impedance, the greater the risk of damaging the regulator from
excessive inrush current. Devices with a pulse-width modulated (PWM) power stage are especially vulnerable to
high inrush current due to a large amount of capacitance inherent to the design. However, voltage regulators that
use SCR-type power stages do not require the protection of an ICRM since these regulators do not have a large
amount of capacitance in the power stage.
When a voltage regulator with a PWM power stage is energized, the ICRM limits the inrush current by adding a
high level of resistance in series with the voltage regulator power input. Once the inrush current subsides, the
series resistance diminishes quickly to allow nominal, steady-state current flow.