The Si91821 is a 300-mA CMOS LDO (low dropout) voltage regulator. The device features ultra low ground current and dropout voltage to prolong battery life in portable electronics. The Si91821 offers line and load transient response and ripple rejection superior to that of bipolar or BiCMOS LDO regulators. The device is designed to maintain regulation while delivering 500-mA peak current. This is useful for systems that have high surge current upon turn-on. The Si91821 is designed to drive the lower cost ceramic, as well as tantalum, output capacitors. The device is guaranteed stable from maximum load current down to 0-mA load. In addition, an external noise bypass