The CAT6218 is a 300 mA CMOS low dropout regulator that provides fast response time during load current and line voltage changes. The quick−start feature allows the use of an external bypass capacitor to reduce the overall output noise without affecting the turn−on time of just 150 s. With zero shutdown current and low ground current of 55 A typical, the CAT6218 is ideal for battery−operated devices with supply voltages from 2.3 V to 5.5 V. An internal under voltage lockout circuit disables the output at supply voltages under 2.1 V typical. The CAT6218 offers 1% initial accuracy and low dropout voltage, 180 mV typical at 300 mA. Stable operation is provided with a small value ceramic capacitor, reducing required board space and component cost. Other features include fold−back current limit and thermal protection. The device is available in the low profile (1 mm max height) 5−lead thin SOT23 package.