Ultra low noise low power LDO design

A low dropout regulator (LDO) with ultra low output noise is described. The proposed structure of LDO with internal noise filter is discussed and related design problems along with their possible solutions are highlighted. The LDO ensures output noise below 1OmuV (10Hz to 100kHz) having quiescent current about 25muA for no load. Maximum output current of 100mA is available. The LDO is stable with a 220nF ceramic output capacitor. In testing, PSRR above 75dB (1kHz), dropout below 80mV (Vout>2.5V), and transient peaks below 30mV (1mA ... 80mA output step) were measured. The solution is patent pending and has been introduced to low noise LDO LP5900