DESCRIPTION
The SUM31XX family of low-dropout (LDO), low-power linear regulators offers very high power supply rejection ratio (PSRR) while maintaining very low 14 μA ground current, suitable for RF applications. The family uses an advanced CMOS process and a PMOSFET pass device to achieve fast start-up, very low noise, excellent transient response, and excellent PSRR performance.
The SUM31XX is stable with a 1.0 μF ceramic output capacitor, and uses a precision voltage reference and feedback loop to achieve a worst-case accuracy of 2% over all load, line, process, and temperature variations. It is fully specified from TJ = - 40°C to +125°C and is offered in a small UTDFN1.0×1.0-4，DFN1.0×1.0-4 and SOT23-5 package, which is ideal for small form factor portable equipment such as wireless handsets and PDAs.

FEATURES

 Wide Input Voltage Range :1.9 V to 5.5 V
 Output Voltage :1.2 V to 4.5 V
 Up to 300 mA Load Current
 Other Output Voltage Options Available on Request
 Very Low IQ: 14 μA
 Low Dropout: 180 mV@3.3 V typical
 Very High PSRR: 90 dB at 1 kHz
 Ultra Low Noise: 10 μVrms at 3.3 V output (load = 1 mA)
 Excellent Load/Line Transient Response
 Line Regulation: 0.02%/V typical
 Short Circuit Protection: 500 mA (Current at short mode) typical
 With Auto Discharge

http://www.sumsemi.com/