1 Features
1• Input Voltage From 1.65 V to 4 V
• Output Voltage From 0.8 V to 3 V
• 1% Accuracy at Room Temperature
• 125-mV Dropout at 300-mA Load
• 50-μA Quiescent Current at 1-mA Load
• Inrush Current Controlled to 600 mA
• PSRR 65 dB at 1 kHz
• 100-μs Start-Up Time for 1.5-V VOUT
• Stable With Ceramic Capacitors as Small as 0402
• Thermal-Overload and Short-Circuit Protection

2 Applications
• Post DC-DC Regulator
• Battery Operated Devices
• Hand-Held Information Appliances

3 Description
Operating from a minimum input voltage of 1.65 V,
the LP3991 LDO has been designed to provide fixed
stable output voltages for load currents up to 300 mA.
This device is suitable where accurate low voltages
are required from low input voltage sources and is
therefore suitable for post regulation of switched
mode regulators. In such applications, significant
improvements in performance and EMI can be
realized, with little reduction in overall efficiency. The
LP3991 provides fixed outputs as low as 1.2 V from a
wide input range from 1.65 V to 4 V Using the enable
(EN) pin, the device may be controlled to provide a
shutdown state, in which negligible supply current is
drawn.
The LP3991 is designed to be stable with spacesaving
ceramic capacitors as small as 0402 case
size.
Performance is specified for a –40°C to +125°C
junction temperature range. For output voltage
options, contact your local Texas Instruments sales
office.