1 Features
1• Input Voltage: 2.5 V to 6 V
• 100-mV Maximum Dropout with 150-mA Load
• 150-mA Verified Output
• 50-dB PSRR at 1 kHz at VIN = VOUT + 0.2 V
• ≤ 1.5-μA Quiescent Current when Shut Down
• Fast Turn-On time: 200 μs (typ.)
• 30-μV RMS Output Noise (typical) over 10 Hz to 100
kHz
• −40°C to 125°C Junction Temperature Range for
Operation
• 2.5-V, 2.6-V, 2.7-V, 2.8-V, 2.85-V, 2.9-V, 3-V, 3.1-
V, 3.2-V, 3.3-V, 4.7-V, 4.75-V, 4.8-V and 5-V
Outputs Standard
• Logic Controlled Enable
• Stable with Ceramic and High-Quality Tantalum
Capacitors
• Fast Turnon
• Thermal Shutdown and Short-Circuit Current Limit

2 Applications
• CDMA Cellular Handsets
• Wideband CDMA Cellular Handsets
• GSM Cellular Handsets
• Portable Information Appliances

3 Description
The LP3985 is designed for portable and wireless
applications with demanding performance and space requirements. LP3985 performance is optimized for
battery-powered systems to deliver ultra low noise,
extremely low dropout voltage, and low quiescent
current. Regulator ground current increases only slightly in dropout, further prolonging the battery life.
The LP3985 is stable with a small 1-μF ±30%
ceramic or high-quality tantalum output capacitor. The
DSBGA requires the smallest possible PC board area
- the total application circuit area can be less than 2
mm x 2.5 mm, a fraction of a 1206 case size.
An optional external bypass capacitor reduces the
output noise without slowing down the load transient
response. Fast startup time is achieved by utilizing an
internal power-on circuit that actively pre-charges the
bypass capacitor.
Power supply rejection is better than 50 dB at low
frequencies and starts to roll off at 1 kHz. High power
supply rejection is maintained down to low input
voltage levels common to battery operated circuits.
The device is ideal for mobile phone and similar
battery-powered wireless applications. It provides up
to 150 mA, from a 2.5-V to 6-V input. The LP3985
consumes less than 1.5 μA in disable mode and has
fast turn-on time less than 200 μs.
The LP3985 is available with fixed output voltages
from 2.5 V to 5 V. Contact Texas Instruments Sales
for specific voltage option needs.