May 2002
LP3985
Micropower, 150mA Low-Noise Ultra Low-Dropout CMOS
Voltage Regulator
2.85V, 2.9V, 3.0V. 3.1V, 3.2V, 3.3V, 4.7V and 5.0V output
voltages. For other output voltage options between 2.5V to
5.0V or for a dual LP3985, please contact National Semicon-
General Description
The LP3985 is designed for portable and wireless applica-
tions with demanding performance and space requirements.
ductor sales office.
±
The LP3985 is stable with a small 1µF 30% ceramic or
high-quality tantalum output capacitor. The micro SMD re-
quires the smallest possible PC board area - the total appli-
cation circuit area can be less than 2.0mm x 2.5mm, a
fraction of a 1206 case size.
Key Specifications
n 2.5 to 6.0V input range
n 150mA guaranteed output
@
n 60dB PSRR at 1kHz, 50dB at 10kHz 3.1VIN
n ≤1.5µA quiescent current when shut down
n Fast Turn-On time: 200 µs (typ.)
n 100mV maximum dropout with 150mA load
n 37µVrms output noise over 10Hz to 100kHz
n −40 to +125˚C junction temperature range for operation
n 2.5V, 2.6V, 2.7V, 2.8V, 2.85V, 2.9V, 3.0V, 3.1V, 3.2V,
3.3V, 4.7V and 5.0V outputs standard
The LP3985’s 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.
An optional external bypass capacitor reduces the output
noise without slowing down the load transient response.
Fast start-up time is achieved by utilizing an internal
power-on circuit that actively pre-charges the bypass capaci-
tor.
Features
n Miniature 5-I/O micro SMD and SOT-23-5 package
n Logic controlled enable
n Stable with ceramic and high quality tantalum capacitors
n Fast turn-on
n Thermal shutdown and short-circuit current limit
Power supply rejection is better than 60 dB at low frequen-
cies and starts to roll off at 10 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 2.5V to 6V input. The LP3985 consumes less than
1.5µA in disable mode and has fast turn-on time less than
200µs.
Applications
n CDMA cellular handsets
n Wideband CDMA cellular handsets
n GSM cellular handsets
The LP3985 is available in a 5 bump small bump micro SMD,
a 5 bump large bump micro SMD, and a 5 pin SOT-23
package. Performance is specified for −40˚C to +125˚C
temperature range and is available in 2.5V, 2.6V, 2.7V, 2.8V,
n Portable information appliances
Typical Application Circuit
10136402
Note: Pin Numbers in parenthesis indicate micro SMD package.
*
Optional Noise Reduction Capacitor.
© 2002 National Semiconductor Corporation
DS101364
www.national.com