LM2771 Datasheet, PDF (1/10 Pages) National Semiconductor (TI) – Low-Ripple 250mA Switched Capacitor Step-Down DC/DC Converter

March 2006
LM2771
Low-Ripple 250mA Switched Capacitor Step-Down
DC/DC Converter
General Description
The LM2771 is a switched capacitor step-down regulator
that produces a 1.5V output without the use of an inductor. It
is capable of supplying loads up to 250mA. The LM2771
operates with an input voltage from 2.7V to 5.5V, and re-
quires only 3 low-cost ceramic capacitors.
The LM2771 uses a regulated 0.5x charge pump to give
power conversion efficiencies nearly twice as high as an
LDO. Pre-regulated 1.1MHz fixed-frequency switching re-
sults in very low ripple and noise on both the input and the
output. When output currents are low (<30mA typ.), the part
automatically switches to a low-ripple PFM regulation mode
to maintain high efficiency over the entire load range. At
input voltages below 3.5V (Typ), the charge pump goes into
pass mode, with efficiencies similar to an LDO.
The LM2771 is available in National’s 10-pad Leadless
Leadframe No-Pullback Package (LLP-10).
Features
n Low-Noise Fixed Frequency Operation
n 1.5V Output Voltage
n Li-Ion (3.6V) to 1.5V with 81% Efficiency
n 1.7% Output Voltage Accuracy
n Very Low Output Ripple: 8mV @ 250mA
n Output Currents up to 250mA
n 2.7V to 5.5V Input Range
n Shutdown Disconnects Load from V_IN
n 1.1MHz Switching Frequency
n No Inductors…Small Solution Size
n Current Limit and Thermal Protection
n LLP-10 Package (3mm x 3mm x 0.8mm)
Applications
n DSP, Memory, and Microprocessor Power Supplies
n Mobile Phones and Pagers
n Portable Electronic Devices
Typical Application Circuit
LM2771 Efficiency vs.
Low-Dropout Linear Regulator (LDO) Efficiency
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