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

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

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Low-Noise Fixed Frequency Operation

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1.5V Output Voltage

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Li-Ion (3.6V) to 1.5V with 81% Efficiency

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1.7% Output Voltage Accuracy

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Output Currents up to 250mA

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2.7V to 5.5V Input Range

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Shutdown Disconnects Load from V

IN

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1.1MHz Switching Frequency

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No Inductors…Small Solution Size

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Current Limit and Thermal Protection

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LLP-10 Package (3mm x 3mm x 0.8mm)

Applications

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DSP, Memory, and Microprocessor Power Supplies

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Mobile Phones and Pagers

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Portable Electronic Devices

Typical Application Circuit

20183801

LM2771 Efficiency vs.

Low-Dropout Linear Regulator (LDO) Efficiency

20183813

March 2006

© 2006 National Semiconductor Corporation

DS201838

www.national.com