LM2771 Datasheet, PDF (1/16 Pages) National Semiconductor (TI) – Low-Ripple 250mA Switched Capacitor Step-Down DC/DC Converter

LM2771
www.ti.com
SNVS435 – MARCH 2006
LM2771 Low-Ripple 250mA Switched Capacitor Step-Down DC/DC Converter
Check for Samples: LM2771
FEATURES
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•2 Low-Noise Fixed Frequency Operation
• 1.5V Output Voltage
• Li-Ion (3.6V) to 1.5V with 81% Efficiency
• 1.7% Output Voltage Accuracy
• Very Low Output Ripple: 8mV @ 250mA
• Output Currents up to 250mA
• 2.7V to 5.5V Input Range
• Shutdown Disconnects Load from V_IN
• 1.1MHz Switching Frequency
• No Inductors…Small Solution Size
• Current Limit and Thermal Protection
• WSON-10 Package (3mm × 3mm × 0.8mm)
APPLICATIONS
• DSP, Memory, and Microprocessor Power
Supplies
• Mobile Phones and Pagers
• Portable Electronic Devices
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 requires 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 results 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 (WSON-10).
Typical Application Circuit
V_IN = 3.0V to 5.5V
V_IN
C_IN
1 PF
V_OUT
V_OUT: 1.5V
I_OUT up to 250 mA
LM2771
C_OUT
4.7PF
GND
EN
C1+
Cfly
1 PF
C1-
LM2771 Efficiency vs.
Low-Dropout Linear Regulator (LDO) Efficiency
Capacitors: 1 PF - TDK C1005X5R1A105K
4.7 PF - TDK C1608X5R0J475K
or equivalent
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Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
All trademarks are the property of their respective owners.
2
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2006, Texas Instruments Incorporated