National Semiconductor LM2771 Technical data

LM2771
Low-Ripple 250mA Switched Capacitor Step-Down
DC/DC Converter

LM2771 Low-Ripple 250mA Switched Capacitor Step-Down DC/DC Converter

March 2006

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 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 (
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).

<

30mA typ.), the part

Typical Application Circuit

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
n Output Currents up to 250mA
n 2.7V to 5.5V Input Range
n Shutdown Disconnects Load from V
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)

@

250mA

IN

Applications

n DSP, Memory, and Microprocessor Power Supplies
n Mobile Phones and Pagers
n Portable Electronic Devices

LM2771 Efficiency vs.

Low-Dropout Linear Regulator (LDO) Efficiency

20183801

20183813

© 2006 National Semiconductor Corporation DS201838 www.national.com

Connection Diagram and Package Mark Information

LM2771

10-Pin Non-Pullback Leadless Frame Package (LLP-10)

National Semiconductor Package Number SDA10A

Pin Descriptions

20183802

Pin # Name Description

1V

2 GND Ground

3V

4 NC No Connect

5 NC No Connect

6 C1- Flying Capacitor 1: Negative Terminal

7 C1+ Flying Capacitor 1: Positive Terminal

8 NC No Connect

9 GND Ground

10 EN Enable Pin Logic Input. Applying a logic HIGH voltage signal enables the part.

IN

OUT

Input Voltage: Recommended VINoperating range 3.0V to 5.5V.

Output Voltage

A logic LOW voltage signal places the the device in shutdown.

Order Information

Output Voltages Order Number Package Mark ID Package Supplied as:

1.5V LM2771SD XXXXX = CZC2CX
YYYYY = L2771

1.5V LM2771SDX XXXXX = CZC2CX
YYYYY = L2771

SDA10A

Non-Pullback LLP

1000 Units, Tape and Reel

4500 Units, Tape and Reel

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LM2771

Absolute Maximum Ratings (Notes 1, 2)

If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.

Pin Voltage -0.3V to 6.0V

V

IN

EN Pin Voltage -0.3V to (V

Continuous Power Dissipation

Internally Limited

(Note 3)

Junction Temperature (T

) 150oC

J-MAX

Storage Temperature Range -65

Maximum Lead Temperature

+0.3V)

IN

w/ 6.0V max

o

C to +150oC

265

o

C

Operating Ratings (Notes 1, 2)

Input Voltage Range 2.7V to 5.5V

Recommended Load Current Range 0mA to 250mA

Junction Temperature (T

Ambient Temperature (T

) Range -30˚C to +110˚C

J

) Range

A

-30˚C to +85˚C

(Note 6)

Thermal Properties

Junction-to-Ambient Thermal
Resistance (θ

), LLP10 Package

JA

(Note 7)

55˚C/W

(Note 4)

ESD Rating (Note 5)

Human Body Model:
Machine Model

2.0kV
200V

Electrical Characteristics (Notes 2, 8)

Limits in standard typeface are for TJ=25oC. Limits in boldface type apply over the full operating junction temperature range
(-30˚C ≤ T
= 3.6V; V(EN) = 1.8V, CIN=C1= 1.0µF, C

Symbol Parameter Condition Min Typ Max Units

V

OUT

V

OUT/IOUT

V

OUT/VIN

E Power Efficiency I

I

Q

V

R

V

R–PFM

I

SD

F

SW

R

OL

I

CL

t

ON

V

IL

V

IH

I

IH

I

IL

Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the component may occur. Operating Ratings are conditions under which operation of
the device is guaranteed. Operating Ratings do not imply guaranteed performance limits. For guaranteed performance limits and associated test conditions, see the
Electrical Characteristics tables.

Note 2: All voltages are with respect to the potential at the GND pins.

Note 3: Internal thermal shutdown circuitry protects the device from permanent damage. Thermal shutdown engages at T

T

=140oC (typ.).

J

≤ +110˚C) . Unless otherwise noted, specifications apply to the LM2771 Typical Application Circuit (pg. 1) with: V

J

1.5V Output Voltage Regulation 3.0V ≤ VIN≤ 5.5V

Output Load Regulation V

= 4.7µF. (Note 9)

OUT

0mA ≤ I

3.0V ≤ V
I

3.0V
0mA ≤ I

0mA ≤ I

OUT

OUT

OUT

IN

= 150mA

<

VIN≤ 5.5V,

OUT

= 1.5V

OUT

≤ 200mA

≤ 5.5V

≤ 250mA

≤ 250mA

1.455

(−3%)

1.475

(−1.7%)

1.445

(−3.7%)

1.5 1.545

(+3%)

1.5 1.525

(+1.7%)

1.5 1.545
(+3%)

0.17 mV/mA

Output Line Regulation 0.1 %/V

= 200mA 81 %

OUT

Quiescent Supply Current I

OUT

= 0mA

45 50 µA

(Note 10)

Fixed Frequency Output Ripple 40mA ≤ I

PFM–Mode Output Ripple I

OUT

<

≤ 250mA 8 mV

OUT

40mA 12 mV

Shutdown Current V(EN) = 0V 0.1 0.5 µA

Switching Frequency 3.2V ≤ VIN≤ 5.5V 0.80 1.1 1.40 MHz

Open–Loop Output Resistance I

OUT

= 200mA

1.0 Ω

(Note 11)

Output Current Limit VIN= 5.5V

0V ≤ V

OUT

≤ 0.2V

500 mA

(Note 12)

Turn-on Time 150 µs

Logic-low Input Voltage 3.0V ≤ VIN≤ 5.5V 0 0.5 V

Logic-high Input Voltage 3.0V ≤ VIN≤ 5.5V 0.95 V

Logic-high Input Current V(EN) = 1.8V

5µA

IN

(Note 13)

Logic-low Input Current Logic Input = 0V 0.1 µA

=150oC (typ.) and disengages at

J

IN

V

V

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