National Semiconductor LM3355 Technical data

December 2001

LM3355
Regulated 50mA Buck-Boost Switched Capacitor DC/DC
Converter

LM3355 Regulated 50 mA Buck-Boost Switched Capacitor DC/DC Converter

General Description

The LM3355 is a CMOS switched capacitor DC/DC con­verter that produces a regulated output voltage by automati­cally stepping up (boost) or stepping down (buck) the input
voltage. It accepts an input voltage between 2.5V and 5.5V.
The LM3355 is available with a standard output voltage of

4.1V (ideal for white LED applications). If other output volt­age options between 1.8V and 4.1V are desired for other
applications, please contact your National Semiconductor
representative.

The LM3355’s proprietary buck-boost architecture enables
up to 50 mA of load current at an average efficiency greater
than 75%. Typical operating current is only 375 µA and the
typical shutdown current is only 2.3 µA.

The LM3355 is available in a 10-pin MSOP package. This
package has a maximum height of only 1.1 mm.

The high efficiency of the LM3355, low operating and shut­down currents, small package size, and the small size of the
overall solution make this device ideal for battery powered,
portable, and hand-held applications.

See the LM3352 for up to 200mA of output current.

Features

n Regulated V
n Standard output voltage of 4.1V
n Custom output voltages available from 1.8V to 4.1V in

100 mV increments

n 2.5V to 5.5V input voltage
n Up to 50 mA output current

>

n

75% average efficiency

n Uses few, low-cost external components
n Very small solution size
n 375 µA typical operating current
n 2.3 µA typical shutdown current
n 1 MHz switching frequency (typical)
n Architecture and control methods provide high load

current and good efficiency

n MSOP-10 package
n Over-temperature protection

with±3% accuracy

OUT

Applications

n White LED display backlights
n 1-cell Lilon battery-operated equipment including PDAs,

hand-held PCs, cellular phones

n Flat panel displays
n Hand-held instruments
n NiCd, NiMH, or alkaline battery powered systems

Typical Operating Circuit

20021901

© 2004 National Semiconductor Corporation DS200219 www.national.com

Connection Diagram

LM3355

Top View

MSOP-10 Pin Package

See NS Package Number MUB10A

20021902

Ordering Information

Order Number Package Type NSC Package Drawing Supplied As

LM3355MMX-4.1 MSOP-10 MUB10A 3.5k Units, Tape and Reel

LM3355MM-4.1 MSOP-10 MUB10A 1k Units, Tape and Reel

Pin Description

Pin Number Name Function

1V

2 C1− Negative Terminal for C1

3 C1+ Positive Terminal for C1

4 GND Ground

5 GND Ground

6C

7SD

8V

9 C2− Negative Terminal for C2

10 C2+ Positive Terminal for C2

IN

FIL

OUT

Input Supply Voltage

Filter Capacitor, a 1µF capacitor is recommended.

Shutdown, active low

Regulated Output Voltage

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LM3355

Absolute Maximum Ratings (Note 1)

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

All Pins −0.5V to 5.6V

Power Dissipation (T

= 25˚C)

A

Operating Ratings

Input Voltage (VIN) 2.5V to 5.5V

Output Voltage (V

Ambient Temperature (T

Junction Temperature (T

) 1.8V to 4.1V

OUT

) (Note 2) −40˚C to +85˚C

A

) (Note 2) −40˚C to +125˚C

J

(Note 2) Internally Limited

(Note 2) 150˚C

T

JMAX

θ

(Note 2) 250˚C/W

JA

Storage Temperature −65˚C to +150˚C

Lead Temperature (Soldering, 5
sec.) 260˚C

ESD Rating (Note 3)

Human Body Model
Machine Model

1.5 kV
100V

Electrical Characteristics

Limits in standard typeface are for TA= 25˚C, and limits in boldface type apply over the full operating temperature range of

−40˚C ≤ T

≤ 85˚C. Unless otherwise specified: C1=C2= 0.33 µF; CIN= 10 µF; C

A

Parameter Conditions Min (Note 5) Typ (Note 4) Max (Note 5) Units

LM3355-4.1

Output Voltage (V

OUT

)

V

= 3.5V; I

IN

50 mA

2.6V<V

<

1mA

IN

I

LOAD

<

LOAD

5.5V;

<

50

=

4.038 4.1 4.162

3.977/3.936 4.1 4.223/4.264

mA

<

<

V

2.5V
1mA

<

IN

I

LOAD

5.5V;

<

40

3.977/3.936 4.1 4.223/4.264

mA

Efficiency I

Output Voltage
Ripple
(Peak-to-Peak)

=10mA 80

LOAD

I

=50mA 75

LOAD

=50mA

I

LOAD

=10µF

C

OUT

ceramic

75 mV

LM3355-ALL OUTPUT VOLTAGE VERSIONS

Operating Quiescent
Current

Shutdown Quiescent
Current

Switching

Measured at Pin
VIN;

= 0A (Note 6)

I

LOAD

SD Pin at 0V (Note

7)

375 475 µA

2.3 5 µA

0.60 1 1.40 MHz

Frequency

<

SD Input Threshold

2.5V

<

V

5.5V 0.2 V

IN

Low

SD Input Threshold

2.5V<V

<

5.5V 0.8 V

IN

IN

High

SD Input Current Measured at SD

Pin;
SD Pin = V

Note 1: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. Operating Ratings are conditions for which the device is
intended to be functional, but device parameter specifications may not be guaranteed. For guaranteed specifications and test conditions, see “Electrical
Characteristics”.

Note 2: As long as T

Note 3: The Human Body Model is a 100 pF capacitor discharged through a 1.5 kΩ resistor into each pin. The Machine Model is a 200 pF capacitor discharged

directly into each pin.

Note 4: Typical numbers are at 25˚C and represent the most likely norm.

≤ +85˚C, all electrical characteristics hold true and the junction temperature should remain below +125˚C.

A

IN

= 5.5V

0.3 µA

OUT

= 10 µF; C

= 1 µF; VIN= 3.5V.

FIL

IN

V

%

P-P

V

V

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