LINEAR TECHNOLOGY LT3461, LT3461A Technical data

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FEATURES

■

Integrated Schottky Rectifier

■

Fixed Frequency 1.3MHz/3MHz Operation

■

High Output Voltage: Up to 38V

■

Low V

■

12V at 70mA from 5V Input

■

5V at 115mA from 3.3V Input

■

Wide Input Range: 2.5V to 16V

■

Uses Small Surface Mount Components

■

Low Shutdown Current: <1µA

■

Soft-Start

■

Low Profile (1mm) SOT-23 (ThinSOTTM) Package

Switch: 260mV at 250mA

CESAT

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APPLICATIO S

■

Digital Cameras

■

CCD Bias Supply

■

XDSL Power Supply

■

TFT-LCD Bias Supply

■

Local 5V or 12V Supply

■

Medical Diagnostic Equipment

■

Battery Backup

LT3461/LT3461A

1.3MHz/3MHz Step-Up

DC/DC Converters with

Integrated Schottky in ThinSOT

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DESCRIPTIO

The LT®3461/LT3461A are general purpose fixed fre­quency current mode step-up DC/DC converters. Both
devices feature an integrated Schottky and a low V
switch allowing a small converter footprint and lower parts
cost. The LT3461 switches at 1.3MHz while the LT3461A
switches at 3MHz. These high switching frequencies en­able the use of tiny, low cost and low height capacitors and
inductors. The constant switching frequency results in
predictable output noise that is easy to filter, and the
inductor based topology ensures an input free from switch­ing noise typically present with charge pump solutions.
The high voltage switch in the LT3461/LT3461A is rated at
40V making the device ideal for boost converters up to
38V.

The LT3461/LT3461A are available in a low profile (1mm)
SOT-23 package.

, LTC and LT are registered trademarks of Linear Technology Corporation.

ThinSOT is a trademark of Linear Technology Corporation.

CESAT

TYPICAL APPLICATIO

5V to 12V, 70mA Step-Up DC/DC Converter

L1

C1
1µF

10µH

6

VINV

4

SHDN

1

SW

LT3461A

GND

2

OUT

5

3

FB

V

IN

5V

OFF ON

U

261k

30.1k

15pF

V

OUT

12V
70mA

C2
1µF

3461 TA01a

85

80

75

70

EFFICIENCY (%)

65

60

0

Efficiency

VIN = 3.3V

20

40

LOAD CURRENT (mA)

VIN = 5V

60

80

3461 TAO1b

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LT3461/LT3461A

6 V

IN

5 V

OUT

4 SHDN

SW 1

TOP VIEW

S6 PACKAGE

6-LEAD PLASTIC TSOT-23

GND 2

FB 3

WW

W

ABSOLUTE AXI U RATI GS

(Note 1)

Input Voltage (VIN) .................................................. 16V

, SW Voltage .................................................... 40V

V

OUT

FB Voltage ................................................................. 5V

SHDN Voltage .......................................................... 16V

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PACKAGE/ORDER I FOR ATIO

ORDER PART

NUMBER

LT3461AES6

LT3461ES6
Operating Ambient

Temperature Range (Note 2) .................. – 40°C to 85°C

T

= 125°C,

Maximum Junction Temperature .......................... 125°C

Storage Temperature Range ................. –65°C to 150°C

Lead Temperature (Soldering, 10 sec).................. 300°C

Consult LTC Marketing for parts specified with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

temperature range, otherwise specifications are at TA = 25°C, VIN = 3V, V

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage 2.5 V

Maximum Operating Voltage 16 V

Feedback Voltage 1.235 1.255 1.275 V

Feedback Line Regulation 0.005 %/V

FB Pin Bias Current ● 40 100 nA

Supply Current FB = 1.3V, Not Switching 2.8 3.6 mA

Switching Frequency (LT3461A) ● 2.1 3.0 3.9 MHz

Switching Frequency (LT3461) ● 1.0 1.3 1.7 MHz

Maximum Duty Cycle (LT3461A) ● 82 %

Maximum Duty Cycle (LT3461) ● 92 %

Switch Current Limit 300 420 600 mA

Switch V

CESAT

Switch Leakage Current VSW = 5V 0.01 1 µA

Schottky Forward Voltage I

Schottky Reverse Leakage V

SHDN Voltage High 1.5 V

SHDN Voltage Low 0.4 V

SHDN Pin Bias Current 35 50 µA

The ● denotes the specifications which apply over the full operating

SHDN

SHDN = 0V 0.1 0.5 µA

ISW = 250mA 260 350 mV

SCHOTTKY

= 250mA 800 1100 mV

– SW = 40V 0.03 4 µA

OUT

JMAX

= 150°C ON BOARD OVER

θ

JA

GROUND PLANE,

= 120°C/W

θ

JC

= 3V, unless otherwise noted.

● 1.225 1.280 V

S6 PART MARKING

LTAHG
LTAEB

Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.

2

Note 2: The LT3461E/LT3461AE is guaranteed to meet specifications from
0°C to 70°C. Specifications over the –40°C to 85°C operating temperature
range are assured by design, characterization and correlation with
statistical process controls.

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TYPICAL PERFOR A CE CHARACTERISTICS

LT3461/LT3461A

Oscillator Frequency (LT3461)

1.6

1.5

1.4

1.3

1.2

FREQUENCY (MHz)

1.1

1.0
–40 20 60

–20 0

TEMPERATURE (°C)

40 80 100

Oscillator Frequency (LT3461A)

3.9

3.6

3.3

3.0

2.7

FREQUENCY (MHz)

2.4

2.1

–60 –40

–20 0

20 60

TEMPERATURE (°C)

3461a G01

40 80 100

3461a G04

Current Limit FB Pin Voltage

480

TA = 25°C

360

240

CURRENT LIMIT (mA)

120

0

10

30

50

DUTY CYCLE (%)

Current Limit in Soft-Start Mode

480

TA = 25°C

420

360

300

240

180

CURRENT LIMIT (mA)

120

60

0

1.5 1.7 2.1

1.3
SHDN PIN VOLTAGE (V)

1.9

70

9080604020

3461a G02

2.3

3461a G05

1.28

1.27

1.26

1.25

FB VOLTAGE (V)

1.24

1.23

1.22
–40 20 60

–20 0

SHDN Pin Current

320

TA = 25°C

280

240

200

160

120

80

SHDN PIN CURRENT (µA)

40

0

0

TEMPERATURE (°C)

40 80 100

3461a G03

4812
SHDN PIN VOLTAGE (V)

3461a G06

16

V

SW

5V/DIV

V

OUT

50mV/DIV

Switching Waveform
Circuit of Figure 4

I

LOAD

= 60mA

0.2µs/DIV

3461a G08

I

LOAD

100mV/DIV

Load Transient Response
Circuit of Figure 4

70mA
35mA

V

OUT

50µs/DIV

3461a G09

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