LINEAR TECHNOLOGY LT3494, LT3494A Technical data

LT3494/LT3494A

Micropower Low Noise

Boost Converters with

Output Disconnect

FEATURES

■

Low Quiescent Current
65μA in Active Mode
1μA in Shutdown Mode

■

Switching Frequency is Non-Audible Over Entire

Load Range

■

Integrated Power NPN:
350mA Current Limit (LT3494A)
180mA Current Limit (LT3494)

■

Integrated Schottky Diode

■

Integrated Output Disconnect

■

Integrated Output Dimming

■

Wide Input Range: 2.3V to 16V

■

Wide Output Range: Up to 40V

■

Tiny 8-Lead 3mm × 2mm DFN Package

APPLICATIONS

■

OLED Power

■

Low Noise Power

■

MP3 Players

DESCRIPTION

The LT®3494/LT3494A are low noise boost converters
with integrated power switch, Schottky diode and output
disconnect circuitry. The parts use a novel* control tech­nique resulting in low output voltage ripple as well as high
effi ciency over a wide load current range. This technique
guarantees that the switching frequency stays above the
audio band for the entire load range. The parts feature a high
performance NPN power switch with a 350mA and 180mA
current limit for the LT3494A and LT3494 respectively. The
quiescent current is a low 65μA, which is further reduced
to less than 1μA in shutdown. The internal disconnect
circuitry allows the output voltage to be isolated from the
input during shutdown. An auxiliary reference input (CTRL
pin) overrides the internal 1.225V feedback reference with
any lower value allowing full control of the output voltage
during operation. The LT3494/LT3494A are available in a
tiny 8-lead 3mm × 2mm DFN package.

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*Patent pending.

TYPICAL APPLICATION

OLED Power Supply from One Li-Ion Cell

4.7μF

15μH

SW CAP

V

V

CC

LT3494

SHDN

CTRL

GND

0.22μF

OUT

2.21M

FB

3494 TA01a

V

TO 4.2V

IN

3V

V

OUT

16V
16mA

2.2μF

Output Voltage Ripple

vs Load Current

15

LT3494
FIGURE 5 CIRCUIT
100MHz MEASUREMENT BW

10

5

PEAK-TO-PEAK RIPPLE (mV)

OUT

V

0

0.1

1 10 100

LOAD CURRENT (mA)

3494 TA01b

Effi ciency and Power Loss

vs Load Current

90

VIN = 3.6V

80

70

60

50

EFFICIENCY (%)

40

30

20

0.1

LOAD FROM
CAPACITOR

LOAD FROM

1 10 100

LOAD CURRENT (mA)

280

240

POWER LOSS (mW)

V

OUT

200

160

120

80

40

0

3494 TA01c

3494fb

1

LT3494/LT3494A

(Note 1)

VCC Voltage ...............................................................16V

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

CAP Voltage ..............................................................40V

Voltage .............................................................40V

V

OUT

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

CTRL Voltage ............................................................16V

FB Voltage ................................................................2.5V

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

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

Storage Temperature Range ................... –65°C to 125°C

PACKAGE/ORDER INFORMATIONABSOLUTE MAXIMUM RATINGS

TOP VIEW

CAP

1SW

GND

2

V

3

CC

CTRL

4

8-LEAD (3mm × 2mm) PLASTIC DFN

EXPOSED PAD (PIN 9) IS GND, MUST BE SOLDERED TO PCB

DDB PACKAGE

T

= 125°C, θJA = 76°C/W

JMAX

ORDER PART NUMBER DDB PART MARKING

8

V

7

9

OUT

FB

6

SHDN

5

LT3494EDDB
LT3494AEDDB

Order Options Tape and Reel: Add #TR
Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF
Lead Free Part Marking: http://www.linear.com/leadfree/

Consult LTC Marketing for parts specifi ed with wider operating temperature ranges.

ELECTRICAL CHARACTERISTICS

The
temperature range, otherwise specifi cations are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

Minimum Operating Voltage 2.3 2.5 V

Maximum Operating Voltage 16 V

Feedback Voltage V

FB Resistor

Quiescent Current Not Switching 65 75 μA

Quiescent Current in Shutdown V

Minimum Switch Off Time After Start-Up Mode, V

Maximum Switch Off Time V

Switch Current Limit LT3494A (Note 5)

Switch V

CESAT

Switch Leakage Current V

Schottky Forward Voltage I

Schottky Reverse Leakage 0.05 1 μA

PMOS Disconnect V

SHDN Input Voltage High 1.5 V

SHDN Input Voltage Low 0.3 V

SHDN Pin Bias Current V

CAP

– V

OUT

CTRL

⎯S⎯H⎯D⎯

During Start-Up Mode, V

FB

LT3494 (Note 5)

LT3494A, ISW = 200mA
LT3494, I

SW

DIODE

I

OUT

SHDN

V

SHDN

= 25°C. VCC = 3V, V

A

= 3V (Note 3)

= 0V, VCC = 3V 0 1 μA

N

= 1.5V

= 100mA

SW

= 5V, V

⎯S⎯H⎯D⎯

= 100mA 900 1100 mV

= 10mA, V

= 3V
= 0V

●

denotes the specifi cations which apply over the full operating

= VCC, unless otherwise noted. (Note 2)

SHDN

●

1.205 1.225 1.245 V

●

179 182 184 kΩ

= 1V, V

FB

= 0.2V, V

FB

= 0 0.01 1 μA

N

= 5V 250 mV

CAP

= 3V (Note 4)

CTRL

CTRL

= 3V (Note 4)

●

15 20 30 μs

225
115

100
450

350
180

180
110

5
0

LCCD
LCRW

450
250

10

0.1

mA
mA

mV
mV

μA
μA

ns
ns

2

3494fb

LT3494/LT3494A

ELECTRICAL CHARACTERISTICS

The
temperature range, otherwise specifi cations are at T

PARAMETER CONDITIONS MIN TYP MAX UNITS

CTRL Pin Bias Current V

CTRL to FB Offset V

Maximum Shunt Current V

CTRL

CTRL

FB

= 25°C. VCC = 3V, V

A

= 0.5V, Current Flows Out of Pin

= 0.5V 8 15 mV

= 1.3V, V

CAP

●

denotes the specifi cations which apply over the full operating

= VCC, unless otherwise noted. (Note 2)

SHDN

●

20 100 nA

= 5V 230 μA

Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.

Note 2: The LT3494/LT3494A are guaranteed to meet performance
specifi cations from 0°C to 85°C. Specifi cations over the –40°C to 85°C
operating temperature range are assured by design, characterization and
correlation with statistical process controls.

Note 3: Internal reference voltage is determined by fi nding V
level which causes quiescent current to increase 20μA above “Not
Switching” level.

Note 4: If CTRL is overriding the internal reference, Start-Up mode occurs
when V

is less then half the voltage on CTRL. If CTRL is not overriding

FB

the internal reference, Start-Up mode occurs when V
voltage of the internal reference.

Note 5: Current limit guaranteed by design and/or correlation to static test.

TYPICAL PERFORMANCE CHARACTERISTICS

Switching Frequency
vs Load Currrent

1400

LT3494
FIGURE 5 CIRCUIT

1200

1000

SWITCHING FREQUENCY (kHz)

800

600

400

200

= 3.6V

V

CC

= 16V

V

OUT

0

0.1

1 10 100

LOAD CURRENT (mA)

3494 G01

Load Regulation V

2.0
LT3494

FIGURE 5 CIRCUIT

1.5

= 3.6V

V

CC

= 16V

V

OUT

1.0

0.5

0

–0.5

VOLTAGE CHANGE (%)

OUT

–1.0

V

–1.5

–2.0

5

0

10

20

15

LOAD CURRENT (mA)

25

30

TA = 25°C unless otherwise noted.

vs CTRL Voltage

OUT

20

LT3494
FIGURE 5 CIRCUIT

= 3.6V

V

CC

= 16V

V

OUT

15

LOAD CURRENT = 1mA

10

VOLTAGE (V)

OUT

V

5

35

3494 G02

40

0

0.1

0.3 0.5 0.7 0.9
CTRL VOLTAGE (V)

voltage

FB

is less then half the

FB

1.1 1.3 1.5

3494 G03

3494fb

3

LT3494/LT3494A

TYPICAL PERFORMANCE CHARACTERISTICS

Output Voltage vs Temperature Minimum Switching Frequency

2.0
LT3494

FIGURE 5 CIRCUIT

1.5

1.0

0.5

0

–0.5

–1.0

OUTPUT VOLTAGE CHANGE (%)

–1.5

–2.0

–40

–20

0

40

20

TEMPERATURE (°C)

60

100

3494 G04

120

80

SHDN Current vs SHDN Voltage Peak Inductor Current (LT3494)

20

15

51.0
VCC = 3.6V

NO LOAD

50.5

50.0

49.5

49.0

48.5

48.0

SWITCHING FREQUENCY (kHz)

47.5

47.0

–20

–40

400

350

300

0

TEMPERATURE (°C)

FIGURE 5 CIRCUIT

= 3.6V

V

CC

= 16V

V

OUT

20

40

60

TA = 25°C unless otherwise noted.

Quiescent Current–Not Switching

100

95

90

85

80

(μA)

75

VCC

I

70

65

60

55

50

3

100

3494 G05

120

80

4

Peak Inductor Current (LT3494A)

700

FIGURE 6 CIRCUIT

= 3.6V

V

CC

650

600

= 16V

V

OUT

5

V

CC

8

(V)

7

6

9

10

3494 G06

10

5

SHDN PIN CURRENT (μA)

0

V

OUT

10mV/DIV

COUPLED

SW

VOLTAGE

10V/DIV

INDUCTOR

CURRENT
50mA/DIV

0

2468

SHDN PIN VOLTAGE (V)

10 12 14 16

LT3494 Switching Waveforms at
No Load

FIGURE 5 CIRCUIT

AC

= 3.6V

V

CC

= 16V

V

OUT

5μs/DIV

3494 G07

3494 G10

250

200

150

PEAK INDUCTOR CURRENT (mA)

100

–40

040

–20 20

TEMPERATURE (°C)

LT3494 Switching Waveforms at
1mA Load

FIGURE 5 CIRCUIT

V

OUT

10mV/DIV

AC

COUPLED

SW

VOLTAGE

10V/DIV

INDUCTOR

CURRENT

100mA/DIV

= 3.6V

V

CC

= 16V

V

OUT

2μs/DIV

550

500

450

PEAK INDUCTOR CURRENT (mA)

400

80

60

100

120

3494 G08

–40

040

–20 20

TEMPERATURE (°C)

80

60

100

120

3494 G09

LT3494 Switching Waveforms at
25mA Load

FIGURE 5 CIRCUIT

V

OUT

10mV/DIV

AC

COUPLED

SW

VOLTAGE

10V/DIV

INDUCTOR

CURRENT

100mA/DIV

3494 G11

V
V

CC
OUT

= 3.6V

= 16V

500ns/DIV

3494 G12

4

3494fb