LINEAR TECHNOLOGY LTC3423, LTC3424 Technical data

FEATURES

LTC3423/LTC3424

Low Output Voltage,

3MHz Micropower Synchronous

Boost Converters

U

DESCRIPTIO

■

1.5V to 5.5V Adjustable Output Voltage

■

Synchronous Rectification: Up to 95% Efficiency

■

1A Switch Current (LTC3423) or
2A Switch Current (LTC3424)

■

Fixed Frequency Operation Up to 3MHz

■

Wide Input Range: 0.5V to 5.5V (Operating)

■

Very Low Quiescent Current: 38µA (Burst Mode

®

Operation)

■

No External Schottky Diode Required

■

Synchronizable Switching Frequency

■

Burst Mode Enable Control

■

OPTI-LOOP® Compensation

■

Very Low Shutdown Current: <1µA

■

Small 10-Pin MSOP Package

U

APPLICATIO S

■

Pagers

■

Handheld Instruments

■

Cordless Phones

■

Wireless Handsets

■

GPS Receivers

■

Battery Backup

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

Burst Mode and OPTI-LOOP are registered trademarks of Linear Technology Corporation.

The LTC®3423 and LTC3424 are high efficiency, fixed
frequency, step-up DC/DC converters that can regulate
output voltages as low as 1.5V from a single cell. An
applied voltage of at least 2.7V to the VDD pin is required
to power the internal control circuitry.

The devices include a 0.16Ω N-channel MOSFET switch
and a 0.21Ω P-channel synchronous rectifier. The LTC3423
is intended for applications requiring less than 0.75W of
output power and the LTC3424 for 1.5W or less. Switching
frequencies up to 3MHz are programmed with an external
timing resistor and the oscillator can be synchronized to
an external clock.

Quiescent current is only 38µA in Burst Mode operation,
maximizing battery life in portable applications. Burst
Mode operation is user controlled and can be enabled by
driving the MODE/SYNC pin high. If the MODE/SYNC pin
has either a clock or is driven low then the operation is at
constant fixed frequency.

Other features include a 1µA shutdown, thermal shutdown
and current limit. The LTC3423 and LTC3424 are available
in the 10-lead MSOP package. For applications requiring
an output voltage greater than 2.6V, the LTC3401 and
LTC3402 are recommended without the need of a separate
voltage for the VDD pin.

TYPICAL APPLICATIO

1-Cell to 1.8V at 600mA Step-Up Converter

V

2.2µF

DD

C1

VDD = 2.7V TO 5.5V

= 0.9V TO 1.5V

V

IN

+

1
CELL

–

C2

10µF

0 = FIXED FREQ

1 = Burst Mode OPERATION

L1

2.2µH

LTC3424

6

V

10

SHDN

3

V

2

MODE/SYNC

1

R

R

t

30.1k

SW

DD

V

OUT

IN

t

FB

V

C

GND

C1: TAIYO YUDEN JMK212BJ225MG
C2: TAIYO YUDEN JMK212BJ106MM
C3: TAIYO YUDEN JMK325BJ226MM
L1: SUMIDA CD43-2R2M

4

7

8

9

5

U

C4
470pF

RC
82k

C5

4.7pF

R1
110k

R2
249k

V

OUT

1.8V
600mA

C3
44µF
(2× 22µF)

3423/24 TA01

100

90

OPERATION

80
70
60
50
40

EFFICIENCY (%)

30
20
10

0

0.1 10 100 10001

Efficiency

VIN = 1.5V

Burst Mode

VDD = 3.3V

= 1.8V

V

OUT

WITH MBRM120T3 SCHOTTKY

OUTPUT CURRENT (mA)

VIN = 1.2V

VIN = 0.9V

3223/24 TA02

34234f

1

LTC3423/LTC3424

PACKAGE/ORDER I FOR ATIO

UU

W

WWWU

ABSOLUTE AXI U RATI GS

(Note 1)

VIN, V

SW Voltage ................................................. –0.5V to 6V

VC, Rt Voltages ......................... –0.5V to (V

SHDN, FB, MODE Voltages ......................... –0.5V to 6V

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

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

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

, VDD Voltages.............................. –0.5V to 6V

OUT

OUT

+ 0.3V)

ORDER PART

TOP VIEW

10

1

R

t

MODE

2

V

3

IN

SW

4

GND

5

MS PACKAGE

10-LEAD PLASTIC MSOP

T

= 125°C

JMAX

= 130°C/W 1 LAYER BOARD

θ

JA

= 100°C/W 4 LAYER BOARD

θ

JA

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

SHDN

9

V

C

FB

8

V

7

OUT

V

6

DD

NUMBER

LTC3423EMS
LTC3424EMS

MS PART MARKING

LTQM

LTQN

ELECTRICAL CHARACTERISTICS

The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 1.2V, VDD = 3.3V, V

PARAMETER CONDITIONS MIN TYP MAX UNITS

VDD Input Voltage Range ● 2.7 5.5 V
VIN Operating Voltage Range (Note 4) ● 0.5 5.5 V
Output Voltage Adjust Range ● 1.5 5.5 V
Feedback Voltage ● 1.22 1.25 1.28 V
Feedback Input Current VFB = 1.25V 1 50 nA
Quiescent Current—Burst Mode Operation VC = 0V, MODE/SYNC = 3.3V (Note 3) 38 65 µA
Quiescent Current—SHDN SHDN = 0V, Not Including Switch Leakage 0.1 1 µA
Quiescent Current—Active VC = 0V, MODE/SYNC = 0V, Rt = 300k (Note 3) 440 800 µA
NMOS Switch Leakage 0.1 5 µA
PMOS Switch Leakage 0.1 10 µA
NMOS Switch On Resistance 0.16 Ω
PMOS Switch On Resistance 0.21 Ω
NMOS Current Limit LTC3423 ● 1 1.6 A

Maximum Duty Cycle Rt = 15k ● 80 85 %
Minimum Duty Cycle ● 0%
Frequency Accuracy Rt = 15k ● 1.6 2 2.4 MHz
MODE/SYNC Input High 1.4 V
MODE/SYNC Input Low 0.4 V
MODE/SYNC Input Current V
Error Amp Transconductance ∆I = –5µA to 5µA, VC = V

= 1.8V, unless otherwise noted.

OUT

LTC3424

MODE/SYNC

● 2 2.8 A

= 5.5V 0.01 1 µA

FB

85 µmhos

2

34234f

LTC3423/LTC3424

ELECTRICAL CHARACTERISTICS

The ● denotes specifications that apply over the full operating temperature range, otherwise specifications are at TA = 25°C.
VIN = 1.2V, V

PARAMETER CONDITIONS MIN TYP MAX UNITS

SHDN Input High V
SHDN Input Low 0.4 V
SHDN Input Current V

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

Note 2: The LTC3423/LTC3424 are guaranteed to meet performance
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.

= 3.3V unless otherwise noted.

OUT

= VIN = V

SHDN

= 5.5V 0.01 1 µA

SHDN

OUT

Note 3: Current is measured into V
bootstrapped to the V

pin. The outputs are not switching.

DD

1V

since the supply current is

DD

Note 4: Once the output is started, the IC is not dependant upon the V
supply.

IN

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Transient Response

Switching Waveform on SW Pin

150mA to 450mA

SW

0.5V/DIV

V

OUT

100mV/DIV

AC COUPLED

SW

1V/DIV

0V

I

= 500mA 100ns/DIV 3423/24 G01

LOAD

V

1.8V

OUT

Burst Mode Operation
at 500µA Load

= 1.2V 1ms/DIV 3423/24 G03

V

IN

V

= 1.8V

OUT

= 44µF

C

OUT

MODE/SYNC PIN = HIGH

V

OUT

100mV/DIV

AC COUPLED

450mA

I

OUT

150mA

V

OUT

100mV/DIV

AC COUPLED

SW

1V/DIV

C

= 44µF 200µs/DIV 3423/24 G02

OUT

L = 2.2µH

= 1MHz

f

OSC

Burst Mode Operation
at 10mA Load

V

= 1.2V 500µs/DIV 3423/24 G04

IN

V

= 1.8V

OUT

= 44µF

C

OUT

MODE/SYNC PIN = HIGH

34234f

3

LTC3423/LTC3424

UW

TYPICAL PERFOR A CE CHARACTERISTICS

Converter Efficiency 1.2V to 1.8V

100

90

Burst Mode

80

OPERATION

70
60
50
40

EFFICIENCY (%)

30
20
10

0

0.1 10 100 1000

300MHz

1MHz

WITH MBRM120T3 SCHOTTKY

1
OUTPUT CURRENT (mA)

EA FB Voltage

1.28

1.27

1.26

1.25

VOLTAGE (V)

1.24

1.23

3MHz

3223/24 G05

LTC3424 Current Limit

3.4

3.2

3.0

2.8

2.6

CURRENT (A)

2.4

2.2

2.0
–15 25 105

–55

TEMPERATURE (°C)

Oscillator Frequency Accuracy

2.10
= 15k

R

T

2.05

2.00

FREQUENCY (MHz)

1.95

LTC3423 Current Limit

1.80

1.75

1.70

1.65

1.60

1.55

CURRENT (A)

1.50

1.45

RESISTANCE (Ω)

1.40

0.30

0.25

0.20

0.15

0.10

–15 25 105

–55

TEMPERATURE (°C)

NMOS R

DS(ON)

V

= 1.8V

OUT

= 3.3V

V

DD

65

125

3423/24 G07

65

125

3423/24 G06

1.22
–55

–15 25 105

TEMPERATURE (°C)

0.40

0.35

0.30

0.25

RESISTANCE (Ω)

0.20

0.15

65

3423/24 G08

PMOS R

–55

DS(ON)

V

= 1.8V

OUT

= 3.3V

V

DD

–15 25 105

TEMPERATURE (°C)

125

1.90
–15 25 105

–55

TEMPERATURE (°C)

65

125

3423/24 G09

0.05
–15 25 105

–55

TEMPERATURE (°C)

65

125

3423/24 G10

Efficiency Loss Without Schottky
vs Frequency

14

T

= 25°C

A

12

10

8

6

4

EFFICIENCY LOSS (%)

2

65

125

3423/24 G11

0

0.2

0.6 1.0
FREQUENCY (MHz)

1.8 2.6 3.0

1.4 2.2

3423/24 G12

34234f

4