LTC3542IDC datasheet, PDF - EEWORLD Datasheet

LTC3542

500mA, 2.25MHz

Synchronous Step-Down

DC/DC Converter

FEATURES

■

DESCRIPTION

The LTC

®

3542 is a high efﬁciency monolithic synchronous

buck converter using a constant frequency, current mode

architecture. Supply current during operation is only

26μA, dropping to <1μA in shutdown. The 2.5V to 5.5V

input voltage range makes the LTC3542 ideally suited for

single Li-Ion battery-powered applications. 100% duty

cycle provides low dropout operation, extending battery

life in portable systems. The output voltage is adjustable

from 0.6V to V

IN

. Internal power switches are optimized

to provide high efﬁciency and eliminate the need for an

external Schottky diode.

Switching frequency is internally set at 2.25MHz, allowing

the use of small surface mount inductors and capacitors,

and it can synchronize to an external clock signal with a

frequency range of 1MHz to 3MHz through the MODE/

SYNC pin. The LTC3542 is speciﬁcally designed to work

well with ceramic output capacitors, achieving very low

output voltage ripple and a small PCB footprint.

The LTC3542 can be conﬁgured for the power saving Burst

Mode

®

Operation. For reduced noise and RF interference,

the MODE/SYNC pin can be conﬁgured for pulse skipping

operation.

, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology

Corporation. All other trademarks are the property of their respective owners.

Protected by U.S. Patents, including 5481178, 6580258, 6304066, 6127815, 6498466,

6611131, 5994885.

High Efﬁciency: Up to 96%

High Peak Switch Current: 1000mA

Low Output Ripple (<20mV

P-P

Typical)

Burst Mode Operation: Only 26μA

Very Low Quiescent Current: Only 26μA

2.5V to 5.5V Input Voltage Range

2.25MHz Constant Frequency Operation

1MHz to 3MHz External Frequency Synchronization

Low Dropout Operation: 100% Duty Cycle

No Schottky Diode Required

Internal Soft-Start Limits Inrush Current

0.6V Reference Allows Low Output Voltages

Shutdown Mode Draws <1μA Supply Current

±2% Output Voltage Accuracy

Current Mode Operation for Excellent Line and Load

Transient Response

Overtemperature Protected

Available in 6-Lead 2mm

×

2mm DFN and Small TSOT

APPLICATIONS

■

Cellular Telephones

Wireless and DSL Modems

Digital Cameras

MP3 Players

PDAs and Other Handheld Devices

TYPICAL APPLICATION

V

IN

2.7V TO 5.5V

2.2μH

C

IN

10μF

CER

V

IN

SW

22pF

V

OUT

1.8V

500mA

Efﬁciency and Power Loss vs Output Current

100

90

80

70

EFFICIENCY (%)

60

50

40

30

20

10

0

0.1

1

10

100

OUTPUT CURRENT (mA)

0.1

1000

3542 TA01b

V

IN

= 3.6V

V

OUT

= 1.8V

1000

100

POWER LOSS (mW)

LTC3542

150k

RUN

GND

V

FB

75k

MODE/SYNC

C

OUT

10μF

CER

3542 TA01a

10

1

3542fa

1

LTC3542

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Input Supply Voltage (V

IN

) ........................... –0.3V to 6V

V

FB

, RUN Voltages .......................................–0.3V to V

IN

MODE Voltage ................................–0.3V to (V

IN

+ 0.3V)

SW Voltage ....................................–0.3V to (V

IN

+ 0.3V)

Operating Temperature Range (Note 2)

LTC3542E ............................................ –40°C to 85°C

LTC3542I ........................................... –40°C to 125°C

Junction Temperature (Note 7) ............................. 125°C

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

Lead Temperature (Soldering, 10 sec)

TSOT-23............................................................ 300°C

Reﬂow Peak Body Temperature (DFN) .................. 260°C

PIN CONFIGURATION

TOP VIEW

V

FB

1

V

IN

2

GND 3

7

6 RUN

5 MODE/

SYNC

4 SW

V

IN

1

GND 2

V

FB

3

6 SW

5 MODE/SYNC

4 RUN

DC PACKAGE

6-LEAD (2mm

×

2mm) PLASTIC DFN

T

JMAX

= 125°C,

θ

JA

= 102°C/W,

θ

JC

= 20°C/W (SOLDERED TO A 4-LAYER BOARD, NOTE 3)

EXPOSED PAD (PIN 7) IS GND, MUST BE SOLDERED TO PCB

S6 PACKAGE

6-LEAD PLASTIC TSOT-23

T

JMAX

= 125°C,

θ

JA

= 215°C/W

ORDER INFORMATION

LEAD FREE FINISH

LTC3542EDC#PBF

LTC3542IDC#PBF

LTC3542ES6#PBF

LTC3542IS6#PBF

TAPE AND REEL

LTC3542EDC#TRPBF

LTC3542IDC#TRPBF

LTC3542ES6#TRPBF

LTC3542IS6#TRPBF

PART MARKING*

LCFR

LCFS

PACKAGE DESCRIPTION

6-Lead (2mm

×

2mm) Plastic DFN

6-Lead (2mm

×

2mm) Plastic DFN

6-Lead Plastic TSOT-23

TEMPERATURE RANGE

–40°C to 85°C

–40°C to 125°C

–40°C to 85°C

–40°C to 125°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

For more information on lead free part marking, go to:

http://www.linear.com/leadfree/

For more information on tape and reel speciﬁcations, go to:

http://www.linear.com/tapeandreel/

The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 3.6V unless otherwise noted.

SYMBOL

V

IN

I

FB

V

FB

ΔV

LINE_REG

ΔV

LOAD_REG

PARAMETER

Operating Voltage Range

Feedback Input Current

Feedback Voltage (Note 4)

Reference Voltage Line Regulation (Note 4) V

IN

= 2.5V to 5.5V

Output Voltage Load Regulation (Note 4)

I

LOAD

= 100mA to 500mA

●

ELECTRICAL CHARACTERISTICS

CONDITIONS

●

MIN

2.5

0.588

TYP

MAX

5.5

±30

UNITS

V

nA

V

%/V

%

0.6

0.04

0.02

0.612

0.2

3542fa

2

LTC3542

ELECTRICAL CHARACTERISTICS

SYMBOL

I

S

PARAMETER

Input DC Supply Current (Note 5)

Active Mode

Sleep Mode

Shutdown

Oscillator Frequency

Synchronous Frequency

Peak Switch Current

P-Channel On Resistance (Note 6)

N-Channel On Resistance (Note 6)

Switch Leakage Current

Undervoltage Lockout Threshold

RUN Threshold

RUN Leakage Current

MODE/SYNC Threshold

MODE/SYNC Leakage Current

The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 3.6V unless otherwise noted.

CONDITIONS

V

FB

= 0.5V

V

FB

= 0.7V, MODE = 0V

RUN = 0V

V

FB

= 0.6V

V

FB

= 0.6V

V

IN

= 3V, V

FB

= 0.5V, Duty Cycle < 35%

I

SW

= 100mA

I

SW

= –100mA

V

IN

= 5V, V

RUN

= 0V, V

SW

= 0V or 5V

V

IN

Rising

V

IN

Falling

●

MIN

TYP

MAX

500

35

1

2.7

3

UNITS

μA

MHz

mA

Ω

μA

V

μA

V

μA

26

0.1

1.8

1

650

1000

0.5

0.35

±0.01

1.8

0.3

±0.01

0.3

±0.01

2.0

1.9

2.25

f

OSC

f

SYNC

I

LIM

R

DS(ON)

I

SW(LKG)

V

UVLO

V

RUN

I

RUN

V

MODE/SYNC

I

MODE/SYNC

0.65

0.55

±1

2.3

1.5

±1

1.2

±1

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. No pin should exceed 6V.

Note 2:

The LTC3542 is guaranteed to meet performance speciﬁcations

from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

with statistical process controls. The LTC3542I is guaranteed over the full

–40°C to 125°C operating temperature range.

Note 3:

Failure to solder the Exposed Pad of the package to the PC board

will result in a thermal resistance much higher than 102°C/W.

Note 4:

The converter is tested in a proprietary test mode that connects

the output of the error ampliﬁer to the SW pin, which is connected to an

external servo loop.

Note 5:

Dynamic supply current is higher due to the internal gate charge

being delivered at the switching frequency.

Note 6:

The DFN switch on resistance is guaranteed by correlation to wafer

level measurements.

Note 7:

T

J

is calculated from the ambient temperature T

A

and power

dissipation P

D

according to the following formula:

T

J

= T

A

+ (P

D

) • (θ

JA

).

TYPICAL PERFORMANCE CHARACTERISTICS

Burst Mode Operation

SW

2V/DIV

T

A

= 25°C unless otherwise speciﬁed.

Start-Up from Shutdown

RUN

2V/DIV

V

OUT

1V/DIV

Pulse Skip Mode Operation

SW

2V/DIV

V

OUT

50mV/DIV

AC COUPLED

I

L

100mA/DIV

V

IN

= 3.6V

2μs/DIV

V

OUT

= 1.8V

I

LOAD

= 25mA

FIGURE 3a CIRCUIT

3542 G01

V

OUT

50mV/DIV

AC COUPLED

I

L

100mA/DIV

I

L

100mA/DIV

V

IN

= 3.6V

400ns/DIV

V

OUT

= 1.8V

I

LOAD

= 25mA

FIGURE 3a CIRCUIT

3542 G02

V

IN

= 3.6V

400μs/DIV

V

OUT

= 1.8V

I

LOAD

= 0A

FIGURE 3a CIRCUIT

3542 G03

3542fa

3

LTC3542

TYPICAL PERFORMANCE CHARACTERISTICS

Start-Up from Shutdown

RUN

2V/DIV

V

OUT

1V/DIV

I

L

500mA/DIV

3542 G04

T

A

= 25°C unless otherwise speciﬁed.

Load Step

V

OUT

100mV/DIV

AC COUPLED

Load Step

V

OUT

100mV/DIV

AC COUPLED

I

L

500mA/DIV

I

L

500mA/DIV

I

LOAD

500mA/DIV

V

IN

= 3.6V

20μs/DIV

V

OUT

= 1.8V

I

LOAD

= 30mA TO 500mA

FIGURE 3a CIRCUIT

3542 G05

I

LOAD

500mA/DIV

400μs/DIV

V

IN

= 3.6V

V

OUT

= 1.8V

I

LOAD

= 500mA

FIGURE 3a CIRCUIT

20μs/DIV

V

IN

= 3.6V

V

OUT

= 1.8V

I

LOAD

= 0mA TO 500mA

FIGURE 3a CIRCUIT

3542 G06

Reference Voltage

vs Temperature

0.6150

0.6125

0.6100

0.6075

0.6050

0.6025

0.6000

0.5975

0.5950

0.5925

0.5900

0.5875

0.5850

0.5825

–50

2.7

2.6

2.5

FREQUENCY (MHz)

Oscillator Frequency

vs Temperature

2.7

2.6

2.5

FREQUENCY (MHz)

2.4

2.3

2.2

2.1

2.0

1.9

1.8

90 110

3542 G08

Oscillator Frequency

vs Supply Voltage

2.4

2.3

2.2

2.1

2.0

1.9

V

REF

(V)

–25

50

25

0

75

TEMPERATURE (°C)

100

125

1.8

–50 –30 –10 10 30 50 70

TEMPERATURE (°C)

2

3

5

4

SUPPLY VOLTAGE (V)

6

3542 G09

3542 G07

Output Voltage vs Supply Voltage

0.5

0.4

0.3

V

OUT

ERROR (%)

V

OUT

ERROR (%)

0.2

0.1

0

1.0

0.5

0

–0.5

–1.0

–1.5

2

2.5

3

3.5 4

4.5 5

INPUT VOLTAGE (V)

5.5

–2.0

6

V

OUT

= 1.8V

I

OUT

= 100mA

2.0

1.5

Output Voltage vs Load Current

0.9

V

IN

= 3.6V

V

OUT

= 1.8V

Burst Mode

OPERATION

R

DS(ON)

(

9

)

0.8

0.7

0.6

R

DS(ON)

vs Input Voltage

MAIN SWITCH

0.5

0.4

0.3

0.2

0.1

0

SYNCHRONOUS

SWITCH

–0.1

–0.2

PULSE SKIP

MODE

–0.3

–0.4

–0.5

1

10

100

LOAD CURRENT (mA)

1000

3542 G11

1

2

3

4

V

IN

(V)

5

6

7

3542 G12

3542 G10

3542fa

4

LTC3542

TYPICAL PERFORMANCE CHARACTERISTICS

R

DS(ON)

vs Temperature

0.9

0.8

LEAKAGE CURRENT (pA)

0.7

0.6

R

DS(ON)

(Ω)

0.5

0.4

0.3

0.2

0.1

0

–50

–25

0

25

50

75

TEMPERATURE (°C)

SYNCHRONOUS

SWITCH

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

100

125

MAIN SWITCH

1000

900

800

700

600

500

400

300

200

100

0

1

2

3

V

IN

(V)

4

5

6

3542 G14

T

A

= 25°C unless otherwise speciﬁed.

Switch Leakage vs Temperature

300

250

SWITCH LEAKAGE (nA)

200

150

100

50

0

–50 –25

MAIN SWITCH

SYNCHRONOUS SWITCH

50

25

75

0

TEMPERATURE (°C)

100

125

Switch Leakage vs Input Voltage

MAIN SWITCH

SYNCHRONOUS

SWITCH

3542 G13

3542 G15

Efﬁciency vs Input Voltage

100

90

80

EFFICIENCY (%)

70

60

50

40

30

2.5

V

OUT

= 1.8V

Burst Mode OPERATION

FIGURE 3a CIRCUIT

I

OUT

= 500mA

I

OUT

= 100mA

I

OUT

= 10mA

I

OUT

= 1mA

I

OUT

= 0.1mA

3

4.5

4

3.5

INPUT VOLTAGE (V)

5

5.5

3542 G16

Efﬁciency vs Load Current

100

90

80

70

EFFICIENCY (%)

60

50

40

30

20

10

V

OUT

= 1.8V

Burst Mode OPERATION

FIGURE 3a CIRCUIT

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

1000

3542 G17

0

0.1

1

10

100

OUTPUT CURRENT (mA)

Efﬁciency vs Load Current

100

90

80

70

EFFICIENCY (%)

60

50

40

30

20

10

V

OUT

= 1.2V

Burst Mode OPERATION

FIGURE 3a CIRCUIT

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

1000

3542 G18

Efﬁciency vs Load Current

100

90

80

70

EFFICIENCY (%)

60

50

40

30

20

10

0

0.1

V

IN

= 3.6V

V

OUT

= 1.8V

FIGURE 3a CIRCUIT

1

10

100

OUTPUT CURRENT (mA)

1000

3542 G19

Burst Mode

OPERATION

PULSE SKIP

MODE

0

0.1

1

10

100

OUTPUT CURRENT (mA)

3542fa

5

LTC3542IDC

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