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LTC3565

1.25A, 4MHz, Synchronous

Step-Down DC/DC Converter

FEATURES

■

DESCRIPTION

The LTC

®

3565 is a constant frequency, synchronous

step-down DC/DC converter. Intended for medium power

applications, it operates from a 2.5V to 5.5V input voltage

range and has a user conﬁgurable operating frequency

up to 4MHz, allowing the use of tiny, low cost capacitors

and inductors 1mm or less in height. The output voltage is

adjustable from 0.6V to 5.5V. Internal synchronous power

switches provide high efﬁciency. The LTC3565’s current

mode architecture and external compensation allow the

transient response to be optimized over a wide range of

loads and output capacitors.

The LTC3565 can be conﬁgured for automatic power

saving Burst Mode operation (I

Q

= 40μA) to reduce gate

charge losses when the load current drops below the level

required for continuous operation. For reduced noise and

RF interference, the SYNC/MODE pin can be conﬁgured to

skip pulses or provide forced continuous operation.

To further maximize battery life, the P-channel MOSFET

is turned on continuously in dropout (100% duty cycle).

In shutdown, the device draws <1μA.

, 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, 6498466, 6611131.

■

High Efﬁciency: Up to 95%

V

IN

Range: 2.5V to 5.5V

High Frequency Operation: Up to 4MHz

Selectable Low Ripple (Typical 25mV

p-p

)

Burst Mode

®

Operation: I

Q

= 40μA

Stable with Ceramic Capacitors

Uses Tiny Capacitors and Inductor

Low R

DS(ON)

Internal Switches: 0.15Ω

Current Mode Operation for Excellent Line

and Load Transient Response

Short-Circuit Protected

Low Dropout Operation: 100% Duty Cycle

Low Shutdown Current: I

Q

≤ 1μA

Output Voltages from 0.6V to 5V

Synchronizable to External Clock

Supports Pre-Biased Outputs

Small 10-Lead (3mm

×

3mm) DFN or MSOP Package

APPLICATIONS

■

Notebook Computers

Digital Cameras

Cellular Phones

Handheld Instruments

Board Mounted Power Supplies

TYPICAL APPLICATION

Step-Down 2.5V/1.25A Regulator

V

IN

2.5V TO 5.5V

22μF

EFFICIENCY (%)

SYNC/MODE SV

IN

PV

IN

RUN

PGOOD

ITH

RT

12.1k

V

FB

GND

680pF

191k

22pF

LTC3565

SW

2.2μH

V

OUT

2.5V

1.25A

22μF

Efﬁciency and Power Loss vs Output Current

100

90

80

70

60

50

40

30

20

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

1

10

100

1000

OUTPUT CURRENT (mA)

0.01

0.1

POWER LOSS (W)

1

0.001

931k

294k

10

0

0.1

0.0001

10000

3565 TA01b

3565 TA01a

3565f

1

LTC3565

ABSOLUTE MAXIMUM RATINGS

(Note 1)

PV

IN

, SV

IN

Voltages ..................................... –0.3V to 6V

V

FB

, ITH, RT Voltages ....................–0.3V to (V

IN

+ 0.3V)

SYNC/MODE, PGOOD Voltage .......–0.3V to (V

IN

+ 0.3V)

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

IN

+ 0.3V)

RUN Voltage ............................................... –0.3V to 6V

Operating Junction Temperature Range

(Notes 2, 5, 8) ........................................ –40°C to 125°C

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

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

PIN CONFIGURATION

TOP VIEW

RT

RUN

SYNC/MODE

SW

GND

1

2

3

4

5

11

10 ITH

9 V

FB

8 PGOOD

7 SV

IN

6 PV

IN

TOP VIEW

RT

RUN

SYNC/MODE

SW

GND

1

2

3

4

5

10

9

8

7

6

ITH

V

FB

PGOOD

SV

IN

PV

IN

11

DD PACKAGE

10-LEAD (3mm × 3mm) PLASTIC DFN

T

JMAX

= 125°C,

θ

JA

= 43°C/W,

θ

JC

= 7.5°C/W

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

MSE PACKAGE

10-LEAD PLASTIC MSOP

T

JMAX

= 125°C,

θ

JA

= 40°C/W,

θ

JC

= 10°C/W

EXPOSED PAD (PIN 11) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LTC3565EDD#PBF

LTC3565IDD#PBF

LTC3565EMSE#PBF

LTC3565IMSE#PBF

TAPE AND REEL

LTC3565EDD#TRPBF

LTC3565IDD#TRPBF

LTC3565EMSE#TRPBF

LTC3565IMSE#TRPBF

PART MARKING*

LTDNR

LTDVJ

PACKAGE DESCRIPTION

10-Lead (3mm × 3mm) Plastic DFN

10-Lead Plastic MSOP

TEMPERATURE RANGE

–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, RT = 125k unless otherwise speciﬁed. (Note 2)

SYMBOL

V

IN

I

FB

V

FB

ΔV

LINEREG

ΔV

LOADREG

g

m(EA)

PARAMETER

Operating Voltage Range

Feedback Pin Input Current

Feedback Voltage

Reference Voltage Line Regulation

Output Voltage Load Regulation

Error Ampliﬁer Transconductance

(Note 3)

V

IN

= 2.5V to 5V

ITH = 0.55V to 0.9V

ITH Pin Load = ±5μA (Note 3)

●

ELECTRICAL CHARACTERISTICS

CONDITIONS

MIN

2.5

0.588

TYP

MAX

5.5

50

UNITS

V

nA

V

%/V

%

μS

0.6

0.04

0.02

300

0.612

0.2

3565f

2

LTC3565

ELECTRICAL CHARACTERISTICS

SYMBOL

I

S

PARAMETER

Input DC Supply Current (Note 4)

Active Mode

Sleep Mode

Shutdown

Oscillator Frequency

Synchronization Frequency

Peak Switch Current Limit

Top Switch On-Resistance

Bottom Switch On-Resistance

I

SW(LKG)

V

RUN

I

RUN

V

UVLO

PGOOD

R

PGOOD

PGOOD Blanking

V

SYNC-MODE

t

SOFT-START

Pulse Skip

Force Continuous

Burst

10% to 90% of Regulation

Switch Leakage Current

RUN Threshold

RUN Leakage Current

Undervoltage Lockout Threshold

Power Good Threshold

Power Good Pull-Down On-Resistance

V

FB

Step from 0V to 0.6V

V

FB

Step from 0.6V to 0V

1.1

V

IN

– 0.75

0.6

V

IN

Ramping Down

V

FB

Ramping Up from 0.45V to 0.6V

V

FB

Ramping Down from 0.69V to 0.6V

The

●

denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 3.6V, RT = 125k unless otherwise speciﬁed. (Note 2)

CONDITIONS

V

SYNC/MODE

= 3.6V, V

FB

= 0.55V

V

SYNC/MODE

= 3.6V, V

FB

= 0.8V

V

RUN

= 0V

RT = 125k

(Note 7)

V

FB

= 0.5V

MSE Package

DD Package (Note 6)

MSE Package

DD Package (Note 6)

V

IN

= 5V, V

RUN

= 0V, V

FB

= 0V

●

MIN

TYP

330

40

0.1

1.5

MAX

450

60

1

1.7

4

2.5

0.2

0.18

1

1.5

±1

2.2

UNITS

μA

MHz

A

Ω

μA

V

μA

V

%

Ω

μs

V

ms

f

OSC

f

SYNC

I

LIM

R

DS(ON)

1.3

0.4

1.5

2.1

0.15

0.13

0.01

0.3

0.8

±0.01

1.9

–7

7

15

40

105

20

0.63

V

IN

– 1.05

0.9

1.2

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 LTC3565E is guaranteed to meet performance speciﬁcations

from 0°C to 125°C junction temperature. Speciﬁcations over the –40°C

to 125°C operating junction temperature range are assured by design,

characterization and correlation with statistical process controls. The

LTC3565I is guaranteed over the full –40°C to 125°C operating junction

temperature range. High junction temperatures degrade operating lifetimes.

Operating lifetime is derated at junction temperatures greater than 125°C.

Note 3:

The LTC3565 is tested in a feedback loop which servos V

FB

to the

midpoint for the error ampliﬁer (V

ITH

= 0.7V).

Note 4:

Dynamic supply current is higher due to the internal gate charge

being delivered at the switching frequency.

Note 5:

T

J

is calculated from the ambient T

A

and power dissipation P

D

according to the following formulas:

LTC3565EDD: T

J

= T

A

+ (P

D

• 43°C/W)

LTC3565EMS: T

J

= T

A

+ (P

D

• 120°C/W)

Note 6:

Switch on-resistance is guaranteed by correlation to wafer level

measurements and assured by design characterization and correlation with

statistical process controls.

Note 7:

4MHz operation is guaranteed by design but not production tested

and is subject to duty cycle limitations (see Applications Information).

Note 8:

This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed 125°C when overtemperature protection is active.

Continuous operation above the speciﬁed maximum operating junction

temperature may impair device reliability.

3565f

3

LTC3565

TYPICAL PERFORMANCE CHARACTERISTICS

otherwise noted.

Efﬁciency vs Input Voltage

100

I

OUT

= 100mA

90

80

EFFICIENCY (%)

70

60

50

40

V

OUT

= 1.8V

30

2.5

3.0

4.5

4.0

3.5

INPUT VOLTAGE(V)

5.0

5.5

3565 G01

T

A

= 25°C, V

IN

= 3.6V, f

O

= 1MHz, unless

Efﬁciency vs Output Current

100

90

80

EFFICIENCY (%)

70

60

50

40

30

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

10000

3565 G02

Efﬁciency vs Output Current

I

OUT

= 10mA

90

80

I

OUT

= 1mA

EFFICIENCY (%)

I

OUT

= 1.25A

70

60

50

40

30

20

10

0

0.1

V

OUT

= 1.8V

1

I

OUT

= 0.1mA

20

10

0

0.1

V

OUT

= 1.5V

1

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

10000

3565 G03

100

1000

10

OUTPUT CURRENT (mA)

10

100

1000

OUTPUT CURRENT (mA)

Efﬁciency vs Output Current

100

90

80

EFFICIENCY (%)

Burst Mode

OPERATION

95

94

93

Efﬁciency vs Frequency

1.00

4.7μH

0.75

2.2μH

92

91

90

89

1μH

V

OUT

ERROR (%)

0.50

Load Regulation

70

60

50

40

30

20

10

0

0.1

PULSE

SKIP

Burst Mode OPERATION

0.25

PULSE SKIP

0.00

FORCED CONTINUOUS

–0.25

V

OUT

= 1.8V

V

OUT

= 1.8V

5

3565

G05

V

OUT

= 1.8V

1

10

100

1000

OUTPUT CURRENT (mA)

10000

3565 G04

88

0

1

3

2

FREQUENCY (MHz)

4

–0.50

0

200

400 600 800 1000 1200 1400

OUTPUT CURRENT(mA)

3565

G06

Line Regulation

0.6

0.4

V

OUT

ERROR (%)

0.2

0.0

–0.2

–0.4

–0.6

2.5

615

610

REFERENCE VOLTAGE (mV)

605

600

595

590

V

OUT

= 1.8V

I

LOAD

= 400mA

3.0

4.5

4.0

3.5

INPUT VOLTAGE(V)

5.0

5.5

3565

G07

Reference Voltage vs

Temperature

6

4

2

0

–2

–4

Frequency Variation vs

Temperature

585

–50 –25

FREQUENCY VARIATION (%)

50

25

75

0

TEMPERATURE (°C)

100

125

–6

–50

–25

50

25

75

0

TEMPERATURE(°C)

100

125

3565 G08

3565 G09

3565f

4

LTC3565

TYPICAL PERFORMANCE CHARACTERISTICS

otherwise noted.

Frequency Variation vs Input

Voltage

6

4

FREQUENCY VARIATION (%)

2

R

DS(ON)

(Ω)

0

–2

–4

0.05

–6

–8

2.5

0.0

2.5

MAIN SWITCH

SYNCHRONOUS SWITCH

3.0

4.5

4.0

3.5

INPUT VOLTAGE (V)

5.0

5.5

3565

G10

T

A

= 25°C, V

IN

= 3.6V, f

O

= 1MHz, unless

R

DS(ON)

vs Input Voltage

0.25

0.30

0.25

0.20

0.15

0.10

0.05

R

DS(ON)

vs Temperature

0.20

0.15

0.10

R

DS(ON)

(Ω)

MAIN SWITCH

SYNCHRONOUS SWITCH

–25

50

25

75

0

TEMPERATURE (°C)

100

125

3.0

4.5

4.0

3.5

INPUT VOLTAGE (V)

5.0

5.5

3565 G11

0.0

–50

3565 G12

Dynamic Supply Current vs Input

Voltage

100

DYNAMIC SUPPLY CURRENT (mA)

100

FORCED CONTINUOUS

Dynamic Supply Current vs

Temperature

2500

Switch Leakage vs Input Voltage

10

FORCED CONTINUOUS

SWITCH LEAKAGE (pA)

2000

MAIN SWITCH

1500

1

PULSE SKIP

0.1

Burst Mode

OPERATION

1

PULSE SKIP

0.1

Burst Mode

OPERATION

1000

SYNCHRONOUS SWITCH

0.01

V

OUT

= 1.8V

I

LOAD

= 0A

3.0

3.5

4.0

4.5

INPUT VOLTAGE (V)

5.0

5.5

3565 G13

0.01

V

OUT

= 1.8V

I

LOAD

= 0A

500

0.001

2.5

0.001

–50

0

–25

0

25

50

75

TEMPERATURE (°C)

100

125

0

1

4

3

2

INPUT VOLTAGE (V)

5

6

3565 G15

3565 G14

Switch Leakage vs Temperature

600

500

SWITCH LEAKAGE (nA)

400

300

200

100

0

–50

MAIN SWITCH

SYNCHRONOUS SWITCH

SW

2V/DIV

V

OUT

50mV/DIV

AC COUPLED

I

L

200mA/DIV

Burst Mode Operation

SW

2V/DIV

V

OUT

50mV/DIV

AC COUPLED

I

L

200mA/DIV

4μs/DIV

V

IN

= 3.6V

V

OUT

= 1.8V

I

LOAD

= 50mA

3565 G17

Pulse Skipping Mode

4μs/DIV

V

IN

= 3.6V

V

OUT

= 1.8V

I

LOAD

= 5mA

3565 G18

–25

50

25

75

0

TEMPERATURE (°C)

100

125

3565 G16

3565f

5

LTC3565

LTC3565概述

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