LTC3568

1.8A, 4MHz, Synchronous

Step-Down DC/DC Converter

FeaTures

Uses Tiny Capacitors and Inductor

n

High Frequency Operation: Up to 4MHz

n

Low R

DS(ON)

Internal Switches: 0.110Ω

n

High Efficiency: Up to 96%

n

Stable with Ceramic Capacitors

n

Current Mode Operation for Excellent Line

and Load Transient Response

n

Short-Circuit Protected

n

Low Dropout Operation: 100% Duty Cycle

n

Low Shutdown Current: I ≤ 1µA

Q

n

Low Quiescent Current: 60µA

n

Output Voltages from 0.8V to 5V

n

Selectable Burst Mode

®

Operation

n

Sychronizable to External Clock

n

Small 3mm

×

3mm, 10-Lead DFN Package

n

DescripTion

The LTC

®

3568 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 2mm or less in height. The output voltage

is adjustable from 0.8V to 5V. Internal sychronous 0.11Ω

power switches with 2.4A peak current ratings provide

high efficiency. The LTC3568’s current mode architecture

and external compensation allow the transient response

to be optimized over a wide range of loads and output

capacitors.

The LTC3568 can be configured for automatic power sav-

ing Burst Mode operation to reduce gate charge losses

when the load current drops below the level required for

continuous operation. For reduced noise and RF interfer-

ence, 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)

with a low quiescent current of 60µA. In shutdown, the

device draws <1µA.

L,

LT, LTC, LTM, Linear Technology, the Linear logo, OPTI-LOOP and Burst Mode are

registered trademarks and ThinSOT is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents including

5481178, 6580258, 6304066, 6127815, 6611131.

applicaTions

n

Notebook Computers

Digital Cameras

Cellular Phones

Handheld Instruments

Board Mounted Power Supplies

Typical applicaTion

V

IN

2.5V TO 5.5V

22µF

V

IN

SYNC/MODE

PGOOD

LTC3568

I

TH

13k

1000pF

324k

NOTE: IN DROPOUT, THE OUTPUT TRACKS

THE INPUT VOLTAGE

SHDN/R

T

SGND

PGND

412k

V

FB

PV

IN

SV

IN

SW

887k

L1

2µH

Efficiency vs Load Current

100

95

EFFICIENCY (%)

90

85

POWER LOSS

80

75

70

V

IN

= 3.3V

V

OUT

= 2.5V

f

O

= 1MHz

Burst Mode

OPERATION

1

10

100

1000

LOAD CURRENT (mA)

10

1000

EFFICIENCY

POWER LOSS (mW)

100

V

OUT

2.5V/1.8A

22µF + 10µF

3568 F01

1

10000

Figure 1. Step-Down 1.8A Regulator

3568 TA01

3568fa

LTC3568

absoluTe MaxiMuM raTings

(Note 1)

pin conFiguraTion

TOP VIEW

SHDN/R

T

SYNC/MODE

SGND

SW

PGND

1

2

3

4

5

11

10 I

TH

9 V

FB

8 PGOOD

7 SV

IN

6 PV

IN

PV

IN

, SV

IN

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

V

FB

, I

TH

, SHDN/R

T

Voltages .......... –0.3V to (V

IN

+ 0.3V)

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

IN

+ 0.3V)

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

IN

+ 0.3V)

PGOOD Voltage ............................................ –0.3V to 6V

Operating Junction Temperature Range

(Note 2) ............................................. –40°C to 125°C

Junction Temperature (Notes 5, 8)........................ 125°C

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

DD PACKAGE

10-LEAD (3mm 3mm) PLASTIC DFN

T

JMAX

= 125°C,

θ

JA

= 43°C/W,

θ

JC

= 3°C/W

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

orDer inForMaTion

LEAD FREE FINISH

LTC3568EDD#PBF

LTC3568IDD#PBF

LEAD BASED FINISH

LTC3568EDD

LTC3568IDD

TAPE AND REEL

LTC3568EDD#TRPBF

LTC3568IDD#TRPBF

TAPE AND REEL

LTC3568EDD#TR

LTC3568IDD#TR

PART MARKING*

LCSG

PART MARKING*

LCSG

PACKAGE DESCRIPTION

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead (3mm

×

3mm) Plastic DFN

PACKAGE DESCRIPTION

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead (3mm

×

3mm) Plastic DFN

TEMPERATURE RANGE

–40°C to 125°C

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.

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

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 3.3V, R

T

= 324k unless otherwise specified. (Note 2)

SYMBOL

V

IN

I

FB

V

FB

ΔV

LINEREG

ΔV

LOADREG

g

m(EA)

I

S

PARAMETER

Operating Voltage Range

Feedback Pin Input Current

Feedback Voltage

Reference Voltage Line Regulation

Output Voltage Load Regulation

Error Amplifier Transconductance

Input DC Supply Current (Note 4)

Active Mode

Sleep Mode

Shutdown

Shutdown Threshold High

Active Oscillator Resistor

(Note 3)

LTC3568E (Note 3)

LTC3568I (Note 3)

V

IN

= 2.25V to 5V

I

TH

= 0.36, (Note 3)

I

TH

= 0.84, (Note 3)

I

TH

Pin Load = ±5µA (Note 3)

V

FB

= 0.75V, SYNC/MODE = 3.3V

V

SYNC/MODE

= 3.3V, V

FB

= 1V

V

SHDN/RT

= 3.3V

l

elecTrical characTerisTics

CONDITIONS

MIN

2.25

0.784

0.780

TYP

MAX

5.5

±0.1

UNITS

V

µA

V

%/V

%

µS

0.8

0.04

0.02

–0.02

800

240

62

0.1

V

IN

– 0.6

324k

0.816

0.2

–0.2

350

100

1

V

IN

– 0.4

1M

µA

V

Ω

V

SHDN/RT

3568fa

LTC3568

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 3.3V, R

T

= 324k unless otherwise specified. (Note 2)

f

OSC

f

SYNC

I

LIM

R

DS(ON)

I

SW(LKG)

V

UVLO

PGOOD

RPGOOD

Oscillator Frequency

Synchronization Frequency

Peak Switch Current Limit

Top Switch On-Resistance (Note 6)

Bottom Switch On-Resistance (Note 6)

Switch Leakage Current

Undervoltage Lockout Threshold

Power Good Threshold

Power Good Pull-Down On-Resistance

R

T

= 324k

(Note 7)

I

TH

= 1.3

V

IN

= 3.3V

V

IN

= 3.3V

V

IN

= 6V, V

ITH/RUN

= 0V, V

FB

= 0V

V

IN

Ramping Down

V

FB

Ramping Up, SHDN/R

T

= 1V

V

FB

Ramping Down, SHDN/R

T

= 1V

0.85

0.4

2.4

3

0.11

0.01

2

6.8

–7.6

118

200

1

1.15

4

0.15

1

2.25

MHz

A

Ω

µA

V

%

Ω

elecTrical characTerisTics

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 LTC3568 is tested under pulsed load conditions such that T

J

=

T

A

. The LTC3568E is guaranteed to meet performance specifications from

0°C to 85°C. Specifications over the –40°C to 125°C operating junction

temperature range are assured by design, characterization and correlation

with statistical process controls. The LTC3568I is guaranteed over the

full –40°C to 125°C operating junction temperature range. The maximum

ambient temperature is determined by specific operating conditions in

conjunction with board layout, the rated package thermal resistors and

other environmental factors.

Note 3:

The LTC3568 is tested in a feedback loop which servos V

FB

to the

midpoint for the error amplifier (V

ITH

= 0.6V).

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 formula:

T

J

= T

A

+ (P

D

• 43°C/W)

Note 6:

Switch on-resistance is guaranteed by correlation to wafer level

measurements.

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.

3568fa

LTC3568

Typical perForMance characTerisTics

Burst Mode Operation

V

OUT

10mV/

DIV

S

W

2V/DIV

I

L

500mA/

DIV

V

IN

= 3.3V

V

OUT

= 2.5V

I

LOAD

= 100mA

10µs/DIV

3568 G01

Pulse Skipping Mode

V

OUT

10mV/

DIV

S

W

2V/DIV

I

L

200mA/

DIV

V

IN

= 3.3V

V

OUT

= 2.5V

I

LOAD

= 100mA

2µs/DIV

3568 G02

Forced Continuous Mode

V

OUT

10mV/

DIV

S

W

2V/DIV

I

L

500mA/

DIV

V

IN

= 3.3V

V

OUT

= 2.5V

I

LOAD

= 100mA

2µs/DIV

3568 G03

Efficiency vs Load Current

100

95

EFFICIENCY (%)

90

85

80

75

70

Burst Mode

OPERATION

100

95

90

EFFICIENCY (%)

85

80

75

70

65

Efficiency vs V

IN

I

OUT

= 500mA

V

OUT

100mV/

DIV

Load Step

I

OUT

= 1.8A

PULSE SKIP

FORCED CONTINUOUS

V

IN

= 3.3V

V

OUT

= 2.5V

CIRCUIT OF FIGURE 7

I

L

1A/

DIV

V

OUT

= 2.5V

CIRCUIT OF FIGURE 7

3.0

3.5

4.0 4.5

V

IN

(V)

5.0

5.5

6.0

50µs/DIV

V

IN

= 3.3V

V

OUT

= 2.5V

I

LOAD

= 180mA TO 1.8A

3568 G06

1

10

100

1000

LOAD CURRENT (mA)

10000

3568 G04

60

2.5

3568 G05

0.6

0.5

0.4

V

OUT

ERROR (%)

0.3

0.2

0.1

0

–0.1

–0.2

–0.3

–0.4

Load Regulation

Burst Mode

OPERATION

PULSE SKIP

V

IN

= 3.3V

V

OUT

= 1.8V

0.20

0.15

0.10

V

OUT

ERROR (%)

0.05

0

–0.05

–0.10

–0.15

Line Regulation

V

OUT

= 1.8V

FREQUENCY VARIATION (%)

10

8

6

4

2

0

–2

–4

–6

–8

Frequency vs V

IN

V

OUT

= 1.8V

I

OUT

= 1.25A

T

A

= 25°C

I

OUT

= 1.8A

I

OUT

= 500mA

FORCED

CONTINUOUS

1

10

100

1000

LOAD CURRENT (mA)

10000

3568 G07

–0.20

2.0

2.5

3.0

3.5

4.0 4.5

V

IN

(V)

5.0

5.5

6.0

–10

2

3

4

V

IN

(V)

5

6

3568 G09

3568 G08

3568fa

LTC3568

Typical perForMance characTerisTics

Frequency Variation

vs Temperature

10

8

REFERENCE VARIATION (%)

6

4

2

0

–2

–4

–6

–8

–10

–50

–25

0

25

50

75

TEMPERATURE (°C)

100

125

85

0

1

3

2

FREQUENCY (MHz)

4

3568 G11

Efficiency vs Frequency

100

V

IN

= 3.3V

V

OUT

= 2.5V

I

OUT

= 500mA

T

A

= 25°C

EFFICIENCY (%)

3568 G10

95

90

120

115

110

105

100

95

R

DS(ON)

vs V

IN

T

A

= 25°C

160

150

140

130

SYNCHRONOUS SWITCH

R

DS(ON)

120

110

100

90

80

70

R

DS(ON)

vs Temperature

V

IN

= 2.5V

V

IN

= 3.3V

R

DS(ON)

(m )

MAIN SWITCH

V

IN

= 5V

90

2.5

3

3.5

4

4.5

V

IN

(V)

5

5.5

6

60

–50

MAIN SWITCH

SYNCHRONOUS SWITCH

–25

0

25

50

75

TEMPERATURE (°C)

100

125

3568 G12

3568 G13

3568fa

参数名称	属性值
Brand Name	Analog Devices Inc
是否无铅	含铅
是否Rohs认证	符合
厂商名称	ADI(亚德诺半导体)
包装说明	3 X 3 MM, LEAD FREE, PLASTIC, MO-229WEED-2, DFN-10
针数	10
制造商包装代码	05-08-1699
Reach Compliance Code	compliant
其他特性	ALSO OPERATES IN ADJUSTABLE MODE FROM 0.8 TO 5V
模拟集成电路 - 其他类型	SWITCHING REGULATOR
控制模式	CURRENT-MODE
最大输入电压	5.5 V
最小输入电压	2.25 V
标称输入电压	3.3 V
JESD-30 代码	S-PDSO-N10
JESD-609代码	e3
长度	3 mm
湿度敏感等级	1
功能数量	1
端子数量	10
最高工作温度	125 °C
最低工作温度	-40 °C
最大输出电流	4 A
封装主体材料	PLASTIC/EPOXY
封装代码	HVSON
封装形状	SQUARE
封装形式	SMALL OUTLINE, HEAT SINK/SLUG, VERY THIN PROFILE
峰值回流温度（摄氏度）	NOT SPECIFIED
认证状态	Not Qualified
座面最大高度	0.8 mm
表面贴装	YES
切换器配置	BUCK
最大切换频率	4000 kHz
技术	CMOS
温度等级	AUTOMOTIVE
端子面层	Matte Tin (Sn)
端子形式	NO LEAD
端子节距	0.5 mm
端子位置	DUAL
处于峰值回流温度下的最长时间	NOT SPECIFIED
宽度	3 mm
Base Number Matches	1

	LTC3568IDD#TRPBF	LTC3568IDD#PBF
描述	开关稳压器 4MHz, 1.8A Synch Step-dwn Regulator	开关稳压器 4MHz, 1.8A Synch Step-dwn Regulator
Brand Name	Analog Devices Inc	Analog Devices Inc
是否无铅	含铅	含铅
是否Rohs认证	符合	符合
厂商名称	ADI(亚德诺半导体)	ADI(亚德诺半导体)
包装说明	3 X 3 MM, LEAD FREE, PLASTIC, MO-229WEED-2, DFN-10	3 X 3 MM, LEAD FREE, PLASTIC, MO-229WEED-2, DFN-10
针数	10	10
制造商包装代码	05-08-1699	05-08-1699
Reach Compliance Code	compliant	compliant
其他特性	ALSO OPERATES IN ADJUSTABLE MODE FROM 0.8 TO 5V	ALSO OPERATES IN ADJUSTABLE MODE FROM 0.8 TO 5V
模拟集成电路 - 其他类型	SWITCHING REGULATOR	SWITCHING REGULATOR
控制模式	CURRENT-MODE	CURRENT-MODE
最大输入电压	5.5 V	5.5 V
最小输入电压	2.25 V	2.25 V
标称输入电压	3.3 V	3.3 V
JESD-30 代码	S-PDSO-N10	S-PDSO-N10
JESD-609代码	e3	e3
长度	3 mm	3 mm
湿度敏感等级	1	1
功能数量	1	1
端子数量	10	10
最高工作温度	125 °C	125 °C
最低工作温度	-40 °C	-40 °C
最大输出电流	4 A	4 A
封装主体材料	PLASTIC/EPOXY	PLASTIC/EPOXY
封装代码	HVSON	HVSON
封装形状	SQUARE	SQUARE
封装形式	SMALL OUTLINE, HEAT SINK/SLUG, VERY THIN PROFILE	SMALL OUTLINE, HEAT SINK/SLUG, VERY THIN PROFILE
峰值回流温度（摄氏度）	NOT SPECIFIED	NOT SPECIFIED
认证状态	Not Qualified	Not Qualified
座面最大高度	0.8 mm	0.8 mm
表面贴装	YES	YES
切换器配置	BUCK	BUCK
最大切换频率	4000 kHz	4000 kHz
技术	CMOS	CMOS
温度等级	AUTOMOTIVE	AUTOMOTIVE
端子面层	Matte Tin (Sn)	Matte Tin (Sn)
端子形式	NO LEAD	NO LEAD
端子节距	0.5 mm	0.5 mm
端子位置	DUAL	DUAL
处于峰值回流温度下的最长时间	NOT SPECIFIED	NOT SPECIFIED
宽度	3 mm	3 mm
Base Number Matches	1	1

LTC3568IDD#TRPBF

LTC3568IDD#TRPBF概述

LTC3568IDD#TRPBF规格参数

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