FEATURES

n

LTC3606B

800mA Synchronous

Step-Down DC/DC with

Average Input Current Limit

DESCRIPTION

The LTC

®

3606B is an 800mA monolithic synchronous

buck regulator using a constant frequency current mode

architecture.

The input supply voltage range is 2.5V to 5.5V, making it

ideal for Li-Ion and USB powered applications. 100% duty

cycle capability provides low dropout operation, extending

the run time in battery-operated systems. Low output

voltages are supported with the 0.6V feedback reference

voltage. The LTC3606B can supply 800mA output current.

The LTC3606B’s programmable average input current limit

is ideal for USB applications and for point-of-load power

supplies because the LTC3606B’s limited input current

will still allow its output to deliver high peak load cur-

rents without collapsing the input supply. The operating

frequency is internally set at 2.25MHz allowing the use of

small surface mount inductors. Internal soft-start reduces

in-rush current during start-up. The LTC3606B is available

in an 8-Lead 3mm

×

3mm DFN package.

L,

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

and Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the

property of their respective owners. Protected by U.S.Patents, including 5481178, 6127815,

6304066, 6498466, 6580258, 6611131.

Programmable Average Input Current Limit:

±5% Accuracy

Step-Down Output: Up to 96% Efﬁciency

Low Noise Pulse-Skipping Operation at Light Loads

Input Voltage Range: 2.5V to 5.5V

Output Voltage Range: 0.6V to 5V

2.25MHz Constant-Frequency Operation

Power Good Output Voltage Monitor

Low Dropout Operation: 100% Duty Cycle

Internal Soft-Start

Current Mode Operation for Excellent Line and Load

Transient Response

±2% Output Voltage Accuracy

Short-Circuit Protected

Shutdown Current ≤ 1μA

Available in Small Thermally Enhanced 8-Lead

3mm

×

3mm DFN Package

APPLICATIONS

n

High Peak Load Current Applications

USB Powered Devices

Supercapacitor Charging

Radio Transmitters and Other Handheld Devices

TYPICAL APPLICATION

Monolithic Buck Regulator with Input Current Limit

V

IN

3.4V

TO 5.5V

C

IN

10μF

PGOOD

499k

1.5μH

V

IN

LTC3606B

RUN

PGOOD

RLIM

GND

1000pF

116k

I

LIM

= 475mA

V

FB

1210k

SW

V

OUT

3.4V AT

800mA

V

OUT

200mV/DIV

V

IN

AC-COUPLED

1V/DIV

I

OUT

500mA/DIV

3606B TA01

GSM Pulse Load

+

2.2mF

2

SuperCap

255k

I

IN

500mA/DIV

1ms/DIV

V

IN

= 5V, 500mA COMPLIANT

I

LOAD

= 0A to 2.2A

3606B TA01b

3606bfb

1

LTC3606B

ABSOLUTE MAXIMUM RATINGS

(Note 1)

PIN CONFIGURATION

TOP VIEW

1

2

3

4

9

GND

8 V

FB

7 RUN

6 PGOOD

5 V

IN

GND

RLIM

GND

SW

Input Supply Voltage (V

IN

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

V

FB

................................................... –0.3V to V

IN

+ 0.3V

RUN, RLIM ....................................... –0.3V to V

IN

+ 0.3V

SW ................................................... –0.3V to V

IN

+ 0.3V

PGOOD............................................. –0.3V to V

IN

+ 0.3V

P-Channel SW Source Current (DC) (Note 2) ..............1A

N-Channel SW Source Current (DC) (Note 2)..............1A

Peak SW Source and Sink Current (Note 2) ............. 2.7A

Operating Junction Temperature Range

(Notes 3, 6, 8) ........................................ –40°C to 125°C

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

Reﬂow Peak Body Temperature ............................ 260°C

DD PACKAGE

8-LEAD (3mm 3mm) PLASTIC DFN

T

JMAX

= 125°C,

θ

JA

= 40°C/W

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

ORDER INFORMATION

LEAD FREE FINISH

LTC3606BEDD#PBF

LTC3606BIDD#PBF

TAPE AND REEL

LTC3606BEDD#TRPBF

LTC3606BIDD#TRPBF

PART MARKING*

LFMB

PACKAGE DESCRIPTION

8-Lead (3mm

×

3mm) Plastic DFN

8-Lead (3mm

×

3mm) Plastic DFN

TEMPERATURE RANGE

–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/

3606bfb

2

LTC3606B

ELECTRICAL CHARACTERISTICS

SYMBOL

V

IN

V

UV

I

FB

V

FBREG

V

LINEREG

V

LOADREG

I

S

PARAMETER

V

IN

Operating Voltage Range

V

IN

Undervoltage Lockout

Feedback Pin Input Current

Feedback Voltage

V

FB

Line Regulation

V

FB

Load Regulation

Supply Current

Active Mode (Note 4)

Shutdown

Oscillator Frequency

Peak Switch Current Limit

Input Average Current Limit

LTC3606BE, –40°C < T

J

< 85°C (Note 7)

LTC3606BI, –40°C < T

J

< 125°C (Note 7)

V

IN

= 2.5V to 5.5V (Note 7)

I

LOAD

= 0mA to 800mA (Note 7)

V

FB

= 0.95

×

V

FBREG

V

RUN

= 0V, V

IN

= 5.5V

V

FB

= V

FBREG

V

IN

= 5V, V

FB

< V

FBREG

, Duty Cycle <35%

RLIM = 116k

RLIM = 116k, LTC3606BE

RLIM = 116k, LTC3606BI

l

The

l

denotes the speciﬁcations which apply over the full operating

junction temperature range, otherwise speciﬁcations are at T

A

= 25°C, V

IN

= 5V, unless otherwise noted.

CONDITIONS

l

MIN

2.5

l

TYP

2.1

MAX

5.5

2.5

±30

0.612

0.618

0.25

UNITS

V

nA

V

%/V

%

V

IN

Low to High

0.588

0.582

0.600

0.01

0.5

420

650

1

2.7

500

513

523

μA

MHz

mA

Ω

f

OSC

I

LIM(PEAK)

I

INLIM

1.8

1800

450

437

427

2.25

2400

475

0.27

0.25

0.01

R

DS(ON)

I

SW(LKG)

t

SOFTSTART

V

RUN

I

RUN

PGOOD

Main Switch On-Resistance (Note 5)

V

IN

= 5V, I

SW

= 100mA

Synchronous Switch On-Resistance (Note 5) V

IN

= 5V, I

SW

= 100mA

Switch Leakage Current

Soft-Start Time

RUN Threshold High

RUN Leakage Current

Power Good Threshold

0V ≤ V

RUN

≤ 5V

Entering Window

V

FB

Ramping Up

V

FB

Ramping Down

Leaving Window

V

FB

Ramping Up

V

FB

Ramping Down

PGOOD Rising and Falling, V

IN

= 5V

8

V

PGOOD

= 5V

V

IN

= 5V, V

RUN

= 0V

V

FB

from 0.06V to 0.54V

l

1

1.3

1.2

1

μA

ms

V

μA

%

0.3

0.4

0.95

1

0.01

–5

5

–7

7

9

–9

90

15

30

±1

11

–11

%

μs

Ω

μA

PGOOD Blanking Power Good Blanking Time

R

PGOOD

I

PGOOD

Power Good Pull-Down On-Resistance

PGOOD Leakage Current

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:

Guaranteed by long term current density limitations.

Note 3:

The LTC3606BE is guaranteed to meet performance speciﬁcations

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

junction temperature range are assured by design, characterization and

correlation with statistical process controls. The LTC3606BI is guaranteed

to meet speciﬁed performance over the full –40°C to 125°C operating

junction temperature range.

Note 4:

Dynamic supply current is higher due to the internal gate charge

being delivered at the switching frequency.

Note 5:

The switch on-resistance is guaranteed by correlation to wafer

level measurements.

Note 6:

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.

Note 7:

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 8:

T

J

is calculated from the ambient temperature T

A

and the power

dissipation as follows: T

J

= T

A

+ (P

D

)(θ

JA

°C/W)

3606bfb

3

LTC3606B

TYPICAL PERFORMANCE CHARACTERISTICS

Pulse-Skipping Mode Operation

550

SW

2V/DIV

SUPPLY CURRENT (μA)

V

OUT

50mV/DIV

AC-

COUPLED

500

450

EFFICIENCY (%)

400

350

300

250

200

–50

V

IN

= 2.7V

T

A

= 25°C, V

IN

= 5V, unless otherwise noted.

Supply Current vs Temperature

RUN = V

IN

I

LOAD

= 0A

V

IN

= 5.5V

100

90

80

70

60

50

40

30

20

Efﬁciency vs Input Voltage

I

L

100mA/DIV

V

IN

= 5V

V

OUT

= 3.3V

I

LOAD

= 5mA

5μs/DIV

3606B G01

I

OUT

= 100mA

I

OUT

= 400mA

I

OUT

= 800mA

V

OUT

= 3.3V

4

4.5

V

IN

(V)

I

OUT

= 10mA

I

OUT

= 1mA

I

OUT

= 0.1mA

10

–25

0

25

50

75

TEMPERATURE (°C)

100

125

0

3.5

5

5.5

3606B G03

3606B G02

Regulated Voltage vs Temperature

1.5

1.0

V

FB

ERROR (%)

0.5

0

–0.5

–1.0

–1.5

–50

FREQUENCY (MHz)

2.5

2.4

Oscillator Frequency

vs Temperature

1000

Switch Leakage vs Input Voltage

800

2.3

2.2

2.1

2.0

1.9

1.8

–50

LEAKAGE CURRENT (pA)

600

MAIN SWITCH

400

SYNCHRONOUS SWITCH

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

V

IN

= 5V

–25

0

25

50

75

TEMPERATURE (°C)

100

125

200

–25

0

25

50

75

TEMPERATURE (°C)

100

125

0

2.5

3

3.5

3606B G04

4

V

IN

(V)

4.5

5

5.5

3606B G06

3606B G05

Switch On-Resistance

vs Input Voltage

600

0.5

0.4

MAIN PFET R

DS(ON)

(Ω)

500

R

DS(ON)

(mΩ)

0.3

0.2

0.1

0

SYNCHRONOUS SWITCH

200

2.5

3

3.5

4

V

IN

(V)

4.5

5

5.5

3606B G07

Switch On-Resistance

vs Temperature

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 5V

0.7

MAIN SWITCH

0.6

0.5

0.4

0.3

0.2

SYNCHRONOUS SWITCH

–0.1

–50

–25

0

25

50

75

TEMPERATURE (°C)

100

0.1

125

SYNCHRONOUS NFET R

DS(ON)

(Ω)

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

10

Efﬁciency vs Load Current

V

OUT

= 3.3V

400

MAIN SWITCH

300

0

0.0001

V

IN

= 3.6V

V

IN

= 4.2V

V

IN

= 5V

0.001

0.01

0.1

OUTPUT CURRENT (A)

1

3606B G11

3606B G09

3606bfb

4

LTC3606B

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency vs Load Current

100

90

80

V

OUT

ERROR (%)

V

OUT

ERROR (%)

EFFICIENCY (%)

70

60

50

40

30

20

10

0

0.0001

V

IN

= 2.7V

V

IN

= 3.6V

V

IN

= 4.2V

V

IN

= 5V

0.001

0.01

0.1

OUTPUT CURRENT (A)

1

3606B G13

T

A

= 25°C, V

IN

= 5V, unless otherwise noted.

Load Regulation

3.0

2.5

2.0

0.2

0

–0.2

–0.4

1.5

1.0

0.5

0

–0.5

–1.0

0

V

OUT

= 1.8V

V

OUT

= 2.5V

V

OUT

= 3.3V

100 200 300 400 500 600 700 800

LOAD CURRENT (mA)

3606B G15

Line Regulation

0.6

0.4

V

OUT

= 1.8V

I

LOAD

= 100mA

V

OUT

= 1.2V

–0.6

2.5

3.0

3.5

4.0

V

IN

(V)

4.5

5.0

5.5

3606B G16

Start-Up from Shutdown

RUN

2V/DIV

RUN

2V/DIV

V

OUT

2V/DIV

V

OUT

1V/DIV

I

L

250mA/DIV

200μs/DIV

V

IN

= 5V, V

OUT

= 3.3V

R

LOAD

= 7Ω

C

LOAD

= 4.7μF

3606B G17

Start-Up from Shutdown

1.2

1.0

0.8

V

RLIM

(V)

0.6

0.4

0.2

0

V

RLIM

vs Input Current

I

LIM

= 475mA

R

LIM

= 116k

R

LIM

1V/DIV

I

IN

500mA/DIV

2ms/DIV

V

IN

= 5V, V

OUT

= 3.4V

R

L

= NO LOAD, C

L

= 4.4mF

,

C

LIM

= 2200pF I

LIM

= 500mA

3606B G18

0

100

200

300

400

I

IN

(mA)

500

600

3606B G18b

Average Input Current Limit

vs Temperature

8

V

IN

= 5V

I

LIM

= 475mA

6

4

I

INLIM

ERROR (%)

2

0

–2

–4

–6

–8

–50

–25

0

25

50

75

TEMPERATURE (°C)

100

125

I

L

1A/DIV

I

LOAD

1A/DIV

V

OUT

200mV/DIV

AC-COUPLED

Load Step

V

OUT

200mV/DIV

AC-COUPLED

Load Step

I

L

1A/DIV

I

LOAD

1A/DIV

20μs/DIV

V

IN

= 5V, V

OUT

= 3.3V

I

LOAD

= 0A TO 800mA

,

C

OUT

= 100μF C

F

= 20pF

3606B G20

20μs/DIV

V

IN

= 5V, V

OUT

= 1.8V

I

LOAD

= 80mA TO 800mA

,

C

OUT

= 100μF C

F

= 20pF

3606B G21

3606B G19

3606bfb

5

参数名称	属性值
功能	降压
输出配置	正
拓扑	降压
输出类型	可调式
输出数	1
电压 - 输入（最小值）	2.5V
电压 - 输入（最大值）	5.5V
电压 - 输出（最小值/固定）	0.6V
电压 - 输出（最大值）	5V
电流 - 输出	800mA
频率 - 开关	2.25MHz
同步整流器	是
工作温度	-40°C ~ 85°C（TJ）
安装类型	表面贴装
封装/外壳	8-WFDFN 裸露焊盘
供应商器件封装	8-DFN（3x3）

	LTC3606BEDD#PBF	LTC3606BIDD#PBF	LTC3606BEDD#TRPBF	LTC3606BIDD#TRPBF
描述	IC REG BUCK ADJ 0.8A SYNC 8DFN	IC REG BUCK ADJ 0.8A SYNC 8DFN	IC REG BUCK ADJ 0.8A SYNC 8DFN	IC REG BUCK ADJ 0.8A SYNC 8DFN
功能	降压	降压	降压	降压
输出配置	正	正	正	正
拓扑	降压	降压	降压	降压
输出类型	可调式	可调式	可调式	可调式
输出数	1	1	1	1
电压 - 输入（最小值）	2.5V	2.5V	2.5V	2.5V
电压 - 输入（最大值）	5.5V	5.5V	5.5V	5.5V
电压 - 输出（最小值/固定）	0.6V	0.6V	0.6V	0.6V
电压 - 输出（最大值）	5V	5V	5V	5V
电流 - 输出	800mA	800mA	800mA	800mA
频率 - 开关	2.25MHz	2.25MHz	2.25MHz	2.25MHz
同步整流器	是	是	是	是
工作温度	-40°C ~ 85°C（TJ）	-40°C ~ 125°C （TJ）	-40°C ~ 85°C（TJ）	-40°C ~ 125°C （TJ）
安装类型	表面贴装	表面贴装	表面贴装	表面贴装
封装/外壳	8-WFDFN 裸露焊盘	8-WFDFN 裸露焊盘	8-WFDFN 裸露焊盘	8-WFDFN 裸露焊盘
供应商器件封装	8-DFN（3x3）	8-DFN（3x3）	8-DFN（3x3）	8-DFN（3x3）

LTC3606BEDD#PBF

LTC3606BEDD#PBF概述

LTC3606BEDD#PBF规格参数

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