FeaTures

n

LT8614

42V, 4A Synchronous

Step-Down Silent Switcher

with 2.5µA Quiescent Current

DescripTion

The

LT

®

8614

step-down regulator features Silent Switcher

architecture designed to minimize EMI/EMC emissions

while delivering high efficiency at frequencies up to 3MHz.

Assembled in a 3mm

×

4mm QFN, the monolithic con-

struction with integrated power switches and inclusion of

all necessary circuitry yields a solution with a minimal PCB

footprint. An ultralow 2.5µA quiescent current—with the

output in full regulation— enables applications requiring

highest efficiency at very small load currents. Transient

response remains excellent and output voltage ripple is

below 10mV

P-P

at any load, from zero to full current.

The LT8614 allows high V

IN

to low V

OUT

conversion at high

frequency with a fast minimum top switch on-time of 30ns.

Operation is safe in overload even with a saturated inductor.

Essential features are included and easy to use: An open-

drain PG pin signals when the output is in regulation. The

SYNC pin allows clock synchronization and choice of Burst

Mode operation or pulse-skipping mode. Soft-start and

tracking functionality is accessed via the TR/SS pin. An

accurate enable threshold can be set using the EN/UV pin

and a resistor at the RT pin programs switch frequency.

L,

LT, LTC, LTM, Linear Technology, the Linear logo, Silent Switcher and Burst Mode are

registered trademarks and Silent Switcher is a trademark of Analog Devices, Inc. All other

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

8823345.

n

Silent Switcher

®

Architecture

n

Ultralow EMI/EMC Emissions

High Efficiency at High Frequency

n

Up to 96% Efficiency at 1MHz, 12V to 5V

IN

OUT

n

Up to 94% Efficiency at 2MHz, 12V to 5V

IN

OUT

Wide Input Voltage Range: 3.4V to 42V

Ultralow Quiescent Current Burst Mode

®

Operation:

n

2.5μA I Regulating 12V to 3.3V

Q

IN

OUT

n

Output Ripple < 10mV

P-P

Fast Minimum Switch On-Time: 30ns

Low Dropout Under All Conditions: 125mV at 1A

Safely Tolerates Inductor Saturation in Overload

Adjustable and Synchronizable: 200kHz to 3MHz

Peak Current Mode Operation

Accurate 1V Enable Pin Threshold

Internal Compensation

Output Soft-Start and Tracking

Small 18-Lead 3mm

×

4mm QFN

applicaTions

n

Automotive and Industrial Supplies

General Purpose Step-Down

GSM Power Supplies

Typical applicaTion

5V 4A Step-Down Converter

V

IN

5.8V TO 42V

4.7µF

1µF

EN/UV

100

95

90

EFFICIENCY (%)

V

IN2

GND2

LT8614

BST

SW

BIAS

4.7pF

INTV

CC

RT

FB

GND

243k

1M

47µF

1µF

85

80

75

70

65

60

0

12V

IN

to 5V

OUT

Efficiency

1MHz

2MHz

V

IN1

GND1

PG

10nF

1µF

41.2k

0.1µF 4.7µH

SYNC/MODE

TR/SS

V

OUT

5V

4A

0.5

1.0

f

SW

= 1MHz

1.5 2.0 2.5 3.0

LOAD CURRENT (A)

3.5

4.0

8614 TA01b

8614 TA01a

8614fd

For more information

www.linear.com/LT8614

1

LT8614

absoluTe MaxiMuM raTings

(Note 1)

pin conFiguraTion

SYNC/MODE

17

16 TR/SS

15 RT

22

SW

21

SW

7

GND1

8

SW

9

SW

10

GND2

14 EN/UV

13 V

IN2

11 GND2

TOP VIEW

GND

V

IN

, EN/UV, PG..........................................................42V

BIAS ..........................................................................30V

BST Pin Above SW Pin................................................4V

FB, TR/SS, RT, INTV

CC

...............................................4V

SYNC Voltage .............................................................6V

Operating Junction Temperature Range (Note 2)

LT8614E ............................................. –40°C to 125°C

LT8614I .............................................. –40°C to 125°C

LT8614H ............................................ –40°C to 150°C

LT8614MP ......................................... –55°C to 150°C

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

20 19 18

BIAS 1

INTV

CC

2

BST 3

V

IN1

4

GND1 6

UDC PACKAGE

18-LEAD (3mm

×

4mm) PLASTIC QFN

θ

JA

= 40°C/W,

θ

JC(PAD)

= 12°C/W (Note 3)

EXPOSED PAD (PINS 21, 22) ARE SW, SHOULD BE SOLDERED TO PCB

NOTE: PINS 5, 12 ARE REMOVED. CONFIGURATION DOES NOT MATCH

JEDEC 20-PIN PACKAGE OUTLINE

orDer inForMaTion

LEAD FREE FINISH

LT8614EUDC#PBF

LT8614IUDC#PBF

LT8614HUDC#PBF

LT8614MPUDC#PBF

TAPE AND REEL

LT8614EUDC#TRPBF

LT8614IUDC#TRPBF

LT8614HUDC#TRPBF

LT8614MPUDC#TRPBF

http://www.linear.com/product/LT8614#orderinfo

PART MARKING*

LGGQ

PACKAGE DESCRIPTION

18-Lead (3mm

×

4mm) Plastic QFN

18-Lead (3mm

×

4mm) Plastic QFN

18-Lead (3mm

×

4mm) Plastic QFN

18-Lead (3mm

×

4mm) Plastic QFN

TEMPERATURE RANGE

–40°C to 125°C

–40°C to 150°C

–55°C to 150°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/.

Some packages are available in 500 unit reels through

designated sales channels with #TRMPBF suffix.

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C.

PARAMETER

Minimum Input Voltage

V

IN

Quiescent Current

V

EN/UV

= 0V

l

elecTrical characTerisTics

CONDITIONS

MIN

l

PG

FB

TYP

2.9

1.0

1.7

0.26

21

210

MAX

3.4

3

8

4

10

0.5

50

350

UNITS

V

µA

mA

µA

8614fd

V

EN/UV

= 2V, Not Switching, V

SYNC

= 0V

l

V

EN/UV

= 2V, Not Switching, V

SYNC

= 2V

V

IN

Current in Regulation

V

OUT

= 0.97V, V

IN

= 6V, Output Load = 100µA

V

OUT

= 0.97V, V

IN

= 6V, Output Load = 1mA

l

2

For more information

www.linear.com/LT8614

LT8614

elecTrical characTerisTics

PARAMETER

Feedback Reference Voltage

Feedback Voltage Line Regulation

Feedback Pin Input Current

INTV

CC

Voltage

INTV

CC

Undervoltage Lockout

BIAS Pin Current Consumption

Minimum On-Time

Minimum Off-Time

Oscillator Frequency

R

T

= 221k, I

LOAD

= 1A

R

T

= 60.4k, I

LOAD

= 1A

R

T

= 18.2k, I

LOAD

= 1A

I

SW

= 1A

l

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C.

CONDITIONS

V

IN

= 6V, I

LOAD

= 0.5A

V

IN

= 6V, I

LOAD

= 0.5A

V

IN

= 4.0V to 42V, I

LOAD

= 0.5A

V

FB

= 1V

I

LOAD

= 0mA, V

BIAS

= 0V

I

LOAD

= 0mA, V

BIAS

= 3.3V

V

BIAS

= 3.3V, I

LOAD

= 1A, 2MHz

I

LOAD

= 1.5A, SYNC = 0V

I

LOAD

= 1.5A, SYNC = 3.3V

l

MIN

0.964

0.958

–20

3.23

3.25

2.5

15

180

665

1.85

5.7

4.5

–1.5

l

TYP

0.970

0.004

3.4

3.29

2.6

9

30

80

210

700

2.00

85

8.5

40

6.9

1.0

40

MAX

0.976

0.982

0.02

20

3.57

3.35

2.7

45

110

240

735

2.15

10

8.5

1.5

1.06

20

UNITS

V

%/V

nA

V

mA

ns

kHz

MHz

mΩ

A

mΩ

A

µA

V

mV

nA

%

nA

Ω

V

nA

µA

Ω

Top Power NMOS On-Resistance

Top Power NMOS Current Limit

Bottom Power NMOS On-Resistance

Bottom Power NMOS Current Limit

SW Leakage Current

EN/UV Pin Threshold

EN/UV Pin Hysteresis

EN/UV Pin Current

PG Upper Threshold Offset from V

FB

PG Lower Threshold Offset from V

FB

PG Hysteresis

PG Leakage

PG Pull-Down Resistance

SYNC Threshold

SYNC Pin Current

TR/SS Source Current

TR/SS Pull-Down Resistance

V

INTVCC

= 3.4V, I

SW

= 1A

V

INTVCC

= 3.4V

V

IN

= 42V, V

SW

= 0V, 42V

EN/UV Rising

V

EN/UV

= 2V

V

FB

Falling

V

FB

Rising

V

PG

= 3.3V

V

PG

= 0.1V

SYNC Falling

SYNC Rising

V

SYNC

= 6V

l

0.94

–20

6

–6

–40

9.0

–9.0

1.2

12

–12

40

650

0.8

1.6

–40

1.5

2.2

200

1.1

2.0

2000

1.4

2.4

40

2.9

Fault Condition, TR/SS = 0.1V

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 LT8614E 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

LT8614I is guaranteed over the full –40°C to 125°C operating junction

temperature range. The LT8614H is guaranteed to meet performance

specifications from –40°C to 150°C operating junction temperature range.

High junction temperatures degrade operating lifetimes. The LT8614MP

is 100% tested and guaranteed over the full –55°C to 150°C operating

junction temperature range. Operating lifetime is derated at junction

temperatures greater than 125°C.

Note 3:

θ

values determined per JEDEC 51-7, 51-12. See the Applications

Information section for information on improving the thermal resistance.

Note 4:

This IC includes overtemperature protection that is intended to

protect the device during overload conditions. Junction temperature will

exceed 150°C when overtemperature protection is active. Continuous

operation above the specified maximum operating junction temperature

will reduce lifetime.

8614fd

For more information

www.linear.com/LT8614

3

LT8614

Typical perForMance characTerisTics

Efficiency at 5V

OUT

100

95

90

EFFICIENCY (%)

85

80

75

70

65

60

55

50

0

0.5

1

f

SW

= 1MHz

L = 4.7µH

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

1.5 2

2.5 3

LOAD CURRENT (A)

3.5

4

100

95

90

EFFICIENCY (%)

85

80

75

70

65

60

55

50

0

0.5

1

f

SW

= 1MHz

L = 2.2µH

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

1.5 2 2.5 3

LOAD CURRENT (A)

3.5

4

Efficiency at 3.3V

OUT

100

90

80

70

60

50

40

30

20

10

Efficiency at 5V

OUT

0

0.01

f

SW

= 1MHz

L = 4.7µH

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

0.1

1

10

100

LOAD CURRENT (mA)

1000

8614 G03

8614 G01

8614 G02

Efficiency at 3.3V

OUT

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

10

0

0.01

0.1

f

SW

= 1MHz

L = 4.7µH

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

1

10

100

LOAD CURRENT (mA)

1000

8614 G04

Efficiency vs Frequency

98

96

94

92

90

88

86

84

0.25

2.25

1.75

2.75

0.75

1.25

SWITCHING FREQUENCY (MHz)

8614 G05

Burst Mode Efficiency

vs Inductor Value

V

OUT

= 5V

I

LOAD

= 1A

L = 8.6µH

EFFICIENCY (%)

95

90

85

80

75

70

65

V

OUT

= 5V

I

LOAD

= 10mA

V

IN

= 12V

V

IN

= 12V

V

IN

= 24V

V

IN

= 24V

0

2

4

6

8

INDUCTOR VALUE (µH)

10

8614 G06

Reference Voltage

0.979

0.977

REFERENCE VOLAGE (V)

0.975

EN THRESHOLD (V)

0.973

0.971

0.969

0.967

0.965

0.963

0.961

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

8614 G07

EN Pin Thresholds

1.03

1.02

CHANGE IN V

OUT

(%)

1.01

1.00

0.99

0.98

0.97

0.96

0.95

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

8614 G08

Load Regulation

0.15

0.10

V

OUT

= 5V

V

IN

= 12V

EN RISING

0.05

0

–0.05

EN FALLING

–0.10

–0.15

0

0.5

1

2.5 3

1.5 2

LOAD CURRENT (A)

3.5

4

8614 G09

4

8614fd

For more information

www.linear.com/LT8614

LT8614

Typical perForMance characTerisTics

Line Regulation

0.10

0.08

0.06

INPUT CURRENT (µA)

CHANGE IN V

OUT

(%)

0.04

0.02

0

V

OUT

= 5V

I

LOAD

= 1A

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

5

10

15

20 25 30 35

INPUT VOLTAGE (V)

40

45

0

5

10

15 20 25 30 35

INPUT VOLTAGE (V)

40

45

0

–55

–25

65

5

95

35

TEMPERATURE (°C)

125

155

INPUT CURRENT (µA)

No-Load Supply Current

V

OUT

= 3.3V

IN REGULATION

25

No-Load Supply Current

V

OUT

= 3.3V

V

IN

= 12V

IN REGULATION

20

15

–0.02

–0.04

–0.06

–0.08

10

5

–0.10

8614 G10

8614 G11

8614 G12

Top FET Current Limit vs Duty Cycle

9.0

8.5

CURRENT LIMIT (A)

8.0

7.5

7.0

6.5

6.0

CURRENT LIMIT (A)

9.5

9.0

Top FET Current Limit

7.5

7.0

CURRENT LIMIT (A)

6.5

6.0

5.5

5.0

4.5

Bottom FET Current Limit

8.5

8.0

7.5

7.0

6.5

5% DC

0

0.2

0.4

0.6

DUTY CYCLE

0.8

1.0

8614 G13

6.0

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

8614 G14

4.0

–50 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

8614 G15

Switch Drop

200

175

SWITCH DROP (mV)

150

125

100

75

50

25

0

–50 –25

0

BOTTOM SWITCH

TOP SWITCH

SWITCH CURRENT = 1A

500

450

400

350

300

250

200

150

100

50

25 50 75 100 125 150

TEMPERATURE (°C)

8614 G16

Switch Drop

40

38

36

MINIMUM ON-TIME (ns)

34

32

30

28

26

24

22

4

8614 G17

Minimum On-Time

I

LOAD

= 1A, V

SYNC

= 0V

I

LOAD

= 1A, V

SYNC

= 3V

I

LOAD

= 2A

I

LOAD

= 4A

TOP SWITCH

BOTTOM SWITCH

0

2

1

3

SWITCH CURRENT (A)

0

20

–50

–25

50

25

0

75

TEMPERATURE (°C)

100

125

8614 G18

8614fd

For more information

www.linear.com/LT8614

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）	3.4V
电压 - 输入（最大值）	42V
电压 - 输出（最小值/固定）	0.97V
电压 - 输出（最大值）	41.8V
电流 - 输出	4A
频率 - 开关	200kHz ~ 3MHz
同步整流器	是
工作温度	-40°C ~ 125°C （TJ）
安装类型	表面贴装
封装/外壳	20-WFQFN，18 引线，裸露焊盘
供应商器件封装	20-QFN（3x4）

	LT8614IUDC#TRPBF	LT8614MPUDC#PBF	LT8614HUDC#PBF	LT8614HUDC#TRPBF	LT8614MPUDC#TRPBF
描述	IC REG BUCK ADJ 4A SYNC 18QFN	42V, 4A SYNCHRONOUS STEP-DOWN SI	IC REG BUCK ADJ 4A SYNC 18QFN	IC REG BUCK ADJ 4A SYNC 18QFN	42V, 4A SYNCHRONOUS STEP-DOWN SI
功能	降压	降压	降压	降压	降压
输出配置	正	正	正	正	正
拓扑	降压	降压	降压	降压	降压
输出类型	可调式	可调式	可调式	可调式	可调式
输出数	1	1	1	1	1
电压 - 输入（最小值）	3.4V	3.4V	3.4V	3.4V	3.4V
电压 - 输入（最大值）	42V	42V	42V	42V	42V
电压 - 输出（最小值/固定）	0.97V	3.3V	0.97V	0.97V	3.3V
电压 - 输出（最大值）	41.8V	30V	41.8V	41.8V	30V
电流 - 输出	4A	4A	4A	4A	4A
频率 - 开关	200kHz ~ 3MHz	200kHz ~ 3MHz	200kHz ~ 3MHz	200kHz ~ 3MHz	200kHz ~ 3MHz
同步整流器	是	无	是	是	无
工作温度	-40°C ~ 125°C （TJ）	-55°C ~ 150°C（TJ）	-40°C ~ 150°C（TJ）	-40°C ~ 150°C（TJ）	-55°C ~ 150°C（TJ）
安装类型	表面贴装	表面贴装	表面贴装	表面贴装	表面贴装
封装/外壳	20-WFQFN，18 引线，裸露焊盘	20-WFQFN，18 引线，裸露焊盘	20-WFQFN，18 引线，裸露焊盘	20-WFQFN，18 引线，裸露焊盘	20-WFQFN，18 引线，裸露焊盘
供应商器件封装	20-QFN（3x4）	20-QFN（3x4）	20-QFN（3x4）	20-QFN（3x4）	20-QFN（3x4）

LT8614IUDC#TRPBF

LT8614IUDC#TRPBF概述

LT8614IUDC#TRPBF规格参数

文档预览

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