LT3971-3.3_15,LT3971-3.3_15 pdf中文资料,LT3971-3.3_15引脚图,LT3971-3.3

LT3971/LT3971-3.3/LT3971-5

38V, 1.2A, 2MHz

Step-Down Regulator with

2.8µA Quiescent Current

FEATURES

n

DESCRIPTION

The LT

®

3971 is an adjustable frequency monolithic buck

switching regulator that accepts a wide input voltage range

up to 38V. Low quiescent current design consumes only

2.8µA of supply current while regulating with no load. Low

ripple Burst Mode operation maintains high efficiency at

low output currents while keeping the output ripple below

15mV in a typical application. An internally compensated

current mode topology is used for fast transient response

and good loop stability. A high efficiency 0.33Ω switch

is included on the die along with a boost Schottky diode

and the necessary oscillator, control and logic circuitry.

An accurate 1V threshold enable pin can be used to shut

down the LT3971, reducing the input supply current to

700nA. A capacitor on the SS pin provides a controlled

inrush current (soft-start). A power good flag signals

when V

OUT

reaches 91% of the programmed output volt-

age. The LT3971 is available in small 10-lead MSOP and

3mm

×

3mm DFN packages with exposed pads for low

thermal resistance. A 16-lead MSOP is also offered which

has enhanced pin-to-pin fault tolerance.

L,

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

of Linear Technology Corporation. All other trademarks are the property of their respective

owners.

n

Ultralow Quiescent Current:

2.8µA I

Q

Regulating 12V

IN

to 3.3V

OUT

Fixed Output Voltages: 3.3V, 5V,

2.1µA I

Q

Regulating 12V

IN

to 3.3V

OUT

Low Ripple Burst Mode

®

Operation:

Output Ripple < 15mV

P-P

Wide Input Voltage Range: 4.3V to 38V

1.2A Maximum Output Current

Adjustable Switching Frequency: 200kHz to 2MHz

Synchronizable Between 250kHz to 2MHz

Fast Transient Response

Accurate 1V Enable Pin Threshold

Low Shutdown Current: I

Q

= 700nA

Power Good Flag

Soft-Start Capability

Internal Compensation

Output Voltage: 1.19V to 30V

Small Thermally Enhanced 10-Lead MSOP 16-Lead

,

MSOP and (3mm

×

3mm) DFN Packages

APPLICATIONS

n

Automotive Battery Regulation

Power for Portable Products

Industrial Supplies

TYPICAL APPLICATION

3.3V Step Down Converter

V

IN

4.5V TO 38V

INPUT CURRENT (µA)

OFF ON

EN

PG

4.7µF

SS

RT

BD

49.9k

f = 800kHz

SYNC

GND

V

OUT

22µF

3971 TA01

No Load Supply Current

3.0

OUTPUT IN REGULATION

V

IN

BOOST

0.47µF

SW

4.7µH

2.5

LT3971-5

LT3971-3.3

2.0

LT3971-3.3

V

OUT

3.3V

1.2A

1.5

1.0

5

10

15

20

25

30

INPUT VOLTAGE (V)

35

3971 TA01b

3971fd

1

LT3971/LT3971-3.3/LT3971-5

ABSOLUTE MAXIMUM RATINGS

(Note 1)

V

IN

, EN Voltage .........................................................38V

BOOST Pin Voltage ...................................................55V

BOOST Pin Above SW Pin.........................................30V

FB, V

OUT

, RT, SYNC, SS Voltage .................................6V

PG, BD Voltage .........................................................30V

Boost Diode Current....................................................1A

Operating Junction Temperature Range (Note 2)

LT3971E ............................................. –40°C to 125°C

LT3971I .............................................. –40°C to 125°C

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

Lead Temperature (Soldering, 10 sec)

(MSE Only) ....................................................... 300°C

PIN CONFIGURATION

LT3971

TOP VIEW

BD

BOOST

SW

V

IN

EN

1

2

3

4

5

11

GND

10 SYNC

9 PG

8 RT

7 SS

6 FB

LT3971

TOP VIEW

BD

BOOST

SW

V

IN

EN

1

2

3

4

5

11

GND

10

9

8

7

6

SYNC

PG

RT

SS

FB

LT3971

TOP VIEW

BD

NC

BOOST

NC

SW

NC

V

IN

EN

1

2

3

4

5

6

7

8

16

15

14

13

12

11

10

9

GND

SYNC

PG

RT

SS

NC

FB

17

GND

DD PACKAGE

10-LEAD (3mm

×

3mm) PLASTIC DFN

θ

JA

= 45°C,

θ

JC

= 10°C/W

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

LT3971-3.3, LT3971-5

TOP VIEW

BD

BOOST

SW

V

IN

EN

1

2

3

4

5

11

GND

MSE PACKAGE

10-LEAD PLASTIC MSOP

θ

JA

= 45°C,

θ

JC

= 10°C/W

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

MSE PACKAGE

16-LEAD PLASTIC MSOP

θ

JA

= 40°C

EXPOSED PAD (PIN 17) IS GND, MUST BE SOLDERED TO PCB

LT3971-3.3, LT3971-5

10 SYNC

9 PG

8 RT

7 SS

6 V

OUT

TOP VIEW

BD

BOOST

SW

V

IN

EN

1

2

3

4

5

11

GND

10

9

8

7

6

SYNC

PG

RT

SS

V

OUT

DD PACKAGE

10-LEAD (3mm

×

3mm) PLASTIC DFN

θ

JA

= 45°C,

θ

JC

= 10°C/W

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

MSE PACKAGE

10-LEAD PLASTIC MSOP

θ

JA

= 45°C,

θ

JC

= 10°C/W

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

ORDER INFORMATION

LEAD FREE FINISH

LT3971EDD#PBF

LT3971IDD#PBF

LT3971EMSE#PBF

LT3971IMSE#PBF

LT3971EMSE16#PBF

LT3971IMSE16#PBF

LT3971EDD-3.3#PBF

LT3971IDD-3.3#PBF

LT3971EMSE-3.3#PBF

LT3971IMSE-3.3#PBF

TAPE AND REEL

LT3971EDD#TRPBF

LT3971IDD#TRPBF

LT3971EMSE#TRPBF

LT3971IMSE#TRPBF

LT3971EMSE16#TRPBF

LT3971IMSE16#TRPBF

LT3971EDD-3.3#TRPBF

LT3971IDD-3.3#TRPBF

LT3971EMSE-3.3#TRPBF

LT3971IMSE-3.3#TRPBF

PART MARKING*

LFJF

LTFJG

3971

LFRM

LTFRN

PACKAGE DESCRIPTION

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead Plastic MSOP

16-Lead Plastic MSOP

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead (3mm

×

3mm) Plastic DFN

10-Lead Plastic MSOP

TEMPERATURE RANGE

–40°C to 125°C

3971fd

2

LT3971/LT3971-3.3/LT3971-5

ORDER INFORMATION

LEAD FREE FINISH

LT3971EDD-5#PBF

LT3971IDD-5#PBF

LT3971EMSE-5#PBF

LT3971IMSE-5#PBF

TAPE AND REEL

LT3971EDD-5#TRPBF

LT3971IDD-5#TRPBF

LT3971EMSE-5#TRPBF

LT3971IMSE-5#TRPBF

PART MARKING*

LFRP

LTFRQ

PACKAGE DESCRIPTION

10-Lead (3mm

×

3mm) Plastic DFN

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/

ELECTRICAL CHARACTERISTICS

PARAMETER

Minimum Input Voltage

Quiescent Current from V

IN

LT3971 FB Pin Current

Internal Feedback Resistor Divider (LT3971-X)

Feedback Voltage

LT3971-3.3 Output Voltage

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 12V, V

EN

= 12V, V

BD

= 3.3V unless otherwise noted. (Note 2)

CONDITIONS

(Note 4)

V

EN

Low

V

EN

High, V

SYNC

Low

V

EN

High, V

SYNC

Low

V

FB

= 1.19V

MIN

l

TYP

4

0.7

1.7

0.1

10

1.19

3.3

5

0.0002

2

1

200

80

110

2.4

330

0.02

770

0.02

1.4

20

1.01

30

0.2

100

20

9

1.3

l

MAX

4.3

1.2

2.7

4.5

12

1.205

1.215

3.35

3.376

5.07

5.11

0.01

2.4

1.2

240

150

3

1

1.8

28

1.07

20

140

12.5

l

LT3971-5 Output Voltage

l

1.175

1.165

3.25

3.224

4.93

4.89

1.6

0.8

160

FB Voltage Line Regulation

Switching Frequency

Minimum Switch On Time

Minimum Switch Off Time

Switch Current Limit

Switch V

CESAT

Switch Leakage Current

Boost Schottky Forward Voltage

Boost Schottky Reverse Leakage

Minimum Boost Voltage (Note 3)

BOOST Pin Current

EN Voltage Threshold

EN Voltage Hysteresis

EN Pin Current

LT3971 PG Threshold Offset from V

FB

LT3971 PG Hysteresis

LT3971-X PG Threshold Offset from V

OUT

LT3971-X PG Hysteresis

4.3V < V

IN

< 38V (Note 4)

R

T

= 11k

R

T

= 35.7k

R

T

= 255k

1.8

I

SW

= 1A

I

SH

= 100mA

V

REVERSE

= 12V

V

IN

= 5V

I

SW

= 1A, V

BOOST

= 15V

EN Rising

l

0.95

V

FB

Rising

V

OUT

Rising

60

5.5

UNITS

V

μA

nA

MΩ

V

%/V

MHz

kHz

ns

A

mV

μA

mV

μA

V

mA

V

mV

nA

mV

%

3971fd

3

LT3971/LT3971-3.3/LT3971-5

ELECTRICAL CHARACTERISTICS

PG Leakage

PG Sink Current

SYNC Threshold

SYNC Pin Current

SS Source Current

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 12V, V

EN

= 12V, V

BD

= 3.3V unless otherwise noted. (Note 2)

V

PG

= 3V

V

PG

= 0.4V

l

300

0.6

V

SS

= 1V

0.02

570

0.8

0.1

1

1.0

1.6

µA

μA

V

nA

μA

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 LT3971E 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

LT3971I 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:

This is the minimum voltage across the boost capacitor needed to

guarantee full saturation of the switch.

Note 4:

This is the minimum input voltage for operation with accurate FB

regulation. Minimum input voltage for output regulation depends on the

application circuit.

TYPICAL PERFORMANCE CHARACTERISTICS

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

V

OUT

= 5V

R1 = 1M

R2 = 309k

0

0.2

0.4

0.6

0.8

LOAD CURRENT (A)

1

1.2

3971 G01

T

A

= 25°C, unless otherwise noted.

Efficiency, V

OUT

= 5V

Efficiency, V

OUT

= 5V

100

V

IN

= 12V

90

80

EFFICIENCY (%)

V

IN

= 36V

V

IN

= 24V

70

60

50

40

30

20

Efficiency, V

OUT

= 3.3V

V

IN

= 12V

EFFICIENCY (%)

100

V

OUT

= 5V

90 R1 = 1M

R2 = 309k

80

70

60

50

40

30

20

10

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

V

IN

= 36V

V

IN

= 24V

0

0.2

0.4

0.6

0.8

LOAD CURRENT (A)

1

1.2

3971 G02

0

0.01

0.1

1

10

100

LOAD CURRENT (mA)

1000

3971 G03

Efficiency, V

OUT

= 3.3V

90

80

70

EFFICIENCY (%)

60

50

40

30

20

10

0

0.01

0.1

1

10

100

LOAD CURRENT (mA)

1000

3971 G04

No Load Supply Current

100

DIODES, INC.

DFLS2100

4.0

3.5

INPUT CURRENT (µA)

3.0

2.5

2.0

1.5

1

–55

1.0

No Load Supply Current

V

IN

= 12V

V

IN

= 24V

V

IN

= 36V

LT3971

V

OUT

= 3.3V

LT3971-5

LT3971-3.3

10

–25

5

35

65

95

TEMPERATURE (°C)

125

155

5

10

3971 G05

15

20

25

30

INPUT VOLTAGE (V)

35

3971 G06

3971fd

4

LT3971/LT3971-3.3/LT3971-5

TYPICAL PERFORMANCE CHARACTERISTICS

LT3971 Feedback Voltage

1.205

1.200

FEEDBACK VOLTAGE (V)

OUTPUT VOLTAGE (V)

1.195

1.190

1.185

1.180

1.175

–55

3.345

3.330

3.315

3.300

3.285

3.270

3.255

–55

OUTPUT VOLTAGE (V)

T

A

= 25°C, unless otherwise noted.

LT3971-3.3 Output Voltage

5.06

5.04

5.02

5.00

4.98

4.96

LT3971-5 Output Voltage

–25

5

35

65

95

TEMPERATURE (°C)

125

155

–25

5

35

65

95

TEMPERATURE (°C)

125

155

4.94

–55

–25

5

35

65

95

TEMPERATURE (°C)

125

155

3971 G07

3971 G28

3971 G29

Maximum Load Current

3.0

2.5

LOAD CURRENT (A)

2.0

1.5

1.0

0.5

0

TYPICAL

MINIMUM

V

OUT

= 3.3V

2.5

Maximum Load Current

V

OUT

= 5V

0.30

0.25

0.20

LOAD REGULATION (%)

TYPICAL

MINIMUM

0.15

0.10

0.05

0

–0.05

–0.10

–0.15

–0.20

–0.25

–0.30

Load Regulation

2.0

1.5

1.0

0.5

5

10

15

20

25

30

INPUT VOLTAGE (V)

35

40

3971 G08

0

REFERENCED FROM V

OUT

AT 0.5A LOAD

0

200

400

600

800 1000

LOAD CURRENT (mA)

1200

5

10

25

30

15

20

INPUT VOLTAGE (V)

35

40

3971 G09

3971 G10

Switching Frequency

1000

950

900

FREQUENCY (kHz)

850

800

750

700

650

600

–55

–25

5

35

65

95

TEMPERATURE (°C)

125

155

SWITCH CURRENT LIMIT (A)

3.0

2.5

2.0

1.5

1.0

0.5

0

Switch Current Limit

2.5

2.4

SWITCH CURRENT LIMIT (A)

2.3

2.2

2.1

2.0

1.9

1.8

1.7

1.6

0

20

40

60

DUTY CYCLE (%)

80

100

3971 G12

Switch Current Limit

DUTY CYCLE = 30%

1.5

–55 –25

5

35

65

95

TEMPERATURE (°C)

125

155

3971 G11

3971 G13

3971fd

5

LT3971-3.3_15

LT3971-3.3_15概述

文档预览

LT3971-3.3_15相似产品对比

推荐资源