LT3748_15,LT3748_15 pdf中文资料,LT3748_15引脚图,LT3748

LT3748

100V Isolated

Flyback Controller

Features

n

Description

The

LT

®

3748

is a switching regulator controller specifically

designed for the isolated flyback topology and capable of

high power. It drives a low side external N-channel power

MOSFET from an internally regulated 7V supply. No third

winding or opto-isolator is required for regulation as the

part senses the isolated output voltage directly from the

primary-side flyback waveform.

The LT3748 utilizes boundary mode to provide a small

magnetic solution without compromising load regulation.

Operating frequency is set by load current and transformer

magnetizing inductance. The gate drive of the LT3748

combined with a suitable external MOSFET allow it to

deliver load power up to several tens of watts from input

voltages as high as 100V.

The LT3748 is available in a high voltage 16-lead MSOP

package with four leads removed.

L,

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

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

Protected by U.S. Patents, including 5438499 and 7471522.

n

5V to 100V Input Voltage Range

1.9A Average Gate Drive Source and Sink Current

Boundary Mode Operation

No Transformer Third Winding or Opto-Isolator

Required for Regulation

Primary-Side Winding Feedback Load Regulation

V

OUT

Set with Two External Resistors

INTV

CC

Pin for Control of Gate Driver Voltage

Programmable Soft Start

Programmable Undervoltage Lockout

Available in MSOP Package

applications

n

Isolated Telecom Converters

High Power Automotive Supplies

Isolated Industrial Power Supplies

Military and High Temperature Applications

typical application

25W, 12V Output, Isolated Telecom Supply

V

IN

36V TO 72V

10µF

412k

EN/UVLO

15.4k

V

IN

R

FB

R

REF

LT3748

TC

SS

V

C

56.2k

2nF

10k

4700pF

4.7µF

GND

GATE

SENSE

INTV

CC

0.033

3748 TA01a

4:1

60.8µH

243k

3.8µH

V

OUT+

12V

2A

100µF

V

OUT–

Output Load and Line Regulation

12.6

12.4

12.2

V

OUT

(V)

12.0

11.8

11.6

11.4

V

IN

= 72V

V

IN

= 48V

V

IN

= 36V

0

0.5

1.0

1.5

LOAD CURRENT (A)

2.0

3748 TA01b

6.04k

3748fb

For more information

www.linear.com/LT3748

1

LT3748

absolute MaxiMuM ratings

(Note 1)

pin conFiguration

TOP VIEW

V

IN

1

EN/UVLO 3

INTV

CC

GATE

SENSE

GND

5

6

7

8

16 R

FB

14 R

REF

12

11

10

9

TC

V

C

SS

GND

V

IN

, R

FB

...................................................................100V

V

IN

to R

FB

..................................................................±5V

EN/UVLO......................................................–0.3V, 100V

INTV

CC

....................................................V

IN

+ 0.3V, 20V

SS, V

C

, TC, R

REF

..........................................................6V

SENSE ......................................................................0.4V

Operating Junction Temperature Range (Note 2)

LT3748E/LT3748I ............................... –40°C to 125°C

LT3748H ............................................ –40°C to 150°C

LT3748MP ......................................... –55°C to 150°C

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

MS PACKAGE

16 (12)-LEAD PLASTIC MSOP

T

JMAX

= 150°C,

θ

JA

= 90°C/W

orDer inForMation

LEAD FREE FINISH

LT3748EMS#PBF

LT3748IMS#PBF

LT3748HMS#PBF

LT3748MPMS#PBF

TAPE AND REEL

LT3748EMS#TRPBF

LT3748IMS#TRPBF

LT3748HMS#TRPBF

LT3748MPMS#TRPBF

PART MARKING*

3748

PACKAGE DESCRIPTION

16-Lead Plastic MSOP

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/

electrical characteristics

PARAMETER

Input Voltage Range

Quiescent Current

V

IN

Quiescent Current, INTV

CC

Overdriven

INTV

CC

Voltage Range

INTV

CC

Pin Regulation Voltage

INTV

CC

Dropout

INTV

CC

Undervoltage Lockout

EN/UVLO Pin Threshold

EN/UVLO Pin Hysteresis Current

Soft-Start Current

Soft-Start Threshold

Soft-Start Reset Current

Not Switching

V

EN/UVLO

= 0.2V

V

INTVCC

= 10V

CONDITIONS

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 10V, unless otherwise noted.

MIN

l

TYP

1.3

0

300

MAX

100

1.75

1

450

20

7.2

3.75

1.25

2.9

UNITS

V

mA

µA

V

µA

V

mA

5

l

4.5

6.8

7

0.7

3.6

1.223

2.4

5

0.65

3

(V

IN

– V

INTVCC

), I

INTVCC

= 10mA, V

IN

= 5V

Falling Threshold

EN/UVLO Pin Voltage Rising

EN/UVLO = 1V

V

SS

= 0.4V (Note 3)

l

3.45

1.19

1.9

2

3748fb

For more information

www.linear.com/LT3748

LT3748

electrical characteristics

PARAMETER

Maximum SENSE Current Limit Threshold

Minimum SENSE Current Limit Threshold

Maximum to Minimum SENSE Threshold

Ratio

SENSE Overcurrent Threshold

SENSE Input Bias Current

R

REF

Voltage

R

REF

Voltage Line Regulation

R

REF

Pin Bias Current

TC Current into R

REF

Error Amplifier Voltage Gain

Error Amplifier Transconductance

V

C

Source Current

V

C

Sink Current

Flyback Comparator Trip Current

Minimum GATE Off-Time

Minimum GATE On-Time

Maximum Discontinuous Off-Time

Maximum GATE Off-Time

Maximum GATE On-Time

GATE Output Rise Time

GATE Output Fall Time

GATE Output Low (V

OL

)

GATE Output High (V

OH

)

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 LT3748E 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

V

INTVCC

– 0.05

V

C

= 0V

V

RREF

= 0.5V

V

SENSE

= 0V

C

L

= 3300pF, 10% to 90%

C

L

= 3300pF, 10% to 90%

∆I

= 10µA

V

C

= 1.1V, V

RREF

= 0.5V

V

C

= 1.1V, V

RREF

= 2V

Current into R

FB

Pin, R

REF

= 6.04k

V

C

= 2.2V

V

SENSE

= 10mV (Note 3)

V

C

= 1.1V

l

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 10V, unless otherwise noted.

CONDITIONS

V

C

= 2.2V

l

MIN

95

90

5.2

115

10

1.20

1.195

TYP

100

15

6.6

130

15

1.223

0.005

MAX

105

110

8.2

145

20

1.24

1.245

0.025

500

UNITS

mV

mV/mV

mV

µA

V

%/V

nA

µA

V/V

µmhos

µA

ns

µs

ns

V

C

= 0V

l

5V < V

IN

< 100V

(Note 3)

R

TC

= 20k

l

35

27.5

115

155

–45

48

10

700

250

24

55

16

0.05

V

LT3748I is guaranteed over the full –40°C to 125°C operating junction

temperature range. The LT3748H is guaranteed over the full –40°C to

150°C operating junction temperature range. The LT3748MP is guaranteed

over the full –55°C to 150°C operating junction temperature range. High

junction temperatures degrade operating lifetimes. Operating lifetime is

derated at junction temperatures greater than 125°C.

Note 3:

Current flows out of the pin.

3748fb

For more information

www.linear.com/LT3748

3

LT3748

typical perForMance characteristics

T

A

= 25°C, unless otherwise noted.

Output Regulation vs Temperature

15.6

15.4

15.2

V

OUT

(V)

15.0

14.8

14.6

14.4

–55 –25

FIGURE 16 CIRCUIT

I

OUT

= 150mA ON EACH OUTPUT

V

IN

= 12V

1.7

Quiescent Current vs Temperature

V

SS

= 0V

1.6 INTV

CC

= OPEN

QUIESCENT CURRENT (mA)

1.5

1.4

1.3

1.2

1.1

1.0

0.9

V

IN

= 12V

V

IN

= 6V

V

IN

= 72V

V

IN

= 36V

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G02

Quiescent Current vs V

IN

Voltage

V

SS

= 0V

INTV

CC

= OPEN

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G01

0.8

–55 –25

0

20

40

60

V

IN

(V)

80

100

3748 G03

INTV

CC

Voltage vs Temperature

7.5

7.4

7.3

INTV

CC

VOLTAGE (V)

7.2

V

INTVCC

(V)

7.1

7.0

6.9

6.8

6.7

6.6

6.5

–55 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G04

INTV

CC

Voltage vs V

IN

Voltage

7.5

7.0

6.5

I

INTVCC

= 0mA

I

INTVCC

= 10mA

INTV

CC

UVLO (V)

4.0

3.9

3.8

3.7

3.6

3.5

3.4

4

6

8

10

20

40

60

80

100

INTV

CC

Undervoltage Lockout

vs Temperature

I

INTVCC

= 0mA

6.0

5.5

5.0

4.5

4.0

RISING THRESHOLD

FALLING THRESHOLD

I

INTVCC

= 10mA

3.3

–55 –25

0

V

IN

VOLTAGE (V)

3748 G05

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G06

3.0

INTV

CC

REGULATOR DROPOUT (V)

2.5

INTV

CC

Regulator Dropout

vs INTV

CC

Current

V

IN

= 5V

3.0

2.5

INTV

CC

DROPOUT (V)

2.0

1.5

INTV

CC

Dropout vs Temperature

V

IN

= 5V

SOFT-START CURRENT (µA)

6

5

4

3

2

1

Soft-Start Current vs Temperature

2.0

1.5

1.0

0.5

0

150°C

100°C

25°C

–50°C

0

10

20

30

INTV

CC

CURRENT (mA)

40

3748 G07

I

INTVCC

= 20mA

I

INTVCC

= 10mA

1.0

0.5

I

INTVCC

= 5mA

0

–55 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G08

0

–55 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G09

4

3748fb

For more information

www.linear.com/LT3748

LT3748

typical perForMance characteristics

EN/UVLO Current vs Temperature

3.0

2.5

EN/UVLO CURRENT (µA)

2.0

1.5

1.0

0.5

0

–55 –25

V

EN/UVLO

= 1.3V

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G10

T

A

= 25°C, unless otherwise noted.

EN/UVLO Threshold

vs Temperature

1.40

1.35

EN/UVLO THRESHOLD (V)

0.9

0.8

0.7

TC VOLTAGE (V)

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G11

TC Pin Voltage vs Temperature

V

EN/UVLO

= 1.1V

V

EN/UVLO

= 0.9V

1.30

1.25

1.20

1.15

1.10

1.05

1.00

–55 –25

0

0.6

0.5

0.4

0.3

0.2

0.1

0

–55 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G12

Error Amplifier Transconductance

vs Temperature

200

190

TRANSCONDUCTANCE (µmhos)

180

170

I

VC

(µA)

160

150

140

130

120

110

100

–55 –25

0

V

IN

= 100V

V

IN

= 6V

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G13

60

50

40

Error Amplifier Output Current

vs R

REF

Pin Voltage

160

140

SENSE THRESHOLD (mV)

120

100

80

60

40

20

1.5

1.0

V

REF

(V)

2.0

2.5

3748 G14

SENSE Pin Threshold

vs Temperature

OVERCURRENT

30

20

10

0

–10

–20

–30

–40

–50

–60

0

150°C

100°C

25°C

–50°C

0.5

V

C

= 2.2V

V

C

= 0.2V

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G15

0

–55 –25

Maximum Discontinuous Off-Time

vs Temperature

30

MAXIMUM DISCONTINUOUS OFF-TIME (µs)

29

GATE RISE AND FALL TIME (ns)

28

27

26

25

24

23

22

21

20

–55 –25

0

25 50 75 100 125 150

TEMPERATURE (°C)

3748 G16

GATE Rise and Fall Time vs Charge

2.0

AVERAGE

CURRENT

50

40

RISE TIME

30

FALL TIME

20

10

0

20

Q=C•V

V

INTVCC

= 7V

t

r

, t

f

10% TO 90%

40

60

80

100

TOTAL GATE CHARGE (nC)

120

0

1.5

1.0

0.5

25

GATE RISE AND FALL TIME (ns)

20

AVERAGE GATE SOURCE, SINK CURRENT (A)

GATE Rise and Fall Time

vs INTV

CC

Voltage

C

GATE

= 3.3nF

t

r

, t

f

10% TO 90%

FALLING

RISING

15

10

5

0

5

10

V

INTVCC

(V)

15

20

3748 G18

3748 G17

3748fb

For more information

www.linear.com/LT3748

5

LT3748_15

LT3748_15概述

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