LTC3787_15,LTC3787_15 pdf中文资料,LTC3787_15引脚图,LTC3787

LTC3787

PolyPhase Synchronous

Boost Controller

FEATURES

n

DESCRIPTION

The LTC

®

3787 is a high performance PolyPhase

®

single

output synchronous boost converter controller that drives

two N-channel power MOSFET stages out-of-phase.

Multiphase operation reduces input and output capacitor

requirements and allows the use of smaller inductors than

the single-phase equivalent. Synchronous rectification in-

creases efficiency, reduces power losses and eases thermal

requirements, enabling high power boost applications.

A 4.5V to 38V input supply range encompasses a wide

range of system architectures and battery chemistries.

When biased from the output of the boost converter or

another auxiliary supply, the LTC3787 can operate from

an input supply as low as 2.5V after start-up. The operat-

ing frequency can be set for a 50kHz to 900kHz range or

synchronized to an external clock using the internal PLL.

PolyPhase operation allows the LTC3787 to be configured

for 2-, 3-, 4-, 6- and 12-phase operation.

The SS pin ramps the output voltage during start-up. The

PLLIN/MODE pin selects Burst Mode

®

operation, pulse-

skipping mode or forced continuous mode at light loads.

L,

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

are registered trademarks and No R

SENSE

and ThinSOT are trademarks of Linear Technology

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

U. S. Patents, including 5408150, 5481178, 5705919, 5929620, 6144194, 6177787, 6580258.

2-Phase Operation Reduces Required Input and

Output Capacitance and Power Supply Induced Noise

Synchronous Operation for Highest Efficiency and

Reduced Heat Dissipation

Wide V

IN

Range: 4.5V to 38V (40V Abs Max) and

Operates Down to 2.5V After Start-Up

Output Voltage Up to 60V

±1% 1.200V Reference Voltage

R

SENSE

or Inductor DCR Current Sensing

100% Duty Cycle Capability for Synchronous MOSFET

Low Quiescent Current: 135μA

Phase-Lockable Frequency (75kHz to 850kHz)

Programmable Fixed Frequency (50kHz to 900kHz)

Power Good Output Voltage Monitor

Low Shutdown Current, I

Q

< 8μA

Internal LDO Powers Gate Drive from VBIAS or EXTV

CC

Thermally Enhanced Low Profile 28-Pin 4mm × 5mm

QFN Package and Narrow SSOP Package

APPLICATIONS

n

Industrial

Automotive

Medical

Military

TYPICAL APPLICATION

12V to 24V/10A 2-Phase Synchronous Boost Converter

V

IN

4.5V TO 24V START-UP VOLTAGE

OPERATES THROUGH TRANSIENTS DOWN TO 2.5V

V

IN

Efficiency and Power Loss

vs Output Current

100

90

10000

4mΩ

4.7μF

TG1 VBIAS INTV

CC

4.7μF

TG2

4mΩ

47μF

80

EFFICIENCY (%)

70

60

50

40

30

1000

POWER LOSS (mW)

100

3.3μH

0.1μF

BOOST1

SW1

BOOST2

SW2

3.3μH

0.1μF

V

OUT

24V AT 10A

10

232k

LTC3787

BG1

BG2

SENSE1

+

SENSE1

–

SENSE2

+

VFB

SENSE2

–

FREQ

PGND

PLLIN/MODE

ITH SS SGND

12.1k

15nF

8.66k

100pF

0.1μF

3787 TA01a

V

IN

= 12V

1

V

OUT

= 24V

10

Burst Mode OPERATION

FIGURE 10 CIRCUIT

0

0.1

1

10

0.00001 0.0001 0.001 0.01

OUTPUT CURRENT (A)

20

220μF

3787 TA01b

BURST EFFICIENCY

BURST LOSS

3787fc

1

LTC3787

ABSOLUTE MAXIMUM RATINGS

(Notes 1, 3)

VBIAS ........................................................ –0.3V to 40V

BOOST1 and BOOST2 ................................ –0.3V to 76V

SW1 and SW2............................................ –0.3V to 70V

RUN ............................................................. –0.3V to 8V

Maximum Current Sourced into Pin

From Source >8V ..............................................100μA

PGOOD, PLLIN/MODE ................................. –0.3V to 6V

INTV

CC

, (BOOST1 - SW1), (BOOST2 - SW2) ...–0.3V to 6V

EXTV

CC

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

SENSE1

+

, SENSE1

–

, SENSE2

+

, SENSE2

–

... –0.3V to 40V

(SENSE1

+

- SENSE1

–

), (SENSE2

+

- SENSE2

–

) ...–0.3V to 0.3V

ILIM, SS, ITH, FREQ, PHASMD, VFB ..... –0.3V to INTV

CC

Operating Junction Temperature

Range (Note 2)........................................–55°C to 150°C

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

PIN CONFIGURATION

TOP VIEW

SENSE1

–

ILIM

SENSE1

+

SENSE1

–

FREQ

PHASMD

CLKOUT

PLLIN/MODE

SGND

RUN

1

2

3

4

5

6

7

8

9

28 PGOOD

27 SW1

26 TG1

25 BOOST1

24 BG1

23 VBIAS

22 PGND

21 EXTV

CC

20 INTV

CC

19 BG2

18 BOOST2

17 TG2

16 SW2

15 NC

FREQ 1

PHASMD 2

CLKOUT 3

PLLIN/MODE 4

SGND 5

RUN 6

SS 7

SENSE2

–

8

9 10 11 12 13 14

VFB

SENSE2

+

ITH

NC

SW2

TG2

29

GND

TOP VIEW

SENSE1

+

PGOOD

SW1

ILIM

TG1

22 BOOST1

21 BG1

20 VBIAS

19 PGND

18 EXTV

CC

17 INTV

CC

16 BG2

15 BOOST2

28 27 26 25 24 23

SS 10

SENSE2

–

11

SENSE2

+

12

VFB 13

ITH 14

GN PACKAGE

28-LEAD PLASTIC SSOP

T

JMAX

= 125°C,

θ

JA

= 90°C/W

UFD PACKAGE

28-LEAD (4mm 5mm) PLASTIC QFN

T

JMAX

= 125°C,

θ

JA

= 43°C/W

EXPOSED PAD (PIN 29) IS GND, MUST BE CONNECTED TO GND

ORDER INFORMATION

LEAD FREE FINISH

LTC3787EUFD#PBF

LTC3787IUFD#PBF

LTC3787HUFD#PBF

LTC3787MPUFD#PBF

LTC3787EGN#PBF

LTC3787IGN#PBF

LTC3787HGN#PBF

LTC3787MPGN#PBF

TAPE AND REEL

LTC3787EUFD#TRPBF

LTC3787IUFD#TRPBF

LTC3787HUFD#TRPBF

LTC3787MPUFD#TRPBF

LTC3787EGN#TRPBF

LTC3787IGN#TRPBF

LTC3787HGN#TRPBF

LTC3787MPGN#TRPBF

PART MARKING*

3787

LTC3787GN

PACKAGE DESCRIPTION

28-Lead (4mm

×

5mm) Plastic QFN

28-Lead (4mm

×

5mm) Plastic QFN

28-Lead (4mm

×

5mm) Plastic QFN

28-Lead (4mm

×

5mm) Plastic QFN

28-Lead Plastic SSOP

TEMPERATURE RANGE

–40°C to 125°C

–40°C to 150°C

–55°C to 150°C

–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/

3787fc

2

LTC3787

ELECTRICAL CHARACTERISTICS

SYMBOL

VBIAS

V

FB

I

FB

V

REFLNREG

V

LOADREG

PARAMETER

Chip Bias Voltage Operating Range

Regulated Feedback Voltage

Feedback Current

Reference Line Voltage Regulation

Output Voltage Load Regulation

(Note 4)

I

TH

= 1.2V (Note 4)

(Note 4)

VBIAS = 6V to 38V

Measured in Servo Loop;

ΔI

TH

Voltage = 1.2V to 0.7V

Measured in Servo Loop;

ΔI

TH

Voltage = 1.2V to 2V

g

m

I

Q

Error Amplifier Transconductance

Input DC Supply Current

Pulse-Skipping or Forced Continuous Mode

Sleep Mode

Shutdown

INTV

CC

Undervoltage Lockout Thresholds

RUN Pin ON Threshold

RUN Pin Hysteresis

RUN Pin Hysteresis Current

RUN Pin Current

Soft-Start Charge Current

Maximum Current Sense Threshold

V

RUN

> 1.28V

V

RUN

< 1.28V

V

SS

= GND

V

FB

= 1.1V, I

LIM

= INTV

CC

V

FB

= 1.1V, I

LIM

= Float

V

FB

= 1.1V, I

LIM

= GND

V

FB

= 1.1V, I

LIM

= INTV

CC

V

FB

= 1.1V, I

LIM

= Float

V

FB

= 1.1V, I

LIM

= GND

l

The

l

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T

A

= 25°C, VBIAS = 12V, unless otherwise noted (Note 2).

CONDITIONS

MIN

4.5

1.188

1.200

±5

0.002

0.01

–0.01

2

1.2

135

8

l

TYP

MAX

38

1.212

±50

0.02

0.1

–0.1

UNITS

V

nA

%/V

%

mmho

mA

μA

V

mV

μA

Main Control Loop

I

TH

= 1.2V

(Note 5)

RUN = 5V; V

FB

= 1.25V (No Load)

RUN = 5V; V

FB

= 1.25V (No Load)

RUN = 0V

V

INTVCC

Ramping Up

V

INTVCC

Ramping Down

V

RUN

Rising

3.6

1.18

300

20

4.3

1.38

UVLO

V

RUN

V

RUNHYS

I

RUNHYS

I

RUN

I

SS

V

SENSE1,2(MAX)

4.1

3.8

1.28

100

4.5

0.5

7

90

68

42

–12

–10

–9

2.5

10

100

75

50

0

13

110

82

56

12

10

9

38

μA

mV

V

μA

ns

Ω

ns

%

ns

3787fc

V

SENSE(MATCH)

Matching Between V

SENSE1(MAX)

and

V

SENSE2(MAX)

SENSE Pins Common Mode Range (BOOST

Converter Input Supply Voltage V

IN

)

SENSE

+

Pin Current

SENSE

–

Pin Current

Top Gate Rise Time

Top Gate Fall Time

Bottom Gate Rise Time

Bottom Gate Fall Time

Top Gate Pull-Up Resistance

Top Gate Pull-Down Resistance

Bottom Gate Pull-Up Resistance

Bottom Gate Pull-Down Resistance

Top Gate Off to Bottom Gate On Switch-On

Delay Time

Bottom Gate Off to Top Gate On Switch-On

Delay Time

Maximum BG Duty Factor

Minimum BG On-Time

V

SENSE(CM)

I

SENSE1,2+

I

SENSE1,2–

t

r(TG1,2)

t

f(TG1,2)

t

r(BG1,2)

t

r(BG1,2)

R

UP(TG1,2)

R

DN(TG1,2)

R

UP(TG1,2)

R

DN(TG1,2)

t

D(TG/BG)

t

D(BG/TG)

DF

BG1,2(MAX)

t

ON(MIN)

V

FB

= 1.1V, I

LIM

= Float

V

FB

= 1.1V, I

LIM

= Float

C

LOAD

= 3300pF (Note 6)

C

LOAD

= 3300pF (Note 6)

C

LOAD

= 3300pF (Note 6)

C

LOAD

= 3300pF (Note 6)

200

20

1.2

300

±1

C

LOAD

= 3300pF (Each Driver)

C

LOAD

= 3300pF (Each Driver)

70

96

(Note 7)

110

3

LTC3787

ELECTRICAL CHARACTERISTICS

SYMBOL

V

INTVCC(VIN)

VLDO INT

V

INTVCC(EXT)

VLDO EXT

V

EXTVCC

V

LDOHYS

f

PROG

PARAMETER

Internal V

CC

Voltage

INTV

CC

Load Regulation

Internal V

CC

Voltage

INTV

CC

Load Regulation

EXTV

CC

Switchover Voltage

EXTV

CC

Hysteresis

Programmable Frequency

R

FREQ

= 25k

R

FREQ

= 60k

R

FREQ

= 100k

V

FREQ

= 0V

V

FREQ

= INTV

CC

PLLIN/MODE = External Clock

I

PGOOD

= 2mA

V

PGOOD

= 5V

V

FB

with Respect to Set Regulated Voltage

V

FB

Ramping Negative

Hysteresis

V

FB

Ramping Positive

Hysteresis

t

PGOOD(DELAY)

I

BOOST1,2

PGOOD Delay

BOOST Charge Pump Available Output

Current

PGOOD Going High to Low

V

SW1,2

= 12V; V

BOOST1,2

– V

SW1,2

= 4.5V;

FREQ = 0V, Forced Continuous or

Pulse-Skipping Mode

BOOST1 and BOOST2 Charge Pump

55

μA

–12

8

–10

2.5

10

2.5

25

–8

12

%

μs

l

The

l

denotes the specifications which apply over the specified operating

junction temperature range, otherwise specifications are at T

A

= 25°C, VBIAS = 12V, unless otherwise noted (Note 2).

CONDITIONS

6V < V

BIAS

< 38V, V

EXTVCC

= 0

I

CC

= 0mA to 50mA

V

EXTVCC

= 6V

I

CC

= 0mA to 40mA, V

EXTVCC

= 6V

EXTV

CC

Ramping Positive

l

MIN

5.2

4.5

TYP

5.4

0.5

5.4

0.5

4.8

250

105

400

760

350

535

MAX

5.6

2

5.6

2

5

UNITS

V

%

V

%

V

mV

kHz

V

μA

INTV

CC

Linear Regulator

Oscillator and Phase-Locked Loop

335

320

488

75

0.2

465

380

585

850

0.4

±1

f

LOW

f

HIGH

f

SYNC

PGOOD Output

V

PGL

I

PGOOD

V

PGOOD

Lowest Fixed Frequency

Highest Fixed Frequency

Synchronizable Frequency

PGOOD Voltage Low

PGOOD Leakage Current

PGOOD Trip Level

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 LTC3787 is tested under pulsed load conditions such that

T

J

≈ T

A

. The LTC3787E is guaranteed to meet specifications from

0°C to 85°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

LTC3787I is guaranteed over the –40°C to 125°C operating junction

temperature range, the LTC3787H is guaranteed over the –40°C to 150°C

operating temperature range and the LTC3787MP is tested and guaranteed

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

junction temperatures degrade operating lifetimes; operating lifetime

is derated for junction temperatures greater than 125°C. Note that the

maximum ambient temperature consistent with these specifications is

determined by specific operating conditions in conjunction with board

layout, the rated package thermal impedance and other environmental

factors. The junction temperature (T

J

, in °C) is calculated from the ambient

temperature (T

A

, in °C) and power dissipation (P

D

, in Watts) according to

the formula: T

J

= T

A

+ (P

D

•

θ

JA

), where

θ

JA

= 43°C/W for the QFN package

and

θ

JA

= 90°C/W for the SSOP package.

Note 3:

This IC includes overtemperature protection that is intended to

protect the device during momentary overload conditions. The maximum

rated junction temperature will be exceeded when this protection is active.

Continuous operation above the specified absolute maximum operating

junction temperature may impair device reliability or permanently damage

the device.

Note 4:

The LTC3787 is tested in a feedback loop that servos V

FB

to the

output of the error amplifier while maintaining I

TH

at the midpoint of the

current limit range.

Note 5:

Dynamic supply current is higher due to the gate charge being

delivered at the switching frequency.

Note 6:

Rise and fall times are measured using 10% and 90% levels. Delay

times are measured using 50% levels.

Note 7:

see Minimum On-Time Considerations in the Applications

Information section.

3787fc

4

LTC3787

TYPICAL PERFORMANCE CHARACTERISTICS

Efficiency and Power Loss

vs Output Current

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

10

0

0.01

V

IN

= 12V

V

OUT

= 24V

FIGURE 10 CIRCUIT

0.1

1

OUTPUT CURRENT (A)

10

3787 G01

Efficiency and Power Loss

vs Output Current

10000

100

90

10000

1000

POWER LOSS (mW)

80

EFFICIENCY (%)

70

60

50

40

30

1000

POWER LOSS (mW)

100

10

1

0.1

V

IN

= 12V

1

V

OUT

= 24V

10

Burst Mode OPERATION

FIGURE 10 CIRCUIT

0

0.1

1

10

0.00001 0.0001 0.001 0.01

OUTPUT CURRENT (A)

20

3787 G02

BURST EFFICIENCY

PULSE-SKIPPING

EFFICIENCY

FORCED CONTINUOUS

MODE EFFICIENCY

BURST LOSS

PULSE-SKIPPING

LOSS

FORCED CONTINUOUS

MODE LOSS

BURST EFFICIENCY

BURST LOSS

Efficiency vs Load Current

100

99

98

EFFICIENCY (%)

97

96

95

94

93

92

91

90

0

5

15

10

INPUT VOLTAGE (V)

20

25

3787 G03

Load Step

Forced Continuous Mode

LOAD STEP

5A/DIV

V

IN

= 12V

I

LOAD

= 2A

FIGURE 10 CIRCUIT

V

OUT

= 12V

V

OUT

= 24V

INDUCTOR

CURRENT

5A/DIV

V

OUT

500mV/DIV

200μs/DIV

V

IN

= 12V

V

OUT

= 24V

LOAD STEP FROM 100mA TO 5A

FIGURE 10 CIRCUIT

3787

G04

Load Step

Burst Mode Operation

LOAD STEP

5A/DIV

INDUCTOR

CURRENT

5A/DIV

V

OUT

500mV/DIV

LOAD STEP

5A/DIV

Load Step

Pulse-Skipping Mode

INDUCTOR

CURRENT

5A/DIV

V

OUT

500mV/DIV

3787

G05

3787

G06

200μs/DIV

V

IN

= 12V

V

OUT

= 24V

LOAD STEP FROM 100mA TO 5A

FIGURE 10 CIRCUIT

200μs/DIV

V

IN

= 12V

V

OUT

= 24V

LOAD STEP FROM 100mA TO 5A

FIGURE 10 CIRCUIT

3787fc

5

LTC3787_15

LTC3787_15概述

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