LTC3851IUD-1-TRPBF,LTC3851IUD-1-TRPBF pdf中文资料,LTC3851IUD-1-TRPBF引脚图,LTC3851IUD-1-TRPBF电路-Datasheet-电子工程世界

FEATURES

n

LTC3851-1

Synchronous

Step-Down Switching

Regulator Controller

DESCRIPTION

The LTC

®

3851-1 is a high performance synchronous

step-down switching regulator controller that drives

an all N-channel synchronous power MOSFET stage. A

constant frequency current mode architecture allows a

phase-lockable frequency of up to 750kHz.

OPTI-LOOP compensation allows the transient response

to be optimized over a wide range of output capacitance

and ESR values. The LTC3851-1 features a precision 0.8V

reference and a power good indicator. A wide 4V to 38V (40V

absolute maximum) input supply range encompasses most

battery conﬁgurations and intermediate bus voltages.

The TK/SS pin ramps the output voltage during start-up

and shutdown with coincident or ratiometric tracking.

Current foldback limits MOSFET heat dissipation during

short-circuit conditions. The MODE/PLLIN pin selects

among Burst Mode operation, pulse skipping mode or

continuous inductor current mode at light loads and allows

the IC to be synchronized to an external clock.

The LTC3851-1 is identical to the LTC3851 except that the

I

LIM

pin is replaced by PGOOD.

L,

LT, LTC, LTM, Burst Mode and OPTI-LOOP are registered 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, 6304066,

6498466, 6580258, 6611131.

Wide V

IN

Range: 4V to 38V Operation

R

SENSE

or DCR Current Sensing

±1% Output Voltage Accuracy

Power Good Output Voltage Monitor

Phase-Lockable Fixed Frequency: 250kHz to 750kHz

Dual N-Channel MOSFET Synchronous Drive

Very Low Dropout Operation: 99% Duty Cycle

Adjustable Output Voltage Soft-Start or Tracking

Output Current Foldback Limiting

Output Overvoltage Protection

OPTI-LOOP

®

Compensation Minimizes C

OUT

Selectable Continuous, Pulse-Skipping or

Burst Mode

®

Operation at Light Loads

Low Shutdown I

Q

: 20μA

V

OUT

Range: 0.8V to 5.5V

Thermally Enhanced 16-Lead MSOP

or 3mm

×

3mm QFN Package

APPLICATIONS

n

Automotive Systems

Telecom Systems

Industrial Equipment

Distributed DC Power Systems

TYPICAL APPLICATION

High Efﬁciency Synchronous Step-Down Converter

100k

INTV

CC

82.5k

0.1μF

PGO0D

V

IN

0.68μH

0.1μF

3.01k

INTV

CC

I

TH

15k

330pF

PLLIN/MODE

SENSE

–

V

FB

BG

GND

SENSE

+

0.047μF

30.1k

154k

4.7μF

FREQ/PLLFLTR TG

RUN

SW

LTC3851-1

BOOST

TK/SS

22μF

V

IN

4.5V TO 38V

V

OUT

3.3V

15A

330μF

2

Efﬁciency and Power Loss

vs Load Current

100

V

IN

= 12V

95 V

OUT

= 3.3V

EFFICIENCY

POWER LOSS (mW)

1000

POWER LOSS

10000

90

EFFICIENCY (%)

85

80

75

70

65

60

55

50

10

0.1μF

2200pF

100

48.7k

38511 TA01a

100

1000

10000

LOAD CURRENT (mA)

10

100000

38511TA01b

38511f

1

LTC3851-1

ABSOLUTE MAXIMUM RATINGS

(Note 1)

Input Supply Voltage (V

IN

) ......................... 40V to –0.3V

Topside Driver Voltage (BOOST) ................ 46V to –0.3V

Switch Voltage (SW) ..................................... 40V to –5V

INTV

CC

, (BOOST – SW), RUN, PGOOD ........ 6V to –0.3V

TK/SS .................................................... INTV

CC

to –0.3V

SENSE

+

, SENSE

–

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

MODE/PLLIN, FREQ/PLLFLTR ............... INTV

CC

to –0.3V

I

TH

, V

FB

Voltages .......................................... 3V to –0.3V

INTV

CC

Peak Output Current ..................................50mA

Operating Junction Temperature Range

(Notes 2, 3) ............................................ –40°C to 125°C

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

Lead Temperature (Soldering, 10 sec)

MSE .................................................................. 300°C

PIN CONFIGURATION

FREQ/PLLFLTR

TOP VIEW

MODE/PLLIN

SW

MODE/PLLIN

FREQ/PLLFLTR

RUN

TK/SS

I

TH

FB

SENSE

–

SENSE

+

1

2

3

4

5

6

7

8

17

16

15

14

13

12

11

10

9

SW

TG

BOOST

V

IN

INTV

CC

BG

GND

PGOOD

16 15 14 13

RUN 1

TK/SS 2

I

TH

3

FB 4

5

SENSE

–

6

+

TG

12 BOOST

11 V

IN

10 INTV

CC

9

BG

8

GND

TOP VIEW

17

T

JMAX

= 125°C,

θ

JA

= 35°C/W TO 40°C/W

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

UD PACKAGE

16-LEAD (3mm 3mm) PLASTIC QFN

T

JMAX

= 125°C,

θ

JA

= 68°C/W,

θ

JC

= 4.2°C/W

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

ORDER INFORMATION

LEAD FREE FINISH

LTC3851EMSE-1#PBF

LTC3851IMSE-1#PBF

LTC3851EUD-1#PBF

LTC3851IUD-1#PBF

TAPE AND REEL

LTC3851EMSE-1#TRPBF

LTC3851IMSE-1#TRPBF

LTC3851EUD-1#TRPBF

LTC3851IUD-1#TRPBF

PART MARKING*

38511

LDNT

PACKAGE DESCRIPTION

16-Lead Plastic MSOP

16-Lead (3mm

×

3mm) Plastic QFN

16-Lead (3mm

×

3mm) Plastic QFN

TEMPERATURE RANGE

–40°C to 85°C

–40°C to 125°C

–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/

SENSE

PGOOD

MSE PACKAGE

16-LEAD PLASTIC MSOP

7

38511f

2

LTC3851-1

ELECTRICAL CHARACTERISTICS

SYMBOL

V

IN

V

FB

I

FB

V

REFLNREG

V

LOADREG

PARAMETER

Input Operating Voltage Range

Regulated Feedback Voltage

Feedback Current

Reference Voltage Line Regulation

Output Voltage Load Regulation

I

TH

= 1.2V (Note 4)

(Note 4)

V

IN

= 6V to 38V (Note 4)

(Note 4)

Measured in Servo Loop,

ΔI

TH

= 1.2V to 0.7V

(Note 4)

Measured in Servo Loop,

ΔI

TH

= 1.2V to 1.6V

g

m

g

m

GBW

I

Q

Transconductance Ampliﬁer g

m

Transconductance Amp Gain Bandwidth

Input DC Supply Current

Normal Mode

Shutdown

Undervoltage Lockout on INTV

CC

UVLO Hysteresis

Feedback Overvoltage Lockout

SENSE Pins Total Current

Soft-Start Charge Current

RUN Pin On Threshold

RUN Pin On Hysteresis

Maximum Current Sense Threshold

TG Driver Pull-Up On-Resistance

TG Driver Pull-Down On-Resistance

BG Driver Pull-Up On-Resistance

BG Driver Pull-Down On-Resistance

TG Transition Time

Rise Time

Fall Time

BG Transition Time

Rise Time

Fall Time

Top Gate Off to Bottom Gate On Delay

Synchronous Switch-On Delay Time

Bottom Gate Off to Top Gate On Delay

Top Switch-On Delay Time

Minimum On-Time

Internal V

CC

Voltage

INTV

CC

Load Regulation

V

FB

= 0.7V, V

SENSE

= 3.3V

TG High

TG Low

BG High

BG Low

(Note 6)

C

LOAD

= 3300pF

C

LOAD

= 3300pF

(Note 6)

C

LOAD

= 3300pF

C

LOAD

= 3300pF

C

LOAD

= 3300pF Each Driver

C

LOAD

= 3300pF Each Driver

(Note 7)

6V < V

IN

< 38V

I

CC

= 0mA to 50mA

4.8

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

= 15V, V

RUN

= 5V unless otherwise noted.

CONDITIONS

MIN

4

0.792

0.800

–10

0.002

0.01

TYP

MAX

38

0.808

–50

0.02

0.1

UNITS

V

nA

%/V

%

Main Control Loops

l

–0.01

2

3

1

20

3.25

0.4

–0.1

%

mmho

MHz

mA

μA

V

I

TH

= 1.2V, Sink/Source = 5μA (Note 4)

I

TH

= 1.2V

(Note 5)

V

OUT

= 5V

V

RUN

= 0V

V

INTVCC

Ramping Down

Measured at V

FB

V

TK/SS

= 0V

V

RUN

Rising

l

35

UVLO

UVLO Hys

V

OVL

I

SENSE

I

TK/SS

V

RUN

V

RUNHYS

V

SENSE(MAX)

TG R

UP

TG R

DOWN

BG R

UP

BG R

DOWN

TG t

r

TG t

f

BG tr

BG tf

TG/BG t

1D

BG/TG t

2D

t

ON(MIN)

V

INTVCC

V

LDO

INT

0.86

0.6

1.10

40

0.88

±1

1

1.22

130

50

2.6

1.5

2.4

1.1

25

30

90

5

0.5

0.90

±2

2

1.35

65

V

μA

V

mV

Ω

ns

INTV

CC

Linear Regulator

5.2

V

%

38511f

3

LTC3851-1

ELECTRICAL CHARACTERISTICS

SYMBOL

f

NOM

f

LOW

f

HIGH

R

MODE/PLLIN

I

FREQ

PARAMETER

Nominal Frequency

Lowest Frequency

Highest Frequency

MODE/PLLIN Input Resistance

Phase Detector Output Current

Sinking Capability

Sourcing Capability

PGOOD Voltage Low

PGOOD Leakage Current

PGOOD Trip Level

f

MODE

> f

OSC

f

MODE

< f

OSC

I

PGOOD

= 2mA

V

PGOOD

= 5V

V

FB

with Respect to Set Regulated Voltage

V

FB

Ramping Negative

V

FB

Ramping Positive

–12

8

–10

10

Oscillator and Phase-Locked Loop

R

FREQ

= 60k

R

FREQ

= 160k

R

FREQ

= 36k

480

220

710

500

250

750

100

–10

10

0.1

0.3

±1

–8

12

530

280

790

kHz

kΩ

μA

V

μA

%

The

l

denotes the speciﬁcations which apply over the full operating

junction temperature range, otherwise speciﬁcations are at T

A

= 25°C. V

IN

= 15V, V

RUN

= 5V unless otherwise noted.

CONDITIONS

MIN

TYP

MAX

UNITS

PGOOD Output

V

PGL

I

PGOOD

V

PG

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 LTC3851E-1 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 LTC3851I-1 is guaranteed

over the –40°C to 125°C operating junction temperature range.

Note 3:

T

J

is calculated from the ambient temperature T

A

and power

dissipation P

D

according to the following formulas:

LTC3851MSE-1: T

J

= T

A

+ (P

D

• 90°C/W)

LTC3851UD-1: T

J

= T

A

+ (P

D

• 68°C/W)

Note 4:

The LTC3851-1 is tested in a feedback loop that servos V

ITH

to a

speciﬁed voltage and measures the resultant V

FB

.

Note 5:

Dynamic supply current is higher due to the gate charge being

delivered at the switching frequency. See Applications Information.

Note 6:

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

times are measured using 50% levels.

Note 7:

The minimum on-time condition is speciﬁed for an inductor

peak-to-peak ripple current ~40% of I

MAX

(see Minimum On-Time

Considerations in the Applications Information section).

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency vs Output Current and

Mode

100

V

IN

= 12V

90 V

OUT

= 1.5V

BURST

PULSE

SKIP

EFFICIENCY(%)

100

90

80

EFFICIENCY (%)

70

60

50

40

30

20

10

0

10

100

1000

10000

LOAD CURRENT (mA)

100000

38511 G01

Efﬁciency vs Output Current

and Mode

100

BURST

90

80

70

60

50

40

30

V

IN

= 12V

V

OUT

= 3.3V

FIGURE 11 CIRCUIT

10

100

1000

10000

LOAD CURRENT (mA)

100000

38511 G02

Efﬁciency vs Output Current and

Mode

80

70

EFFICIENCY(%)

60

50

40

30

20

10

0

BURST

PULSE

SKIP

CCM

PULSE

SKIP

CCM

20

10

0

10

V

IN

= 12V

V

OUT

= 5V

100

1000

10000

LOAD CURRENT (mA)

100000

38511 G03

38511f

4

LTC3851-1

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency and Power Loss vs

Input Voltage

100

95

90

85

80

75

70

4

8

16

12

24

20

INPUT VOLTAGE (V)

28

32

1000

EFFICIENCY,

I

OUT

= 5A

POWER LOSS,

I

OUT

= 5A

POWER LOSS (mW)

10000

I

LOAD

5A/DIV

0.2A TO 7.5A

I

L

5A/DIV

V

OUT

100mV/DIV

AC COUPLED

V

OUT

= 1.5V

100μs/DIV

V

IN

= 12V

FIGURE 11 CIRCUIT

100

38511 G05

Load Step

(Burst Mode Operation)

I

LOAD

5A/DIV

0.2A TO 7.5A

I

L

5A/DIV

V

OUT

100mV/DIV

AC COUPLED

Load Step

(Forced Continuous Mode)

EFFICIENCY (%)

EFFICIENCY,

I

OUT

= 0.5A

POWER LOSS,

I

OUT

= 0.5A

V

IN

= 12V

V

OUT

= 3.3V

FIGURE 11 CIRCUIT

V

OUT

= 1.5V

100μs/DIV

V

IN

= 12V

FIGURE 11 CIRCUIT

38511 G06

38511 G04

Load Step

(Pulse skip Mode)

I

LOAD

5A/DIV

0.2A TO 7.5A

I

L

5A/DIV

V

OUT

100mV/DIV

AC COUPLED

V

OUT

= 1.5V

100μs/DIV

V

IN

= 12V

FIGURE 11 CIRCUIT

3851 G07

Inductor Current at Light Load

FORCED

CONTINOUS

MODE

5A/DIV

Burst Mode

OPERATION

5A/DIV

PULSE SKIP

MODE

5A/DIV

V

OUT

= 1.5V

1μs/DIV

V

IN

= 12V

I

LOAD

= 1mA

FIGURE 11 CIRCUIT

38511 G08

Start-Up with Prebiased Output

at 2V

V

OUT

2V/DIV

TK/SS

0.5V/DIV

V

FB

0.5V/DIV

20ms/DIV

38511 G09

Coincident Tracking with Master

Supply

V

MASTER

0.5V/DIV

Ratiometric Tracking with Master

Supply

3.0

V

MASTER

0.5V/DIV

2.5

SUPPLY CURRENT (mA)

10ms/DIV

38511 G11

Input DC Supply Current vs Input

Voltage

V

OUT

2A LOAD

0.5V/DIV

2.0

1.5

1.0

0.5

0

4

8

12

16 20 24 28 32

INPUT VOLTAGE (V)

36

40

V

OUT

2A LOAD

0.5V/DIV

10ms/DIV

38511 G10

38511 G12

38511f

5

LTC3851IUD-1-TRPBF

LTC3851IUD-1-TRPBF概述

文档预览

LTC3851IUD-1-TRPBF相似产品对比

推荐资源