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LT8705A

80V V

IN

and V

OUT

Synchronous 4-Switch Buck-

Boost DC/DC Controller

FeaTures

n

DescripTion

The

LT

®

8705A

is a high performance buck-boost switch-

ing regulator controller that operates from input voltages

above, below or equal to the output voltage. The part has

integrated input current, input voltage, output current

and output voltage feedback loops. With a wide 2.8V to

80V input and 1.3V to 80V output range, the LT8705A

is compatible with most solar, automotive, telecom and

battery-powered systems. The LT8705A is an improved pin

compatible version of the LT8705 and is recommended for

new designs. See LT8705A vs LT8705 in the Applications

Information section for more information.

The LT8705A includes a MODE pin to select among Burst

Mode

®

operation, discontinuous or continuous conduc-

tion mode at light loads. Additional features include a

3.3V/12mA LDO, a synchronizable fixed operating fre-

quency, and onboard gate drivers.

L,

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

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

respective owners.

n

Single Inductor Allows V

IN

Above, Below, or Equal

to Regulated V

OUT

V

IN

Range 2.8V (Need EXTV

CC

> 6.4V) to 80V

V

OUT

Range: 1.3V to 80V

Quad N-Channel MOSFET Gate Drivers

Synchronous Rectification: Up to 98% Efficiency

Input and Output Current Monitor Pins

Synchronizable Fixed Frequency: 100kHz to 400kHz

Integrated Input Current, Input Voltage, Output Cur-

rent and Output Voltage Feedback Loops

Improved Light Load Transition from DCM to FCM

Improved IMON_OUT, IMON_IN Offset When Cold

Clock Output Usable To Monitor Die Temperature

applicaTions

n

High Voltage Buck-Boost Converters

Input or Output Current Limited Converters

Typical applicaTion

Telecom Voltage Stabilizer

V

IN

36V TO

80V

+

M1

×2

220µF

×2

4.7µF

×4

M2

TO

DIODE

0.22µF

2

×2

TG1 BOOST1 SW1 BG1 CSP

CSNIN

CSPIN

V

IN

100k

SHDN

SWEN

LDO33

MODE

FBIN

RT

1nF

22µH

M3

×2

10

M4

4.7µF

×6

+

TO

DIODE

0.22µF

V

OUT

48V

220µF 5A

×2

10m

2

×2

392k

100

Efficiency and Power Loss

6

5

95

POWER LOSS (W)

EFFICIENCY (%)

4

90

3

2

85

V

OUT

= 48V

I

LOAD

= 2A

30

40

50

60

V

IN

(V)

70

80

8705A TA01b

CSN

GND BG2 SW2 BOOST2 TG2

CSPOUT

CSNOUT

EXTV

CC

FBOUT

INTV

CC

10k

4.7µF

4

GATEV

CC

SRVO_FBIN

SRVO_FBOUT

SRVO_IIN

SRVO_IOUT

IMON_IN

IMON_OUT

TO

BOOST1 BOOST2

LT8705A

1

0

71.5k

1µF

20k

4.7µF

215k

SS

80

V

C

56.2k

1µF

220pF

3.3nF

CLKOUT

202kHz

SYNC

8705A TA01

8705af

For more information

www.linear.com/LT8705A

1

LT8705A

absoluTe MaxiMuM raTings

(Note 1)

V

CSP

-V

CSN

, V

CSPIN

-V

CSNIN

,

V

CSPOUT

-V

CSNOUT

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

SS, CLKOUT, CSP, CSN Voltage ................... –0.3V to 3V

V

C

Voltage (Note 2) ................................... –0.3V to 2.2V

RT, LDO33, FBOUT Voltage .......................... –0.3V to 5V

IMON_IN, IMON_OUT Voltage ..................... –0.3V to 5V

SYNC Voltage............................................ –0.3V to 5.5V

INTV

CC

, GATEV

CC

Voltage ............................ –0.3V to 7V

V

BOOST1

-V

SW1

, V

BOOST2

-V

SW2

..................... –0.3V to 7V

SWEN, MODE Voltage .................................. –0.3V to 7V

SRVO_FBIN, SRVO_FBOUT Voltage ........... –0.3V to 30V

SRVO_IIN, SRVO_IOUT Voltage ................. –0.3V to 30V

FBIN,

SHDN

Voltage ................................... –0.3V to 30V

CSNIN, CSPIN, CSPOUT, CSNOUT Voltage ..–0.3V to 80V

V

IN

, EXTV

CC

Voltage .................................. –0.3V to 80V

SW1, SW2 Voltage ......................................81V (Note 7)

BOOST1, BOOST2 Voltage ......................... –0.3V to 87V

BG1, BG2, TG1, TG2 ........................................... (Note 6)

Operating Junction Temperature Range

LT8705AE (Notes 3, 8)....................... –40°C to 125°C

LT8705AI (Notes 3, 8)........................ –40°C to 125°C

LT8705AH (Notes 3, 8) ...................... –40°C to 150°C

LT8705AMP (Notes 3, 8) ................... –55°C to 150°C

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

Lead Temperature (Soldering, 10 sec)

FE Package ....................................................... 300°C

pin conFiguraTion

TOP VIEW

IMON_IN

INTV

CC

CSNIN

CSPIN

MODE

SWEN

V

IN

INTV

CC

MODE

IMON_IN

SHDN

31 CSPOUT

30 CSNOUT

29 EXTV

CC

28 SRVO_FBOUT

27 SRVO_IOUT

39

GND

26 SRVO_IIN

25 SRVO_FBIN

24 NC

23 BOOST1

22 TG1

21 SW1

20 NC

13 14 15 16 17 18 19

BG2

BOOST2

TG2

GATEV

CC

SW2

GND

BG1

CSN

CSP

LDO33

FBIN

FBOUT

1

2

3

4

5

6

7

8

9

39

GND

30

EXTV

CC

28

BOOST1

26

TG1

24

SW1

22

SW2

21

TG2

20

BOOST2

32

CSNOUT

34

CSPOUT

38

V

IN

37

CSPIN

36

CSNIN

38 37 36 35 34 33 32

SHDN

1

CSN 2

CSP 3

LDO33 4

FBIN 5

FBOUT 6

IMON_OUT 7

V

C

8

SS 9

CLKOUT 10

SYNC 11

RT 12

IMON_OUT

10

V

C

11

SS

12

CLKOUT

13

SYNC

14

RT

15

GND

16

BG1

17

GATEV

CC

18

BG2

19

UHF PACKAGE

38-LEAD (5mm

×

7mm) PLASTIC QFN

T

JMAX

= 125°C,

θ

JA

= 34°C/W

EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB

FE PACKAGE

VARIATION: FE38(31)

38-LEAD PLASTIC TSSOP

T

JMAX

= 125°C,

θ

JA

= 25°C/W

EXPOSED PAD (PIN 39) IS GND, MUST BE SOLDERED TO PCB

8705af

2

For more information

www.linear.com/LT8705A

LT8705A

orDer inForMaTion

LEAD FREE FINISH

LT8705AEUHF#PBF

LT8705AIUHF#PBF

LT8705AEFE#PBF

LT8705AIFE#PBF

LT8705AHFE#PBF

LT8705AMPFE#PBF

TAPE AND REEL

LT8705AEUHF#TRPBF

LT8705AIUHF#TRPBF

LT8705AEFE#TRPBF

LT8705AIFE#TRPBF

LT8705AHFE#TRPBF

LT8705AMPFE#TRPBF

http://www.linear.com/product/LT8705A#orderinfo

PART MARKING*

8705A

LT8705AFE

PACKAGE DESCRIPTION

38-Lead (5mm

×

7mm) Plastic QFN

38-Lead (5mm

×

7mm) Plastic QFN

38-Lead Plastic TSSOP

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.

elecTrical characTerisTics

PARAMETER

Voltage Supplies and Regulators

V

IN

Operating Voltage Range

V

IN

Quiescent Current

V

IN

Quiescent Current in Shutdown

EXTV

CC

Switchover Voltage

EXTV

CC

Switchover Hysteresis

INTV

CC

Current Limit

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 12V,

SHDN

= 3V unless otherwise noted. (Note 3)

CONDITIONS

EXTV

CC

= 0V

EXTV

CC

= 7.5V

Not Switching, V

EXTVCC

= 0

V

SHDN

= 0V

I

INTVCC

= 20mA, V

EXTVCC

Rising

l

MIN

5.5

2.8

TYP

MAX

80

UNITS

V

mA

µA

V

2.65

0

6.15

6.4

0.18

4.2

1

6.6

Maximum Current Draw from INTV

CC

and LDO33

Pins Combined. Regulated from V

IN

or EXTV

CC

(12V)

l

INTV

CC

= 5.25V

l

INTV

CC

= 4.5V

Regulated from V

IN

, I

INTVCC

= 20mA

Regulated from EXTV

CC

(12V), I

INTVCC

= 20mA

I

INTVCC

= 0mA to 50mA

INTV

CC

Falling, GATEV

CC

Connected to INTV

CC

GATEV

CC

Connected to INTV

CC

V

IN

-V

INTVCC

, I

INTVCC

= 20mA

5mA from LDO33 Pin

I

LDO33

= 0.1mA to 5mA

l

90

28

6.15

4.45

127

42

6.35

–0.5

4.65

160

245

165

55

6.55

–1.5

4.85

mA

V

%

V

mV

INTV

CC

Voltage

INTV

CC

Load Regulation

INTV

CC

, GATEV

CC

Undervoltage Lockout

INTV

CC

, GATEV

CC

Undervoltage Lockout Hysteresis

INTV

CC

Regulator Dropout Voltage

LDO33 Pin Voltage

LDO33 Pin Load Regulation

LDO33 Pin Current Limit

LDO33 Pin Undervoltage Lockout

LDO33 Pin Undervoltage Lockout Hysteresis

Switching Regulator Control

Maximum Current Sense Threshold (V

CSP

– V

CSN

)

Maximum Current Sense Threshold (V

CSN

– V

CSP

)

3.23

12

2.96

3.295

–0.25

17.25

3.04

35

3.35

–1

22

3.12

V

%

mA

V

mV

LDO33 Falling

Boost Mode, Minimum M3 Switch Duty Cycle

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

Buck Mode, Minimum M2 Switch Duty Cycle

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

l

102

100

69

67

117

86

132

134

102

104

mV

8705af

For more information

www.linear.com/LT8705A

3

LT8705A

elecTrical characTerisTics

PARAMETER

Gain from V

C

to Maximum Current Sense Voltage

(V

CSP

-V

CSN

) (A5 in the Block Diagram)

SHDN

Input Voltage High

SHDN

Input Voltage High Hysteresis

SHDN

Input Voltage Low

Device Disabled, Low Quiescent Current

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

V

SHDN

= 3V

V

SHDN

= 12V

l

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 12V,

SHDN

= 3V unless otherwise noted. (Note 3)

CONDITIONS

Boost Mode

Buck Mode

SHDN

Rising to Enable the Device

l

MIN

TYP

150

–150

MAX

UNITS

mV/V

V

mV

1.184 1.234 1.284

50

0.35

0.3

0

11

22

1

22

V

µA

V

mV

V

SHDN

Pin Bias Current

SWEN Rising Threshold Voltage (Note 5)

SWEN Threshold Voltage Hysteresis (Note 5)

MODE Pin Forced Continuous Mode Threshold

MODE Pin Burst Mode Range

MODE Pin Discontinuous Mode Threshold

Soft-Start Charging Current

Soft-Start Discharge Current

Regulation Voltage for FBOUT

Regulation Voltage for FBIN

Line Regulation for FBOUT and FBIN Error Amp Reference

Voltage

FBOUT Pin Bias Current

FBOUT Error Amp EA4 g

m

FBOUT Error Amp EA4 Voltage Gain

FBIN Pin Bias Current

FBIN Error Amp EA3 g

m

FBIN Error Amp EA3 Voltage Gain

SRVO_FBIN Activation Threshold (Note 5)

SRVO_FBIN Activation Threshold Hysteresis (Note 5)

SRVO_FBOUT Activation Threshold (Note 5)

SRVO_FBOUT Activation Threshold Hysteresis (Note 5)

SRVO_FBIN, SRVO_FBOUT Low Voltage (Note 5)

SRVO_FBIN, SRVO_FBOUT Leakage Current (Note 5)

Regulation Voltages for IMON_IN and IMON_OUT

Line Regulation for IMON_IN and IMON_OUT Error Amp

Reference Voltage

CSPIN, CSNIN Bias Current

1.156 1.206 1.256

0.4

1.0

13

19

9.5

1.7

2.3

25

l

V

µA

V

%/V

nA

µmho

V/V

nA

µmho

V/V

V

SS

= 0.5V

V

SS

= 0.5V

V

C

= 1.2V (LT8705AE, LT8705AI)

V

C

= 1.2V (LT8705AH, LT8705AMP)

V

C

= 1.2V (LT8705AE, LT8705AI)

V

C

= 1.2V (LT8705AH, LT8705AMP)

V

IN

= 12V to 80V; Not Switching

Current Out of Pin

l

Voltage Regulator Loops (Refer to Block Diagram to Locate Amplifiers)

1.193 1.207 1.222

1.191 1.207 1.222

1.184 1.205 1.226

1.182 1.205 1.226

0.002 0.005

15

315

220

Current Out of Pin

10

130

90

(V

FBIN

Falling) – (Regulation Voltage for FBIN),

V

FBOUT

= V

IMON_IN

= V

IMON_OUT

= 0V

V

FBOUT

= V

IMON_IN

= V

IMON_OUT

= 0V

(V

FBOUT

Rising) – (Regulation Voltage for FBOUT),

V

FBIN

= 3V, V

IMON_IN

= V

IMON_OUT

= 0V

V

FBIN

= 3V, V

IMON_IN

= 0V, V

IMON_OUT

= 0V

I = 100μA

V

SRVO_FBIN

= V

SRVO_FBOUT

= 2.5V

V

C

= 1.2V

V

IN

= 12V to 80V; Not Switching

BOOST Capacitor Charge Control Block Not Active

I

CSPIN

+ I

CSNIN

, V

CSPIN

= V

CSNIN

= 12V

l

56

72

33

89

mV

–37

–29

15

110

0

–21

mV

330

1

mV

µA

V

%/V

Current Regulation Loops (Refer to Block Diagram to Locate Amplifiers)

l

1.187 1.208 1.229

0.002 0.005

31

µA

8705af

4

For more information

www.linear.com/LT8705A

LT8705A

elecTrical characTerisTics

PARAMETER

CSPIN, CSNIN Common Mode Operating Voltage Range

CSPIN, CSNIN Differential Operating Voltage Range

V

CSPIN-CSNIN

to IMON_IN Amplifier A7 g

m

V

CSPIN

– V

CSNIN

= 50mV, V

CSPIN

= 5.025V

(All Grades)

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

The

l

denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T

A

= 25°C. V

IN

= 12V,

SHDN

= 3V unless otherwise noted. (Note 2)

CONDITIONS

l

MIN

1.5

–100

0.95

0.94

0.93

100

1.55

TYP

MAX

80

100

UNITS

V

mV

mmho

µA

V

µmho

V/V

µA

l

1

1.61

185

130

1.05

1.06

1.07

1.67

IMON_IN Maximum Output Current

IMON_IN Overvoltage Threshold

IMON_IN Error Amp EA2 g

m

IMON_IN Error Amp EA2 Voltage Gain

CSPOUT, CSNOUT Bias Current

BOOST Capacitor Charge Control Block Not Active

I

CSPOUT

+ I

CSNOUT

, V

CSPOUT

= V

CSNOUT

= 12V

I

CSPOUT

+ I

CSNOUT

, V

CSPOUT

= V

CSNOUT

= 1.5V

45

4

l

CSPOUT, CSNOUT Common Mode Operating Voltage Range

CSPOUT, CSNOUT Differential Mode Operating Voltage

Range

V

CSPOUT-CSNOUT

to IMON_OUT Amplifier A6 g

m

V

CSPOUT

– V

CSNOUT

= 50mV, V

CSPOUT

= 5.025V

(All Grades)

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

V

CSPOUT

– V

CSNOUT

= 5mV, V

CSPOUT

= 5.0025V

(All Grades)

(LT8705AE, LT8705AI)

(LT8705AH, LT8705AMP)

0

–100

80

100

V

mV

l

0.95

0.94

0.93

0.65

0.55

0.5

100

1.55

1

1.61

185

130

1.05

1.085

1.095

1.35

1.6

1.65

1.67

mmho

µA

V

µmho

V/V

l

IMON_OUT Maximum Output Current

IMON_OUT Overvoltage Threshold

IMON_OUT Error Amp EA1 g

m

IMON_OUT Error Amp EA1 Voltage Gain

SRVO_IIN Activation Threshold (Note 5)

SRVO_IIN Activation Threshold Hysteresis (Note 5)

SRVO_IOUT Activation Threshold (Note 5)

SRVO_IOUT Activation Threshold Hysteresis (Note 5)

SRVO_IIN, SRVO_IOUT Low Voltage (Note 5)

SRVO_IIN, SRVO_IOUT Leakage Current (Note 5)

NMOS Gate Drivers

TG1, TG2 Rise Time

TG1, TG2 Fall Time

BG1, BG2 Rise Time

BG1, BG2 Fall Time

TG1 Off to BG1 On Delay

BG1 Off to TG1 On Delay

TG2 Off to BG2 On Delay

C

LOAD

= 3300pF (Note 4)

C

LOAD

= 3300pF (Note 4)

C

LOAD

= 3300pF (Note 4)

C

LOAD

= 3300pF (Note 4)

C

LOAD

= 3300pF Each Driver

C

LOAD

= 3300pF Each Driver

C

LOAD

= 3300pF Each Driver

(V

IMON_IN

Rising) – (Regulation Voltage for

IMON_IN), V

FBIN

= 3V, V

FBOUT

= 0V, V

IMON_OUT

= 0V

V

FBIN

= 3V, V

FBOUT

= 0V, V

IMON_OUT

= 0V

(V

IMON_OUT

Rising) – (Regulation Voltage for IMON_

OUT), V

FBIN

= 3V, V

FBOUT

= 0V, V

IMON_IN

= 0V

V

FBIN

= 3V, V

FBOUT

= 0V, V

IMON_IN

= 0V

I = 100μA

V

SRVO_IIN

= V

SRVO_IOUT

= 2.5V

–60

–49

22

–37

mV

–62

–51

22

–39

mV

l

110

0

20

100

80

100

330

1

mV

µA

ns

8705af

For more information

www.linear.com/LT8705A

5

参数名称	属性值
输出类型	晶体管驱动器
功能	升压/降压
输出配置	正
拓扑	降压升压
输出数	2
输出阶段	2
电压 - 电源（Vcc/Vdd）	2.8 V ~ 80 V
频率 - 开关	100kHz ~ 400kHz
同步整流器	是
时钟同步	是
控制特性	使能，频率控制，软启动
工作温度	-55°C ~ 125°C
封装/外壳	38-TFSOP（0.173"，4.40mm 宽）31 引线，裸露焊盘
供应商器件封装	38-TSSOP-EP

LT8705AMPFE#PBF

LT8705AMPFE#PBF概述

LT8705AMPFE#PBF规格参数

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