LT8410_15_技术文档

LT8410/LT8410-1

Ultralow Power Boost

Converter with Output

Disconnect

FEATURES

DESCRIPTION

TheLT^®8410/LT8410-1areultralowpowerboostconverters

with integrated power switch, Schottky diode and output

disconnect circuitry. The parts control power delivery by

varying both the peak inductor current and switch off-

time. This control scheme results in low output voltage

ripple as well as high efﬁciency over a wide load range.

The quiescent current is a low 8.5μA, which is further

reduced to 0μA in shutdown. The internal disconnect

circuitry allows the output voltage to be blocked from the

input during shutdown. High value (12.4M/0.4M) resis-

tors are integrated on chip for output voltage detection,

signiﬁcantlyreducinginputreferredquiescentcurrent.The

LT8410/LT8410-1alsofeaturesacomparatorbuiltintothe

n

Ultralow Quiescent Current

8.5μA in Active Mode

0μA in Shutdown Mode

n

Comparator Built into SHDN Pin

n

Low Noise Control Scheme

n

Adjustable FB Reference Voltage

n

Wide Input Range: 2.5V to 16V

n

Wide Output Range: Up to 40V

n

Integrated Power NPN Switch

25mA Current Limit (LT8410)

8mA Current Limit (LT8410-1)

n

Integrated Schottky Diode

n

Integrated Output Disconnect

n

High Value (12.4M/0.4M) Feedback Resistors

SHDN pin, overvoltage protection for the CAP and V

OUT

Integrated

pins, built in soft-start and comes in a tiny 8-pin 2mm ×

n

Built in Soft-Start (Optional Capacitor from V

2mm DFN package.

REF

to GND)

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

Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other

trademarks are the property of their respective owners. Protected by U.S. Patents, including

5481178, 6580258, 6304066, 6127815, 6498466, 6611131.

n

Overvoltage Protection for CAP and V

Pins

OUT

Tiny 8-Pin 2mm × 2mm DFN Package

APPLICATIONS

n

Sensor Power

n

RF Mems Relay Power

n

General Purpose Bias

TYPICAL APPLICATION

General Purpose Bias with Wide Input Voltage

Output Voltage Ripple

vs Load Current

Efﬁciency vs Load Current

10

8

100

90

80

70

60

50

40

V

IN

2.5V to 16V

V

= 3.6V

100µH

IN

V

= 12V

IN

2.2µF

0.1µF

V

SW

CAP

V

= 5V

IN

= 16V

OUT

V

CC

OUT

6

V

= 3.6V

IN

LT8410

V

0.1µF*

CHIP

ENABLE

REF

SHDN

4

604k

0.1µF

GND

FBP

2

412k

*HIGHER VALUE CAPACITOR IS REQUIRED

WHEN THE V IS HIGHER THAN 5V

8410-1 TA01a

IN

0

0.01

0.1

1

10

0.01

0.1

1

10

100

LOAD CURRENT (mA)

8410-1 TA02

LOAD CURRENT (mA)

8410-1 TA03

84101fb

1

LT8410/LT8410-1

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

TOP VIEW

V

Voltage................................................–0.3V to 16V

CC

8

7

6

5

SHDN

1

2

3

4

FBP

SW Voltage ................................................–0.3V to 40V

CAP Voltage ...............................................–0.3V to 40V

V

CC

V

REF

9

GND

SW

CAP

V

Voltage..............................................–0.3V to 40V

OUT

V

OUT

SHDN Voltage ............................................–0.3V to 16V

REF

FBP Voltage ..............................................–0.3V to 2.5V

Maximum Junction Temperature .......................... 125°C

Operating Temperature Range (Note 2)..–40°C to 125°C

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

DC PACKAGE

V

Voltage..............................................–0.3V to 2.5V

8-LEAD (2mm × 2mm) PLASTIC DFN

T

= 125°C, θ = 88°C/W

JMAX JA

EXPOSED PAD (PIN #9) IS GND, MUST BE SOLDERED TO PCB

ORDER INFORMATION

LEAD FREE FINISH

LT8410EDC#PBF

LT8410IDC#PBF

TAPE AND REEL

PART MARKING*

LDQR

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LT8410EDC#TRPBF

LT8410IDC#TRPBF

LT8410EDC-1#TRPBF

LT8410IDC-1#TRPBF

–40°C to 125°C

8-Lead (2mm × 2mm) Plastic DFN

LDQR

LT8410EDC-1#PBF

LT8410IDC-1#PBF

LFCC

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 ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_CC= 3V, V_SHDN= V_CCunless otherwise noted. (Note 2)

PARAMETER

CONDITIONS

MIN

TYP

MAX

2.5

UNITS

V

Minimum Operating Voltage

Maximum Operating Voltage

Reference Voltage

2.2

16

V

l

1.220

1.235

10

1.255

V

REF

V

REF

V

REF

Current Limit

(Note 3)

µA

µS

%/V

µA

Discharge Time

Line Regulation

70

0.01

8.5

0

l

Quiescent Current

Not Switching

12

1

Quiescent Current in Shutdown

V = 0V

SHDN

Quiescent Current from V

and CAP

V

= 16V

OUT

3

OUT

Minimum Switch Off Time

After Start-Up (Note 4)

During Start-Up (Note 4)

240

600

nS

l

Switch Current Limit

LT8410

LT8410-1

20

6

25

8

30

10

mA

84101fb

2

LT8410/LT8410-1

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the full operating

temperature range, otherwise speciﬁcations are at T_A= 25°C. V_CC= 3V, V_SHDN= V_CCunless otherwise noted. (Note 2)

PARAMETER

Switch V

CONDITIONS

LT8410, I = 10mA

MIN

TYP

MAX

UNITS

150

100

mV

CESAT

SW

LT8410-1, I = 4mA

SW

Switch Leakage Current

Schottky Forward Voltage

Schottky Reverse Leakage

V

= 5V

0

1

µA

SW

I

= 10mA

650

850

mV

DIODE

V

CAP

V

CAP

– V = 5

0

0.5

1

µA

SW

– V = 40

SW

PMOS Disconnect Current Limit

LT8410

LT8410-1

14

2.5

19

4

25

5

mA

PMOS Disconnect V

– V

I = 1mA

OUT

50

31.85

1.3

mV

CAP

OUT

l

V

OUT

Resistor Divider Ratio

31.6

1.20

0.08

32.2

30

FBP Pin Bias Current

V

FBP

= 0.5V, Current Flows Out of Pin

nA

V

SHDN Minimum Input Voltage High

SHDN Input Voltage High Hysteresis

SHDN Hysteresis Current

SHDN Rising

1.30

60

1.45

mV

µA

V

0.1

0.14

0.3

(Note 3)

SHDN Input Voltage Low

SHDN Pin Bias Current

V

SHDN

V

SHDN

= 3V

= 16V

0

2

1

3

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 3: See the Applications Information section for more information.

Note 4: Start-up mode occurs when V is less than V • 64/3.

OUT

FBP

Note 2: The LT8410E/LT8410E-1 are 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 LT8410I/LT8410I-1 are guaranteed over the full –40°C to 125°C

operating junction temperature range.

TYPICAL PERFORMANCE CHARACTERISTICS ^T_A^{= 25°C, unless otherwise noted.}

Switching Frequency

vs Load Current

Load Regulation

V_OUTvs FBP Voltage

1000

800

600

400

200

0

0.6

50

40

30

20

10

0

V

= 3.6V

V

= 3.6V

CC

= 16V

OUT

0.4

0.2

0

FIGURE 4 CIRCUIT

–0.2

–0.4

–0.6

0

1

2

3

0

1

2

3

0

0.5

1

1.5

2

LOAD CURRENT (mA)

FBP VOLTAGE (V)

8410-1 G01

8410-1 G02

8410-1 G03

84101fb

3

LT8410/LT8410-1

TYPICAL PERFORMANCE CHARACTERISTICS

Output Voltage vs Temperature

Quiescent Current—Not Switching

Quiescent Current vs Temperature

1.00

0.75

12

10

8

10

8

V

= 3.6V, V

= 16V

OUT

CC

LOAD = 0.5mA

FIGURE 4 CIRCUIT

0.50

0.25

6

0

6

4

–0.25

–0.50

–0.75

–1.00

4

2

V

= 3.6V

0

CC

0

–40

0

40

80

120

0

4

8

12

16

–40

40

80

120

TEMPERATURE (°C)

V

VOLTAGE (V)

TEMPERATURE (°C)

CC

8410-1 G04

8410-1 G05

8410-1 G06

Quiescent Current

vs SHDN Voltage

Quiescent Current in Regulation

with No Load

SHDN Current vs SHDN Voltage

10

8

1000

100

10

2.5

2.0

1.5

1.0

0.5

0

V

= 3.6V

V

= 3.6V

CC

6

4

2

V

CC

= 3.6V

0

–0.5

0

1

2

3

4

5

0

10

20

30

40

0

4

8

12

16

SHDN VOLTAGE (V)

OUTPUT VOLTAGE (V)

SHDN VOLTAGE (V)

8410-1 G07

8410-1 G08

8410-1 G09

Peak Inductor Current

vs Temperature (LT8410)

Peak Inductor Current

vs Temperature (LT8410-1)

V_REFVoltage vs Temperature

40

36

32

28

24

20

15

13

11

9

1.235

1.234

1.233

1.232

1.231

1.230

V

= 3.6V

= 16V

V

= 3.6V

= 16V

CC

OUT

CC

OUT

FIGURE 4 CIRCUIT

FIGURE 5 CIRCUIT

7

V

= 3.6V

CC

5

–40

0

40

TEMPERATURE (°C)

80

120

–40

0

40

TEMPERATURE (°C)

80

120

–40

0

40

TEMPERATURE (°C)

80

120

8410-1 G10

8410-1 G11

8410-1 G12

84101fb

4

LT8410/LT8410-1

TYPICAL PERFORMANCE CHARACTERISTICS

LT8410 Switching Waveform

at No Load

LT8410 Switching Waveform

at 0.5mA Load

V

VOLTAGE

2mV/DIV

V

VOLTAGE

10mV/DIV

OUT

AC COUPLED

SW VOLTAGE

10V/DIV

SW VOLTAGE

10V/DIV

INDUCTOR

CURRENT

20mA/DIV

INDUCTOR

CURRENT

10mA/DIV

8410-1 G13

8410-1 G14

V

= 3.6V

OUT

50µs/DIV

V

= 3.6V

OUT

2µs/DIV

CC

= 16V

LT8410 Switching Waveform

at 3mA Load

UVLO vs Temperature

2.6

2.4

V

VOLTAGE

10mV/DIV

OUT

AC COUPLED

V

RISING

CC

2.2

2.0

1.8

1.6

SW VOLTAGE

10V/DIV

V

FALLING

CC

INDUCTOR

CURRENT

20mA/DIV

8410-1 G15

V

= 3.6V

OUT

500ns/DIV

CC

= 16V

1.4

–40

0

40

TEMPERATURE (°C)

80

120

8410-1 G16

SHDN Minimum Input Voltage

High vs Temperature

Line Regulation

0.30

0.25

0.20

0.15

0.10

0.05

0

1.5

1.4

1.3

1.2

1.1

1.0

V

= 16V

OUT

SHDN RISING

SHDN FALLING

0

4

8

12

16

–40

0

40

80

120

V

VOLTAGE (V)

TEMPERATURE (°C)

CC

8410-1 G17

8410-1 G18

84101fb

5

LT8410/LT8410-1

TYPICAL PERFORMANCE CHARACTERISTICS

Output Disconnect PMOS Current

vs CAP to V_OUTVoltage Difference

LT8410 Start-Up Waveforms

without Capacitor at V_REFPin

25

SHDN VOLTAGE

V

= 16V

CAP

5V/DIV

LT8410

INDUCTOR

CURRENT

20mA/DIV

20

15

10

5

CAP VOLTAGE

5V/DIV

V

OUT

VOLTAGE

5V/DIV

LT8410-1

8

8410-1 G20

V

= 3.6V

OUT

200µs/DIV

CC

= 16V

0

4

CAP TO V

12

16

VOLTAGE DIFFERENCE (V)

OUT

8410-1 G19

LT8410 Start-Up Waveforms with

0.1μF Capacitor at V_REFPin

LT8410 Transient Response

0.5mA→1.5mA→ 0.5mA Load Pulse

SHDN VOLTAGE

V

VOLTAGE

5V/DIV

OUT

200mV/DIV

INDUCTOR

CURRENT

20mA/DIV

AC COUPLED

INDUCTOR

CURRENT

20mA/DIV

LOAD

CURRENT

0.5mA/DIV

CAP VOLTAGE

5V/DIV

V

VOLTAGE

5V/DIV

OUT

8410-1 G21

8410-1 G22

V

= 3.6V

OUT

2ms/DIV

V

= 3.6V

OUT

2ms/DIV

CC

= 16V

SW Saturation Voltage

vs Switch Current (LT8410)

300

250

200

150

100

50

0

5

10

15

20

25

SWITCH CURRENT (mA)

8410-1 G24

84101fb

6

LT8410/LT8410-1

PIN FUNCTIONS

SHDN (Pin 1): Shutdown Pin. This pin is used to enable/

disablethechip.Drivebelow0.3Vtodisablethechip.Drive

above 1.45V to activate the chip. Do not ﬂoat this pin.

V

(Pin 7): Reference Pin. Soft-start can be achieved

REF

by placing a capacitor from this pin to GND. This cap

will be discharged for 70µs (typical) at the beginning

of start-up and then be charged to 1.235V with a 10μA

current source.

V

(Pin 2): Input Supply Pin. Must be locally bypassed

CC

to GND. See the Typical Applications section.

FBP (Pin 8): Positive Feedback Pin. This pin is the error

GND (Pin 3): Ground. Tie directly to local ground plane.

ampliﬁer’s positive input terminal. To achieve the desired

SW (Pin 4): Switch Pin. This is the collector of the inter-

nal NPN power switch. Minimize the metal trace area

connected to this pin to minimize EMI.

output voltage, choose the FBP pin voltage (V ) accord-

FBP

ing to the following formula:

V_OUT

31.85

V_FBP

=

V

(Pin 5): Drain of Output Disconnect PMOS. Place

OUT

a bypass capacitor from this pin to GND.

Forprotectionpurposes,theoutputvoltagecannotexceed

40V even if V is driven higher than V

CAP (Pin 6): Cathode of the Internal Schottky Diode. Place

a bypass capacitor from this pin to GND.

.

FBP

REF

ExposedPad(Pin9):Pin9isﬂoatingbutmustbeground-

ed for proper shielding.

BLOCK DIAGRAM

2

1

5

6

4

V

OUT

SHDN

CAP

SW

CC

ENABLE

CHIP

MAX

10µA

12.4M

400k

1.235V

+

–

+

–

OUTPUT DISCONNECT

CONTROL

V

REF

1.235V

7

DISCHARGE

CONTROL

SWITCH

CONTROL

TIMING AND PEAK

CURRENT CONTROL

–

+

FB

FBP

VC

+

8

1.235V

–

EXPOSED PAD

(GND)

GND

9

3

84101fb

7

LT8410/LT8410-1

OPERATION

The LT8410 series utilizes a variable peak current, variable

off-time control scheme to provide high efﬁciency over a

wide output current range.

the circuit, special precautions are taken to ensure that

the inductor current remains under control

The LT8410 series also has a PMOS output disconnect

switch. The PMOS switch is turned on when the part is

enabled via the SHDN pin. When the part is in shutdown,

The operation of the part can be better understood by

referring to the Block Diagram. The part senses the output

voltage by monitoring the internal FB node, and servoing

the FB node voltage to be equal to the FBP pin voltage.

The chip integrates an accurate high value resistor divider

the PMOS switch turns off, allowing the V

node to

OUT

go to ground. This type of disconnect function is often

required in power supplies.

(12.4M/0.4M) from the V

pin. The output voltage is set

OUT

The differences between the LT8410 and LT8410-1 are

the SW current limit and the output disconnect PMOS

current limit. For the LT8410, the SW current limit and

PMOS current limit are approximately 25mA and 19mA,

respectively,whilethoseoftheLT8410-1areapproximately

8mA and 4mA, respectively.

by the FBP pin voltage, which in turn is set by an external

resistor divider from the V pin. The FBP pin voltage can

REF

also bedirectly biasedwith anexternalreference, allowing

full control of the output voltage during operation.

The switch control block senses the output of the ampli-

ﬁer and adjusts the switching frequency as well as other

parameters to achieve regulation. During the start-up of

APPLICATIONS INFORMATION

Inductor Selection

Table 1. Recommended Inductors for LT8410/ LT8410-1

L

DCR

SIZE

Several inductors that work well with the LT8410 and

LT8410-1arelistedinTable1. Thetablesarenotcomplete,

and there are many other manufacturers and devices that

can be used. Consult each manufacturer for more detailed

information and for their entire selection of related parts,

as many different sizes and shapes are available.

PART

(µH) (Ω)

(mm)

VENDOR

Murata

www.murata.com

LQH2MCN680K02 68 6.6

LQH32CN101K53 100 3.5

2.0 × 1.6 × 0.9

3.2 × 2.5 × 2.0

DO2010-683ML

LPS3015-104ML

LPS3015-154ML

LPS3314-154ML

68

8.8

Coilcraft

www.coilcraft.com

2.0 × 2.0 × 1.0

3.0 × 3.0 × 1.4

3.3 × 3.3 × 1.3

100 3.4

150 6.1

150 4.1

Inductorswithavalueof47μHorhigherarerecommended

for most LT8410 series designs. Inductors with low core

losses and small DCR (copper wire resistance) are good

choices for LT8410 series applications. For full output

power,theinductorshouldhaveasaturationcurrentrating

higher than the peak inductor current. The peak inductor

current can be calculated as:

Capacitor Selection

The small size and low ESR of ceramic capacitors make

them suitable for most LT8410 applications. X5R and

X7R types are recommended because they retain their

capacitance over wider voltage and temperature ranges

than other types such as Y5V or Z5U. A 2.2μF or higher

input capacitor, and a 0.1μF to 1μF output capacitor, are

sufﬁcient for most applications. Always use a capacitor

with a sufﬁcient voltage rating. Many ceramic capacitors

rated at 0.1μF to 1μF have greatly reduced capacitance

when bias voltages are applied. Be sure to check actual

capacitanceatthedesiredoutputvoltage.Generally,a0603

V • 150 • 10^–6

IN

I_PK= I_LIMIT

+

mA

L

where the worst case I

is 30mA and 10mA for LT8410

LIMIT

and LT8410-1, respectively. L is the inductance value in

henrys and V is the input voltage to the boost circuit.

IN

84101fb

8

LT8410/LT8410-1

APPLICATIONS INFORMATION

or 0805 size capacitor will be adequate. A 0.1μF to 1μF

capacitorplacedontheCAPnodeisrecommendedtoﬁlter

the inductor current, while a 0.1μF to 1μF capacitor placed

Connecting the Load to the CAP Node

The efﬁciency of the converter can be improved by con-

necting the load to the CAP pin instead of the V pin.

OUT

on the V

node will give excellent transient response

OUT

The power loss in the PMOS disconnect circuit is then

made negligible. No quiescent current will be consumed

in the internal feedback resistor divider string during

shutdown since the PMOS transistor will be open and the

and stability. To make the V pin less sensitive to noise,

REF

puttingacapacitorontheV pinisrecommended,butnot

required.A47nFto220nF0402capacitorwillbesufﬁcient.

Table 2 shows a list of several capacitor manufacturers.

Consult the manufacturers for more detailed information

and for their entire selection of related parts.

internal feedback resistor divider is connected at the V

OUT

pin. The disadvantage of this method is that the CAP node

cannot go to ground during shutdown, but will be limited

Table 2. Recommended Ceramic Capacitor Manufacturers

to around a diode drop below V . Loads connected to the

CC

MANUFACTURER

Taiyo Yuden

Murata

PHONE

WEB SITE

www.t-yuden.com

part should only sink current. Never force external power

(408) 573-4150

(814) 237-1431

(843) 448-9411

(408) 986-0424

(847) 803-6100

supplies onto the CAP or V

pins.

OUT

www.murata.com

www.avxcorp.com

www.kemet.com

www.tdk.com

AVX

Maximum Output Load Current

Kemet

ThemaximumoutputcurrentofaparticularLT8410series

circuitisafunctionofseveralcircuitvariables.Thefollowing

method can be helpful in predicting the maximum load

current for a given circuit:

TDK

Setting Output Voltage

The output voltage is set by the FBP pin voltage. V

is

OUT

Step 1. Calculate the peak inductor current:

equal to 31.85 • V

when the output is regulated, as

FBP

V • 150 • 10^–6

shown in Figure 1. Since the V

pin provides a good

REF

IN

I_PK= I_LIMIT

where I

+

mA

reference (1.235V), the FBP voltage can be easily set by

L

a resistor divider from the V pin to ground. The series

REF

is 25mA and 8mA for LT8410 and LT8410-1

LIMIT

resistanceofthisresistordividershouldbekeptlargerthan

respectively. L is the inductance value in henrys and V

is the input voltage to the boost circuit.

200KΩ to prevent loading down the V pin. The FBP pin

IN

REF

can also be biased directly by an external reference. For

overvoltage protection, the output voltage is limited to

Step 2. Calculate the inductor ripple current:

40V. Therefore, if V

voltage will stay at 40V.

is higher than 1.235V, the output

FBP

V

+ 1– V • 200 • 10^–6

(

)

OUT

IN

I_RIPPLE

=

mA

L

50

where V

is the desired output voltage. If the inductor

OUT

40

30

20

10

0

ripple current is less than the peak current, then the circuit

will only operate in discontinuous conduction mode. The

inductor value should be increased so that I

< I .

RIPPLE

PK

An application circuit can be designed to operate only in

discontinuous mode, but the output current capability

will be reduced.

Step 3. Calculate the average input current:

0

0.5

1

1.5

2

I

^RIPPLEmA

2

FBP VOLTAGE (V)

I

= I_PK

–

IN(AVG)

8410-1 F01

Figure 1. FBP to V_OUTTransfer Curve

84101fb

9

LT8410/LT8410-1

APPLICATIONS INFORMATION

Step 4. Calculate the nominal output current:

protection against pin glitches and slow ramping), then

an internal 10μA current source pulls the V pin slowly

REF

I

• V • 0.7

IN

IN(AVG)

to 1.235V. Since the V

voltage is set by the FBP pin

I_OUT(NOM)

=

mA

OUT

V_OUT

Step 5. Derate output current:

= I • 0.8

voltage, the V

voltage will also slowly increase to the

OUT

regulated voltage, which results in lower peak inductor

current. The voltage ramp rate on the pin can be set by

I

OUT

OUT(NOM)

the value of the V pin capacitor.

REF

For low output voltages the output current capability will

beincreased. Whenusingoutputdisconnect(loadcurrent

Output Disconnect

taken from V ), these higher currents will cause the

The LT8410 series has an output disconnect PMOS that

blocks the load from the input during shutdown. The

maximumcurrentthroughthePMOSislimitedbycircuitry

inside the chip, helping the chip survive output shorts.

OUT

drop in the PMOS switch to be higher resulting in lower

output current capability than predicted by the preceding

equations.

Inrush Current

SHDN Pin Comparator and Hysteresis Current

WhenV issteppedfromgroundtotheoperatingvoltage

CC

An internal comparator compares the SHDN pin voltage

with an internal voltage reference (1.3V) which gives a

preciseturn-onvoltagelevel.Theinternalhysteresisofthis

turn-onvoltageisabout60mV.Whenthechipisturnedon,

and the SHDN pin voltage is close to this turn-on voltage,

0.1μA current ﬂows out of the SHDN pin. This current is

calledSHDNpinhysteresiscurrent, andwillgoawaywhen

the chip is off. By connecting the external resistors as in

Figure 2, a user-programmable enable voltage function

can be realized.

while the output capacitor is discharged, a high level of

inrushcurrentmayﬂowthroughtheinductorandSchottky

diode into the output capacitor. Conditions that increase

inrush current include a larger more abrupt voltage step

at V , a larger output capacitor tied to the CAP pin and

CC

an inductor with a low saturation current. While the chip is

designed to handle such events, the inrush current should

not be allowed to exceed 0.3A. For circuits that use output

capacitor values within the recommended range and have

input voltages of less than 6V, inrush current remains low,

posing no hazard to the device. In cases where there are

The turn-on voltage for the conﬁguration is:

large steps at V (more than 6V) and/or a large capacitor

CC

R1

R2







1.30 • 1+

is used at the CAP pin, inrush current should be measured

to ensure safe operation.







and the turn-off voltage is:

Soft-Start

R1

R2







1.24− R3 •10^{− 7}• 1+

− (R1•10^{− 7})

(

)







The LT8410 series contains a soft-start circuit to limit

peak switch currents during start-up. High start-up cur-

rent is inherent in switching regulators, in general, since

where R1, R2 and R3 are resistance value in Ω.

the feedback loop is saturated due to V

being far from

OUT

ENABLE VOLTAGE

its ﬁnal value. The regulator tries to charge the output

capacitor as quickly as possible, which results in large

peak current.

R1

R3

CONNECT TO

SHDN PIN

WhentheFBPpinvoltageisgeneratedbyaresistordivider

from the V

pin, the start-up current can be limited by

R2

REF

connecting an external capacitor (typically 47nF to 220nF)

84101 F02

to the V pin. When the part is brought out of shutdown,

REF

Figure 2. Programming Enable Voltage by Using External Resistors

thiscapacitorisﬁrstdischargedforabout70μs(providing

84101fb

10

LT8410/LT8410-1

APPLICATIONS INFORMATION

Board Layout Considerations

V

IN

SHDN

As with all switching regulators, careful attention must

be paid to the PCB layout and component placement. To

maximize efﬁciency, switch rise and fall times are made as

shortaspossible.Topreventelectromagneticinterference

(EMI) problems, proper layout of the high frequency

switchingpathisessential.ThevoltagesignaloftheSWpin

hassharprisingandfallingedges.Minimizethelengthand

area of all traces connected to the SW pin and always use

a ground plane under the switching regulator to minimize

SHDN

FBP

V

CC

V

REF

GND

SW

CAP

GND

interplane coupling. In addition, the FBP pin and V pin

REF

V

OUT

are sensitive to noise. Minimize the length and area of all

traces to these two pins is recommended. Recommended

component placement is shown in Figure 3.

8410-1 F03

CAPACITOR GROUNDS MUST BE

RETURNED DIRECTLY TO IC GROUND

Figure 3. Recommended Board Layout

84101fb

11

LT8410/LT8410-1

TYPICAL APPLICATIONS

L1

Efﬁciency vs Load Current

V

IN

100µH

2.5V to 16V

100

90

80

70

60

50

40

C2

0.1µF

C1

2.2µF

V

= 12V

IN

SW

CAP

V

= 16V

C3

OUT

C4

V

CC

OUT

V

= 5V

IN

LT8410

V

0.1µF

V

= 3.6V

REF

IN

TURN ON/OFF

SHDN

604k

0.1µF

GND

FBP

412k

C1: 2.2μF, 16V, X5R, 0603

C2: 0.1μF, 25V, X5R, 0603

8410-1 TA05

C3: 0.1μF, 25V, X5R, 0603 *

C4: 0.1μF, 16V, X7R, 0402

L1: MURATA LQH32CN101K53

0.01

0.1

1

10

100

8410-1 TA07

LOAD CURRENT (mA)

* HIGHER CAPACITANCE VALUE IS REQUIRED FOR

C3 WHEN THE V IS HIGHER THAN 5V

IN

V

(V)

I

(mA)

IN

OUT

Figure 4. 16V Output Converter with Wide Input Voltage

3.6

2.2

5

3.6

13

16V Output Converter with 2mm × 2mm Inductor

12

L1

68µH

V

IN

2.5V to 16V

C2

C1

Efﬁciency vs Load Current

0.1µF

2.2µF

90

80

70

60

50

40

SW

CAP

V

= 16V

C3

OUT

C4

V

IN

= 12V

V

CC

OUT

LT8410

V

= 5V

IN

0.1µF

REF

TURN ON/OFF

SHDN

R1

301k

V

= 3.6V

IN

0.1µF

GND

FBP

R2

210k

C1: 2.2μF, 16V, X5R, 0603

C2: 0.1μF, 25V, X5R, 0603

C3: 0.1μF, 25V, X5R, 0603 *

C4: 0.1μF, 16V, X7R, 0402

L1: COILCRAFT DO2010-683ML

8410 TA06

* HIGHER CAPACITANCE VALUE IS REQUIRED FOR

C3 WHEN THE V IS HIGHER THAN 5V

0.01

0.1

1

10

100

IN

LOAD CURRENT (mA)

8410-1 TA08

LT8410 Maximum Output Current vs Output Voltage

RESISTOR DIVIDER

MAXIMUM OUTPUT CURRENT (mA)

FROM V

REF

V

(V)

R1 (kΩ) / R2 ( kΩ)

V

IN

= 2.8V

0.5

0.7

0.8

1

V

= 3.6V

0.7

0.9

1

V

IN

= 5V

V

IN

= 12V

3.6

4.4

5.5

7.2

9.7

14

OUT

IN

40

NA

1.1

35

30

25

20

15

10

5

110/887

237/768

365/634

487/511

619/383

750/255

866/127

1.4

1.5

2.1

2.9

4

1.4

1.9

2.4

4.6

11

1.4

1.6

3.3

8

7

NA

17

NA

84101fb

12

LT8410/LT8410-1

TYPICAL APPLICATIONS

34V Output Converter with Wide Input Voltage

Efﬁciency vs Load Current

90

80

70

60

50

40

L1

V

IN

V

= 12V

IN

150µH

2.5V to 16V

C2

C1

V

= 5V

IN

0.1µF

2.2µF

SW

CAP

V

= 34V

C3

OUT

C4

V

CC

OUT

V

= 3.6V

IN

LT8410

V

0.1µF

REF

TURN ON/OFF

SHDN

133k

0.1µF

GND

FBP

866k

C1: 2.2μF, 16V, X5R, 0603

8410-1 TA09

C2: 0.1μF, 100V, X5R, 0603

C3: 0.1μF, 100V, X5R, 0603 *

C4: 0.1μF, 16V, X7R, 0402

0.01

0.1

1

10

LOAD CURRENT (mA)

8410-1 TA10

L1: COILCRAFT LPS3314-154ML

* HIGHER CAPACITANCE VALUE IS REQUIRED FOR

V

IN

(V)

I

(mA)

OUT

C3 WHEN THE V IS HIGHER THAN 8V

IN

3.6

0.8

5

1.2

4

12

L1

220µH

V

IN

2.5V to 16V

C2

1.0µF

C1

2.2µF

SW

CAP

V

= 16V

OUT

V

SHDN VOLTAGE

CC

OUT

C3

10000µF

2V/DIV

LT8410-1

V

REF

TURN ON/OFF

SHDN

R1

604k

C4

V

OUT

VOLTAGE

10V/DIV

0.1µF

GND

FBP

R2

412k

INPUT CURRENT

5mA/DIV

C1: 2.2μF, 16V, X5R, 0603

C2: 1.0μF, 25V, X5R, 0603 *

8410-1 TA10a

INDUCTOR

CURRENT

10mA/DIV

C3: 10000μF, ELECTROLYTIC CAPACITOR

C4: 0.1μF, 16V, X7R, 0402

8410-1 G10b

V

= 3.6V

20s/DIV

IN

L1: COILCRAFT LPS3008-224ML

* HIGHER CAPACITANCE VALUE IS REQUIRED FOR

C2 WHEN THE V IS HIGHER THAN 12V

IN

Figure 5. Capacitor Charger with the LT8410-1

LT8410-1 Maximum Output Current vs Output Voltage

FEEDBACK RESISTOR

DIVIDER

R1 (kΩ) / R2 ( kΩ)

MAXIMUM OUTPUT CURRENT (mA)

V

(V)

V

IN

= 2.8V

V

= 3.6V = 5V

V

V = 12V

IN

OUT

IN

40

NA

0.12

0.14

0.18

0.25

0.34

0.48

0.84

2.3

0.16

0.19

0.25

0.35

0.48

0.69

1.2

0.24

0.89

35

30

25

20

15

10

5

110/887

237/768

365/634

487/511

619/383

750/255

866/127

0.3

0.38

0.55

0.76

1.1

1.5

2

2.9

3.5

NA

2.1

3.3

3.5

84101fb

13

LT8410/LT8410-1

PACKAGE DESCRIPTION

DC Package

8-Lead Plastic DFN (2mm × 2mm)

(Reference LTC DWG # 05-08-1719 Rev A)

0.70 ±0.05

2.55 ±0.05

0.64 ±0.05

1.15 ±0.05

(2 SIDES)

PACKAGE

OUTLINE

0.25 ± 0.05

0.45 BSC

1.37 ±0.05

(2 SIDES)

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

R = 0.115

TYP

5

8

R = 0.05

TYP

0.40 ± 0.10

PIN 1 NOTCH

2.00 ±0.10 0.64 ± 0.10

(4 SIDES)

(2 SIDES)

R = 0.20 OR

0.25 × 45°

CHAMFER

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

(DC8) DFN 0409 REVA

4

1

0.23 ± 0.05

0.45 BSC

0.75 ±0.05

0.200 REF

1.37 ±0.10

(2 SIDES)

BOTTOM VIEW—EXPOSED PAD

0.00 – 0.05

NOTE:

1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE

2. DRAWING NOT TO SCALE

3. ALL DIMENSIONS ARE IN MILLIMETERS

4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE

MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE

5. EXPOSED PAD SHALL BE SOLDER PLATED

6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE

TOP AND BOTTOM OF PACKAGE

84101fb

14

LT8410/LT8410-1

REVISION HISTORY ^{(Revision history begins at Rev B)}

REV

DATE

01/11 Corrected Pin Conﬁguration

Revised Note 2 in Electrical Characteristics

DESCRIPTION

PAGE NUMBER

B

2

3

84101fb

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-

tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.

15

LT8410/LT8410-1

TYPICAL APPLICATION

High Voltage Power Supply Does Not Need a Transformer

DANGER HIGH VOLTAGE! OPERATION BY HIGH VOLTAGE TRAINED PERSONNEL ONLY

C3, 0.1µF

C5, 0.1µF

D2

L1

100µH

V

IN

2.5V to 16V

D1

C4

D3

C6

D4

C2

0.1µF

C1

2.2µF

0.1µF

SW

CAP

V

OUT

CC

C7

LT8410

OUTPUT = 100V

0.1µF

0.4mA (V = 5V)

IN

V

TURN ON/OFF

C1: 2.2μF, 16V, X5R, 0603

REF

SHDN

1.4mA (V = 12V)

IN

C8

0.1µF

143k

787k

C2 – C7: 0.1μF, 100V, X5R, 0603

C8: 0.1μF, 16V, X7R, 0402

GND

FBP

D1 – D4: ON SEMI RB751S40T1G

L1: MURATA LQH32CN101K53

8410-1 TA11

Output Voltage vs FBP Voltage

Efﬁciency vs Load Current

140

120

100

90

80

70

60

50

40

V

= 5V

IN

V

= 100V

OUT

V

= 12V

IN

80

60

40

20

V

= 5V

IN

0

0.5

1

1.5

2

0.01

0.1

1

10

FBP VOLTAGE (V)

LOAD CURRENT (mA)

8410-1 TA12

8410-1 TA13

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

: 2.45V to 16V, V

LT1946/LT1946A

1.5A (I ), 1.2MHz/2.7MHz, High Efﬁciency Step-Up DC/DC

V

= 34V, I = 3.2mA, I < 1µA,

OUT(MAX) Q SD

SW

IN

Converters

8-Lead MS Package

LT3464

85mA (I ), High Efﬁciency Step-Up DC/DC Converter with

V

: 2.3V to 10V, V

= 34V, I = 25µA, I < 1µA,

OUT(MAX) Q SD

SW

IN

Integrated Schottky and PNP Disconnect

ThinSOT™ Package

LT3471

Dual Output, Boost/Inverter, 1.3A (I ), High Efﬁciency

V

: 2.4V to 16V, V

= 40V, I = 2.5mA, I < 1µA,

Q SD

SW

IN

OUT(MAX)

Boost-Inverting DC/DC Converter

DFN Package

LT3473/LT3473A

LT3494/LT3494A

LT3495/LT3495B/

1A (I ), 1.2MHz, High Efﬁciency Step-Up DC/DC Converter

V

: 2.2V to 16V, V

= 36V, I = 100µA, I < 1µA,

Q SD

SW

IN

with Integrated Schottky Diode and Output Disconnect

DFN Package

180mA/350mA (I ), High Efﬁciency, Low Noise Step-Up

V

: 2.1V to 16V, V

= 40V, I = 65µA, I < 1µA,

Q SD

SW

IN

DC/DC Converter with Output Disconnect

DFN Package

650mA/350mA (I ), High Efﬁciency, Low Noise Step-Up

V

: 2.3 V to 16V, V

= 40V, I = 60µA, I < 1µA,

OUT(MAX) Q SD

SW

IN

LT3495-1/LT3495B-1 DC/DC Converter with Output Disconnect

DFN Package

84101fb

LT 0211 REV B • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

16

●

 LINEAR TECHNOLOGY CORPORATION 2008

(408) 432-1900 FAX: (408) 434-0507 www.linear.com


型号：	LT8410_15
厂家：	Linear
描述：	Ultralow Power Boost Converter with Output Disconnect
文件：	总16页 (文件大小：319K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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