LTC3539_技术文档

LTC3539/LTC3539-2

2A, 1MHz/2MHz

Synchronous Step-Up

DC/DC Converters

FEATURES

DESCRIPTION

The LTC^®3539/LTC3539-2 are synchronous, 2A step-up

DC/DC converters with output disconnect. Synchronous

rectiﬁcation enables high efﬁciency in the low proﬁle

2mm × 3mm DFN package. Battery life is extended with

a 700mV start-up voltage and operation down to 500mV

once started.

n

Delivers 3.3V at 900mA From 2 Alkaline/NiMH Cells

n

Delivers 5V at 900mA From a Lithium-Polymer

Battery

n

V Start-Up Voltage: 700mV

IN

n

1.5V to 5.25V V

Range

OUT

n

Up to 94% Efﬁciency

V > V Operation

IN

OUT

A switching frequency of 1MHz (LTC3539) or 2MHz

(LTC3539-2) minimizes solution footprint by allowing the

use of tiny, low proﬁle inductors and ceramic capacitors.

The current mode PWM design is internally compensated,

reducing external parts count. The LTC3539/LTC3539-2

feature a pin-enabled automatic Burst Mode operation at

light load conditions. Anti-ring circuitry reduces EMI by

damping the inductor in discontinuous mode. Additional

features include a low shutdown current of under 1μA and

thermal overload protection.

1MHz (LTC3539) or 2MHz (LTC3539-2) Fixed

Frequency Operation

n

Output Disconnect

Selectable Burst Mode^®or PWM Operation

10μA Quiescent Current

Logic Controlled Shutdown: <1μA

Requires Only 6 External Components

Low Proﬁle (2mm × 3mm × 0.75mm) DFN Package

APPLICATIONS

The LTC3539/LTC3539-2 are offered in a 2mm × 3mm ×

0.75mm DFN package.

L, LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

n

Medical Instruments

n

Portable Bar Code Scanners

n

Noise Canceling Headphones

Portable GPS Navigation

Handheld PCs

n

TYPICAL APPLICATION

Wide V_IN, High Power 3.3V Regulator

Efﬁciency and Power Loss vs

Load Current

4.7μH

100

90

80

70

60

50

40

30

20

10

0

1000

100

10

V

IN

1.8V TO 3.6V

2.2μF

EFFICIENCY

V

SW

IN

LTC3539

V

OUT

PWM BURST

OFF ON

MODE

V

OUT

3.3V

V

= 2.4V

IN

OUT

600mA

1M

22pF

= 3.3V

POWER LOSS

SHDN

FB

22μF

GND PGND

562k

1

3539 TA01a

FREQUENCY = 1MHz

FREQUENCY = 2MHz

0.1

1000

0.1

1

10

100

I

AVERAGE (mA)

LOAD

3539 TA01b

3539f

1

LTC3539/LTC3539-2

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

TOP VIEW

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

IN

8

7

6

5

SW

PGND

GND

1

2

3

4

V

OUT

SW Voltage

MODE

FB

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

Pulsed <100ns......................................... –0.3V to 7V

SHDN, FB, MODE Voltage ............................ –0.3V to 6V

9

V

IN

SHDN

DCB PACKAGE

8-LEAD (2mm s 3mm) PLASTIC DFN

V

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

OUT

Operating Temperature (Notes 2, 5)......... –40°C to 85°C

Storage Temperature Range................... –65°C to 125°C

T

= 125°C, θ = 60°C/W TO 85°C/W (NOTE 6)

JA

JMAX

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

ORDER INFORMATION

LEAD FREE FINISH

LTC3539EDCB#PBF

LTC3539EDCB-2#PBF

TAPE AND REEL

PART MARKING

LDCS

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTC3539EDCB#TRPBF

LTC3539EDCB-2#TRPBF

–40°C to 85°C

8-Lead (2mm × 3mm) Plastic DFN

LDPH

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges.

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 speciﬁed

temperature range of –40°C to 85°C, otherwise speciﬁcations are at T_A= 25°C. V_IN= 1.2V, V_OUT= 3.3V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

5

UNITS

V

Input Voltage Range

After Start-Up

0.5

Minimum Start-Up Voltage

I

= 1mA, V

= 0V

OUT

0.7

0.88

5.25

1.230

50

V

LOAD

l

Output Voltage Adjust Range

Feedback Voltage

1.5

V

1.170

1.200

1

V

Feedback Input Current

V

= 1.2V

nA

μA

Ω

FB

Quiescent Current - Shutdown

Quiescent Current - Active

= 0V, Not Including Switch Leakage, V

= 0V

0.01

300

10

1

SHDN

OUT

Measured on V , Non-Switching

500

18

OUT

Quiescent Current - Burst

Measured on V , FB >1.230V

OUT

N-Channel MOSFET Switch Leakage Current

P-Channel MOSFET Switch Leakage Current

N-Channel MOSFET Switch On Resistance

P-Channel MOSFET Switch On Resistance

N-Channel MOSFET Current Limit

V

= 5V

0.1

10

SW

= 5V, V

= 0V

OUT

0.1

20

SW

= 3.3V

0.09

0.125

2.6

OUT

Ω

l

2

A

3539f

2

LTC3539/LTC3539-2

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the speciﬁed

temperature range of –40°C to 85°C, otherwise speciﬁcations are at T_A= 25°C. V_IN= 1.2V, V_OUT= 3.3V, unless otherwise noted.

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

%

l

Maximum Duty Cycle

Minimum Duty Cycle

Switching Frequency

V

FB

V

FB

= 1.15V

= 1.3V

87

90

0

%

l

LTC3539

LTC3539-2

0.7

1.8

1

2

1.3

2.4

MHz

MODE Input High Voltage

MODE Input Low Voltage

MODE Input Current

0.88

V

0.3

1

V

= 1.2V

0.3

μA

V

MODE

SHDN Input High Voltage

SHDN Input Low Voltage

SHDN Input Current

0.88

0.3

V

SHDN

V

SHDN

= 1.2V

= 3.3V

0.3

1

2

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 2: The LTC3539E/LTC3539E-2 is guaranteed to meet performance

speciﬁcations from 0°C to 85°C. Speciﬁcations over –40°C to 85°C

operating temperature range are assured by design, characterization and

correlation with statistical process controls.

Note 4: Current measurements are made when the output is not switching.

Note 5: This IC includes overtemperature protection that is intended

to protect the device during momentary overload conditions. Junction

temperature will exceed 125°C when overtemperature protection is active.

Continuous operation above the speciﬁed maximum operating junction

temperature may result in device degradation or failure.

Note 6: Failure to solder the exposed backside of the package to the PC

board ground plane will result in a thermal resistance much higher than

60°C/W.

Note 3: Speciﬁcation is guaranteed by design and not 100% tested in

production.

3539f

3

LTC3539/LTC3539-2

(T_A= 25°C unless otherwise noted)

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency vs Load Current and

V_IN, V_OUT= 1.8V

Efﬁciency vs Load Current and

V_IN, V_OUT= 3.3V

1000

100

90

80

70

60

50

40

30

20

10

0

1000

100

10

100

90

80

70

60

50

40

30

20

10

0

100

EFFICIENCY

10

POWER LOSS

1

POWER LOSS

1

0.1

0.01

V

= 1V

= 1.2V

= 1.5V

V

= 1.2V

= 1.8V

= 3V

IN

0.1

1000

0.1

1

10

100

1000

0.1

1

10

100

LOAD CURRENT (mA)

3539 G01

3539 G02

Efﬁciency vs Load Current and

V_IN, V_OUT= 5V

No Load Input Current vs V_IN

Maximum Output Current vs V_IN

100

90

80

70

60

50

40

30

20

10

0

100

2000

1800

1600

1400

1200

1000

800

1000

100

10

V

= 1.8V

= 2.5V

= 3.3V

= 5V

OUT

90

80

70

60

50

40

30

20

10

0

EFFICIENCY

POWER LOSS

600

1

V

= 1.8V

= 2.5V

= 3.3V

= 5V

OUT

400

V

= 2.4V

= 3.6V

= 4.2V

IN

200

0.1

1000

0

0.1

1

10

100

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

(V)

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

(V)

LOAD CURRENT (mA)

V

IN

3539 G03

3539 G04

3539 G05

Minimum Load Resistance During

Start-Up vs V_IN

Burst Mode Threshold Current vs

V_INand V_OUT

Normalized Current Limit vs V_OUT

1.10

1.05

1.00

0.95

0.90

0.85

0.80

10000

1000

100

10

60

50

40

30

20

10

0

V

OUT

= 3.3V

V

= 1.8V

OUT

= 2.5V

= 3.3V

= 5V

0.1

1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0

0.65

0.75

0.85

0.95

(V)

1.05

1.15

0

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5

V

OUT

(V)

V

IN

INPUT VOLTAGE (V)

3539 G16

3539 G06

3539 G11

3539f

4

LTC3539/LTC3539-2

TYPICAL PERFORMANCE CHARACTERISTICS

R_DS(ON)vs V_OUT

R_DS(ON)Change vs Temperature

V_FBvs Temperature

0.30

0.25

0.20

0.15

0.10

0.05

0

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.50

0.25

0

PMOS

–0.25

–0.50

–0.75

–1.00

NMOS

1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5

–50 –30 –10 10

30

50

70

90

–60 –40 –20

0

20 40 60 80 100

V

(V)

TEMPERATURE (°C)

OUT

3539 G07

3539 G08

3539 G09

Start-Up Voltage vs Temperature

Fixed Frequency SW and I_L(AC)

Burst Mode SW and I_L(AC)

0.80

0.75

0.70

0.65

0.60

0.55

0.50

SW PIN

2V/DIV

SW PIN

5V/DIV

V

OUT

1mA LOAD

NO LOAD

OUT

20mV/DIV

AC-COUPLED

INDUCTOR

CURRENT

500mA/DIV

INDUCTOR

CURRENT

200mA/DIV

3539 G12

3539 G13

500ns/DIV

= 3.3V AT 400mA

5μs/DIV

V

C

= 2.4V

V

C

= 3.3V

IN

= 5V

OUT

= 22μF

–50

–25

0

25

50

75

100

TEMPERATURE (°C)

3539 G10

Load Step, Fixed Frequency

Load Step, Burst Mode Operation

V

OUT

50mV/DIV

AC-COUPLED

LOAD

CURRENT

200mA/DIV

LOAD

CURRENT

200mA/DIV

3539 G14

3539 G15

500μs/DIV

V

C

= 2.4V

V

C

= 2.4V

IN

= 3.3V

OUT

= 22μF

= 100mA TO 250mA STEP

= 22μF

= 20mA TO 170mA

I

LOAD

3539f

5

LTC3539/LTC3539-2

PIN FUNCTIONS

SW (Pin 1): Switch Pin. Connect inductor between SW

FB (Pin 6): Feedback Input to the g Error Ampliﬁer. Con-

m

and V . Keep PCB trace lengths as short and wide as pos-

nect resistor divider tap to this pin. The output voltage

IN

sible to reduce EMI. If the inductor current falls to zero,

can be adjusted from 1.5V to 5.25V by: V

= 1.20V •

OUT

or SHDN is low, an internal anti-ring resistor is connected

[1 + (R2/R1)]

from SW to V to minimize EMI.

IN

MODE (Pin 7): Burst Mode Pin. A logic controlled input

to select either automatic Burst Mode operation or forced

ﬁxed frequency operation.

PGND (Pin 2), GND (Pin 3): Signal and Power Ground.

Provide a short direct PCB path between PGND, GND and

the (–) side of the input and output capacitors.

MODE = High: Burst Mode operation at light loads

MODE = Low: Fixed frequency PWM Mode

V

(Pin 4): Battery Input Voltage. Connect a minimum

IN

of 2.2μF ceramic decoupling capacitor from this pin to

V

(Pin 8): Output Voltage Sense and Drain of the

ground.

OUT

Internal Synchronous Rectiﬁer. PCB trace length from

SHDN (Pin 5): Logic Controlled Shutdown Input. There

is an internal 4MΩ pull-down on this pin.

V

OUT

to the output ﬁlter capacitor should be as short and

wide as possible.

SHDN = High: Normal operation.

Exposed Pad (Pin 9): The exposed pad must be soldered

to the PCB ground plane. It serves as another ground

connection, and as a means of conducting heat away

from the die.

SHDN = Low: Shutdown, quiescent current <1μA.

BLOCK DIAGRAM

V

IN

1

4

SW

V

IN

V

OUT

V

SEL

WELL

SWITCH

V

BEST

V

B

V

8

6

OUT

V

OUT

R2

R1

GATE DRIVERS

AND

ANTI-CROSS

CONDUCTION

I

ZERO

COMPARATOR

FB

OFF ON

5

SHUTDOWN

SHDN

I

PK

COMPARATOR

3

–

+

–

SLOPE

COMPARATOR

V

REF

V

REF

I

UVLO

PK

UVLO

+

FB

START-UP

ZERO

ERROR

AMPLIFIER/SLEEP

COMPARATOR

LOGIC AND

BURST MODE

CONTROL

CLK

TSD

1MHz/2MHz

OSC

BURST

WAKE

PWM BURST

7

CLAMP

MODE

THERMAL

SHUTDOWN

SOFT-START

EXPOSED PAD

PGND

GND

9

2

3

3539 BD

3539f

6

LTC3539/LTC3539-2

OPERATION

DETAILED DESCRIPTION

to series resistance become critical, and greatly limit the

power delivery capability of the converter.

TheLTC3539isahighpowersynchronousboostconverter

in an 8-lead 2mm × 3mm DFN package. With the ability

to start up and operate from inputs of 700mV, the device

features ﬁxed frequency, current mode PWM control for

exceptional line and load regulation. The current mode

architecture with adaptive slope compensation provides

excellenttransientloadresponse,requiringminimaloutput

ﬁltering. Internal soft-start and internal loop compensa-

tion simpliﬁes the design process while minimizing the

number of external components. The switching frequency

of the LTC3539 is nominally 1MHz, while the LTC3539-2

switchesat2MHz.OperationoftheLTC3539andLTC3539-2

is identical in all other respects.

Low Noise Fixed Frequency Operation

Soft-Start: The LTC3539/LTC3539-2 contains internal

circuitry to provide soft-start operation. The internal

soft-start circuitry ramps the peak inductor current from

zero to its peak value of 2.6A (typical) in approximately

0.5ms, allowing start-up into heavy loads. The soft-start

circuitry is reset in the event of a thermal shutdown or

shutdown command.

Oscillator: An internal oscillator sets the switching

frequency to 1MHz for the LTC3539, and 2MHz for the

LTC3539-2.

With its low R

and low gate charge internal N-chan-

DS(ON)

Shutdown: The part is shutdown by pulling the SHDN

pin below 0.3V, and activated by pulling the SHDN pin

nel MOSFET switch and P-channel MOSFET synchronous

rectiﬁer, the LTC3539 achieves high efﬁciency over a wide

range of load current. Burst Mode operation maintains

high efﬁciency at very light loads, reducing the quiescent

current to just 10μA.

above 0.88V. Note that SHDN can be driven above V

IN

or V , as long as it is limited to less than the absolute

OUT

maximum rating.

Error Ampliﬁer: The error ampliﬁer is a transconductance

type. The non-inverting input is internally connected to

the 1.2V reference and the inverting input is connected

to FB. Clamps limit the minimum and maximum error

amp output voltage for improved large signal transient

response. Power converter control loop compensation is

Converter operation can be best understood by referring

to the Block Diagram.

Low Voltage Start-Up

The LTC3539 includes an independent start-up oscillator

designed to start up at an input voltage of 0.7V (typical).

Soft-start and inrush current limiting are provided during

start-up, as well as normal mode.

provided internally. A voltage divider from V

to ground

OUT

programs the output voltage via FB from 1.5V to 5.25V.

= 1.2V • [1 + (R2/R1)].

V

OUT

When either V or V

exceeds 1.4V typical, the IC

OUT

Current Sensing: Lossless current sensing converts the

peak current signal of the N-channel MOSFET switch

into a voltage which is summed with the internal slope

compensation. The summed signal is compared to the

error ampliﬁer output to provide a peak current control

command for the PWM.

IN

enters normal operating mode. Once the output voltage

exceeds the input by 0.24V, the IC powers itself from

V

instead of V . At this point the internal circuitry has

IN

OUT

no dependency on the V input voltage, eliminating the

IN

requirement for a large input capacitor. The input voltage

can drop as low as 0.5V. The limiting factor for the appli-

cation becomes the ability of the power source to supply

sufﬁcient energy to the output at the low voltages, and the

maximum duty cycle, which is clamped at 90% typical.

Note that at low input voltages, small voltage drops due

Current Limit: The current limit comparator shuts off the

N-channel MOSFET switch once its threshold is reached.

Peak switch current is limited to approximately 2.6A,

independent of input or output voltage, unless V

falls

OUT

below 0.7V, in which case the current limit is cut in half.

3539f

7

LTC3539/LTC3539-2

OPERATION

Zero Current Comparator: The zero current comparator

monitors the inductor current to the output and shuts off

the synchronous rectiﬁer once this current reduces to ap-

proximately40mA.Thispreventstheinductorcurrentfrom

reversing in polarity, improving efﬁciency at light loads.

enter Burst Mode operation at light load current, then

return to ﬁxed frequency PWM mode when the load in-

creases. Refer to the typical performance characteristics

to see the output load Burst Mode threshold vs V . The

IN

load current at which Burst Mode operation is entered can

be changed by adjusting the inductor value. Raising the

inductor value will lower the load current at which Burst

Mode operation is entered.

Synchronous Rectiﬁer: The P-channel MOSFET synchro-

nousrectiﬁerisdisabledwhenV

ismuchlessthanV .

OUT

IN

This is to control inrush current and to prevent inductor

current from running away

In Burst Mode operation, the LTC3539 still switches at a

ﬁxed frequency, using the same error ampliﬁer and loop

compensation for peak current mode control. This control

method eliminates any output transient when switching

between modes. In Burst Mode operation, energy is deliv-

ered to the output until it reaches the nominal regulation

value, then the LTC3539 transitions to Sleep mode where

the outputs are off and the LTC3539 consumes only 10μA

Anti-ringing Control: The anti-ringing control connects

a resistor across the inductor to prevent high frequency

ringing on the SW pin during discontinuous current mode

operation. The ringing of the resonant circuit formed by L

and C (capacitance on SW pin) is low energy, but can

SW

cause EMI radiation.

Output Disconnect: The LTC3539 is designed to allow true

of quiescent current from V . When the output voltage

OUT

outputdisconnectbyeliminatingbodydiodeconductionof

droops slightly, switching resumes. This maximizes ef-

ﬁciency at very light loads by minimizing switching and

quiescentcurrentlosses.BurstModeoutputvoltageripple,

which is typically 1% peak to peak, can be reduced by

using more output capacitance (47μF or greater).

the internal P-channel MOSFET rectiﬁer. This allows V

OUT

to go to zero volts during shutdown, drawing no current

from the input source. It also provides inrush current

limiting at turn-on, minimizing surge currents seen by

the input supply. Note that to obtain the advantages of

output disconnect, there must not be an external Schottky

Astheloadincreases,theLTC3539willautomaticallyleave

Burst Mode operation. Once the LTC3539 has left Burst

Mode operation and returned to normal operation, it will

remain there until the output load is reduced below the

burst threshold.

diodeconnectedbetweentheSWpinandV . Theoutput

OUT

disconnect feature also allows V

to be pulled high,

without any reverse current into a battery on V .

OUT

IN

ThermalShutdown:Ifthedietemperatureexceeds160°C,

the device will go into thermal shutdown. All switches will

be turned off and the internal soft-start capacitor will be

discharged. The device will be enabled again when the die

temperature drops by about 15°C.

Burst Mode operation is inhibited during start-up until

soft-start is complete and V

is at least 0.24V greater

OUT

than V .

IN

When the MODE pin is below 0.3V, the LTC3539 features

continuous PWM operation. In this mode, at very light

loads, the LTC3539 will exhibit pulse-skip operation. If the

Burst Mode Operation

MODE pin voltage exceeds the greater of V or V

by

IN

OUT

When Burst Mode operation is enabled by bringing the

MODE pin above 0.88V, the LTC3539 will automatically

0.5V, the MODE pin will sink additional current.

3539f

8

LTC3539/LTC3539-2

APPLICATIONS INFORMATION

COMPONENT SELECTION

V > V

Operation

IN

OUT

The LTC3539 will maintain output voltage regulation

even when the input voltage is above the desired output.

Note that the efﬁciency and the maximum output current

capability are reduced. Refer to Typical Performance

Characteristics.

Inductor Selection

The LTC3539 can utilize small surface mount and chip

inductors due to the high switching frequency. Inductor

values between 3.3μH and 4.7μH for the LTC3539 and

between 1.5μH and 2.5μH for the LTC3539-2 are suitable

for most applications*. Larger values of inductance will

allow slightly greater output current capability (and lower

the Burst Mode threshold) by reducing the inductor ripple

current. However, increasing the inductance above 10μH

will increase size while providing little improvement in

output current capability.

Short-Circuit Protection

The LTC3539 output disconnect feature allows an output

short circuit while maintaining a maximum internally set

current limit. To reduce power dissipation under short-

circuit conditions, the peak switch current limit is reduced

to 1.4A (typical).

The minimum inductance value is given by:

Schottky Diode

V

_IN(MIN)•(V_OUT(MAX)− V

)

IN(MIN)

L >

Although it is not required, adding a Schottky diode from

Ripple • V_OUT(MAX)• f

SW to V

will improve efﬁciency by about 2%. Note that

OUT

this defeats the output disconnect, V > V

operation

IN

OUT

Where:

and short circuit protection features.

f = 1 for the LTC3539 or 2.2 for the LTC3539-2

Ripple = allowable inductor current ripple (Amps

peak-to-peak)

PCB LAYOUT GUIDELINES

ThehighspeedoperationoftheLTC3539demandscareful

attention to board layout. A careless layout will result in

reduced performance. Figure 1 shows the recommended

componentplacement.Alargegroundpincopperareawill

help to lower the die temperature. A multilayer board with

a separate ground plane is ideal.

V

= minimum input voltage

OUT(MAX)

IN(MIN)

= maximum output voltage

The inductor current ripple is typically set for 20% to 40%

of the maximum inductor current. High frequency ferrite

core inductor materials improve efﬁciency by reducing

frequency dependent power losses compared to cheaper

powdered iron types. The inductor should have low ESR

2

(seriesresistanceofthewindings)toreducetheI Rpower

LTC3539

losses, and must accomodate the peak inductor current

withoutsaturating.Moldedchokesandsomechipinductors

usually do not have enough core area to support the peak

inductorcurrentof2.6AseenontheLTC3539.Tominimize

radiated noise, use a shielded inductor. See Table 1 for

suggested suppliers and representative components.

SW

PGND

GND

V

OUT

1

2

3

4

8

7

6

5

MODE

FB

MINIMIZE

TRACE ON FB

AND SW

V

IN

SHDN

+

*Single cell applications (V < 1.6V) should use a 2.2μH inductor for the LTC3539

IN

V

IN

MULTIPLE VIAS

TO GROUND PLANE

3539 F01

Figure 1. Recommended Component Placement for

Single Layer Board

3539f

9

LTC3539/LTC3539-2

APPLICATIONS INFORMATION

Table 1. Representative Inductors

An output capacitor of up to 100μF is required at lower

output voltages. Even with V greater than 3V, larger

OUT

VENDOR

PART/STYLE

values up to 100μF may be used to obtain extremely low

outputvoltagerippleandimprovetransientresponse.X5R

and X7R dielectric materials are preferred for their ability

tomaintaincapacitanceoverwidevoltageandtemperature

ranges. Y5V types should not be used.

Coilcraft

MSS5131

(847) 639-6400

www.coilcraft.com

LPS4018-222

MSS6132

MOS6020

Murata

www.murata.com

LQH55D

LQH66S

Sumida

CDRH4D22

CDRH4D28C

CDRH5D28

CDR6D23

Asmallceramiccapacitorinparallelwithalargertantalum

capacitor may be used in demanding applications which

havelargeloadtransients. Afeedforwardcapacitoracross

(847) 956-0666

www.sumida.com

TDK

VLF5014ST

the top resistor of the feedback divider (from V

to FB)

OUT

(847) 803-6100

www.component.tdk.com

isusuallyrequiredtoimprovetransientresponse.Atypical

value of 22pF will generally sufﬁce.

Toko

(408) 432-8282

www.tokoam.com

D53LC

D63LCB

LowESRinputcapacitorsreduceinputswitchingnoiseand

reduce the peak current drawn from the battery. It follows

that ceramic capacitors are also a good choice for input

decoupling and should be located as close as possible to

the device. A 2.2μF input capacitor is sufﬁcient for most

applications. Larger values may be used without limita-

tions. Table 2 shows a list of several ceramic capacitor

manufacturers. Consult the manufacturers directly for

detailed information on their selection of ceramic parts.

Wurth

(201) 785-8800

www.we-online.com

WE-TPC Type LH, X

WE-PD Type XS

Output and Input Capacitor Selection

TheinternalloopcompensationoftheLTC3539isdesigned

tobestablewithoutputcapacitorvaluesof10μForgreater.

Although ceramic capacitors are recommended, low ESR

(equivalent series resistance) tantalum capacitors may be

used as well.

Table 2. Capacitor Vendor Information

SUPPLIER

AVX

PHONE

WEBSITE

(803) 448-9411

(714) 852-2001

(408) 573-4150

(847) 803-6100

www.avxcorp.com

www.murata.com

www.t-yuden.com

www.component.tdk.com

Low ESR capacitors should be used to minimize the

output voltage ripple. Multilayer ceramic capacitors are

an excellent choice as they have extremely low ESR and

are available in small footprints. A 22μF to 47μF output

capacitor is sufﬁcient for output voltages of 3V or greater.

Murata

Taiyo-Yuden

TDK

TYPICAL APPLICATIONS

1 Cell to 1.8V

1 Cell to 3.3V

Li-Ion Cell to 5V

2.2μH

V

IN

1V TO 1.6V

IN

0.9V TO 1.6V

IN

3V TO 4.5V

2.2μF

V

SW

V

SW

LTC3539

V

SW

LTC3539-2

IN

LTC3539

V

OUT

PWM BURST

OFF ON

PWM BURST

OFF ON

PWM BURST

OFF ON

MODE

V

MODE

V

MODE V

OUT

1.8V

3.3V

5V

500mA

350mA

750mA

1M

22pF

1M

22pF

1M

22pF

SHDN

FB

SHDN

FB

SHDN

FB

22μF*

x5

22μF

x2

22μF

GND PGND

1.91M

562k

309k

*AT HIGH LOAD CURRENTS, A

TANTALUM CAPACITOR WILL

IMPROVE PERFORMANCE.

3539 TA02

3539 TA03

3539 TA04

3539f

10

LTC3539/LTC3539-2

PACKAGE DESCRIPTION

DCB Package

8-Lead Plastic DFN (2mm × 3mm)

(Reference LTC DWG # 05-08-1718 Rev A)

0.70 0.05

1.35 0.05

1.65 0.05

3.50 0.05

2.10 0.05

PACKAGE

OUTLINE

0.25 0.05

0.45 BSC

1.35 REF

RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS

APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED

R = 0.115

2.00 0.10

(2 SIDES)

0.40 0.10

8

TYP

5

R = 0.05

TYP

1.35 0.10

1.65 0.10

3.00 0.10

(2 SIDES)

PIN 1 NOTCH

R = 0.20 OR 0.25

× 45° CHAMFER

PIN 1 BAR

TOP MARK

(SEE NOTE 6)

(DCB8) DFN 0106 REV A

4

1

0.23 0.05

0.45 BSC

0.75 0.05

0.200 REF

1.35 REF

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

3539f

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.

11

LTC3539/LTC3539-2

RELATED PARTS

PART NUMBER DESCRIPTION

COMMENTS

LTC3400/

LTC3400B

600mA I , 1.2MHz, Synchronous Step-Up DC/DC

92% Efﬁciency V : 0.85V to 5V, V

= 5V, I = 19μA/300μA, I <1μA,

OUT(MAX) Q SD

SW

IN

Converters

ThinSOT™ Package

LTC3401

LTC3402

LTC3421

LTC3422

1A I , 3MHz, Synchronous Step-Up DC/DC Converter 97% Efﬁciency V : 0.5V to 5V, V

= 6V, I = 38μA, I <1μA, 10-Lead

Q SD

SW

IN

OUT(MAX)

MS Package

2A I , 3MHz, Synchronous Step-Up DC/DC Converter 97% Efﬁciency V : 0.5V to 5V, V

= 6V, I = 38μA, I <1μA, 10-Lead

SW

IN

OUT(MAX)

Q

SD

MS Package

3A I , 3MHz, Synchronous Step-Up DC/DC Converter 95% Efﬁciency V : 0.5V to 4.5V, V

= 5.25V, I = 12μA, I <1μA,

Q SD

SW

IN

OUT(MAX)

with Output Disconnect

QFN24 Package

1.5A I , 3MHz Synchronous Step-Up DC/DC

95% Efﬁciency V : 0.5V to 4.5V, V

= 5.25V, I = 25μA, I <1μA,

Q SD

SW

IN

Converter with Output Disconnect

3mm × 3mm DFN Package

LTC3423/

LTC3424

1A/2A I , 3MHz, Synchronous Step-Up DC/DC

95% Efﬁciency V : 0.5V to 5.5V, V

= 5.5V, I = 38μA, I <1μA,

Q SD

SW

IN

Converter

10-Lead MS Package

LTC3426

LTC3428

2A I , 1.2MHz, Step-Up DC/DC Converter

92% Efﬁciency V : 1.6V to 4.3V, V

= 5V, I <1μA, SOT-23 Package

SD

SW

IN

500mA I , 1.25MHz/2.5MHz, Synchronous Step-Up

92% Efﬁciency V : 1.8V to 5V, V

= 5.25V, I <1μA, 3mm × 3mm

SW

IN

OUT(MAX) SD

DC/DC Converters with Output Disconnect

DFN Package

LTC3429

LTC3458

LTC3458L

600mA I , 500kHz, Synchronous Step-Up DC/DC

96% Efﬁciency V : 0.5V to 4.4V, V

= 5V, I = 20μA/300μA,

SW

IN

OUT(MAX) Q

Converter with Output Disconnect and Soft-Start

1.4A I , 1.5MHz, Synchronous Step-Up DC/DC

93% Efﬁciency V : 1.5V to 6V, V

= 7.5V, I = 15μA, I <1μA,

SW

IN

OUT(MAX) Q SD

Converter/Output Disconnect/Burst Mode Operation

DFN12 Package

1.7A I , 1.5MHz, Synchronous Step-Up DC/DC

94% Efﬁciency V = 6V, I = 12μA, DFN12 Package

OUT(MAX) Q

SW

Converter with Output Disconnect, Automatic Burst

Mode Operation

LTC3459

70mA I , 10V Micropower Synchronous Boost

V : 1.5V to 5.5V, V

= 10V, I = 10μA, I <1μA, ThinSOT Package

SW

IN

OUT(MAX)

Q

SD

Converter/Output Disconnect/Burst Mode Operation

LTC3525-3/

LTC3525-3.3/

LTC3525-5

400mA Micropower Synchronous Step-Up DC/DC

Converter with Output Disconnect

95% Efﬁciency V : 1V to 4.5V, V

= 3.3V or 5V, I = 7μA, I <1μA,

OUT(MAX) Q SD

IN

SC-70 Package

LTC3525L-3

400mA Micropower Synchronous Step-Up DC/DC

Converter with Output Disconnect

95% Efﬁciency V : 0.88V to 4.5V, V

= 3V, I = 7μA, I <1μA,

OUT(MAX) Q SD

IN

SC-70 Package

LTC3526/

LTC3526B

500mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efﬁciency V : 0.85V to 5V, V

= 5.25V, I = 9μA, I <1μA,

Q SD

IN

OUT(MAX)

with Output Disconnect

2mm × 2mm DFN-6 Package

LTC3526L

550mA, 1MHz Synchronous Step-Up DC/DC Converter 94% Efﬁciency V : 0.68V to 5V, V

= 5.25V, I = 9μA, I <1μA,

Q SD

IN

with Output Disconnect

2mm × 2mm DFN-6 Package

LTC3527/

LTC3527-1

Dual 800mA/400mA, 1.2MHz/2.2MHz Synchronous

Step-Up DC/DC Converter with Output Disconnect

94% Efﬁciency V : 0.68V to 5V, V

= 5.25V, I = 12μA, I <1μA,

Q SD

IN

3mm × 3mm QFN-16 Package

LTC3528/

LTC3528B

1A, 1MHz Synchronous Step-Up DC/DC Converter with 94% Efﬁciency V : 0.68V to 5V, V

= 5.25V, I = 12μA, I <1μA,

Q SD

IN

Output Disconnect

2mm × 3mm DFN-8 Package

ThinSOT is a trademark of Linear Technology Corporation.

3539f

LT 0408 • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

12

●

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


型号：	LTC3539
厂家：	Linear
描述：	2A, 1MHz/2MHz Synchronous Step-Up DC/DC Converters 2A ， 1MHz的/ 2MHz的同步升压型DC / DC转换器转换器
文件：	总12页 (文件大小：171K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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