LTM4605IV#PBF_技术文档

LTM4605

High Efficiency

Buck-Boost DC/DC

µModule Regulator

Features

Description

The LTM^®4605 is a high efficiency switching mode buck-

boost power supply. Included in the package are the

switchingcontroller,powerFETs,andsupportcomponents.

Operating over an input voltage range of 4.5V to 20V, the

LTM4605 supports an output voltage range of 0.8V to

16V, set by a resistor. This high efficiency design delivers

up to 5A continuous current in boost mode (12A in buck

mode). Only the inductor, sense resistor, bulk input and

output capacitors are needed to finish the design.

n

Single Inductor Architecture Allows V Above,

IN

Below or Equal to V

OUT

n

Wide V Range: 4.5V to 20V

IN

OUT

Wide V

Range: 0.8V to 16V

5A DC Typical (12A DC Typical at Buck Mode)

High Efficiency Up to 98%

Current Mode Control

Power Good Output Signal

Phase-Lockable Fixed Frequency: 200kHz to 400kHz

Ultrafast Transient Response

Thelowprofilepackageenablesutilizationofunusedspace

on the bottom of PC boards for high density point of load

regulation. The high switching frequency and current

mode architecture enable a very fast transient response

to line and load changes. The LTM4605 can be frequency

synchronized with an external clock to reduce undesirable

frequency harmonics.

Current Foldback Protection

Output Overvoltage Protection

Small, Low Profile Surface Mount LGA Package

(15mm × 15mm × 2.8mm)

applications

Faultprotectionfeaturesincludeovervoltageandfoldback

current protection. The DC/DC µModule^®regulator is of-

fered in a small and thermally enhanced 15mm × 15mm

× 2.8mm LGA package. The LTM4605 is Pb-free and

RoHS compliant.

n

Telecom, Servers and Networking Equipment

n

Industrial and Automotive Equipment

n

High Power Battery-Operated Devices

L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule ad PolyPhase are registered

trademarks and No R

is a trademark of Linear Technology Corporation. All other

SENSE

trademarks are the property of their respective owners.

typical application

12V/5A Buck-Boost DC/DC µModule Regulator with 4.5V to 20V Input

Efficiency and Power Loss

vs Input Voltage

V

IN

CLOCK SYNC

99

98

97

96

95

94

93

92

91

90

8

7

6

5

4

3

2

1

0

4.5V TO 20V

10µF

35V

V

I

= 12V

= 5A

OUT

LOAD

f = 200kHz

V

12V

5A

OUT

V

PLLIN

IN

V

OUT

+

10µF

35V

330µF

25V

FCB

ON/OFF

RUN

LTM4605

4.7µH

SW1

SW2

R

SENSE

+

SENSE

0.1µF

6mΩ

–

SS

SENSE

SGND

V

FB

PGND

7.15k

5

6

7

8

9 10 11 12 13 14 15 16 17 18 19 20

(V)

V

4605 TA01

IN

4605 TA01b

4605fd

1

For more information www.linear.com/LTM4605

LTM4605

absolute MaxiMuM ratings

pin conFiguration

(Note 1)

(See Table 6. Pin Assignment)

V ............................................................. –0.3V to 20V

OUT

IN

TOP VIEW

BANK 2

V

..............................................................0.8V to 16V

INTV , EXTV , RUN, SS, PGOOD.............–0.3V to 7V

M

L

CC

SW1, SW2 (Note 6).......................................–5V to 20V

V , COMP................................................ –0.3V to 2.4V

BANK 4

BANK 1

BANK 3

FB

K

FCB, STBYMD.......................................–0.3V to INTV

CC

J

PLLIN........................................................ –0.3V to 5.5V

PLLFLTR ................................................... –0.3V to 2.7V

Operating Temperature Range

H

G

BANK 5

F

(Note 2) ...............................................–40°C to 85°C

Storage Temperature Range .................. –55°C to 125°C

E

D

C

BANK 6

B

A

1

2

3

4

5

6

7

8

9

10

11

12

LGA PACKAGE

141-LEAD (15mm × 15mm × 2.8mm)

T

JMAX

= 125°C, θ = 4°C/W

JP

WEIGHT = 1.5g

orDer inForMation

PART MARKING*

PACKAGE

TYPE

MSL

TEMPERATURE RANGE

(SEE NOTE 2)

PART NUMBER

LTM4605EV#PBF

LTM4605IV#PBF

PAD OR BALL FINISH

Au (RoHS)

DEVICE

FINISH CODE

RATING

LTM4605V

e4

LGA

3

–40°C to 85°C

Au (RoHS)

Consult Marketing for parts specified with wider operating temperature

ranges. *Device temperature grade is indicated by a label on the shipping

container. Pad or ball finish code is per IPC/JEDEC J-STD-609.

•ꢀRecommended LGA and BGA PCB Assembly and Manufacturing

Procedures:

www.linear.com/umodule/pcbassembly

•ꢀLGA and BGA Package and Tray Drawings:

www.linear.com/packaging

•ꢀTerminal Finish Part Marking:

www.linear.com/leadfree

electrical characteristics ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C (Note 2), V_IN= 12V. Per typical application (front page) configuration.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Input Specifications

l

V

Input DC Voltage

4.5

20

4

V

IN(DC)

IN(UVLO)

Q(VIN)

Undervoltage Lockout Threshold

V

Falling

3.4

IN

I

Input Supply Bias Current

Normal

2.8

1.6

35

mA

µA

Standby

Shutdown Supply Current

V

RUN

V

RUN

= 0V, V

> 2V

= Open

STBYMD

60

4605fd

2

For more information www.linear.com/LTM4605

LTM4605

electrical characteristics ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C (Note 2), V_IN= 12V. Per typical application (front page) configuration.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Output Specifications

I

Output Continuous Current Range

(See Output Current Derating Curves

V

= 12V, V = 5V

OUT

12

5

A

OUTDC

IN

= 6V, V

= 12V

OUT

for Different V , V

and T )

A

IN OUT

ΔV /V

FB FB(NOM)

Reference Voltage Line Regulation

Accuracy

V

IN

= 4.5V to 20V, V = 1.2V (Note 3)

COMP

0.002

0.02

%/V

l

ΔV /V

FB FB(LOAD)

Load Regulation Accuracy

V

COMP

V

COMP

= 1.2V to 0.7V

= 1.2V to 1.8V (Note 3)

0.15

–0.15

0.5

–0.5

%

Switch Section

M1 t

M3 t

Turn-On Time (Note 4)

Turn-Off Time

Drain to Source Voltage V = 12V,

50

40

ns

r

f

r

f

DS

Bias Current I = 10mA

SW

Drain to Source Voltage V = 12V,

DS

Bias Current I = 10mA

SW

Turn-On Time

Drain to Source Voltage V = 12V,

25

DS

Bias Current I = 10mA

SW

Turn-Off Time

Drain to Source Voltage V = 12V,

20

DS

Bias Current I = 10mA

SW

M2, M4 t

Turn-On Time

Drain to Source Voltage V = 12V,

20

r

f

DS

Bias Current I = 10mA

SW

Turn-Off Time

Drain to Source Voltage V = 12V,

20

DS

Bias Current I = 10mA

SW

t

M1 Off to M2 On Delay (Note 4)

M2 Off to M1 On Delay

M3 Off to M4 On Delay

M4 Off to M3 On Delay

M2 Off to M4 On Delay

M4 Off to M2 On Delay

Drain to Source Voltage V = 12V,

50

1d

2d

3d

4d

DS

Bias Current I = 10mA

SW

Drain to Source Voltage V = 12V,

50

DS

Bias Current I = 10mA

SW

Drain to Source Voltage V = 12V,

50

DS

Bias Current I = 10mA

SW

Drain to Source Voltage V = 12V,

50

DS

Bias Current I = 10mA

SW

Mode Transition 1

Mode Transition 2

Drain to Source Voltage V = 12V,

220

DS

Bias Current I = 10mA

SW

Drain to Source Voltage V = 12V,

DS

Bias Current I = 10mA

SW

M1 R

M2 R

M3 R

M4 R

Static Drain-to-Source On-Resistance

Bias Current I = 3A

6.5

8

mΩ

DS(ON)

SW

Bias Current I = 3A

12

SW

Bias Current I = 3A

8

SW

Bias Current I = 3A

8

SW

Oscillator and Phase-Locked Loop

f

Nominal Frequency

V

= 1.2V

= 0V

260

170

340

300

200

400

50

330

220

440

kHz

kΩ

NOM

LOW

HIGH

PLLFLTR

Lowest Frequency

Highest Frequency

= 2.4V

R

PLLIN Input Resistance

Phase Detector Output Current

PLLIN

I

f

< f

> f

–15

15

µA

PLLFLTR

PLLIN

OSC

4605fd

3

For more information www.linear.com/LTM4605

LTM4605

electrical characteristics ^Thel denotes the specifications which apply over the full operating

temperature range, otherwise specifications are at T_A= 25°C (Note 2), V_IN= 12V. Per typical application (front page) configuration.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

Control Section

l

V

Feedback Reference Voltage

RUN Pin ON/OFF Threshold

Soft-Start Charging Current

Start-Up Threshold

V

= 1.2V

0.792

1

0.8

1.6

0.808

2.2

V

FB

COMP

RUN

I

V

= 2.2V

1

1.7

µA

V

SS

RUN

V

Rising

0.4

0.7

STBYMD(START)

STBYMD(KA)

FCB

STBYMD

Keep-Active Power On Threshold

Forced Continuous Threshold

Forced Continuous Pin Current

Rising, V

= 0V

1.25

0.8

V

RUN

0.76

–0.3

0.84

–0.1

5.5

V

I

V

FCB

= 0.85V

–0.2

5.3

µA

V

FCB

V

Burst Inhibit (Constant Frequency)

Threshold

Measured at FCB Pin

BURST

DF

Maximum Duty Factor

% Switch M4 On

% Switch M1 On

Switch M1 (Note 5)

99

%

ns

(BOOST, MAX)

(BUCK, MAX)

t

Minimum On-Time for Synchronous

Switch in Buck Operation

200

250

ON(MIN, BUCK)

RFBHI

Resistor Between V

and V Pins

99.5

5.7

100

100.5

kΩ

OUT

FB

Internal V Regulator

CC

l

INTV

Internal V Voltage

V

> 7V, V = 5V

EXTVCC

6

6.3

2

V

%

CC

IN

CC

ΔV /V

LDO LDO

Internal V Load Regulation

I

= 0mA to 20mA, V

= 5V

0.3

5.6

300

60

CC

EXTVCC

V

EXTV Switchover Voltage

= 20mA, V

Rising

5.4

V

EXTVCC

CC

EXTVCC

ΔV

EXTV Switchover Hysteresis

mV

EXTVCC(HYS)

EXTVCC

CC

EXTV Switch Drop Voltage

I

= 20mA, V

= 6V

150

CC

Current Sensing Section

l

V

Maximum Current Sense Threshold

Boost Mode

Buck Mode

160

–130

190

–150

mV

SENSE(MAX)

–95

V

Minimum Current Sense Threshold

Sense Pins Total Source Current

Discontinuous Mode

–6

mV

µA

SENSE(MIN, BUCK)

SENSE

–

+

I

V

SENSE

= V

= 0V

SENSE

–380

PGOOD

ΔV

PGOOD Upper Threshold

PGOOD Lower Threshold

PGOOD Hysteresis

V

Rising

Falling

5.5

7.5

–7.5

2.5

10

%

V

FBH

FB

–5.5

–10

FBL

FB

Returning

FB(HYS)

FB

V

PGL

PGOOD Low Voltage

I

= 2mA

= 5V

0.2

0.3

1

PGOOD

I

PGOOD Leakage Current

V

µA

PGOOD

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: The LTM4605 is tested in a feedback loop that servos V

to a

COMP

specified voltage and measures the resultant V

.

FB

Note 4: Turn-on and turn-off time are measured using 10% and 90%

levels. Transition delay time is measured using 50% levels.

Note 2: The LTM4605E is guaranteed to meet specifications from the 0°C

to 85°C operating temperature range. Specifications over the –40°C to

85°C operating temperature range are assured by design, characterization

and correlation with statistical process controls. The LTM4605I is

guaranteed over the –40°C to 85°C operating temperature range.

Note 5: 100% tested at wafer level only.

Note 6: Absolute Maximum Rating of –5V on SW1 and SW2 is under

transient condition only.

4605fd

4

For more information www.linear.com/LTM4605

LTM4605

typical perForMance characteristics ^{(Refer to Figure 16)}

Efficiency vs Load Current

6V_INto 12V_OUT

Efficiency vs Load Current

12V_INto 12V_OUT

Efficiency vs Load Current

18V_INto 12V_OUT

100

90

80

70

60

50

40

30

20

10

0

100

90

80

70

60

50

40

30

20

10

0

95

85

75

65

55

45

35

25

15

CCM

DCM

SKIP CYCLE

CCM

DCM

BURST

0.01

0.1

1

10

100

0.01

0.1

1

10

0.01

0.1

1

10

LOAD CURRENT (A)

4605 G03

4605 G01

4605 G02

Efficiency vs Load Current

3.3µH Inductor (CCM)

Efficiency vs Load Current

1.5µH Inductor (CCM)

Efficiency vs Load Current

1.5µH Inductor (CCM)

100

95

90

85

80

75

70

65

60

100

95

90

85

80

75

70

65

60

55

50

100

95

90

85

80

75

70

65

60

55

50

18V TO 5V

18V TO 3.3V

18V TO 2.5V

IN

OUT

IN

OUT

IN

OUT

12V TO 5V

12V TO 3.3V

12V TO 2.5V

IN

5V TO 5V

IN

5V TO 3.3V

IN

5V TO 2.5V

IN OUT

0

3

6

9

12

0

3

6

9

12

0

3

6

9

12

LOAD CURRENT (A)

4605 G04

4605 G05

4605 G06

Transient Response from

6V_INto 12V_OUT

Transient Response from

12V_INto 12V_OUT

Transient Response from

18V_INto 12V_OUT

I

OUT

2A/DIV

V

OUT

200mV/DIV

100mV/DIV

4605 G07

4605 G08

4605 G09

200µs/DIV

LOAD STEP: 0A TO 3A AT CCM

LOAD STEP: 0A TO 4A AT CCM

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

2x 15mΩ SENSING RESISTORS

4605fd

5

For more information www.linear.com/LTM4605

LTM4605

typical perForMance characteristics

Start-Up with 6V_INto 12V_OUT

at I_OUT= 5A

Start-Up with 18V_INto 12V_OUT

at I_OUT= 5A

V

OUT

5V/DIV

I

IN

I

IN

5A/DIV

2A/DIV

I

L

5A/DIV

L

5A/DIV

4605 G10

4605 G11

50ms/DIV

0.22µF SOFT-START CAP

50ms/DIV

0.22µF SOFT-START CAP

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

2x 15mΩ SENSING RESISTORS

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

2x 15mΩ SENSING RESISTORS

Short Circuit with 6V_INto 12V_OUT

at I_OUT= 5A

Short Circuit with 18V_INto 12V_OUT

at I_OUT= 5A

V

OUT

V

5V/DIV

OUT

10V/DIV

I

IN

I

IN

5A/DIV

10A/DIV

4605 G12

4605 G13

20µs/DIV

100µs/DIV

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

2x 15mΩ SENSING RESISTORS

OUTPUT CAPS: 4x 22µF CERAMIC CAPS AND

2x 180µF ELECTROLYTIC CAPS

2x 15mΩ SENSING RESISTORS

4605fd

6

For more information www.linear.com/LTM4605

LTM4605

pin Functions

V (Bank 1): Power Input Pins. Apply input voltage be-

STBYMD (Pin A10): LDO Control Pin. Determine whether

theinternalLDOremainsactivewhenthecontrollerisshut

down. See Operations section for details. If the STBYMD

pin is pulled to ground, the SS pin is internally pulled to

ground to disable start-up and thereby providing a single

control pin for turning off the controller. An internal de-

coupling capacitor is tied to this pin.

IN

tween these pins and PGND pins. Recommend placing

input decoupling capacitance directly between V pins

IN

and PGND pins.

V

(Bank 5): Power Output Pins. Apply output load

OUT

between these pins and PGND pins. Recommend placing

outputdecouplingcapacitancedirectlybetweenthesepins

and PGND pins.

V

(Pin B6): The Negative Input of the Error Amplifier.

FB

Internally, this pin is connected to V

with a 100k preci-

OUT

PGND (Bank 6): Power Ground Pins for Both Input and

Output Returns.

sionresistor.Differentoutputvoltagescanbeprogrammed

with an additional resistor between V and SGND pins.

FB

SW1, SW2 (Bank 4, Bank 2): Switch Nodes. The power

inductor is connected between SW1 and SW2.

See the Applications Information section.

FCB (Pin A9): Forced Continuous Control Input. The

voltage applied to this pin sets the operating mode of the

module. When the applied voltage is less than 0.8V, the

forced continuous current mode is active. When this pin

is allowed to float, the Burst Mode operation is active in

boost operation and the skip cycle mode is active in buck

R

(Bank3):SensingResistorPin. Thesensingresis-

SENSE

tor is connected from this pin to PGND.

+

SENSE (Pin A4): Positive Input to the Current Sense and

Reverse Current Detect Comparators.

–

SENSE (Pin A5): Negative Input to the Current Sense

operation. When the pin is tied to INTV , the constant

CC

and Reverse Current Detect Comparators.

frequency discontinuous current mode is active in buck or

boostoperation.SeetheApplicationsInformationsection.

EXTV (PinF6):ExternalV Input.WhenEXTV exceeds

CC

5.7V, an internal switch connects this pin to INTV and

CC

SGND (Pin A7): Signal Ground Pin. This pin connects to

PGND at output capacitor point.

shutsdowntheinternalregulatorsothatthecontrollerand

gate drive power is drawn from EXTV . Do not exceed

CC

COMP (Pin B7): Current Control Threshold and Error

Amplifier Compensation Point. The current comparator

threshold increases with this control voltage. The voltage

ranges from 0V to 2.4V.

7V at this pin and ensure that EXTV < V .

CC

IN

INTV (Pin F5): Internal 6V Regulator Output. This pin

CC

is for additional decoupling of the 6V internal regulator.

PLLIN (Pin B9): External Clock Synchronization Input

to the Phase Detector. This pin is internally terminated

to SGND with a 50k resistor. The phase-locked loop will

force the rising bottom gate signal of the controller to be

synchronized with the rising edge of PLLIN signal.

PGOOD (Pin B5): Output Voltage Power Good Indicator.

Open drain logic output that is pulled to ground when the

output voltage is not within 7.5% of the regulation point.

RUN (Pin A8): Run Control Pin. A voltage below 1.6V will

turn off the module. There is a 100k resistor between the

RUN pin and SGND in the module. Do not apply more

than 6V to this pin. See Applications Information section.

PLLFLTR (Pin B8): The lowpass filter of the phase-locked

loop is tied to this pin. This pin can also be used to set the

frequency of the internal oscillator with an AC or DC volt-

age. See the Applications Information section for details.

SS (Pin A6): Soft-Start Pin. Soft-start reduces the input

power sources’ surge currents by gradually increasing

the controller’s current limit.

4605fd

7

For more information www.linear.com/LTM4605

LTM4605

siMpliFieD block DiagraM

V

IN

4.5V TO 20V

EXTV

CC

C1

C

IN

M1

M2

SW2

INTV

PGOOD

RUN

L

SW1

ON/OFF

V

OUT

100k

12V

5A

STBYMD

COMP

CO1

M3

M4

C

OUT

0.1µF

100k

R

FB

V

FB

7.15k

CONTROLLER

R

SENSE

INT

COMP

+

SS

SENSE

SS

0.1µF

PLLIN

PLLFLTR

INT

FILTER

R

SENSE

–

SENSE

INT

FILTER

PGND

FCB

1000pF

SGND

TO PGND PLANE AS

SHOWN IN FIGURE 13

4605 BD

Figure 1. Simplified LTM4605 Block Diagram

Decoupling requireMents _{T = 25°C. Use Figure 1 configuration.}

A

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

C

IN

External Input Capacitor Requirement

I

= 5A

10

µF

OUT

(V = 4.5V to 20V, V

= 12V)

IN

OUT

C

OUT

External Output Capacitor Requirement

(V = 4.5V to 20V, V = 12V)

I

= 5A

200

300

µF

OUT

IN

OUT

4605fd

8

For more information www.linear.com/LTM4605

LTM4605

operation

Power Module Description

Alternatively, its frequency can be synchronized by the

input clock signal from the PLLIN pin. The typical switch-

ing frequency is 400kHz.

The LTM4605 is a non-isolated buck-boost DC/DC power

supply.Itcandeliverawiderangeoutputvoltagefrom0.8V

to 16V over a wide input range from 4.5V to 20V, by only

adding the sensing resistor, inductor and some external

inputandoutputcapacitors.Itprovidespreciselyregulated

output voltage programmable via one external resistor.

The typical application schematic is shown in Figure 16.

The Burst Mode and skip-cycle mode operations can

be enabled at light loads in the LTM4605 to improve its

efficiency, while the forced continuous mode and discon-

tinuous mode operations are used for constant frequency

applications. Foldback current limiting is activated in an

overcurrent condition as V drops. Internal overvoltage

FB

The LTM4605 has an integrated current mode buck-boost

controller,ultralowR

andundervoltagecomparatorspulltheopen-drainPGOOD

output low if the output feedback voltage exits the 10%

window around the regulation point. Pulling the RUN pin

below 1.6V forces the controller into its shutdown state.

FETswithfastswitchingspeed

DS(ON)

andintegratedSchottkydiodes.Withcurrentmodecontrol

and internal feedback loop compensation, the LTM4605

modulehassufficientstabilitymarginsandgoodtransient

performance under a wide range of operating conditions

and with a wide range of output capacitors. The operating

frequency of the LTM4605 can be adjusted from 200kHz

to 400kHz by setting the voltage on the PLLFLTR pin.

If an external bias supply is applied on the EXTV pin,

CC

then an efficiency improvement will occur due to the re-

duced power loss in the internal linear regulator. This is

especially true at the higher input voltage range.

applications inForMation

Table 1. R_FBResistor (0.5%) vs Various Output Voltages

The typical LTM4605 application circuit is shown in

Figure 16. External component selection is primarily

determined by the maximum load current and output

voltage. Refer to Table 3 for specific external capacitor

requirements for a particular application.

V

0.8V

Open

8V

1.5V

115k

9V

2.5V

47.5k

10V

3.3V

32.4k

12V

5V

19k

6V

OUT

R

15.4k

16V

FB

V

15V

5.62k

OUT

R

FB

11k

9.76k

8.66k

7.15k

5.23k

Output Voltage Programming

Operation Frequency Selection

ThePWM controllerhasaninternal0.8Vreferencevoltage.

As shown in the Block Diagram, a 100k, internal feedback

The LTM4605 uses current mode control architecture at

constant switching frequency, which is determined by the

internal oscillator’s capacitor. This internal capacitor is

charged by a fixed current plus an additional current that

is proportional to the voltage applied to the PLLFLTR pin.

resistor connects V

and V pins together. Adding a

FB

OUT

FB

resistor R from the V pin to the SGND pin programs

FB

the output voltage:

100k+R_FB

V_OUT= 0.8V •

R_FB

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Table 2 shows the different operation modes.

The PLLFLTR pin can be grounded to lower the frequency

to 200kHz or tied to 2.4V to yield approximately 400kHz.

When PLLFLTR is left open, the PLLFLTR pin goes low,

forcing the oscillator to its minimum frequency.

Table 2. Different Operating Modes

FCB PIN

0V to 0.75V

0.85V to

BUCK

Force Continuous Mode Force Continuous Mode

Skip-Cycle Mode Burst Mode Operation

BOOST

A graph for the voltage applied to the PLLFLTR pin vs

frequency is given in Figure 2. As the operating frequency

increases, the gate charge losses will be higher, thus the

efficiency is lower. The maximum switching frequency is

approximately 400kHz.

V

– 1V

INTVCC

>5.3V

DCM with Constant Freq DCM with Constant Freq

WhentheFCBpinvoltageislowerthan0.8V, thecontroller

behavesasacontinuous,PWM currentmodesynchronous

switching regulator. When the FCB pin voltage is below

450

400

350

300

250

200

150

100

50

V

– 1V, but greater than 0.85V, where V

is

INTVCC

6V, the controller enters Burst Mode operation in boost

operation or enters skip-cycle mode in buck operation.

Duringboostoperation, BurstModeoperationisactivated

if the load current is lower than the preset minimum out-

put current level. The MOSFETs will turn on for several

cycles, followed by a variable “sleep” interval depending

upon the load current. During buck operation, skip-cycle

mode sets a minimum positive inductor current level. In

this mode, some cycles will be skipped when the output

load current drops below 1% of the maximum designed

load in order to maintain the output voltage.

0

0.5

1.0

1.5

2.0

2.5

PLLFLTR PIN VOLTAGE (V)

4605 F02

Figure 2. Frequency vs PLLFLTR Pin Voltage

FREꢀUENCY SYNCHRONIꢁATION

When the FCB pin is tied to the INTV pin, the controller

CC

enters constant frequency discontinuous current mode

(DCM). For boost operation, if the output voltage is high

enough, the controller can enter the continuous current

buck mode for one cycle to discharge inductor current.

In the following cycle, the controller will resume DCM

boost operation. For buck operation, constant frequency

discontinuous current mode is turned on if the preset

minimum negative inductor current level is reached. At

very light loads, this constant frequency operation is not

as efficient as Burst Mode operation or skip-cycle, but

does provide low noise, constant frequency operation.

The LTM4605 can also be synchronized to an external

sourceviathePLLINpininsteadofadjustingthevoltageon

the PLLFLTR pin directly. The power module has a phase-

locked loop comprised of an internal voltage controlled

oscillator and a phase detector. This allows turning on the

internal top MOSFET for locking to the rising edge of the

external clock. A pulse detection circuit is used to detect a

clock on the PLLIN pin to turn on the phase-locked loop.

The input pulse width of the clock has to be at least 400ns,

and 2V in amplitude. The synchronized frequency ranges

from 200kHz to 400kHz, corresponding to a DC voltage

input from 0V to 2.4V at PLLFLTR. During the start-up of

the regulator, the phase-locked loop function is disabled.

Input Capacitors

In boost mode, since the input current is continuous, only

minimuminputcapacitorsarerequired.However,theinput

current is discontinuous in buck mode, so the selection

Low Current Operation

To improve the efficiency at low output current operation,

LTM4605 provides three modes for both buck and boost

operations by accepting a logic input on the FCB pin.

of input capacitor C is driven by the need of filtering the

IN

input square wave current.

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For a buck converter, the switching duty-cycle can be

estimated as:

The LTM4605 is designed for low output voltage ripple.

The bulk output capacitors defined as C

are chosen

OUT

with low enough ESR to meet the output voltage ripple

and transient requirements. C can be a low ESR tanta-

V_OUT

D =

OUT

V

IN

lum capacitor, a low ESR polymer capacitor or a ceramic

capacitor. Multiple capacitors can be placed in parallel to

meet the ESR and RMS current handling requirements.

Thetypicalcapacitanceis300µF.Additionaloutputfiltering

may be required by the system designer, if further reduc-

tionofoutputrippleordynamictransientspikeisrequired.

Table 3 shows a matrix of different output voltages and

output capacitors to minimize the voltage droop and

overshoot at a current transient.

Without considering the inductor current ripple, the RMS

current of the input capacitor can be estimated as:

I_OUT(MAX)

I_CIN(RMS)

=

• D•(1−D)

η

In the above equation, η is the estimated efficiency of the

power module. C can be a switcher-rated electrolytic

IN

aluminum capacitor, OS-CON capacitor or high volume

ceramic capacitors. Note the capacitor ripple current rat-

ings are often based on temperature and hours of life. This

makes it advisable to properly derate the input capacitor,

or choose a capacitor rated at a higher temperature than

required. Always contact the capacitor manufacturer for

derating requirements.

Inductor Selection

The inductor is chiefly decided by the required ripple cur-

rent and the operating frequency. The inductor current

ripple ΔI is typically set to 20% to 40% of the maximum

L

inductor current. In the inductor design, the worst cases

in continuous mode are considered as follows:

V • V

− V

IN

(

)

IN

OUT(MAX)

Output Capacitors

L_BOOST

≥

V_OUT(MAX)• f •I_OUT(MAX)•Ripple%

In boost mode, the discontinuous current shifts from the

input to the output, so the output capacitor C

capable of reducing the output voltage ripple.

must be

OUT

V_OUT• V_IN(MAX)− V

(

)

OUT

L_BUCK

where:

≥

V

_IN(MAX)• f •I_OUT(MAX)•Ripple%

For boost and buck modes, the steady ripple due to charg-

ing and discharging the bulk capacitance is given by:

I_OUT(MAX)• V − V

(

)

IN(MIN)

OUT

f is operating frequency, Hz

V_RIPPLE,BOOST

=

C_OUT• V_OUT• f

Ripple% is allowable inductor current ripple, %

V_OUT• V_IN(MAX)− V

8 •L •C_OUT• V_IN(MAX)• f²

V

I

is maximum output voltage, V

(

)

OUT

OUT(MAX)

V_RIPPLE,BUCK

=

is maximum input voltage, V

IN(MAX)

is output voltage, V

OUT

The steady ripple due to the voltage drop across the ESR

(effective series resistance) is given by:

is maximum output load current, A

OUT(MAX)

The inductor should have low DC resistance to reduce the

V

= ΔI_L(MAX)•ESR

ESR,BUCK

2

I R losses, and must be able to handle the peak inductor

current without saturation. To minimize radiated noise,

use a toroid, pot core or shielded bobbin inductor. Please

refer to Table 3 for the recommended inductors for dif-

ferent cases.

V

=I_L(MAX)•ESR

ESR,BOOST

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R

SENSE

Selection and Maximum Output Current

of the internal reference and the output voltage. The total

soft-start time can be calculated as:

R

is chosen based on the required inductor current.

SENSE

Since the maximum inductor valley current at buck mode

is much lower than the inductor peak current at boost

mode, different sensing resistors are suggested to use

in buck and boost modes.

2.4V •C_SS

1.7µA

t_SOFTSTART

=

When the RUN pin falls below 1.6V, then soft-start pin

is reset to allow for proper soft-start control when the

regulator is enabled again. Current foldback and force

continuous mode are disabled during the soft-start pro-

cess. The soft-start function can also be used to control

the output ramp up time, so that another regulator can be

easily tracked. Do not apply more than 6V to the SS pin.

The current comparator threshold sets the peak of the

inductorcurrentinboostmodeandthemaximuminductor

valley current in buck mode. In boost mode, the allowed

maximum average load current is:

⎛

⎜

⎝

⎞

⎟

⎠

160mV ΔI_L

V

IN

V_OUT

I_{OUT(MAX,BOOST)}

=

−

•

R

2

SENSE

Run Enable

where ΔI is peak-to-peak inductor ripple current.

The RUN pin is used to enable the power module. The

pin can be driven with a logic input, and not exceed 6V.

L

In buck mode, the allowed maximum average load cur-

rent is:

The RUN pin can also be used as an undervoltage lockout

(UVLO) function by connecting a resistor from the input

supply to the RUN pin. The equation:

130mV ΔI_L

I_{OUT(MAX,BUCK)}

=

+

R_SENSE

2

R+100k

100k

V_UVLO =

•1.6V

The maximum current sensing R

mode is:

value for the boost

SENSE

Power Good

R_{SENSE(MAX,BOOST)}

=

The PGOOD pin is an open drain pin that can be used to

monitor valid output voltage regulation. This pin monitors

a 7.5% window around the regulation point, and tracks

with margining.

2 •160mV • V

2 •I_{OUT(MAX,BOOST)}• V_OUT+ΔI_L• V

IN

The maximum current sensing R

mode is:

value for the buck

SENSE

COMP Pin

2 •130mV

R_{SENSE(MAX,BUCK)}

=

This pin is the external compensation pin. The module

has already been internally compensated for most output

voltages. A spice model is available for other control loop

optimization.

2 •I_{OUT(MAX,BUCK)}– ΔI_L

A 20% to 30% margin on the calculated sensing resistor

is usually recommended. Please refer to Table 3 for the

recommendedsensingresistorsfordifferentapplications.

Fault Conditions: Current Limit and Overcurrent

Foldback

Soft-Start

LTM4605 has a current mode controller, which inherently

limitsthecycle-by-cycleinductorcurrentnotonlyinsteady

state operation, but also in transient. Refer to Table 3.

The SS pin provides a means to soft-start the regulator.

A capacitor on this pin will program the ramp rate of the

output voltage. A 1.7µA current source will charge up the

external soft-start capacitor. This will control the ramp

To further limit current in the event of an overload condi-

tion,theLTM4605providesfoldbackcurrentlimiting.Ifthe

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output voltage falls by more than 70%, then the maximum

output current is progressively lowered to about 30% of

its full current limit value for boost mode and about 40%

for buck mode.

2. EXTV connected directly to V

(5.7V < V

< 7V).

CC

OUT

This is the normal connection for a 6V regulator and

provides the highest efficiency.

3. EXTV connected to an external supply. If an external

CC

supply is available in the 5.5V to 7V range, it may be

Standby Mode (STBYMD)

used to power EXTV provided it is compatible with

CC

Thestandbymode(STBYMD)pinprovidesseveralchoices

for start-up and standby operational modes. If the pin is

pulled to ground, the SS pin is internally pulled to ground,

preventing start-up and thereby providing a single control

pin for turning off the controller. If the pin is left open or

decoupledwithacapacitortoground,theSSpinisinternally

providedwithastartingcurrent,permittingexternalcontrol

for turning on the controller. If the pin is connected to a

the MOSFET gate drive requirements.

Thermal Considerations and Output Current Derating

In different applications, the LTM4605 operates in a variety

of thermal environments. The maximum output current is

limited by the environmental thermal condition. Sufficient

cooling should be provided to ensure reliable operation.

When the cooling is limited, proper output current derating

is necessary, considering ambient temperature, airflow,

input/outputcondition,andtheneedforincreasedreliability.

voltagegreaterthan1.25V, theinternalregulator(INTV )

CC

will be on even when the controller is shut down (RUN

pin voltage <1.6V). In this mode, the onboard 6V linear

regulator can provide power to keep-alive functions such

as a keyboard controller.

The power loss curves in Figures 5 and 6 can be used

in coordination with the load current derating curves in

Figures 7 to 12 for calculating an approximate θ for

JA

INTV and EXTV

the module. Column designation delineates between no

heat sink, and a BGA heat sink. Each of the load current

derating curves will lower the maximum load current as

a function of the increased ambient temperature to keep

the maximum junction temperature of the power module

at 115°C maximum. This will allow a safe margin to work

at the maximum operating temperature below 125°C.

Each of the derating curves and the power loss curve that

corresponds to the correct output voltage can be used to

CC

An internal P-channel low dropout regulator produces 6V

at the INTV pin from the V supply pin. INTV powers

CC

IN

CC

the control chip and internal circuitry within the module.

TheLTM4605alsoprovidestheexternalsupplyvoltagepin

EXTV . When the voltage applied to EXTV rises above

CC

5.7V, the internal regulator is turned off and an internal

switch connects the EXTV pin to the INTV pin thereby

CC

supplyinginternalpower.Theswitchremainsclosedaslong

solve for the approximate θ of the condition.

JA

as the voltage applied to EXTV remains above 5.5V. This

CC

allows the MOSFET driver and control power to be derived

DESIGN EXAMPLES

from the output when (5.7V < V

< 7V) and from the

OUT

internalregulatorwhentheoutputisoutofregulation(start-

Buck Mode Operation

up, short-circuit). If more current is required through the

As a design example, use input voltage V = 12V to 20V,

IN

EXTV switchthanisspecified,anexternalSchottkydiode

CC

V

OUT

= 12V and f = 400kHz.

can be interposed between the EXTV and INTV pins.

CC

Ensure that EXTV ≤ V .

Set the PLLFLTR pin at 2.4V or more for 400kHz frequency

and connect FCB to ground for continuous current mode

operation.Ifadividerisusedtosetthefrequencyasshown

in Figure 14, the bottom resistor R3 is recommended not

to exceed 1k.

CC

IN

The following list summarizes the three possible connec-

tions for EXTV :

CC

1. EXTV left open (or grounded). This will cause INTV

CC

to be powered from the internal 6V regulator at the cost

of a small efficiency penalty.

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To set the output voltage at 12V, the resistor R from V

Consider the safety margin about 30%, we can choose

the sensing resistor as 8mΩ.

FB

pin to ground should be chosen as:

0.8V •100k

For the input capacitor, use a low ESR sized capacitor

to handle the maximum RMS current. Input capacitors

are required to be placed adjacent to the module. In Fig-

ure 14, the 10µF ceramic input capacitors are selected

for their ability to handle the large RMS current into the

converter. The 100µF bulk capacitor is only needed if the

inputsourceimpedanceiscompromisedbylonginductive

leads or traces.

R_FB=

≈ 7.15k

V_OUT−0.8V

To choose a proper inductor, we need to know the current

ripples at different input voltages. The inductor should

be chosen by considering the worst case in the practi-

cal operating region. If the maximum output power P is

150W at buck mode, we can get the current ripple ratio

of the current ripple ΔI to the maximum inductor current

I as follows:

L

For the output capacitor, the output voltage ripple and

transient requirements require low ESR capacitors. If

assuming that the ESR dominates the output ripple, the

output ripple is as follows:

L

2

ΔI_L(V – V_OUT)• V_OUT

IN

=

I_L

V •L • f •P

IN

ΔV_OUT(P-P)=ESR • ΔI_L

Figure 3 shows the current ripple ratio at different input

voltages based on the inductor values: 1.5µH, 2.5µH,

3.3µH and 4.7µH. If we need 30% ripple current ratio at

all inputs, the 3.3µH inductor can be selected.

If a total low ESR of about 5mΩ is chosen for output

capacitors, the maximum output ripple of 17.5mV occurs

at the input voltage of 20V with the current ripple at 3.5A.

0.8

Boost Mode Operation

V

= 12V

OUT

ƒ = 400kHz

For boost mode operation, use input voltage V = 5V to

IN

0.6

0.4

0.2

0

12V, V

= 12V and f = 400kHz.

OUT

1.5µH

Set the PLLFLTR pin and R as in buck mode.

FB

If the maximum output power P is 60W at boost mode

2.5µH

and the module efficiency η is about 95%, we can get

3.3µH

4.7µH

the current ripple ratio of the current ripple ΔI to the

L

maximum inductor current I as follows:

L

ΔI_L(V_OUT− V )• V ²η

12

14

16

18

20

IN

INPUT VOLTAGE V (V)

=

IN

4605 F03

I_L

V_OUT•L • f •P

Figure 3. Current Ripple Ratio at Different Inputs for Buck Mode

Figure 4. shows the current ripple ratio at different input

voltages based on the inductor values: 1.5µH, 2.5µH,

3.3µH and 4.7µH. If we need 30% ripple current ratio at

all inputs, the 3.3µH inductor can be selected.

At buck mode, sensing resistor selection is based on

the maximum output current and the allowed maximum

sensing threshold 130mV.

2 •130mV

2 •(P / V_OUT)−ΔI_L

R_SENSE

=

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0.6

If a total low ESR about 5mΩ is chosen for output capaci-

tors, the maximum output ripple of 70mV occurs at the

input voltage of 5V with the peak inductor current at 14A.

V

= 12V

OUT

ƒ = 400kHz

1.5µH

0.4

0.2

0

2.5µH

3.3µH

Wide Input Mode Operation

If a wide input range is required from 5V to 20V, the mod-

ule will work in different operation modes. If input voltage

4.7µH

V = 5V to 20V, V

= 12V and f = 400kHz, the design

IN

OUT

needs to consider the worst case in buck or boost mode

design. Therefore, the maximum output power is limited

to 60W. The sensing resistor is chosen at 7mΩ, the input

capacitor is the same as the buck mode design and the

output capacitor uses the boost mode design. Since the

maximum output ripple normally occurs at boost mode

in the wide input mode design, more inductor ripple cur-

rent, up to 150% of the inductor current, is allowed at

buck mode to meet the ripple design requirement. Thus,

a 3.3µH inductor is chosen at the wide input mode. The

maximum output ripple voltage is still 70mV if the total

ESR is about 5mΩ.

5

6

7

8

9

10

11

12

INPUT VOLTAGE V (V)

IN

4605 F04

Figure 4. Current Ripple Ratio at Different Inputs for Boost Mode

At boost mode, sensing resistor selection is based on

the maximum input current and the allowed maximum

sensing threshold 160mV.

2 •160mV

R_SENSE

=

P

2 •

+ΔI_L

η• V

IN(MIN)

Additionally, thecurrentlimitmaybecomeveryhighwhen

the module runs at buck mode due to the low sensing

resistor used in the wide input mode operation.

Consider the safety margin about 30%, we can choose

the sensing resistor as 7mΩ.

For the input capacitor, only minimum capacitors are

needed to handle the maximum RMS current, since it

is a continuous input current at boost mode. A 100µF

capacitor is only needed if the input source impedance is

compromised by long inductive leads or traces.

Safety Considerations

The LTM4605 modules do not provide isolation from V

IN

to V . There is no internal fuse. If required, a slow blow

OUT

fuse with a rating twice the maximum input current needs

tobeprovidedtoprotecteachunitfromcatastrophicfailure.

Since the output capacitors at boost mode need to filter

the square wave current, more capacitors are expected

to achieve the same output ripples as the buck mode. If

assuming that the ESR dominates the output ripple, the

output ripple is as follows:

ΔV_OUT(P-P)=ESR •I_L(MAX)

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Table 3. Typical Components (f = 400kHz)

C

VENDORS

PART NUMBER

C

OUT2

VENDORS

PART NUMBER

OUT1

TDK

C4532X7R1E226M (22µF, 25V)

PART NUMBER

Sanyo

16SVP180MX (180µF, 16V)

PART NUMBER

INDUCTOR VENDORS

R

SENSE

VENDORS

Toko

FDA1254

Vishay

Panasonic

Power Metal Strip Resistors WSL1206-18

Thick Film Chip Resistors ERJ12

Sumida

CDEP134, CDEP145

V

(V)

V

R

Inductor

(µH)

C

I

*

IN

OUT

SENSE

IN

OUT1

OUT2

OUT(MAX)

(V)

2.5

3.3

5

(0.5W RATING)

2x 16mΩ 0.5W

2x 18mΩ 0.5W

2x 14mΩ 0.5W

2x 18mΩ 0.5W

2x 16mΩ 0.5W

2x 18mΩ 0.5W

2x 14mΩ 0.5W

2x 16mΩ 0.5W

2x 18mΩ 0.5W

2x 15mΩ 0.5W

2x 14mΩ 0.5W

2x 12mΩ 0.5W

2x 18mΩ 0.5W

(CERAMIC)

3x 10µF 25V

2x 10µF 25V

3x 10µF 25V

2x 10µF 25V

3x 10µF 25V

2x 10µF 25V

None

(BULK)

(CERAMIC)

2x 22µF 25V

4x 22µF 25V

2x 22µF 25V

4x 22µF 25V

2x 22µF 25V

4x 22µF 25V

2x 22µF 25V

4x 22µF 25V

2x 22µF 25V

(BULK)

(A)

5

1

150µF 35V

1x 180µF 16V

2x 180µF 16V

2x 150µF 20V

12

8

12

5

1.5

1

12

20

5

1.5

2.2

2.5

1.5

2.2

3.3

2.2

3.3

2.2

3.3

2.2

5

8

12

20

5

8

3x 10µF 25V

None

12

6

8

10

12

16

15

20

6

3x 10µF 25V

None

12

6

16

20

5

2x 10µF 25V

3x 10µF 25V

None

12

3.5

6

8

None

12

20

None

10

12

2x 10µF 25V

INDUCTOR MANUFACTURER

WEBSITE

PHONE NUMBER

408-321-9660

847-297-0070

Sumida

Toko

www.sumida.com

www.toko.com

SENSING RESISTOR MANUFACTURER

WEBSITE

PHONE NUMBER

949-462-1816

814-362-5536

800-433-5700

Panasonic

KOA

www.panasonic.com/industrial/components

www.koaspeer.com

Vishay

www.vishay.com

*Maximum load current is based on the Linear Technology Demo board DC1198A at room temperature with natural convection. Poor board layout design

may decrease the maximum load current.

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9

8

7

6

5

4

3

2

1

0

8

7

6

5

4

3

2

1

0

20V TO 12V

IN

OUT

5V TO 16V

IN

OUT

5V TO 12V

IN

OUT

0

1

2

3

4

5

0

2

4

6

8

10

12

OUTPUT CURRENT (A)

4605 F05

4605 F06

Figure 5. 5V_INPower Loss

Figure 6. 20V_INPower Loss

5

4

3

2

1

0

5

4

3

2

1

0

5V TO 12V

IN

WITH 0LFM

WITH 200LFM

WITH 400LFM

5V TO 12V

IN

WITH 0LFM

WITH 200LFM

WITH 400LFM

OUT

5V TO 12V

IN

5V TO 12V

IN

5V TO 12V

IN

5V TO 12V

IN

25 35 45 55 65 75 85 95 105 115

25

45

65

85

105

125

AMBIENT TEMPERATURE (°C)

4605 F07

4605 F08

Figure 7. 5V_INto 12V_OUTwithout Heat Sink

Figure 8. 5V_INto 12V_OUTwith Heat Sink

4.0

3.5

3.0

2.5

2.0

1.5

1.0

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

5V TO 16V

WITH 0LFM

WITH 200LFM

WITH 400LFM

5V TO 16V

WITH 0LFM

WITH 200LFM

WITH 400LFM

IN

OUT

IN

OUT

0.5

0

5V TO 16V

IN

5V TO 16V

IN

25 35 45 55 65 75 85 95 105

AMBIENT TEMPERATURE (°C)

4605 F09

4605 F10

Figure 9. 5V_INto 16V_OUTwithout Heat Sink

Figure 10. 5V_INto 16V_OUTwith Heat Sink

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No Heat Sink

BGA Heat Sink

12

10

8

12

10

8

6

4

2

0

35

45

55

65

75

85

95 105

35

45

55

65

75

85

95 105

AMBIENT TEMPERATURE (°C)

20V TO 12V

WITH 0LFM

20V TO 12V

WITH 0LFM

IN

OUT

IN

OUT

20V TO 12V

WITH 200LFM

20V TO 12V

WITH 200LFM

IN

20V TO 12V

WITH 400LFM 4605 F11

20V TO 12V

WITH 400LFM 4605 F12

IN

Figure 11. 20V_INto 12V_OUTwithout Heat Sink

Figure 12. 20V_INto 12V_OUTwith Heat Sink

Table 4. 5V Output

DERATING CURVE

Figure 7, 9

V

(V)

POWER LOSS CURVE

Figure 5

AIR FLOW (LFM)

HEAT SINK

None

θ

JA

(°C/W)*

11.2

8.3

IN

12, 16

0

Figure 7, 9

Figure 5

200

400

0

None

Figure 7, 9

Figure 5

None

7.2

Figure 8, 10

Figure 5

BGA Heat Sink

10.7

7.7

Figure 5

200

400

Figure 5

6.6

Table 5. 20V Input and 12V Output

DERATING CURVE

Figure 11

V

(V)

POWER LOSS CURVE

Figure 6

AIR FLOW (LFM)

HEAT SINK

None

θ

JA

(°C/W)*

8.2

IN

20

0

Figure 11

20

Figure 6

200

400

0

None

5.8

Figure 11

Figure 6

None

5.3

Figure 12

Figure 6

BGA Heat Sink

7.6

Figure 12

Figure 6

200

400

5.3

Figure 12

Figure 6

4.8

HEAT SINK MANUFACTURER

PART NUMBER

PHONE NUMBER

Wakefield Engineering

LTN20069

603-635-2600

*The results of thermal resistance from junction to ambient θ are based on the demo board of DC1198A. Thus, the maximum temperature on board is

JA

treated as the junction temperature (which is in the µModule for most cases) and the power losses from all components are counted for calculations. It has

to be mentioned that poor board design may increase the θ

.

JA

4605fd

18

For more information www.linear.com/LTM4605

LTM4605

applications inForMation

Layout Checklist/Example

•ꢀ Place a dedicated power ground layer underneath the

unit.

The high integration of LTM4605 makes the PCB board

layout very simple and easy. However, to optimize its

electrical and thermal performance, some layout consid-

erations are still necessary.

•ꢀ To minimizetheviaconductionlossandreducemodule

thermal stress, use multiple vias for interconnection

between the top layer and other power layers

•ꢀ UselargePCBcopperareasforhighcurrentpath,includ-

•ꢀ Do not put vias directly on pads, unless the vias are

ing V , R

, SW1, SW2, PGND and V . It helps to

capped.

IN SENSE

OUT

minimize the PCB conduction loss and thermal stress.

•ꢀ Use a separated SGND ground copper area for com-

ponents connected to signal pins. Connect the SGND

to PGND underneath the unit.

•ꢀ Place high frequency input and output ceramic capaci-

tors next to the V , PGND and V

pins to minimize

IN

OUT

high frequency noise

Figure 13. gives a good example of the recommended

layout.

–

+

•ꢀ RouteSENSE andSENSE leadstogetherwithminimum

PC trace spacing. Avoid sense lines passing through

noisy areas, such as switch nodes.

SW1

SW2

V

IN

L1

C

IN

R

V

SENSE

OUT

C

OUT

+

–

SGND

PGND

4605 F13

R

SENSE

KELVIN CONNECTIONS TO R

SENSE

Figure 13. Recommended PCB Layout

4605fd

19

For more information www.linear.com/LTM4605

LTM4605

typical applications

V

IN

12V TO 20V

10µF

35V

x2

V

12V

12A

OUT

V

PLLIN

IN

PGOOD

RUN

V

OUT

+

100µF

25V

ON/OFF

FCB

L1

3.3µH

LTM4605

COMP

INTV

SW1

SW2

CC

R1

1.5k

PLLFLTR

EXTV

R

CC

SENSE

+

STBYMD

SENSE

C3

0.1µF

R3

1k

R2

8mΩ

–

SS

SENSE

SGND

V

FB

PGND

R

FB

7.15k

4605 TA02

Figure 14. Buck Mode Operation with 12V to 20V Input

V

IN

4.5V TO 12V

4.7µF

V

12V

5A

OUT

V

PLLIN

35V

IN

PGOOD

RUN

V

OUT

+

22µF

25V

x2

330µF

25V

ON/OFF

FCB

LTM4605

COMP

2200pF

2Ω

INTV

SW1

SW2

CC

R1

1.5k

PLLFLTR

L1

3.3µH

OPTIONAL

FOR LOW

SWITCHING NOISE

EXTV

R

CC

SENSE

+

R3

1k

STBYMD

SENSE

C3

0.1µF

R2

7mΩ

–

SS

SENSE

SGND

V

FB

PGND

R

FB

7.15k

4605 TA03

Figure 15. Boost Mode Operation with 4.5V to 12V Input

4605fd

20

For more information www.linear.com/LTM4605

LTM4605

typical applications

V

IN

4.5V TO 20V

10µF

35V

x2

V

12V

5A

OUT

V

PLLIN

IN

PGOOD

RUN

V

OUT

+

22µF

25V

x2

330µF

25V

ON/OFF

FCB

L1

3.3µH

LTM4605

COMP

INTV

SW1

SW2

CC

R1

1.5k

PLLFLTR

EXTV

R

CC

SENSE

+

STBYMD

SENSE

C3

0.1µF

R3

1k

R2

7mΩ

–

SS

SENSE

SGND

V

FB

PGND

R

FB

7.15k

4605 TA04

Figure 16. Wide Input Mode with 4.5V to 20V Input, 12V at 5A Output

V

IN

4.5V TO 20V

10µF

35V

x2

V

OUT

V

PLLIN

IN

5V

PGOOD

RUN

V

OUT

+

12A

100µF

25V

ON/OFF

FCB

L1

2.5µH

LTM4605

COMP

INTV

SW1

SW2

CC

R1

1.5k

PLLFLTR

EXTV

OPTIONAL

2Ω

R

CC

SENSE

+

2200pF

STBYMD

SENSE

C3

0.1µF

R3

1k

R2

8mΩ

–

SS

SENSE

SGND

V

FB

PGND

R

FB

19k

4605 TA05

Figure 17. 5V at 12A Design with Low Switching Noise (Optional)

4605fd

21

For more information www.linear.com/LTM4605

LTM4605

typical applications

V

IN

4.5V TO 20V

CLOCK SYNC 0° PHASE

PLLIN

10µF

35V

V

12V

10A

OUT

R5

100k

V

IN

PGOOD

RUN

V

OUT

+

C2

22µF

×2

330µF

25V

FCB

L1

3.3µH

LTM4605

COMP

SW1

SW2

200Ω

INTV

CC

LTC6908-1

PLLFLTR

R

5.1V

ZENER

SENSE

+

C1

EXTV

CC

SENSE

0.1µF

+

V

OUT1

OUT2

MOD

R2

7mΩ

STBYMD

R4

324k

–

GND

SET

SS

SENSE

C3

0.1µF

SGND

V

FB

PGND

R

FB

2-PHASE OSCILLATOR

3.57k

CLOCK SYNC 180° PHASE

PLLIN

10µF

35V

V

IN

PGOOD

V

OUT

+

C4

22µF

×2

330µF

25V

FCB

L2

3.3µH

LTM4605

RUN

COMP

SW1

SW2

INTV

CC

PLLFLTR

EXTV

R

SENSE

+

SENSE

CC

R3

7mΩ

STBYMD

–

SS

SENSE

SGND

V

FB

PGND

4605 TA06

Figure 18. Two-Phase Parallel, 12V at 10A Design

V

IN

Efficiency vs Load

6V TO 15V

10µF

35V

×2

95

V

PLLIN

IN

PGOOD

RUN

V

GND

180µF

16V

×2

OUT

90

85

80

75

70

65

60

55

50

+

22µF

16V

×2

ON/OFF

FCB

–5V

L1

LTM4605

COMP

3.5µH

INTV

SW1

SW2

CC

–5V

R1

4.64k

PLLFLTR

EXTV

R

CC

SENSE

+

STBYMD

SENSE

C3

10nF

R3

1.21k

R2

8mΩ

–

V = –5V

OUT

SS

SENSE

V

= 6V

= 12V

= 15V

IN

SGND

V

FB

PGND

–5V

R

FB

4605 TA08

–5V

19.1k

0

1

2

3

4

5

6

–5V

LOAD CURRENT (A)

4605 TA08b

–5V

Figure 19. Buck Mode Operation with Positive Input to Negative –5V Output Converter

4605fd

22

For more information www.linear.com/LTM4605

LTM4605

package Description

Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.

Z

b b b

Z

6 . 9 8 5 0

5 . 7 1 5 0

4 . 4 4 5 0

3 . 1 7 5 0

1 . 9 0 5 0

0 . 6 3 5 0

0 . 0 0 0 0

0 . 6 3 5 0

1 . 9 0 5 0

3 . 1 7 5 0

4 . 4 4 5 0

5 . 7 1 5 0

6 . 9 8 5 0

4605fd

23

For more information www.linear.com/LTM4605

LTM4605

package Description

Pin Assignment Table 6

(Arranged by Pin Number)

PIN NAME

A1 PGND

A2 PGND

A3 PGND

A4 SENSE

A5 SENSE

A6 SS

PIN NAME

J1 SW1

J2 SW1

J3 SW1

J4 SW1

PIN NAME

L1 SW1

L2 SW1

L3 SW1

L4 SW1

C1 PGND

C2 PGND

C3 PGND

C4 PGND

C5 PGND

C6 PGND

C7 PGND

C8 PGND

C9 PGND

E1

E2

V

G1

V

OUT

G2

E3 PGND

E4 PGND

E5 PGND

E6 PGND

E7 PGND

E8 PGND

E9 PGND

E10 PGND

E11 PGND

E12 PGND

G3

+

–

G4

G5

R

J5

J6

J7

R

L5

L6

R

SENSE

OUT

SENSE

G6

A7 SGND

A8 RUN

A9 FCB

G7

L7 SW2

L8 SW2

L9 SW2

G8

J8 SW2

J9 SW2

G9

A10 STBYMD C10 PGND

G10

G11

G12

H1

J10

J11

J12

V

L10

L11

L12

V

IN

A11 PGND

A12 PGND

B1 PGND

B2 PGND

B3 PGND

B4 PGND

C11 PGND

C12 PGND

D1 PGND

D2 PGND

D3 PGND

D4 PGND

F1

F2

F3

F4

V

K1 SW1

K2 SW1

K3 SW1

K4 SW1

M1 SW1

M2 SW1

M3 SW1

M4 SW1

OUT

H2

OUT

H3

OUT

H4

OUT

B5 PGOOD D5 PGND

F5 INTV

H5

R

K5

K6

R

M5

M6

R

CC

SENSE

B6

V

D6 PGND

D7 PGND

F6 EXTV

H6

FB

CC

B7 COMP

F7

–

H7

K7 SW2

K8 SW2

K9 SW2

M7 SW2

M8 SW2

M9 SW2

B8 PLLFLTR D8 PGND

F8

–

H8

B9 PLLIN

B10 PGND

B11 PGND

B12 PGND

D9 PGND

D10 PGND

D11 PGND

D12 PGND

F9

–

H9

F10

F11

F12

R

H10

H11

H12

K10

K11

K12

V

M10 V

M11 V

M12 V

SENSE

IN

4605fd

24

For more information www.linear.com/LTM4605

LTM4605

revision history ^{(Revision history begins at Rev C)}

REV

DATE

DESCRIPTION

PAGE NUMBER

C

01/11 Updated Absolute Maximum Ratings section.

Updated Electrical Characteristics section.

Updated the FCB Pin description in the Pin Functions section.

Updated the Block Diagram.

2

2, 3, 4

7

8

Updated the Applications Information section.

Text added to Figures 3 and 4.

9, 10

14, 15

22

Updated Figure 18.

Added new Figure 19.

22

Updated the Related Parts section.

04/14 Updated the Order Information table.

Updated circuit schematics.

26

D

2

20-22

4605fd

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.

25

For more information www.linear.com/LTM4605

LTM4605

typical application

Buck Mode Operation with 12V to 20V Input

V

IN

12V TO 20V

10µF

35V

x2

V

12V

12A

OUT

V

PLLIN

IN

PGOOD

RUN

V

OUT

+

100µF

25V

ON/OFF

FCB

L1

3.3µH

LTM4605

COMP

INTV

SW1

SW2

CC

R1

1.5k

PLLFLTR

EXTV

R

CC

SENSE

+

STBYMD

SENSE

C3

0.1µF

R3

1k

R2

8mΩ

–

SS

SENSE

SGND

V

FB

PGND

R

FB

7.15k

4605 TA07

relateD parts

PART NUMBER

DESCRIPTION

COMMENTS

LTC2900

Quad Supply Monitor with Adjustable Reset Timer

Power Supply Tracking Controller

36V Buck-Boost Controller

Monitors Four Supplies; Adjustable Reset Timer

Tracks Both Up and Down; Power Supply Sequencing

Synchronous Operation, Single Inductor

LTC2923

LTC3780

LTC3785

10V Buck-Boost Controller

Synchronous Operation, No R

™, 2.7V ≤ V ≤ 10V, 2.7V ≤ V

≤ 10V

SENSE

IN

OUT

LTM4600

10A DC/DC µModule Regulator

Basic 10A DC/DC µModule Regulator

LTM4601/

LTM4601A

12A DC/DC µModule Regulator with PLL, Output

Tracking/ Margining and Remote Sensing

Synchronizable, PolyPhase^®Operation to 48A, LTM4601-1 Version Has

No Remote Sensing

LTM4618

6A DC/DC µModule Regulator with PLL and Output Synchronizable, PolyPhase Operation

Tracking/Margining and Remote Sensing

LTM4604A

LTM4608A

4A Low Voltage DC/DC µModule Regulator

8A DC/DC µModule Regulator

2.375 ≤ V ≤ 5V, 0.8V ≤ V

≤ 5V, 9mm × 15mm × 2.3mm Package

IN

OUT

2.7V to 5.5V Input, 0.6V to 5V Output, PLL, Tracking

4605fd

LT 0414 REV D • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

26

For more information www.linear.com/LTM4605

(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTM4605

●

 LINEAR TECHNOLOGY CORPORATION 2007


型号：	LTM4605IV#PBF
厂家：	Linear
描述：	LTM4605 - High Efficiency Buck-Boost DC/DC µModule (Power Module) Regulator; Package: LGA; Pins: 141; Temperature Range: -40°C to 85°C 开关
文件：	总26页 (文件大小：302K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTM4605IV#PBF [Linear]

相关型号：

LTM4605IV-PBF

LTM4605V

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LTM4606EY#PBF

LTM4606IV-PBF

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LTM4606MPV-PBF

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