LTM4605IV-PBF_技术文档

LTM4605

High Efﬁciency

Buck-Boost DC/DC µModule

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

Ultra-Fast Transient Response

Current Foldback Protection

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.

Output Overvoltage Protection

Small, Low Proﬁle Surface Mount LGA Package

(15mm × 15mm × 2.8mm)

APPLICATIONS

n

Telecom, Servers and Networking Equipment

Faultprotectionfeaturesincludeovervoltageandfoldback

current protection. The DC/DC μModule™ is offered in a

smallandthermallyenhanced15mm×15mm×2.8mmLGA

package. The LTM4605 is Pb-free and RoHS compliant.

n

Industrial and Automotive Equipment

n

High Power Battery-Operated Devices

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

is a registered trademark of Linear Technology Corporation. μModule is a trademark of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

TYPICAL APPLICATION

Efﬁciency and Power Loss vs

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

Input Voltage

99

98

97

96

95

94

93

92

91

90

8

7

6

5

4

3

2

1

0

V

IN

V

I

= 12V

= 5A

CLOCK SYNC

OUT

LOAD

f = 200kHz

4.5V TO 20V

10μF

V

12V

5A

OUT

V

PLLIN

35V

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

5

6

7

8

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

7.15k

V

(V)

IN

4605 TA01b

4605 TA01

4605fa

1

LTM4605

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(See Table 6. Pin Assignment)

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

OUT

IN

V

TOP VIEW

BANK 2

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

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

M

L

CC

SW1, SW2 .................................................... –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

Junction Temperature ........................................... 125°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 s 15mm s 2.8mm)

T

= 125°C, θ = 4°C/W

JMAX

JP

WEIGHT = 1.5g

ORDER INFORMATION

LEAD FREE FINISH

LTM4605EV#PBF

LTM4605IV#PBF

PART MARKING*

PACKAGE DESCRIPTION

TEMPERATURE RANGE

–40°C to 85°C

LTM4605V

141-Lead (15mm × 15mm × 2.8mm) LGA

LTM4605V

–40°C to 85°C

Consult LTC Marketing for parts speciﬁed with wider operating temperature ranges. *The temperature grade is identiﬁed by a label on the shipping container.

For more information on lead free part marking, go to: http://www.linear.com/leadfree/

This product is only offered in trays. For more information go to: http://www.linear.com/packaging/

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the –40°C to 85°C

temperature range, otherwise speciﬁcations are at T_A= 25°C, 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

4605fa

2

LTM4605

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the –40°C to 85°C

temperature range, otherwise speciﬁcations are at T_A= 25°C, 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

Reference Voltage Line Regulation

Accuracy

V

IN

= 4.5V to 20V, V

= 1.2V (Note 3)

0.002

0.02

%

ΔV /V

FB FB(NOM)

COMP

l

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

%

ΔV /V

FB FB(LOAD)

Switch Section

M1 t

M3 t

Turn-On Time (Note 4)

Turn-Off Time

Drain to Source Voltage V = 12V, Bias

50

40

25

20

50

220

6.5

8

ns

r

f

r

f

DS

Current I = 10mA

SW

Drain to Source Voltage V = 12V, Bias

DS

Current I = 10mA

SW

Turn-On Time

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

Turn-Off Time

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

M2, M4 t

Turn-On Time

Drain to Source Voltage V = 12V, Bias

ns

r

f

DS

Current I = 10mA

SW

Turn-Off Time

Drain to Source Voltage V = 12V, Bias

ns

DS

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, Bias

ns

1d

2d

3d

4d

DS

Current I = 10mA

SW

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

Mode Transition 1

Mode Transition 2

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

Drain to Source Voltage V = 12V, Bias

ns

DS

Current I = 10mA

SW

M1 R

Static Drain-to-Source On-

Resistance

Bias Current I = 3A

mΩ

DS(ON)

SW

M2 R

Static Drain-to-Source On-

Resistance

Bias Current I = 3A

12

DS(ON)

SW

M3 R

Static Drain-to-Source On-

Resistance

Bias Current I = 3A

8

DS(ON)

SW

M4 R

Static Drain-to-Source On-

Resistance

Bias Current I = 3A

8

DS(ON)

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

4605fa

3

LTM4605

ELECTRICAL CHARACTERISTICS ^Thel denotes the speciﬁcations which apply over the –40°C to 85°C

temperature range, otherwise speciﬁcations are at T_A= 25°C, 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

SS

V

= 2.2V

1

1.7

μA

V

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

= 0.85V

FCB

–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

99

%

ns

(BOOST, MAX)

(BUCK, MAX)

t

Minimum On-Time for Synchronous Switch M1 (Note 5)

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

I

> 7V, V = 5V

EXTVCC

6

6.3

2

V

%

CC

IN

Internal V Load Regulation

= 0mA to 20mA, V

= 5V

0.3

5.6

300

60

ΔV /V

LDO LDO

CC

EXTVCC

V

EXTV Switchover Voltage

I

= 20mA, V

Rising

5.4

V

EXTVCC

CC

EXTVCC

EXTV Switchover Hysteresis

mV

ΔV

CC

EXTVCC(HYS)

EXTV Switch Drop Voltage

I

CC

= 20mA, V

= 6V

150

CC

EXTVCC

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 Discontinuous Mode

–6

mV

μA

SENSE(MIN, BUCK)

SENSE

–

+

I

Sense Pins Total Source Current

V

SENSE

= V

= 0V

SENSE

–380

PGOOD

PGOOD Upper Threshold

PGOOD Lower Threshold

PGOOD Hysteresis

V

Rising

Falling

5.5

7.5

–7.5

2.5

10

%

V

ΔV

FB

FBH

–5.5

–10

ΔV

FB

FBL

Returning

ΔV

FB

FB(HYS)

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.

with statistical process controls. The LTM4605I is guaranteed over the

–40°C to 85°C temperature range.

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 2: The LTM4605E is guaranteed to meet performance speciﬁcations

from 0°C to 85°C. Speciﬁcations over the –40°C to 85°C operating

temperature range are assured by design, characterization and correlation

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

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

Note 5: 100% tested at wafer level only.

4605fa

4

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

4605fa

5

LTM4605

TYPICAL PERFORMANCE CHARACTERISTICS

Start-Up with 6V_INto 12V_OUTat

I_OUT= 5A

Start-Up with 18V_INto 12V_OUTat

_OUT= 5A

I

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

4605fa

6

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(PinA9):ForcedContinuousControlInput.Thevoltage

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 in boost operation and

the skip cycle mode is active in buck operation. When the

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.

pinistiedtoINTV ,theconstantfrequencydiscontinuous

CC

–

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

current mode is active in buck or boost operation. See the

Reverse Current Detect Comparators.

Applications Information section.

EXTV (PinF6):ExternalV Input.WhenEXTV exceeds

CC

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

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

CC

PGND at output capacitor point.

shutsdowntheinternalregulatorsothatthecontrollerand

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.

gate drive power is drawn from EXTV . Do not exceed

CC

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

CC

IN

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

CC

for additional decoupling of the 6V internal regulator.

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

Open drain logic output that is pulled to ground when the

output voltage is not within 10% of the regulation point,

after a 25μs power bad mask timer expires.

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.

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

frequencyoftheinternaloscillatorwithanACorDCvoltage.

See the Applications Information section for details.

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

powersources’surgecurrentsbygraduallyincreasingthe

controller’s current limit.

4605fa

7

LTM4605

SIMPLIFIED BLOCK DIAGRAM

V

IN

4.5V TO 20V

EXTV

CC

C1

C

IN

M1

M2

SW2

INTV

CC

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

External Input Capacitor Requirement

I

= 5A

10

μF

IN

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

4605fa

8

LTM4605

OPERATION

Power Module Description

frequency can be synchronized by the input clock signal

from the PLLIN pin. The typical switching frequency is

400kHz.

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

supply. It can deliver a wide range output voltage from

0.8V to 16V over a wide input range from 4.5V to 20V,

by only adding the sensing resistor, inductor and some

external input and output capacitors. It provides precisely

regulated 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

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.

The LTM4605 has an integrated current mode buck-boost

control, ultralow R

FETs with fast switching speed

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 frequency

of LTM4605 can be operated from 200kHz to 400kHz by

setting the voltage on the PLLFLTR pin. Alternatively, its

IfanexternalbiassupplyisappliedontheEXTV pin,then

CC

an efﬁciency improvement will occur due to the reduced

powerlossintheinternallinearregulator.Thisisespecially

true at the higher input voltage range.

APPLICATIONS INFORMATION

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.

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

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

11k

9.76k

8.66k

7.15k

5.23k

FB

Output Voltage Programming

Operation Frequency Selection

The PWM controller has an internal 0.8V 1% reference

voltage. As shown in the Block Diagram, a 100k, 0.5%

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.

internal feedback resistor connects V

and V pins

FB

OUT

FB

together. Adding a resistor R from the V pin to the

FB

SGND pin programs the output voltage:

100k +R_FB

V_OUT= 0.8V •

R_FB

4605fa

9

LTM4605

APPLICATIONS INFORMATION

The PLLFLTR pin can be grounded to lower the frequency

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

When PLLIN is left open, the PLLFLTR pin goes low, forc-

ing the oscillator to its minimum frequency.

by accepting a logic input on the FCB pin. Table 2 shows

the different operation modes.

Table 2. Different Operating Modes

FCB PIN

0V to 0.75V

0.85V to 5V

>5.3V

BUCK

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 low. The maximum switching frequency is

approximately 400kHz.

Force Continuous Mode

Skip-Cycle Mode

Force Continuous Mode

Burst Mode Operation

DCM with Constant Freq

When the FCB pin voltage is lower than 0.8V, the controller

behavesasacontinuous,PWMcurrentmodesynchronous

switching regulator. When the FCB pin voltage is below

450

400

350

300

250

200

150

100

50

V

– 1V, but greater than 0.8V, the controller enters

INTVCC

Burst Mode operation in boost operation or enters skip-

cycle mode in buck operation. During boost operation,

Burst Mode operation is activated if the load current is

lower than the preset minimum output 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

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

CC

FREQUENCY SYNCHRONIZATION

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

verylightloads,thisconstantfrequencyoperationisnotas

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 lock 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-lock 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

Toimprovetheefﬁciencyatlowcurrentoperation,LTM4605

provides three modes for both buck and boost operations

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

IN

input square wave current.

4605fa

10

LTM4605

APPLICATIONS INFORMATION

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

meettheESRandRMScurrenthandlingrequirements.The

typicalcapacitanceis300μF.Additionaloutputﬁlteringmay

be required by the system designer, if further reduction of

output ripple or dynamic transient spike is required. 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_OUT(MAX)− V

(

)

IN

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_OUT− V

(

)

IN(MIN)

f is operating frequency, Hz

V_RIPPLE,BOOST

=

C_OUT• V_OUT• f

Ripple% is allowable inductor current ripple, %

V

is maximum output voltage, V

V_OUT• V_IN(MAX)− V_OUT

8 •L •C_OUT• V_IN(MAX)• f²

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:

I

is maximum output load current, A

OUT(MAX)

The inductor should have low DC resistance to reduce the

V_ESR,BUCK= ΔI_L(MAX)•ESR

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_ESR,BOOST=I_L(MAX)•ESR

4605fa

11

LTM4605

APPLICATIONS INFORMATION

R

SENSE

Selection and Maximum Output Current

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

resettoallowforpropersoft-startcontrolwhentheregula-

torisenabledagain.Currentfoldbackandforcecontinuous

mode are disabled during the soft-start process. 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:

⎛

⎞

ΔI_L

2

V

IN

V_OUT

160mV

I_{OUT(MAX,BOOST)}

=

−

•

⎜

⎟

R

⎝

⎠

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:

ΔI_L

2

130mV

R_SENSE

I_{OUT(MAX,BUCK)}

=

+

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

2•I_{OUT(MAX,BUCK)}– ΔI_L

This pin is the external compensation pin. The module

has already been internally compensated for most output

voltages. A spice model will be provided for other control

loop optimization.

R_{SENSE(MAX,BUCK)}

=

A20%to30%marginonthecalculatedsensingresistoris

usually recommended. Please refer to Table 3 for the rec-

ommended sensing resistors for different applications.

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 of

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

tion,theLTM4605providesfoldbackcurrentlimiting.Ifthe

4605fa

12

LTM4605

APPLICATIONS INFORMATION

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

7V). This is the normal connection for a 6V regulator and

provides the highest efﬁciency.

(5.7V < V

<

CC

OUT

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 the

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

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.

Whenthecoolingislimited,properoutputcurrentde-ratingis

necessary,consideringambienttemperature,airﬂow,input/

output condition, and the need for increased reliability.

voltage greater than 1.25V, the internal regulator (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

heatsink, and a BGA heatsink. 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.Theswitchremainscloseaslong

solve for the approximate θ of the condition. A complete

JA

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

CC

explanation of the thermal characteristics is provided in

allows the MOSFET driver and control power to be derived

the thermal application note for the LTM4605.

from the output when (5.7V < V

< 7V) and from the

OUT

internalregulatorwhentheoutputisoutofregulation(start-

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

DESIGN EXAMPLES

EXTV switchthanisspeciﬁed,anexternalSchottkydiode

CC

Buck Mode Operation

can be interposed between the EXTV and INTV pins.

CC

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

IN

Ensure that EXTV ≤ V .

CC

IN

V

= 12V and f = 400kHz.

OUT

The following list summarizes the three possible connec-

tions for EXTV :

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

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.

4605fa

13

LTM4605

APPLICATIONS INFORMATION

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:

For the input capacitor, use a low ESR sized capacitor to

handle the maximum RMS current. Input capacitors are

required to be placed adjacenttothe module. InFigure 14,

the 10μF ceramic input capacitors are selected for their

ability to handle the large RMS current into the converter.

The100μFbulkcapacitorisonlyneedediftheinputsource

impedance is compromised by long inductive leads or

traces.

0.8V •100k

V_OUT− 0.8V

R_FB=

≈7.15k

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 practical

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

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:

follows:

2

(V – V_OUT)• V_OUT

ΔI_L

I_L

IN

=

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 ca-

pacitors, 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

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

IN

0.6

12V, V

= 12V and f = 400kHz.

OUT

1.5μH

Set the PLLFLTR pin and R as in buck mode.

FB

0.4

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

0.2

the current ripple ratio of the current ripple ΔI to the

L

maximum inductor current I as follows:

L

0

2

12

14

16

18

20

(V_OUT− V )• V η

ΔI_L

I_L

IN

INPUT VOLTAGE V (V)

IN

=

4605 F03

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

=

4605fa

14

LTM4605

APPLICATIONS INFORMATION

0.6

output ripple is as follows:

1.5μH

ΔV_OUT(P-P)=ESR •I_L(MAX)

0.4

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

tors,themaximumoutputrippleof70mVoccursattheinput

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

2.5μH

3.3μH

0.2

4.7μH

Wide Input Mode Operation

Ifawideinputrangeisrequiredfrom5Vto20V,themodule

will work in different operation modes. If input voltage

0

5

6

7

8

9

10

11

12

INPUT VOLTAGE V (V)

IN

V = 5V to 20V, V

= 12V and f = 400kHz, the design

4605 F04

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.

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)

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.

Additionally, the current limit may become very high when

the module runs at buck mode due to the low sensing

resistor used in the wide input mode operation.

Safety Considerations

TheLTM4605modulesdonotprovideisolationfromV to

OUT

with a rating twice the maximum input current needs to be

provided to protect each unit from catastrophic failure.

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

IN

V

.Thereisnointernalfuse.Ifrequired,aslowblowfuse

4605fa

15

LTM4605

APPLICATIONS INFORMATION

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

*

OUT(MAX)

IN

OUT

SENSE

IN

OUT1

OUT2

(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 temperture with natural convection. Poor board layout design

may decrease the maximum load current.

4605fa

16

LTM4605

TYPICAL APPLICATIONS ^{Power loss includes all external components}

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

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 Heatsink

Figure 8. 5V_INto 12V_OUTwith Heatsink

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 Heatsink

Figure 10. 5V_INto 16V_OUTwith Heatsink

4605fa

17

LTM4605

TYPICAL APPLICATIONS ^{Power loss includes all external components}

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 Heatsink

Figure 12. 20V_INto 12V_OUTwith Heatsink

4605fa

18

LTM4605

APPLICATIONS INFORMATION

Table 4. 5V Output

DERATING CURVE

Figure 7, 9

V

(V)

POWER LOSS CURVE

Figure 5

AIR FLOW (LFM)

HEATSINK

none

θ

(°C/W)*

11.2

8.3

IN

JA

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 Heatsink

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)

HEATSINK

none

θ

(°C/W)*

8.2

IN

JA

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 Heatsink

7.6

Figure 12

Figure 6

200

400

5.3

Figure 12

Figure 6

4.8

HEATSINK 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

4605fa

19

LTM4605

APPLICATIONS INFORMATION

Layout Checklist/Example

• Use a separated SGND ground copper area for com-

ponents connected to signal pins. Connect the SGND

to PGND underneath the unit.

The high integration of LTM4605 makes the PCB board

layoutverysimpleandeasy.However,tooptimizeitselectri-

cal and thermal performance, some layout considerations

are still necessary.

Figure 13. gives a good example of the recommended

layout.

• UselargePCBcopperareasforhighcurrentpath,includ-

SW1

SW2

V

IN

ing V , R

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

IN SENSE

OUT

minimize the PCB conduction loss and thermal stress.

L1

• Place high frequency input and output ceramic capaci-

tors next to the V , PGND and V

pins to minimize

IN

OUT

high frequency noise

–

+

• RouteSENSE andSENSE leadstogetherwithminimum

PC trace spacing. Avoid sense lines passing through

noisy areas, such as switch nodes.

C

IN

R

V

SENSE

OUT

• Place a dedicated power ground layer underneath the

unit.

C

OUT

• Tominimizetheviaconductionlossandreducemodule

thermal stress, use multiple vias for interconnection

between the top layer and other power layers

+

–

SGND

PGND

4605 F13

R

SENSE

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

capped.

KELVIN CONNECTIONS TO R

SENSE

Figure 13. Recommended PCB Layout

TYPICAL APPLICATIONS

V

IN

CLOCK SYNC

12V TO 20V

10μF

35V

x2

V

12V

12A

OUT

V

PLLIN

IN

PGOOD

RUN

V

OUT

FCB

+

100μF

25V

ON/OFF

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

4605fa

20

LTM4605

TYPICAL APPLICATIONS

V

IN

CLOCK SYNC

4.5V TO 12V

4.7μF

35V

V

12V

5A

OUT

V

PLLIN

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

V

IN

CLOCK SYNC

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

4605fa

21

LTM4605

TYPICAL APPLICATIONS

V

IN

CLOCK SYNC

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)

V

IN

4.5V TO 20V

CLOCK SYNC 0° PHASE

10μF

R5

V

12V

10A

OUT

V

PLLIN

35V

IN

PGOOD

RUN

V

OUT

100k

+

C2

22μF

x2

330μF

25V

FCB

L1

3.3μH

LTM4605

COMP

SW1

SW2

INTV

CC

LTC6908-1

PLLFLTR

R

5.1V

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

x2

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

4605fa

22

LTM4605

PACKAGE DESCRIPTION

Z

b b b

Z

5 8 0 6 . 9

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

5 8 0 6 . 9

4605fa

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.

23

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

V

OUT

V

OUT

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

SENSE

R

SENSE

R

SENSE

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

IN

V

IN

V

IN

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

OUT

V

OUT

V

OUT

V

OUT

V

K1 SW1

K2 SW1

K3 SW1

K4 SW1

M1 SW1

M2 SW1

M3 SW1

M4 SW1

H2

OUT

H3

OUT

H4

OUT

B5 PGOOD D5 PGND

F5 INTV

H5

R

SENSE

R

SENSE

R

SENSE

R

SENSE

R

SENSE

R

SENSE

R

SENSE

R

SENSE

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

SENSE

R

SENSE

R

SENSE

H10

H11

H12

K10

K11

K12

V

IN

V

IN

V

IN

M10 V

M11 V

M12 V

IN

RELATED PARTS

PART NUMBER

LTC2900

DESCRIPTION

COMMENTS

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

LT3825/LT3837

LTM4600

Synchronous Isolated Flyback Controllers

10A DC/DC μModule

No Optocoupler Required; 3.3V, 12A Output; Simple Design

Basic 10A DC/DC μModule

LTM4601/

LTM4601A

12A DC/DC μModule with PLL, Output Tracking/

Margining and Remote Sensing

Synchronizable, PolyPhase Operation to 48A, LTM4601-1 Version has no

Remote Sensing

LTM4602

LTM4603

6A DC/DC μModule

Pin Compatible with the LTM4600

6A DC/DC μModule with PLL and Output Tracking/ Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote

Margining and Remote Sensing

Sensing, Pin Compatible with the LTM4601

LTM4604

4A Low Voltage DC/DC μModule

2.375 ≤ V ≤ 5V, 0.8V ≤ V ≤ 5V, 9mm × 15mm × 2.3mm Package

IN

OUT

No R

is a Trademark of Linear Technology Corporation.

SENSE

4605fa

LT 0108 REV A • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

24

●

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


型号：	LTM4605IV-PBF
厂家：	Linear
描述：	High Effi ciency Buck-Boost DC/DC μModule 高艾菲效率降压 - 升压型DC / DC微型模块
文件：	总24页 (文件大小：278K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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