LTM4602V_技术文档

LTM4602

6A High Efﬁciency

DC/DC µModule

FEATURES

DESCRIPTION

Complete Switch Mode Power Supply

The LTM^®4602 is a complete 6A DC/DC step down power

supply. Included in the package are the switching control-

ler, power FETs, inductor, and all support components.

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

LTM4602 supports an output voltage range of 0.6V to 5V,

setbyasingleresistor. Thishighefﬁciency design delivers

6A continuous current (8A peak), needing no heat sinks or

airﬂow to meet power speciﬁcations. Only bulk input and

output capacitors are needed to ﬁnish the design.

n

Wide Input Voltage Range: 4.5V to 20V

n

6A DC, 8A Peak Output Current

n

0.6V to 5V Output Voltage

n

1.5% Output Voltage Regulation

n

Ultrafast Transient Response

n

Current Mode Control

n

Pb-Free (e4) RoHS Compliant Package with Gold-

Pad Finish

Pin Compatible with the LTM4600

n

The low proﬁle package (2.8mm) enables utilization of

unused space on the bottom of PC boards for high density

point of load regulation. High switching frequency and an

adaptiveon-timecurrentmodearchitectureenablesavery

fast transient response to line and load changes without

sacriﬁcing stability. Fault protection features include

integrated overvoltage and short circuit protection with

a defeatable shutdown timer. A built-in soft-start timer is

adjustable with a small capacitor.

n

Up to 92% Efﬁciency

Programmable Soft-Start

Output Overvoltage Protection

n

Optional Short-Circuit Shutdown Timer

n

See the LTM4602HV for Operation Up to 28V

IN

n

Small Footprint, Low Proﬁle (15mm × 15mm ×

2.8mm) Surface Mount LGA Package

APPLICATIONS

TheLTM4602ispackagedinathermallyenhanced,compact

(15mm × 15mm) and low proﬁle (2.8mm) over-molded

Land Grid Array (LGA) package suitable for automated as-

semblybystandardsurfacemountequipment.Forthe4.5V

to 28V input range version, refer to the LTM4602HV.

n

Telecom and Networking Equipment

n

Servers

Industrial Equipment

n

Point of Load Regulation

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

μModule is a trademark of Linear Technology Corporation. All other trademarks are the property

of their respective owners. Protected by U.S. Patents including 5481178, 6100678, 6580258,

5847554, 6304066.

Efﬁciency vs Load Current

with 12V_IN(FCB = 0)

TYPICAL APPLICATION

100

90

6A μModule^TMPower Supply with 4.5V to 20V Input

80

V

1.5V

6A

OUT

V

IN

4.5V TO 20V

70

V

IN

V

OUT

C

OUT

60

IN

LTM4602

0.8V

1.2V

1.5V

1.8V

2.5V

3.3V

OUT

50

40

30

20

10

0

V

OSET

PGND SGND

R

SET

66.5k

(950kHz)*

4602 TA01a

*950kHz INSTEAD OF 1.3MHz

INCREASES 3.3V EFFICIENCY 2%

0

2

4

6

8

LOAD CURRENT (A)

4602 TA01b

4602fa

1

LTM4602

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(Note 1)

TOP VIEW

FCB, EXTV , PGOOD, RUN/SS, V .......... –0.3V to 6V

CC

OUT

V , SV , f ............................................ –0.3V to 20V

IN

IN ADJ

V

OSET

, COMP............................................. –0.3V to 2.7V

COMP

SGND

RUN/SS

FCB

V

IN

Operating Temperature Range (Note 2).... –40°C to 85°C

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

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

PGOOD

PGND

V

OUT

LGA PACKAGE

104-LEAD (15mm × 15mm × 2.8mm)

T

= 125°C, θ = 15°C/W, θ = 6°C/W,

JMAX

JA JC

θ

DERIVED FROM 95mm × 76mm PCB WITH 4 LAYERS

JA

WEIGHT = 1.7g

ORDER INFORMATION

LEAD FREE FINISH

LTM4602EV#PBF

LTM4602IV#PBF

PART MARKING*

PACKAGE DESCRIPTION

TEMPERATURE RANGE

LTM4602V

104-Lead (15mm × 15mm × 2.8mm) LGA

–40°C to 85°C

LTM4602V

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

Consult LTC Marketing for information on non-standard lead based ﬁnish parts.

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

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

The ^ldenotes the speciﬁcations which apply over the –40°C to 85°C

ELECTRICAL CHARACTERISTICS

temperature range, otherwise speciﬁcations are at T_A= 25°C, V_IN= 12V. External C_IN= 120μF, C_OUT= 200μF/Ceramic per typical

application (front page) conﬁguration.

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

Input DC Voltage

Output Voltage

4.5

20

V

IN(DC)

FCB = 0V

OUT(DC)

V

= 5V or 12V, V

= 1.5V, I = 0A

OUT

1.478

1.470

1.50

1.522

1.530

V

IN

OUT

Input Speciﬁcations

V

Under Voltage Lockout Threshold

Input Inrush Current at Startup

I

= 0A

3.4

4

V

IN(UVLO)

OUT

I

= 0A. V

= 1.5V, FCB = 0

OUT

INRUSH(VIN)

OUT

V

= 5V

= 12V

0.6

0.7

A

IN

V

I

Input Supply Bias Current

I

= 0A, EXTV Open

Q(VIN)

OUT CC

V

= 12V, V

= 1.5V, FCB = 5V

1.2

42

mA

μA

IN

OUT

V

= 1.5V, FCB = 0V

= 5V, V

= 1.5V, FCB = 5V

= 1.5V, FCB = 0V

1.0

52

OUT

Shutdown, RUN = 0.8V, V = 12V

50

100

IN

4602fa

2

LTM4602

ELECTRICAL CHARACTERISTICS

The l 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

I

Input Supply Current

V

IN

V

IN

V

IN

= 12V, V

= 1.5V, I

= 3.3V, I

= 6A

0.88

1.80

2.08

A

S(VIN)

OUT

= 5V, V

= 1.5V, I

= 6 A

OUT

Output Speciﬁcations

I

Output Continuous Current Range

V

IN

= 12V, V = 1.5V

OUT

0

6

A

OUTDC

(See Output Current Derating Curves for

Different V , V

and T )

A

IN OUT

l

ΔV

Line Regulation Accuracy

V

= 1.5V, I = 0A, FCB = 0V,

OUT

0.15

0.3

%

OUT(LINE)

OUT

IN

= 4.5V to 20V

V

OUT

Load Regulation Accuracy

V

= 1.5V, I = 0A to 6A, FCB = 0V,

OUT

OUT(LOAD)

OUT

IN

= 5V, V = 12V (Note 3)

0.25

0.15

0.5

1.0

%

IN

V

OUT

V

Output Ripple Voltage

Output Ripple Voltage Frequency

Turn-On Time

V

= 12V, V

= 1.5V, I

= 0A, FCB = 0V

10

15

mV

P-P

OUT(AC)

IN

OUT

fs

= 1.5V, I

= 6A, FCB = 0V

= 1A

850

kHz

OUT

t

= 1.5V, I

IN

START

OUT

V

= 12V

= 5V

0.5

0.7

ms

V

ΔV

OUTLS

Voltage Drop for Dynamic Load Step

V

C

= 1.5V, Load Step: 0A/μs to 3A/μs

= 22μF 6.3V, 330μF 4V POSCAP,

30

mV

OUT

See Table 2

t

I

Settling Time for Dynamic Load Step

Output Current Limit

Load: 10% to 50% to 10% of Full Load

25

μs

SETTLE

Output Voltage in Foldback

OUTPK

V

IN

V

IN

= 12V, V

= 1.5V

9

A

OUT

= 5V, V

= 1.5V

OUT

Control Stage

l

V

Voltage at V

I

= 0A, V = 1.5V

OUT

0.591

0.8

0.6

1.5

–1.2

1.8

100

16

0.609

V

OSET

OUT

RUN ON/OFF Threshold

2

–3

3

RUN/SS

I

Soft-Start Charging Current

Soft-Start Discharging Current

V

= 0V

= 4V

–0.5

0.8

μA

mV

mA

RUN(C)/SS

RUN(D)/SS

RUN/SS

V

IN

– SV

EXTV = 0V, FCB = 0V

CC

IN

I

Current into EXTV Pin

EXTV = 5V, FCB = 0V, V

I

= 1.5V,

OUT

EXTVCC

CC

= 0A

OUT

R

Resistor Between V

and V Pins

OSET

100

0.6

–1

kΩ

V

FBHI

OUT

V

FCB

Forced Continuous Threshold

0.57

0.63

–2

I

Forced Continuous Pin Current

V

FCB

= 0.6V

μA

FCB

PGOOD Output

ΔV

PGOOD Upper Threshold

PGOOD Lower Threshold

PGOOD Hysteresis

V

Rising

7.5

10

–10

2

12.5

%

V

OSETH

OSET

Falling

–7.5

–12.5

OSETL

OSET

Returning

OSET(HYS)

OSET

V

PGL

PGOOD Low Voltage

I

= 5mA

0.15

0.4

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 2: The LTM4602E 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

with statistical process controls. The LTM4602I is guaranteed over the

–40°C to 85°C temperature range.

Note 3: Test assumes current derating versus temperature.

4602fa

3

LTM4602

TYPICAL PERFORMANCE CHARACTERISTICS

(See Figure 21 for all curves)

Efﬁciency vs Load Current

with 20V_IN(FCB = 0)

Efﬁciency vs Load Current

with 5V_IN(FCB = 0)

Efﬁciency vs Load Current

with 12V_IN(FCB = 0)

100

90

80

70

60

50

40

30

100

90

80

70

60

50

40

30

100

90

80

70

60

50

40

30

0.8V

OUT

0.8V

1.2V

1.5V

1.8V

2.5V

3.3V

OUT

1.2V

OUT

1.5V

OUT

1.8V

OUT

2.5V

OUT

1.2V

1.5V

1.8V

2.5V

3.3V

OUT

3.3V

OUT

*

3.3V

OUT

(950kHz)*

*FOR 5V TO 3.3V CONVERSION,

SEE FREQUENCY ADJUSTMENT

IN APPLICATIONS INFORMATION

*950kHz INSTEAD OF 1.3MHz

INCREASES 3.3V EFFICIENCY 2%

0

2

4

6

8

4

8

0

2

6

4

0

2

6

8

LOAD CURRENT (A)

4602 G01

4602 G02

4602 G03

Light Load Efﬁciency vs

Load Current with 12V_IN

(FCB > 0.7V, <5V)

1.2V Transient Response

1.5V Transient Response

100

90

80

70

60

50

40

30

V

OUT

50mV/DIV

I

OUT

2A/DIV

4602 G05

20μs/DIV

1.2V AT 3A/μs LOAD STEP

4602 G06

20μs/DIV

1.5V AT 3A/μs LOAD STEP

1.2V

1.5V

1.8V

2.5V

3.3V

C

= 1 × 22μF, 6.3V CERAMICS

OUT

C

= 1 × 22μF, 6.3V CERAMICS

OUT

330μF, 4V SANYO POSCAP

0

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

LOAD CURRENT (A)

1

4602 G04

1.8V Transient Response

2.5V Transient Response

3.3V Transient Response

V

OUT

50mV/DIV

I

OUT

I

OUT

2A/DIV

OUT

2A/DIV

4602 G09

4602 G07

4602 G08

20μs/DIV

3.3V AT 3A/μs LOAD STEP

1.8V AT 3A/μs LOAD STEP

2.5V AT 3A/μs LOAD STEP

C

= 1 × 22μF, 6.3V CERAMICS

C

= 1 × 22μF, 6.3V CERAMICS

C

= 1 × 22μF, 6.3V CERAMICS

OUT

330μF, 4V SANYO POSCAP

4602fa

4

LTM4602

TYPICAL PERFORMANCE CHARACTERISTICS _{(See Figure 21 for all curves)}

Short-Circuit Protection,

I_OUT= 0A

Start-Up, I_OUT= 6A

(Resistive Load)

Start-Up, No Load, I_OUT= 0A

V

OUT

0.5V/DIV

V

OUT

0.5V/DIV

I

IN

I

IN

0.5A/DIV

4602 G10

4602 G12

4602 G11

200μs/DIV

20μs/DIV

V

C

= 12V

OUT

500μs/DIV

V

= 12V

V

C

= 12V

OUT

IN

= 1.5V

V

C

= 1.5V

OUT

= 1 × 22μF, 6.3V X5R

330μF, 4V SANYO POSCAP

NO EXTERNAL SOFT-START CAPACITOR

Short-Circuit Protection,

I_OUT= 6A

V_INto V_OUTStep-Down Ratio

5.5

5.0

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

f

= OPEN

ADJ

5V

V

OUT

0.5V/DIV

3.3V

I

IN

2.5V

1.8V

0.5A/DIV

4602 G13

20μs/DIV

= 1 × 22μF, 6.3V X5R

V

C

= 12V

OUT

IN

1.5V

= 1.5V

1.2V

10

330μF, 4V SANYO POSCAP

0.6V

NO EXTERNAL SOFT-START CAPACITOR

20

0

5

15

V

IN

(V)

SEE FREQUENCY ADJUSTMENT DISCUSSION

FOR 12V TO 5V

AND 5V TO 3.3V

IN

OUT

IN OUT

CONVERSION

4602 G14

4602fa

5

LTM4602

PIN FUNCTIONS

(See Package Description for Pin Assignment)

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

SGND (Pin D23): Signal Ground Pin. All small-signal

components should connect to this ground, which in turn

connects to PGND at one point.

IN

tween these pins and PGND pins. Recommend placing

input decoupling capacitance directly between V pins

IN

and PGND pins.

RUN/SS (Pin F23): Run and Soft-Start Control. Forcing

this pin below 0.8V will shut down the power supply.

Inside the power module, there is a 1000pF capacitor

which provides approximately 0.7ms soft-start time with

200μF output capacitance. Additional soft-start time can

be achieved by adding additional capacitance between the

RUN/SSandSGNDpins. Theinternalshort-circuitlatchoff

can be disabled by adding a resistor between this pin and

f

(Pin A15): A 110k resistor from V to this pin sets

IN

ADJ

the one-shot timer current, thereby setting the switching

frequency. The LTM4602 switching frequency is typically

850kHz. An external resistor to ground can be selected to

reducetheone-shottimercurrent,thuslowertheswitching

frequency to accommodate a higher duty cycle step down

requirement. See the applications section.

the V pin. This pullup resistor must supply a minimum

IN

SV (PinA17):SupplyPinforInternalPWMController.Leave

IN

5μA pull up current.

this pin open or add additional decoupling capacitance.

FCB (Pin G23): Forced Continuous Input. Grounding this

pin enables forced continuous mode operation regardless

of load conditions. Tying this pin above 0.63V enables

discontinuousconductionmodetoachievehighefﬁciency

operation at light loads. There is an internal 4.75k resistor

between the FCB and SGND pins.

EXTV (Pin A19): External 5V supply pin for controller. If

CC

left open or grounded, the internal 5V linear regulator will

power the controller and MOSFET drivers. For high input

voltage applications, connecting this pin to an external

5V will reduce the power loss in the power module. The

EXTV voltage should never be higher than V .

CC

IN

PGOOD (Pin J23): Output Voltage Power Good Indicator.

When the output voltage is within 10% of the nominal

voltage, the PGOOD is open drain output. Otherwise, this

pin is pulled to ground.

V

(Pin A21): The Negative Input of The Error Ampliﬁer.

OSET

Internally,thispinisconnectedtoV witha100kprecision

OUT

resistor.Differentoutputvoltagescanbeprogrammedwith

additional resistors between the V

and SGND pins.

OSET

PGND (Bank 2): Power ground pins for both input and

output returns.

COMP (Pin B23): 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 with 0.8V corresponding to zero

sense voltage (zero current).

V

OUT

(Bank 3): Power Output Pins. Apply output load

between these pins and PGND pins. Recommend placing

High Frequency output decoupling capacitance directly

between these pins and PGND pins.

TOP VIEW

2

3

4

5

6

7

16

17

18

19

A

C

E

1

20

21

22

23

24

B

D

F

COMP

SGND

RUN/SS

FCB

9

10

14

11

15

V

IN

8

BANK 1

13

12

25

32

G

J

26

33

27

34

28

35

29

36

30

37

31

38

H

K

PGOOD

48

59

39

50

61

40

51

62

41

52

63

42

53

64

43

54

65

44

55

66

45

56

67

46

57

68

47

58

69

49

60

71

PGND

BANK 2

L

M

N

70

73

84

95

74

85

96

75

86

97

76

87

98

77

88

99

78

89

79

90

80

91

81

92

72

83

94

82

93

P

R

T

V

OUT

BANK 3

100

101

102

103

104

1

3

5

7

9

11

13

15

17

19

21

23

2

4

6

8

10

12

14

16

18

20

22

4602 PN01

4602fa

6

LTM4602

SIMPLIFIED BLOCK DIAGRAM

SV

IN

RUN/SS

1000pF

V

IN

4.5V TO 20V

C

1.5μF

IN

PGOOD

Q1

COMP

FCB

INT

COMP

V

OUT

1.5V

6A MAX

OUT

4.75k

15μF

6.3V

CONTROLLER

Q2

f

ADJ

PGND

10Ω

SGND

EXTV

CC

100k

0.5%

V

OSET

R

SET

66.5k

4602 F01

Figure 1. Simpliﬁed LTM4602 Block Diagram

DECOUPLING REQUIREMENTS _{T = 25°C, V}

_IN= 12V. Use Figure 1 conﬁguration.

A

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

C

IN

External Input Capacitor Requirement

I

= 6A

20

μF

OUT

(V = 4.5V to 20V, V

= 1.5V)

IN

OUT

C

OUT

External Output Capacitor Requirement

(V = 4.5V to 20V, V = 1.5V)

I

= 6A, Refer to Table 2 in the

100

200

μF

OUT

Applications Information Section

IN

OUT

4602fa

7

LTM4602

OPERATION

μModule Description

in an overvoltage condition, internal top FET Q1 is turned

off and bottom FET Q2 is turned on and held on until the

overvoltage condition clears.

The LTM4602 is a standalone nonisolated synchronous

switching DC/DC power supply. It can deliver up to 6A of

DC output current with only bulk external input and output

capacitors. This module provides a precisely regulated

outputvoltageprogrammableviaoneexternalresistorfrom

Pulling the RUN/SS pin low forces the controller into its

shutdown state, turning off both Q1 and Q2. Releasing the

pin allows an internal 1.2μA current source to charge up

the soft-start capacitor. When this voltage reaches 1.5V,

the controller turns on and begins switching.

0.6V to 5.0V , not to exceed 80% of the input voltage.

DC

The input voltage range is 4.5V to 20V. A simpliﬁed block

diagram is shown in Figure 1 and the typical application

schematic is shown in Figure 21.

At low load current the module works in continuous cur-

rent mode by default to achieve minimum output voltage

ripple. It can be programmed to operate in discontinuous

current mode for improved light load efﬁciency when the

FCB pin is pulled up above 0.8V and no higher than 6V.

The FCB pin has a 4.75k resistor to ground, so a resistor

TheLTM4602containsanintegratedLTCconstanton-time

current-mode regulator, ultralow R

FETs with fast

DS(ON)

switchingspeedandintegratedSchottkydiode.Thetypical

switching frequency is 850kHz at full load. With current

mode control and internal feedback loop compensation,

the LTM4602 module has sufﬁcient stability margins and

good transient performance under a wide range of operat-

ing conditions and with a wide range of output capacitors,

even all ceramic output capacitors (X5R or X7R).

to V can set the voltage on the FCB pin.

IN

When EXTV pin is grounded or open, an integrated 5V

CC

linear regulator powers the controller and MOSFET gate

drivers. If a minimum 4.7V external bias supply is ap-

plied on the EXTV pin, the internal regulator is turned

CC

Current mode control provides cycle-by-cycle fast current

limit. In addition, foldback current limiting is provided in

an overcurrent condition while V

LTM4602 has defeatable short-circuit latch off. Internal

overvoltage and undervoltage comparators pull the open-

drainPGOODoutputlowiftheoutputfeedbackvoltageexits

a 10%windowaroundtheregulationpoint. Furthermore,

off, and an internal switch connects EXTV to the gate

CC

driver voltage. This eliminates the linear regulator power

drops. Also, the

loss with high input voltage, reducing the thermal stress

OSET

on the controller. The maximum voltage on EXTV pin is

CC

6V. The EXTV voltage should never be higher than the

CC

V voltage. Also EXTV must be sequenced after V .

IN

CC

IN

4602fa

8

LTM4602

APPLICATIONS INFORMATION

The typical LTM4602 application circuit is shown in Fig-

ure 21. External component selection is primarily deter-

mined by the maximum load current and output voltage.

voltage V

needs to be margined up/down by M%,

OUT

the resistor values of R and R

can be calculated

UP

DOWN

from the following equations:

(R_SETR_UP)• V_OUT•(1+M%)

(R_SETR_UP)+100kꢀ

Output Voltage Programming and Margining

= 0.6V

The PWM controller of the LTM4602 has an internal

0.6V reference voltage. As shown in the block diagram,

a 100k/0.5% internal feedback resistor connects V

R_SET• V_OUT•(1–M%)

OUT

pin to

= 0.6V

R

_SET+(100kꢀ R_DOWN

)

and V

pins. Adding a resistor R from V

OSET

SET

OSET

SGND pin programs the output voltage:

Input Capacitors

100k +R_SET

V

_OUT= 0.6V •

R_SET

The LTM4602 μModule should be connected to a low

AC-impedance DC source. High frequency, low ESR input

capacitors are required to be placed adjacent to the mod-

Table 1 shows the standard values of 1% R

for typical output voltages:

resistor

SET

ule. In Figure 21, the bulk input capacitor C is selected

IN

for its ability to handle the large RMS current into the

converter. For a buck converter, the switching duty cycle

can be estimated as:

Table 1

R

SET

Open 100

0.6 1.2

66.5

1.5

49.9

1.8

43.2

2

31.6

2.5

22.1

3.3

13.7

5

(kΩ)

V

OUT

(V)

V_OUT

D=

V

Voltagemarginingisthedynamicadjustmentoftheoutput

voltage to its worst case operating range in production

testing to stress the load circuitry, verify control/protec-

tion functionality of the board and improve the system

reliability. Figure 2 shows how to implement margining

function with the LTM4602. In addition to the feedback

resistor R , several external components are added.

Turn off both transistor Q and Q

margining. When Q is on and Q

IN

Without considering the inductor current ripple, the RMS

current of the input capacitor can be estimated as:

I_OUT(MAX)

I_CIN(RMS)

=

• D•(1ꢁD)

ꢀ%

SET

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

the power module. C1 can be a switcher-rated electrolytic

aluminum capacitor, OS-CON capacitor or high volume

ceramic capacitors. Note the capacitor ripple current

ratings are often based on only 2000 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.

to disable the

is off, the output

UP

DOWN

UP

voltage is margined up. The output voltage is margined

down when Q

is on and Q is off. If the output

DOWN

UP

V

OUT

LTM4602

R

DOWN

Q

100k

DOWN

2N7002

OSET

InFigure21,theinputcapacitorsareusedashighfrequency

inputdecouplingcapacitors.Inatypical6Aoutputapplica-

tion, 1-2piecesofverylowESRX5RorX7R, 10μFceramic

capacitors are recommended. This decoupling capacitor

should be placed directly adjacent the module input pins

in the PCB layout to minimize the trace inductance and

high frequency AC noise.

PGND

SGND

R

SET

UP

Q

UP

2N7002

4602 F02

Figure 2. LTM4602 Margining Implementation

4602fa

9

LTM4602

APPLICATIONS INFORMATION

Output Capacitors

Soft-Start and Latchoff with the RUN/SS pin

TheLTM4602isdesignedforlowoutputvoltageripple.The

The RUN/SS pin provides a means to shut down the

LTM4602 as well as a timer for soft-start and overcurrent

latchoff. Pulling the RUN/SS pin below 0.8V puts the

bulk output capacitors C

is chosen with low enough

OUT

effectiveseriesresistance(ESR)tomeettheoutputvoltage

ripple and transient requirements. C can be low ESR

LTM4602 into a low quiescent current shutdown (I ≤

OUT

Q

tantalum capacitor, low ESR polymer capacitor or ceramic

capacitor (X5R or X7R). The typical capacitance is 200μF

if all ceramic output capacitors are used. The internally

optimized loop compensation provides sufﬁcient stability

margin for all ceramic capacitors applications. Additional

output ﬁltering may be required by the system designer,

if further reduction of output ripple or dynamic transient

spike is required. Refer to Table 2 for an output capaci-

tance matrix for each output voltage droop, peak to peak

deviation and recovery time during a 3A/μs transient with

a speciﬁc output capacitance.

100μA). Releasing the pin allows an internal 1.2μA cur-

rent source to charge up the timing capacitor C . Inside

SS

LTM4602, thereisaninternal1000pFcapacitorfromRUN/

SS pin to ground. If RUN/SS pin has an external capacitor

C

to ground, the delay before starting is about:

SS_EXT

1.5V

1.2μA

t_DELAY

=

•(C_{SS_EXT}+1000pF)

WhenthevoltageonRUN/SSpinreaches1.5V,theLTM4602

internal switches are operating with a clamping of the

maximum output inductor current limited by the RUN/SS

pintotalsoft-startcapacitance. AstheRUN/SSpinvoltage

rises to 3V, the soft-start clamping of the inductor current

is released.

Fault Conditions: Current Limit and Overcurrent

Foldback

The LTM4602 has a current mode controller, which inher-

ently limits the cycle-by-cycle inductor current not only in

steady-state operation, but also in transient.

V to V

Step-Down Ratios

IN

OUT

There are restrictions in the maximum V to V

step

IN

OUT

To further limit current in the event of an over load condi-

tion,theLTM4602providesfoldbackcurrentlimiting.Ifthe

output voltage falls by more than 50%, then the maximum

output current is progressively lowered to about one sixth

of its full current limit value.

down ratio that can be achieved for a given input voltage.

These constraints are shown in the Typical Performance

Characteristics curves labeled “V to V

Step-Down

IN

OUT

Ratio”.Notethatadditionalthermalderatingmayapply.See

the Thermal Considerations and Output Current Derating

sections of this data sheet.

4602fa

10

LTM4602

APPLICATIONS INFORMATION

Table 2. Output Voltage Response Versus Component Matrix (Refer to Figure 21), 0A to 3A Step (Typical Values)

TYPICAL MEASURED VALUES

C

OUT1

VENDORS

PART NUMBER

C

OUT2

VENDORS

PART NUMBER

TDK

C4532X5R0J107MZ (100μF,6.3V)

JMK432BJ107MU-T ( 100μF, 6.3V)

JMK316BJ226ML-T501 ( 22μF, 6.3V)

SANYO POSCAP

6TPE330MIL (330μF, 6.3V)

2R5TPE470M9 (470μF, 2.5V)

4TPE470MCL (470μF, 4V)

TAIYO YUDEN

V

C

C3

V

IN

(V)

DROOP

(mV)

PEAK TO PEAK

RECOVERY TIME

(μs)

LOAD STEP

(A/μs)

OUT

IN

OUT1

OUT2

COMP

(V)

1.2

1.5

1.8

2.5

3.3

5

(CERAMIC)

2 × 10μF 25V

(BULK)

(CERAMIC)

(BULK)

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

(mV)

60

54

55

60

54

50

55

50

54

59

55

54

59

54

50

60

50

60

50

54

64

60

64

58

60

64

160

150μF 35V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

3 × 22μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

1 × 100μF 6.3V

2 × 100μF 6.3V

3 × 22μF 6.3V

4 × 100μF 6.3V

1 × 100μF 6.3V

3 × 22μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

2 × 100μF 6.3V

1 × 100μF 6.3V

3 × 22μF 6.3V

4 × 100μF 6.3V

1 × 100μF 6.3V

3 × 22μF 6.3V

2 × 100μF 6.3V

4 × 100μF 6.3V

1 × 100μF 6.3V

NONE 100pF

NONE 220pF

NONE 100pF

5

50

30

25

30

25

28

26

25

28

26

25

29

25

29

25

27

32

30

32

38

30

32

80

25

20

25

20

25

20

25

20

30

20

30

20

30

25

30

25

30

35

25

30

35

30

25

3

5

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

12

5

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

5

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

12

5

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

5

470μF 4V

470μF 2.5V

330μF 6.3V

NONE

12

5

470μF 4V

330μF 6.3V

470μF 4V

NONE

5

470μF 4V

330μF 6.3V

NONE

12

7

330μF 6.3V

470μF 4V

NONE

7

470μF 4V

330μF 6.3V

NONE

12

15

20

NONE

5

NONE

4602fa

11

LTM4602

APPLICATIONS INFORMATION

After the controller has been started and given adequate

4V maximum latchoff threshold and overcome the 4μA

maximumdischargecurrent.Figure 3showsaconceptual

time to charge up the output capacitor, C is used as a

SS

short-circuittimer.AftertheRUN/SSpinchargesabove4V,

if the output voltage falls below 75% of its regulated value,

then a short-circuit fault is assumed. A 1.8μA current then

drawing of V

during start-up and short circuit.

RUN

V

RUN/SS

beginsdischargingC . Ifthefaultconditionpersistsuntil

SS

4V

3.5V

the RUN/SS pin drops to 3.5V, then the controller turns

off both power MOSFETs, shutting down the converter

permanently. The RUN/SS pin must be actively pulled

down to ground in order to restart operation.

3V

1.5V

SHORT-CIRCUIT

LATCH ARMED

t

The overcurrent protection timer requires the soft-start

SOFT-START

CLAMPING

L

SHORT-CIRCUIT

LATCHOFF

OUTPUT

OVERLOAD

HAPPENS

timing capacitor C be made large enough to guarantee

SS

OF I RELEASED

that the output regulation by the time C has reached the

SS

V

OUT

4V threshold. In general, this will depend upon the size of

the output capacitance, output voltage and load current

characteristic. A minimum external soft-start capacitor

can be estimated from:

75%V

O

t

SWITCHING

STARTS

4602 F03

C

_{SS_EXT}+1000pF >C_OUT• V_OUT(10^–3[F / V_S])

Figure 3. RUN/SS Pin Voltage During Startup and

Short-Circuit Protection

Generally 0.1μF is more than sufﬁcient.

Sincetheloadcurrentisalreadylimitedbythecurrentmode

controlandcurrentfoldbackcircuitryduringashortcircuit,

overcurrent latchoff operation is NOT always needed or

desired, especially if the output has large capacitance or

the load draws high current during start up. The latchoff

featurecanbeoverriddenbyapull-upcurrentgreaterthan

5μA but less than 80μA to the RUN/SS pin. The additional

V

IN

R

LTM4602

RUN/SS

PGND SGND

RECOMMENDED VALUES FOR R

RUN/SS

V

IN

R

RUN/SS

current prevents the discharge of C during a fault and

SS

4.5V TO 5.5V

10.8V TO 13.8V

16V TO 20V

50k

150k

330k

also shortens the soft-start period. Using a resistor from

RUN/SSpintoV isasimplesolutiontodefeatlatchoff.Any

4602 F04

IN

pull-up network must be able to maintain RUN/SS above

Figure 4. Defeat Short-Circuit Latchoff with a Pull-Up

Resistor to V_IN

4602fa

12

LTM4602

APPLICATIONS INFORMATION

Enable

EXTV Connection

CC

The RUN/SS pin can be driven from logic as shown in

Figure 5. This function allows the LTM4602 to be turned

on or off remotely. The ON signal can also control the

sequence of the output voltage.

An internal low dropout regulator produces an internal 5V

supply that powers the control circuitry and FET drivers.

Therefore, if the system does not have a 5V power rail,

the LTM4602 can be directly powered by V . The gate

IN

driver current through LDO is about 18mA. The internal

LDO power dissipation can be calculated as:

RUN/SS

P

= 18mA • (V – 5V)

IN

LDO_LOSS

LTM4602

ON

The LTM4602 also provides an external gate driver volt-

PGND SGND

age pin EXTV . If there is a 5V rail in the system, it is

CC

2N7002

recommended to connect EXTV pin to the external 5V

4602 F05

CC

rail. Whenever the EXTV pin is above 4.7V, the inter-

CC

Figure 5. Enable Circuit with External Logic

nal 5V LDO is shut off and an internal 50mA P-channel

switch connects the EXTV to internal 5V. Internal 5V is

CC

Output Voltage Tracking

supplied from EXTV until this pin drops below 4.5V. Do

CC

not apply more than 6V to the EXTV pin and ensure that

CC

For the applications that require output voltage tracking,

several LTM4602 modules can be programmed by the

power supply tracking controller such as the LTC2923.

Figure 6 shows a typical schematic with LTC2923. Coin-

cident, ratiometric and offset tracking for V

falling can be implemented with different sets of resistor

values. See the LTC2923 data sheet for more details.

EXTV < V . The following list summaries the possible

CC

IN

connections for EXTV :

CC

1. EXTV grounded. Internal 5V LDO is always powered

CC

rising and

from the internal 5V regulator.

OUT

2. EXTV connected to an external supply. Internal LDO

CC

is shut off. A high efﬁciency supply compatible with the

MOSFET gate drive requirements (typically 5V) can im-

prove overall efﬁciency. With this connection, it is always

Q1

V

IN

DC/DC

3.3V

5V

required that the EXTV voltage can not be higher than

CC

V

V pin voltage.

IN

Discontinuous Operation and FCB Pin

R

ONB

V

GATE

RAMP

FB1

CC

LTM4602

V

1.8V

ON

OSET

OUT

The FCB pin determines whether the internal bottom

MOSFET remains on when the inductor current reverses.

There is an internal 4.75k pull-down resistor connecting

this pin to ground. The default light load operation mode

is forced continuous (PWM) current mode. This mode

provides minimum output voltage ripple.

R

SET

49.9k

ONA

LTC2923

STATUS

SDO

RAMPBUF

TRACK1

TRACK2

V

IN

R

TB1

TA1

IN

R

TB2

LTM4602

V

FB2

1.5V

OSET

OUT

R

GND

SET

R

TA2

In the application where the light load efﬁciency is im-

portant, tying the FCB pin above 0.6V threshold enables

discontinuous operation where the bottom MOSFET turns

offwheninductorcurrentreverses.Therefore,theconduc-

66.5k

4602 F06

Figure 6. Output Voltage Tracking with the LTC2923 Controller

4602fa

13

LTM4602

APPLICATIONS INFORMATION

tionlossisminimizedandlightloadefﬁciencyisimproved.

The penalty is that the controller may skip cycle and the

output voltage ripple increases at light load.

sinking methods. Thermal models are derived from

several temperature measurements at the bench,

and thermal modeling analysis. Application Note 103

provides a detailed explanation of the analysis for the

thermal models, and the derating curves. Tables 3

and 4 provide a summary of the equivalent θ_JAfor the

noted conditions. These equivalent θ_JAparameters are

correlated to the measured values, and improve with

air-ﬂow. The case temperature is maintained at 100°C

or below for the derating curves. This allows for 4W

maximum power dissipation in the total module with

top and bottom heat sinking, and 2W power dissipation

through the top of the module with an approximate

θ_JCbetween 6°C/W to 9°C/W. This equates to a total

of 124°C at the junction of the device. The θ_JAvalues

in Tables 3 and 4 can be used to derive the derating

curves for other output voltages.

Paralleling Operation with Load Sharing

TwoormoreLTM4602modulescanbeparalleledtoprovide

higher than 6A output current. Figure 7 shows the neces-

saryinterconnectionbetweentwoparalleledmodules.The

OPTI-LOOP^®current mode control ensures good current

sharing among modules to balance the thermal stress.

The new feedback equation for two or more LTM4602s

in parallel is:

100k

+R_SET

N

V_OUT= 0.6V •

R_SET

where N is the number of LTM4602s in parallel.

Thermal Considerations and Output Current Derating

Safety Considerations

The power loss curves in Figures 8 and 13 can be used

in coordination with the load current derating curves

in Figures 9 to 12, and Figures 14 to 15 for calculating

an approximate θ_JAfor the module with various heat

TheLTM4602modulesdonotprovideisolationfromV to

OUT

with a rating twice the maximum input current should be

provided to protect each unit from catastrophic failure.

IN

V

.Thereisnointernalfuse.Ifrequired,aslowblowfuse

OPTI-LOOP is a registered trademark of Linear Technology Corporation.

V

PULLUP

100k

PGOOD

V

OUT

V

IN

V

IN

V

OUT

LTM4602

12A MAX

PGND COMP V

SGND

OSET

R

SET

PGOOD COMP V

SGND

OSET

V

IN

LTM4602

V

OUT

PGND

4602 F07

Figure 7. Parallel Two μModules with Load Sharing

4602fa

14

LTM4602

APPLICATIONS INFORMATION

2.0

1.8

1.6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0

7

6

5

4

3

2

1

0

5

4

3

2

1

0

12V TO 1.5V

LOSS

5V TO 1.5V

LOSS

0LFM

200LFM

400LFM

0LFM

200LFM

400LFM

0.6

1.0

3.1

4.1

5.1

6.1

2.1

60

70

80

100

50

60

70

80

90

100

50

90

CURRENT (A)

TEMPERATURE (°C)

4602 F08

4602 F09

4602 F10

Figure 10. 5V to 1.5V, BGA Heat Sink

Figure 9. 5V to 1.5V, No Heat Sink

Figure 8. 1.5V Power Loss vs Load Current

7

6

7

6

4.0

5V TO 3.3V LOSS

12V TO 3.3V LOSS

3.5

3.0

2.5

12V TO 3.3V (950kHz) LOSS

5

4

3

2

5

4

3

2

1

0

2.0

1.5

1.0

0.5

0

0LFM

200LFM

400LFM

1

200LFM

400LFM

0

60

70

80

100

50

90

1.0

2.1

4.1

60

70

80

100

0.5

5.1

6.1

50

90

3.1

TEMPERATURE (°C)

CURRENT (A)

TEMPERATURE (°C)

4602 F11

4601 F13

4602 F09

Figure 11. 12V to 1.5V, No Heat Sink

Figure 12. 12v to 1.5V, BGA Heat Sink

Figure 13. 3.3V Power Loss

vs Load Current

7

6

7

6

5

4

3

2

1

0

5

4

3

2

1

0

0LFM

200LFM

400LFM

0LFM

200LFM

400LFM

60

70

80

100

60

70

80

100

50

90

50

90

TEMPERATURE (°C)

4602 F14

4602 F15

Figure 14. 5V to 3.3V, No Heat Sink

Figure 15. 5V to 3.3V, BGA Heat Sink

4602fa

15

LTM4602

APPLICATIONS INFORMATION

7

6

5

4

3

2

5

4

3

2

1

0

0LFM

200LFM

400LFM

1

200LFM

400LFM

0

60

70

80

100

50

90

60

70

80

100

50

90

TEMPERATURE (°C)

4602 F16

Figure 17. 12V to 3.3V, BGA Heat Sink

Figure 16. 12V to 3.3V, No Heat Sink

Table 3. 1.5V Output

Table 4. 3.3V Output

AIR FLOW (LFM)

HEAT SINK

None

θ

(°C/W)

JA

AIR FLOW (LFM)

HEAT SINK

None

θ

(°C/W)

JA

0

15.2

14

0

15.2

14.6

13.4

13.9

11.1

10.5

200

400

0

None

200

400

0

None

12

None

BGA Heat Sink

13.9

11.3

10.25

BGA Heat Sink

200

400

200

400

• Use a separated SGND ground copper area for com-

ponents connected to signal pins. Connect the SGND

to PGND underneath the unit.

Layout Checklist/Example

The high integration of the LTM4602 makes the PCB board

layoutverysimpleandeasy.However,tooptimizeitselectri-

cal and thermal performance, some layout considerations

are still necessary.

Figure 18 gives a good example of the recommended

layout.

• Use large PCB copper areas for high current path,

LTM4602 Frequency Adjustment

including V , PGND and V . It helps to minimize the

IN

OUT

The LTM4602 is designed to typically operate at 850kHz

across most input and output conditions. The control ar-

chitectureisconstantontimevalleymodecurrentcontrol.

PCB conduction loss and thermal stress.

• Place high frequency ceramic input and output capaci-

tors next to the V , PGND and V

pins to minimize

IN

OUT

The f

pin is typically left open or decoupled with an

ADJ

high frequency noise.

optional 1000pF capacitor. The switching frequency has

beenoptimizedtomaintainconstantoutputrippleoverthe

operatingconditions.Theequationsforsettingtheoperat-

ing frequency are set around a programmable constant on

time.Thisontimeisdevelopedbyaprogrammablecurrent

into an on board 10pF capacitor that establishes a ramp

that is compared to a voltage threshold equal to the output

• Place a dedicated power ground layer underneath

the unit.

• To minimize the via conduction loss and reduce module

thermal stress, use multiple vias for interconnection

between top layer and other power layers.

• Do not put vias directly on pads unless they are capped.

voltage up to a 2.4V clamp. This I current is equal to:

ON

I

= (V – 0.7V)/110k, with the 110k onboard resistor

ON

IN

4602fa

16

LTM4602

APPLICATIONS INFORMATION

V

to ~1.2MHz for 3.3V, and ~1.7MHz for 5V outputs due

IN

to Frequency = (DC/t ) When the switching frequency

ON

increases to 1.2MHz, then the time period t is reduced

S

to ~833 nanoseconds and at 1.7MHz the switching period

reduces to ~588 nanoseconds. When higher duty cycle

conversions like 5V to 3.3V and 12V to 5V need to be

accommodated, then the switching frequency can be

lowered to alleviate the violation of the 400ns minimum

C

IN

off time. Since the total switching period is t = t + t

,

PGND

S

ON OFF

t

will be below the 400ns minimum off time. A resistor

OFF

from the f

pin to ground can shunt current away from

ADJ

V

OUT

the on time generator, thus allowing for a longer on time

and a lower switching frequency. 12V to 5V and 5V to

3.3V derivations are explained in the data sheet to lower

switching frequency and accommodate these step-down

conversions.

4600 F16

LOAD

TOP LAYER

Figure 18. Recommended PCB Layout

Equations for setting frequency for 12V to 5V:

from V to f . The on time is equal to t = (V /I )

IN

ADJ

ON

OUT ON

• 10pF and t = t – t . The frequency is equal to: Freq.

OFF

s

ON

I

= (V – 0.7V)/110k; I = 103μA

IN ON

ON

= DC/t . The I current is proportional to V , and the

ON

IN

frequency = (I /[2.4V • 10pF]) • DC = 1.79MHz;

ON

regulator duty cycle is inversely proportional to V , there-

IN

DC = duty cycle, duty cycle is (V /V )

OUT IN

forethestep-downregulatorwillremainrelativelyconstant

frequency as the duty cycle adjustment takes place with

t = t + t , t = on-time, t = off-time of the

OFF

S

ON

OFF ON

lowering V . The on time is proportional to V

up to a

switching period; t = 1/frequency

IN

OUT

S

2.4V clamp. This will hold frequency relatively constant

with different output voltages up to 2.4V. The regulator

switching period is comprised of the on time and off time

as depicted in Figure 19.

t

must be greater than 400ns, or t – t > 400ns.

S ON

OFF

t

= DC • t

S

ON

1MHz frequency or 1μs period is chosen for 12V to 5V.

t

ON

(DC) DUTY CYCLE =

t

= 0.41 • 1μs ≅ 410ns

t

s

ON

t

V

OUT

ON

DC =

=

t

s

V

IN

= 1μs – 410ns ≅ 590ns

OFF

DC

FREQ =

t

ON

t

and t are above the minimums with adequate guard

OFF

t

ON

OFF

ON

band.

4602 F19

PERIOD t

s

Using the frequency = (I /[2.4V • 10pF]) • DC, solve for

ON

I

= (1MHz • 2.4V • 10pF) • (1/0.41) ≅ 58μA. I current

ON

Figure 19. LTM4602 Switching Period

calculated from 12V input was 103μA, so a resistor from

f

to ground = (0.7V/15k) = 46μA. 103μA – 46μA =

TheLTM4602hasaminimum(t )ontimeof100nanosec-

ADJ

ON

57μA, sets the adequate I current for proper frequency

onds and a minimum (t ) off time of 400 nanoseconds.

ON

OFF

range for the higher duty cycle conversion of 12V to

The 2.4V clamp on the ramp threshold as a function of

5V. Input voltage range is limited to 9V to 16V. Higher

V

will cause the switching frequency to increase by the

OUT

input voltages can be used without the 15k on f . The

ratio of V /2.4V for 3.3V and 5V outputs. This is due to

ADJ

OUT

inductor ripple current gets too high above 16V, and the

the fact the on time will not increase as V

increases

OUT

400ns minimum off-time is limited below 9V.

past 2.4V. Therefore, if the nominal switching frequency

is 850kHz, then the switching frequency will increase

4602fa

17

LTM4602

APPLICATIONS INFORMATION

Equations for setting frequency for 5V to 3.3V:

Using the frequency = (I /[2.4V • 10pF]) • DC, solve for

ON

I

= (450kHz • 2.4V • 10pF) • (1/0.66) ≅ 16μA. I current

ON

I

= (V – 0.7V)/110k; I = 39μA

IN ON

ON

calculated from 5V input was 39μA, so a resistor from f

ADJ

frequency = (I /[2.4V • 10pF]) • DC = 1.07MHz;

ON

to ground = (0.7V/30.1k) = 23μA. 39μA – 23μA = 16μA,

DC = duty cycle, duty cycle is (V /V )

OUT IN

sets the adequate I current for proper frequency range

ON

for the higher duty cycle conversion of 5V to 3.3V. Input

t = t + t , t = on-time, t = off-time of the

OFF

S

ON

OFF ON

voltagerangeislimitedto4.5Vto7V.Higherinputvoltages

switching period; t = 1/frequency

S

can be used without the 30.1k on f . The inductor ripple

ADJ

t

must be greater than 400ns, or t – t > 400ns.

S ON

OFF

current gets too high above 7V, and the 400ns minimum

off-time is limited below 4.5V.

t

= DC • t

S

ON

In 12V to 3.3V applications, if a 35k resistor is added from

~450kHz frequency or 2.22μs period is chosen for 5V to

3.3V. Frequency range is about 450kHz to 650kHz from

4.5V to 7V input.

the f

pin to ground, then a 2% efﬁciency gain will be

ADJ

achieved as shown in the 12V efﬁciency graph in the Typi-

cal Performance Characteristics. This is due to the lower

transition losses in the power MOSFETs after lowering the

switching frequency down from 1.3MHz to 950kHz.

t

= 0.66 • 2.22μs ≅ 1.46μs

= 2.22μs – 1.46μs ≅ 760ns

ON

OFF

t

and t are above the minimums with adequate guard

OFF

ON

band.

4602fa

18

LTM4602

APPLICATIONS INFORMATION

5V to 3.3V at 5A

R1

30.1k

V

IN

4.5V TO 7V

C5

100pF

C3

10μF

25V

C1

10μF

25V

V

EFFICIENCY = 94%

AT 5A LOAD

V

f

OUT

3.3V AT 5A

IN

ADJ

EXTV

FCB

V

CC

OUT

+

C4

C2

22μF

330μF

V

OSET

6.3V

R

22.1k

1%

SET

LTM4602

RUN/SOFT-START

RUN/SS

COMP

SV

IN

PGOOD

PGND

OPEN DRAIN

SGND

4602 F20a

5V TO 3.3V AT 5A WITH f

= 30.1k

C1, C3: TDK C3216X5R1E106MT

C2: TAIYO YUDEN, JMK316BJ226ML

C4: SANYO POSCAP, 6TPE330MIL

ADJ

12V to 5V at 5A

R1

15k

V

IN

7V TO 20V

C5

100pF

C3

10μF

25V

C1

10μF

25V

V

IN

f

V

EFFICIENCY = 92.5%

AT 5A LOAD

ADJ

OUT

5V AT 5A

EXTV

CC

V

OUT

+

C4

330μF

6.3V

C2

22μF

FCB

V

OSET

R

13.7k

1%

SET

LTM4602

RUN/SOFT-START

RUN/SS

COMP

SV

IN

PGOOD

PGND

OPEN DRAIN

SGND

4602 F20b

7V TO 20V AT 5A WITH f

= 15k

C1, C3: TDK C3216X5R1E106MT

C2: TAIYO YUDEN, JMK316BJ226ML

C4: SANYO POSCAP, 6TPE330MIL

ADJ

Figure 20. V_INto V_OUTStep-Down Ratio for 12V_INto 5V_OUTand 5V_INto 3.3V_OUT

V

IN

5V TO 20V

GND

C

IN

C

+

IN

10μF

×2

150μF

BULK

V

IN

(MULTIPLE PINS)

CER

V

OUT

6A

EXTV

CC

V

OUT

(MULTIPLE PINS)

C3

100pF

SV

IN

C

+

OUT2

OUT1

REFER TO

TABLE 2

REFER TO

TABLE 2

f

ADJ

V

OSET

OUT

LTM4602

COMP

FCB

R

SET

66.5k

REFER TO

TABLE 1

RUN/SS

C4

OPT

PGOOD

0.6V TO 5V

SGND

REFER TO STEP-DOWN

RATIO GRAPH

PGND

(MULTIPLE PINS)

GND

4602 F21

Figure 21. Typical Application, 5V to 20V Input, 0.6V to 5V Output, 6A Max

4602fa

19

LTM4602

TYPICAL APPLICATION

Parallel Operation and Load Sharing

V

IN

4.5V TO 20V

V

= 0.6V • ([100k/N] + R )/R

SET SET

OUT

C7

WHERE N = 2

10μF

25V

V

IN

f

ADJ

EXTV

FCB

V

CC

OUT

+

C10

330μF

4V

C9

22μF

V

OSET

R

15.8k

1%

SET

LTM4602

RUN

SV

IN

COMP

PGOOD

PGND

SGND

V

2.5V

12A

OUT

RUN/SOFT-START

C1

10μF

25V

C4

220pF

V

IN

f

ADJ

EXTV

V

CC

OUT

+

C5

330μF

4V

C2

22μF

FCB

V

OSET

LTM4602

R1

100k

RUN

SV

IN

COMP

PGOOD

PGND

SGND

C1, C7: TDK C3216X5R1E106MT

C2, C9: TAIYO YUDEN, JMK316BJ226ML-T501

C5, C10: SANYO POSCAP, 4TPE330MI

4602 TA02

Current Sharing Between Two

LTM4602 Modules

6

12V

IN

OUT

MAX

2.5V

12A

4

2

0

I

OUT2

I

OUT1

0

12

6

TOTAL LOAD

4602 TA03

4602fa

20

LTM4602

PACKAGE DESCRIPTION

Z

b b b

Z

6 . 9 8 6 5

5 . 7 1 4 2

6 . 3 5 0 0

3 . 8 1 0 0

1 . 2 7 0 0

5 . 0 8 0 0

4 . 4 4 4 2

3 . 1 7 4 2

1 . 9 0 4 2

2 . 5 4 0 0

0 . 0 0 0 0

0 . 6 3 4 2

0 . 0 0 0 0

0 . 3 1 7 5

0 . 6 3 5 8

1 . 2 7 0 0

3 . 8 1 0 0

6 . 3 5 0 0

1 . 9 0 5 8

3 . 1 7 5 8

2 . 5 4 0 0

5 . 0 8 0 0

4 . 4 4 5 8

5 . 7 1 5 8

6 . 9 4 2 1

4602fa

21

LTM4602

PACKAGE DESCRIPTION

Pin Assignment Tables

(Arranged by Pin Number)

PIN NAME

C1

PIN NAME

E1

PIN NAME

A1

-

B1

V

-

V

-

V

-

V

-

D1

V

-

V

-

V

-

V

-

F1

V

-

G1 PGND

H1

-

IN

A2

-

B2

C2

D2

E2

F2

G2

-

H2

H3

H4

H5

H6

A3

V

-

B3

C3

D3

E3

F3

G3

IN

A4

B4

C4

D4

E4

F4

G4

A5

V

-

B5

C5

D5

E5

F5

G5

IN

A6

B6

C6

D6

E6

F6

G6

A7

V

-

B7

C7

D7

E7

F7

G7

H7 PGND

H8

H9 PGND

H10

H11 PGND

H12

H13 PGND

H14

H15 PGND

H16

H17 PGND

IN

A8

B8

C8

D8

E8

F8

G8

-

A9

V

-

B9

C9

D9

E9

F9

G9

IN

A10

A11

A12

A13

A14

A15

A16

B10

B11

B12

B13

B14

B15

B16

B17

B18

B19

B20

B21

B22

C10

C11

C12

C13

C14

C15

C16

C17

C18

C19

C20

C21

C22

C23

D10

D11

D12

D13

D14

D15

D16

D17

D18

D19

D20

D21

D22

E10

E11

E12

E13

E14

E15

E16

E17

E18

E19

E20

E21

E22

E23

F10

F11

F12

F13

F14

F15

F16

F17

F18

F19

F20

F21

F22

G10

G11

G12

G13

G14

G15

G16

G17

G18

G19

G20

G21

G22

-

IN

V

-

IN

-

V

-

IN

-

f

ADJ

-

A17 SV

IN

A18

-

H18

H19

H20

H21

H22

H23

-

A19 EXTV

CC

A20

A21

A22

A23

-

V

-

OSET

-

B23 COMP

D23 SGND

F23 RUN/SS G23 FCB

PIN NAME

PIN NAME PIN NAME

PIN NAME

J1 PGND

K1

K2

K3

K4

K5

K6

-

L1

-

M1

M2 PGND

M3

M4 PGND

M5

M6 PGND

M7

M8 PGND

M9

-

N1

-

P1

-

R1

-

T1

-

J2

-

L2 PGND

N2 PGND

P2

V

-

R2

V

-

T2

V

-

OUT

J3

L3

L4 PGND

L5

L6 PGND

L7

L8 PGND

L9

L10 PGND

L11

L12 PGND

L13

L14 PGND

L15

L16 PGND

L17

L18 PGND

L19

L20 PGND

L21

L22 PGND

L23

-

N3

N4 PGND

N5

N6 PGND

N7

N8 PGND

N9

N10 PGND

N11

N12 PGND

N13

N14 PGND

N15

N16 PGND

N17

N18 PGND

N19

N20 PGND

N21

N22 PGND

N23

-

P3

R3

T3

J4

P4

V

-

R4

V

-

T4

V

-

J5

-

P5

R5

T5

J6

P6

V

-

R6

V

-

T6

V

-

J7

K7 PGND

K8

-

P7

R7

T7

J8

P8

V

-

R8

V

-

T8

V

-

J9

K9 PGND

K10

-

P9

R9

T9

J10

J11

J12

J13

J14

J15

J16

J17

J18

J19

J20

J21

J22

M10 PGND

M11 -

P10

P11

P12

P13

P14

P15

P16

P17

P18

P19

P20

P21

P22

P23

V

-

R10

R11

R12

R13

R14

R15

R16

R17

R18

R19

R20

R21

R22

R23

V

-

T10

T11

T12

T13

T14

T15

T16

T17

T18

T19

T20

T21

T22

T23

V

-

K11 PGND

-

K12

K13 PGND

K14

K15 PGND

K16

K17 PGND

-

M12 PGND

M13 -

V

-

V

-

V

-

M14 PGND

M15 -

V

-

V

-

V

-

M16 PGND

M17 -

V

-

V

-

V

-

K18

K19

K20

K21

K22

-

M18 PGND

M19 -

V

-

V

-

V

-

M20 PGND

M21 -

V

-

V

-

V

-

M22 PGND

M23 -

V

-

V

-

V

-

J23 PGOOD K23

-

4602fa

22

LTM4602

PACKAGE DESCRIPTION

Pin Assignment Tables

(Arranged by Pin Number)

PIN NAME

G1

PGND

P2

V

A3

V

A15

A17

A19

A21

B23

D23

F23

G23

J23

f

ADJ

OUT

IN

P4

V

A5

H7

H9

H11

H13

H15

H17

PGND

SV

IN

P6

P8

A7

A9

A11

A13

EXTV

V

CC

P10

P12

P14

P16

P18

P20

P22

OSET

COMP

B1

V

IN

SGND

RUN/SS

FCB

J1

PGND

C10

C12

C14

V

IN

V

IN

V

IN

K7

K9

K11

K13

K15

K17

PGND

D1

V

R2

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

IN

PGOOD

R4

E10

E12

E14

V

IN

V

IN

V

IN

R6

R8

R10

R12

R14

R16

R18

R20

R22

L2

PGND

F1

V

IN

L4

L6

L8

L10

L12

L14

L16

L18

L20

L22

T2

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

T4

T6

T8

T10

T12

T14

T16

T18

T20

T22

M2

PGND

M4

M6

M8

M10

M12

M14

M16

M18

M20

M22

N2

PGND

N4

N6

N8

N10

N12

N14

N16

N18

N20

N22

4602fa

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

LTM4602

TYPICAL APPLICATION

1.8V, 6A Regulator

V

IN

4.5V TO 20V

C2

10μF

25V

C1

C5

100pF

10μF

V

OUT

V

IN

f

ADJ

25V

1.8V AT 6A

EXTV

FCB

V

CC

OUT

+

C4

330μF

4V

C3

22μF

V

OSET

R1

100k

LTM4602

RUN

SV

IN

COMP

PGOOD

PGND

PGOOD

R

49.9k

1%

SET

SGND

C1, C2: TDK C3216X5R1E106MT

C3: TAIYO YUDEN, JMK316BJ226ML-T501

C4: SANYO POSCAP, 4TPE330MI

4602 TA04

RELATED PARTS

PART NUMBER

DESCRIPTION

COMMENTS

LTC2900

Quad Supply Monitor with Adjustable Reset Timer

Power Supply Tracking Controller

Synchronous Isolated Flyback Controllers

10A DC/DC μModule

Monitors Four Supplies; Adjustable Reset Timer

Tracks Both Up and Down; Power Supply Sequencing

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

10A Basic DC/DC Module

LTC2923

LT3825/LT3837

LTM4600

®

LTM4601

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

Margining and Remote Sensing

Synchronizable, PolyPhase Operation, LTM4601-1 Version has no Remote

Sensing, Fast Transient Response

LTM4603

6A DC/DC μModule with PLL and Output Tracking/

Margining and Remote Sensing

Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote

Sensing, Fast Transient Response

PolyPhase is a registered trademark of Linear Technology Corporation.

®

This product contains technology licensed from Silicon Semiconductor Corporation.

4602fa

LT 0807 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：	LTM4602V
厂家：	Linear
描述：	6A High Effi ciency DC/DC μModule 6A高艾菲效率DC / DC微型模块
文件：	总24页 (文件大小：326K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

LTM4602V [Linear]

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