LTM4614_技术文档

LTM4614

Dual 4A per Channel

Low V DC/DC

IN

µModule Regulator

FEATURES

DESCRIPTION

The LTM^®4614 is a complete 4A dual output switching

mode DC/DC power supply. Included in the package are

the switching controllers, power FETs, inductors and all

support components. The dual 4A DC/DC converters

operate over an input voltage range of 2.375V to 5.5V.

TheLTM4614supportsoutputvoltagesrangingfrom0.8V

to 5V. The regulator output voltages are set by a single

resistor for each output. Only bulk input and output ca-

pacitors are needed to complete the design.

n

Dual 4A Output Power Supply

n

Input Voltage Range: 2.375V to 5.5V

n

4A DC Typical, 5A Peak Output Current Each

n

0.8V Up to 5V Output Each, Parallelable

n

2% Total DC Output Error (0°C ≤ T ≤ 125°C)

J

n

Output Voltage Tracking

Up to 95% Efﬁciency

Programmable Soft-Start

Short-Circuit and Overtemperature Protection

Power Good Indicators

The low proﬁle package (2.82mm) enables utilization of

unused space on the bottom of PC boards for high density

point of load regulation.

Small and Very Low Proﬁle Package:

15mm × 15mm × 2.82mm

Additional features include overvoltage protection, foldback

overcurrentprotection,thermalshutdownandprogrammable

soft-start. The power module is offered in a space saving

and thermally enhanced 15mm × 15mm × 2.82mm LGA

package. The LTM4614 is Pb-free and RoHS compliant.

APPLICATIONS

n

Telecom and Networking Equipment

n

FPGA Power

n

SERDES and Other Low Noise Applications

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

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

owners. Protected by U.S. Patents including 5481178, 6580258, 6304066, 6127815, 6498466,

6611131, 6724174.

Different Combinations of Input and Output Voltages

NUMBER OF INPUTS

NUMBER OF OUTPUTS

I

OUT(MAX)

2

1

4A, 4A

2 (Current Share,

Ex. 3.3V and 5V)

8A

1

2

1

4A, 4A

8A, see LTM4608A

TYPICAL APPLICATION

Efﬁciency vs Output Current

Dual Output 4A DC/DC μModule^®Regulator

91

89

87

85

83

81

79

77

75

V

IN

= 3.3V

V

OUT1

V

OUT

IN1

OUT1

FB1

1.5V

3.3V TO 5V

1.2V/4A

10μF

100μF

10k

V

LTM4614

OUT

1.2V

V

OUT2

IN2

V

IN2

OUT2

FB2

1.5V/4A

3.3V TO 5V

5.76k

GND1

GND2

4614 F01a

2

0

1

3

4

LOAD CURRENT (A)

4614 TA01b

4614fa

1

LTM4614

ABSOLUTE MAXIMUM RATINGS

PIN CONFIGURATION

(See Pin Functions, Pin Conﬁguration Table)

(Note 1)

V

, V , PGOOD1, PGOOD2 .....................–0.3V to 6V

IN1 IN2

TOP VIEW

COMP1, COMP2, RUN/SS1, RUN/SS2

M

L

K

J

FB1, FB2,TRACK1, TRACK2 ........................ –0.3V to V

SW1, SW2, V

IN

, V

.............. –0.3V to (V + 0.3V)

OUT1 OUT2 IN

Internal Operating Temperature Range

H

G

F

(Note 2)..................................................–40°C to 125°C

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

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

Body Temperature, Solder Reﬂow (Note 3)........... 245°C

E

D

C

B

A

1

2

3

4

5

6

7

8

9

10

11

12

LGA PACKAGE

144-LEAD (15mm s 15mm s 2.8mm)

T

JMAX

= 125°C, θ

= 2-3°C/W, θ = 15°C/W, θ = 25°C/W, Weight = 1.61g

JC-BOT

JA

JC-TOP

ORDER INFORMATION

LEAD FREE FINISH

LTM4614EV#PBF

LTM4614IV#PBF

TRAY

PART MARKING*

LTM4614V

PACKAGE DESCRIPTION

TEMPERATURE RANGE

–40°C to 125°C

LTM4614EV#PBF

LTM4614IV#PBF

144-Lead (15mm × 15mm × 2.8mm) LGA

LTM4614V

–40°C to 125°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 full internal

operating temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= 5V unless otherwise noted. Refer to Figure 1.

Speciﬁed as each channel (Note 6).

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

l

V

Input DC Voltage

Output Voltage

2.375

5.5

V

IN(DC)

C

IN

= 22μF, C

IN

= 100μF, R = 5.76k

OUT FB

OUT(DC)

V

= 2.375V to 5.5V, I

= 0A to 4A (Note 5)

OUT

0°C ≤ T ≤ 125°C

1.460

1.45

1.49

1.508

1.512

V

J

l

V

Undervoltage Lockout Threshold

Input Inrush Current at Start-Up

I

= 0A

1.6

2

2.3

12

V

IN(UVLO)

OUT

I

= 0A, C = 22μF, C

= 100μF, V

= 1.5V

OUT

INRUSH(VIN)

OUT

IN

OUT

V

IN

= 5.5V

0.35

A

I

Input Supply Bias Current

Input Supply Current

V

= 2.375V, V = 1.5V, Switching Continuous

OUT

= 5.5V, V

20

35

7

mA

μA

Q(VIN)

S(VIN)

IN

= 1.5V, Switching Continuous

OUT

Shutdown, RUN = 0, V = 5V

IN

I

V

= 2.375V, V

= 5.5V, V

= 1.5V, I = 4A

OUT

3.15

1.35

A

IN

OUT

= 1.5V, I

= 4A

OUT

4614fa

2

LTM4614

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

operating temperature range, otherwise speciﬁcations are at T_A= 25°C. V_IN= 5V unless otherwise noted. Refer to Figure 1.

Speciﬁed as each channel (Note 6).

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

4

UNITS

I

Output Continuous Current Range

Line Regulation Accuracy

V

= 3.3V, V = 1.5V (Note 5)

OUT

0

A

OUT(DC)

IN

l

= 1.5V, V from 2.375V to 5.5V, I = 0A

OUT

0.1

0.3

%

ΔV

OUT(LINE)

OUT

IN

V

OUT

Load Regulation Accuracy

Output Ripple Voltage

V

= 1.5V, 0A to 4A (Note 5), V = 2.375V to 5.5V

ΔV

OUT IN

OUT(LOAD)

0°C ≤ T ≤ 125°C

0.7

1.2

1.25

1.5

%

J

V

OUT

V

I

= 0A, C

IN

= 100μF (X5R)

OUT

OUT(AC)

OUT

V

= 5V, V

= 1.5V

12

mV

P-P

OUT

f

Output Ripple Voltage Frequency

Turn-On Overshoot

= 4A, V = 5V, V = 1.5V

OUT

1.25

MHz

s

OUT

IN

C

OUT

= 100μF, V

= 0A

= 1.5V, RUN/SS = 10nF,

ΔV

OUT(START)

OUT

I

V

= 3.3V

= 5V

20

mV

IN

V

t

Turn-On Time

C

= 100μF, V

= 1.5V, I

= 1A Resistive Load,

OUT

START

OUT

TRACK = V and RUN/SS = Float

IN

V

= 5V

0.5

25

ms

mV

IN

Peak Deviation for Dynamic Load

Load: 0% to 50% to 0% of Full Load,

= 100μF, V = 5V, V = 1.5V

ΔV

OUT(LS)

C

OUT

IN

OUT

t

Settling Time for Dynamic Load

Step

Load: 0% to 50% to 0% of Full Load,

10

μs

SETTLE

V

= 5V, V

= 1.5V

IN

OUT

I

Output Current Limit

C

OUT

V

= 100μF

IN

OUT(PK)

= 5V, V

= 1.5V

8

A

OUT

V

Voltage at FB Pin

I

= 0A, V = 1.5V

OUT

0.792

0.788

0.8

0.808

0.810

V

FB

OUT

l

I

0.2

0.75

0.2

μA

V

FB

V

RUN Pin On/Off Threshold

TRACK Pin Current

Offset Voltage

0.6

0.9

RUN

I

μA

mV

V

TRACK

V

TRACK = 0.4V

30

TRACK(OFFSET)

V

Tracking Input Range

0

0.8

TRACK(RANGE)

R

Resistor Between V

and FB Pins

OUT

4.96

4.99

7.5

90

5.025

kΩ

%

FBHI

PGOOD Range

ΔV

PGOOD

R

PGOOD Resistance

Open-Drain Pull-Down

150

Ω

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 LTM4614E is guaranteed to meet performance speciﬁcations

over the 0°C to 125°C internal operating temperature range. Speciﬁcations

over the –40°C to 125°C internal operating temperature range are assured

by design, characterization and correlation with statistical process

controls. The LTM4614I is guaranteed to meet speciﬁcations over the full

internal operating temperature range. Note that the maximum ambient

temperature is determined by speciﬁc operating conditions in conjunction

with board layout, the rated package thermal resistance and other

environmental factors.

Note 3: See Application Note 100.

Note 4: The IC has overtemperature protection that is intended to protect

the device during momentary overload conditions. Junction temperatures

will exceed 125°C when overtemperature is activated. Continuous

overtemperature activation can impair long-term reliability.

Note 5: See output current derating curves for different V , V

Note 6: Two channels are tested separately and the speciﬁed test

and T .

A

IN OUT

conditions are applied to each channel.

4614fa

3

LTM4614

TYPICAL PERFORMANCE CHARACTERISTICS

Efﬁciency vs Output Current

V_IN= 2.5V

Efﬁciency vs Output Current

V_IN= 3.3V

Efﬁciency vs Output Current

V_IN= 5V

100

95

90

100

95

90

85

80

85

80

75

85

80

75

70

65

V

= 3.3V

= 2.5V

= 1.8V

= 1.5V

= 1.2V

= 0.8V

OUT

75

70

65

V

= 2.5V

= 1.8V

= 1.5V

= 1.2V

= 0.8V

OUT

V

= 1.8V

= 1.5V

= 1.2V

= 0.8V

OUT

70

65

1

2

4

1

2

4

0

3

0

1

2

3

4

0

3

OUTPUT CURRENT (A)

4614 G02

4614 G03

4614 G01

Minimum Input Voltage

at 4A Load

Load Transient Response

3.5

3.0

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

V

OUT

= 3.3V

= 2.5V

= 1.8V

= 1.5V

= 1.2V

= 0.8V

I

LOAD

2.5

2A/DIV

V

OUT

2.0

1.5

1.0

0.5

V

OUT

20mV/DIV

4614 G06

V

C

= 5V

20μs/DIV

IN

4614 G05

V

C

= 5V

20μs/DIV

IN

= 1.5V

OUT

= 1.2V

OUT

= 100μF, 6.3V CERAMICS

0

1.5

2.5

2

3

3.5

4 4.5

5 5.5

0.5

1

V

(V)

IN

4614 G04

Load Transient Response

I

LOAD

2A/DIV

I

LOAD

2A/DIV

V

OUT

V

OUT

20mV/DIV

OUT

20mV/DIV

4614 G07

4614 G08

4614 G09

V

C

= 5V

20μs/DIV

V

C

= 5V

20μs/DIV

V

C

= 5V

OUT

20μs/DIV

= 100μF, 6.3V CERAMICS

IN

= 1.8V

= 2.5V

= 3.3V

OUT

= 100μF, 6.3V CERAMICS

4614fa

4

LTM4614

TYPICAL PERFORMANCE CHARACTERISTICS

Start-Up

V_FBvs Temperature

806

804

V

OUT

1V/DIV

OUT

1V/DIV

802

800

I

IN

I

IN

1A/DIV

798

796

794

4614 G10

4614 G11

V

C

= 5V

200μs/DIV

V

C

= 5V

200μs/DIV

IN

= 2.5V

OUT

= 100μF

NO LOAD

4A LOAD

(0.01μF SOFT-START CAPACITOR)

–50 –25

0

25

50

75 100 125

TEMPERATURE (°C)

4614 G12

Short-Circuit Protection

1.5V Short, No Load

Short-Circuit Protection

1.5V Short, 4A Load

Current Limit Foldback

1.6

1.4

1.2

1.0

V

OUT

0.5V/DIV

I

IN

I

IN

1A/DIV

0.8

0.6

4A/DIV

V

= 1.5V

0.4

0.2

0

OUT

4614 G15

4614 G14

100μs/DIV

20μs/DIV

V

IN

V

IN

V

IN

= 5V

= 3.3V

= 2.5V

4

5

7

3

8

6

OUTPUT CURRENT (A)

4614 G13

4614fa

5

LTM4614

PIN FUNCTIONS

V

, V (J1-J6, K1-K6); (C1-C6, D1-D6): Power Input

FB1, FB2 (L6, E6): The Negative Input of the Switching

IN1 IN2

Pins. Apply input voltage between these pins and GND

Regulators’ Error Ampliﬁer. Internally, these pins are con-

pins. Recommend placing input decoupling capacitance

directly between V pins and GND pins.

nected to V

with a 4.99k precision resistor. Different

OUT

output voltages can be programmed with an additional

resistorbetweentheFBandGNDpins.Twopowermodules

can current share when this pin is connected in parallel

with the adjacent module’s FB pin. See Applications In-

formation section.

IN

V

,V

(K9-K12,J9-J12,L9-L12,M9-M12);(C9-C12,

OUT1 OUT2

D9-D12, E9-E12, F9-F12): Power Output Pins. Apply out-

put load between these pins and GND pins. Recommend

placing output decoupling capacitance directly between

these pins and GND pins. Review Table 4.

COMP1, COMP2 (L5, E5): Current Control Threshold

and Error Ampliﬁer Compensation Point. The current

comparator threshold increases with this control voltage.

Two power modules can current share when this pin is

connected in parallel with the adjacent module’s COMP

pin. Each channel has been internally compensated. See

Applications Information section.

GND1, GND2, (G1-G12, H1, H7-H12, J7-J8, K7-K8, L1,

L7-L8, M1-M8); (A1-A12, B1, B7-B12, C7-C8, D7-D8,

E1, E7-E8, F1-F8): Power Ground Pins for Both Input

and Output Returns.

TRACK1, TRACK2 (L3, E3): Output Voltage Tracking Pins.

When the module is conﬁgured as a master output, then a

soft-start capacitor is placed on the RUN/SS pin to ground

to control the master ramp rate, or an external ramp can

be applied to the master regulator’s track pin to control it.

Slave operation is performed by putting a resistor divider

from the master output to the ground, and connecting the

center point of the divider to this pin on the slave regulator.

If tracking is not desired, then connect the TRACK pin to

PGOOD1, PGOOD2 (L4, E4): Output Voltage Power

Good Indicator. Open-drain logic output that is pulled to

ground when the output voltage is not within 7.5% of

the regulation point.

RUN/SS1, RUN/SS2 (L2, E2): Run Control and Soft-Start

Pin.Avoltageabove0.8Vwillturnonthemodule,andbelow

0.5V will turn off the module. This pin has a 1M resistor

V . Load current must be present for tracking. See Ap-

plications Information section.

to V and a 1000pF capacitor to GND. See Applications

IN

Information section for soft-start information.

SW1, SW2 (H2-H6, B2-B6): The switching node of the

circuitisusedfortestingpurposes.Thiscanbeconnectedto

copper on the board for improved thermal performance.

4614fa

6

LTM4614

SIMPLIFIED BLOCK DIAGRAM

V

PGOOD

IN

V

IN

2.375V TO 5.5V

22μF

6.3V

4.7μF

6.3V

R

SS

1M

RUN/SS

C

SS

1000pF

SSEXT

M1

M2

V

L

V

OUT

CONTROL, DRIVE

POWER FETS

4.99k

TRACK

COMP

1.5V

TRACK

SUPPLY

C2

470pF

4.7μF

6.3V

4A

5.76k

100μF

X5R

R1

4.99k

INTERNAL

COMP

GND

FB

SW

4614 F01

R

FB

5.76k

Figure 1. Simpliﬁed LTM4614 Block Diagram of Each Switching Regulator Channel

DECOUPLING REQUIREMENTS ^T_A^{= 25°C. Use Figure 1 conﬁguration for each channel.}

SYMBOL

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

C

External Input Capacitor Requirement

I

= 4A

22

μF

IN

OUT

(V = 2.375V to 5.5V, V

= 1.5V)

IN

OUT

C

OUT

External Output Capacitor Requirement

(V = 2.375V to 5.5V, V = 1.5V)

I

= 4A

66

100

μF

OUT

IN

OUT

4614fa

7

LTM4614

OPERATION

LTM4614 POWER MODULE DESCRIPTION

open-drain PGOOD outputs low if the particular output

feedback voltage exits a 7.5% window around the regu-

lation point. Furthermore, in an overvoltage condition,

internal top FET, M1, is turned off and bottom FET, M2,

is turned on and held on until the overvoltage condition

clears, or current limit is exceeded.

The LTM4614 is a standalone dual nonisolated switching

mode DC/DC power supply. It can deliver up to 4A of DC

output current for each channel with few external input

andoutputcapacitors.Thismoduleprovidestwoprecisely

regulated output voltages programmable via one external

resistor for each channel from 0.8V DC to 5V DC over

a 2.375V to 5.5V input voltage. The typical application

schematic is shown in Figure 12.

Pulling each speciﬁc RUN pin below 0.8V forces the spe-

ciﬁc regulator controller into its shutdown state, turning

off both M1 and M2 for each power stage. At low load

current, each regulator works in continuous current mode

by default to achieve minimum output voltage ripple.

The LTM4614 has two integrated constant frequency cur-

rent mode regulators, with built-in power MOSFETs with

fast switching speed. The typical switching frequency is

1.25MHz.Withcurrentmodecontrolandinternalfeedback

loop compensation, these switching regulators have suf-

ﬁcient stability margins and good transient performance

under a wide range of operating conditions, and with a

wide range of output capacitors, even all ceramic output

capacitors.

The TRACK/SS pins are used for power supply tracking

and soft-start programming for each speciﬁc regulator.

See Applications Information section.

The LTM4614 is internally compensated to be stable over

the operating conditions. Table 4 provides a guideline for

input and output capacitance for several operating condi-

tions. The Linear Technology ꢀModule Power Design Tool

will be provided for transient and stability analysis.

Current mode control provides cycle-by-cycle fast cur-

rent limit. Besides, current limiting is provided in an

overcurrent condition with thermal shutdown. In addition,

internalovervoltageandundervoltagecomparatorspullthe

The FB pins are used to program the speciﬁc output volt-

age with a single resistor to ground.

4614fa

8

LTM4614

APPLICATIONS INFORMATION

Dual Switching Regulator

For a buck converter, the switching duty cycle can be

estimated as:

AtypicalLTM4614applicationcircuitisshowninFigure 12.

External component selection is primarily determined by

the maximum load current and output voltage. Refer to

Table 4 for speciﬁc external capacitor requirements for a

particular application.

V_OUT

D=

V_IN

Without considering the inductor current ripple, the RMS

current of the input capacitor can be estimated as:

V to V

Step-Down Ratios

IN

OUT

I_OUT(MAX)

There are restrictions in the maximum V and V

step-

I_CIN(RMS)

=

• D• 1–D

(

)

IN

OUT

η%

down ratio than can be achieved for a given input voltage

on the two switching regulators. The LTM4614 is 100%

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

the power module. The bulk capacitor can be a switcher-

rated electrolytic aluminum OS-CON capacitor for bulk

input capacitance due to high inductance traces or leads.

If a low inductance plane is used to power the device,

then no input capacitance is required. The internal 4.7μF

ceramicsoneachchannelinputaretypicallyratedfor1Aof

RMS ripple current up to 85°C operation. The worst-case

ripple current for the 4A maximum current is 2A or less.

An additional 10μF or 22μF ceramic capacitor can be used

to supplement the internal capacitor with an additional 1A

to 2A ripple current rating.

duty cycle, but the V to V

minimum dropout will be

OUT

IN

a function the load current. A typical 0.5V minimum is

sufﬁcient.

Output Voltage Programming

Each regulator channel has an internal 0.8V reference

voltage. As shown in the Block Diagram, a 4.99k internal

feedback resistor connects the V

and FB pins together.

OUT

The output voltage will default to 0.8V with no feedback

resistor. Adding a resistor R from the FB pin to GND

FB

programs the output voltage:

4.99k +R_FB

V_OUT= 0.8V •

R_FB

Output Capacitors

The LTM4614 switchers are designed for low output volt-

age ripple on each channel. The bulk output capacitors are

chosen with low enough effective series resistance (ESR)

to meet the output voltage ripple and transient require-

ments. The output capacitors can be a low ESR tantalum

capacitor,lowESRpolymercapacitororceramiccapacitor.

The typical output capacitance range is 66μF to 100μF.

Additional output ﬁltering may be required by the system

designer, if further reduction of output ripple or dynamic

transient spike is required. Table 4 shows a matrix of dif-

ferent output voltages and output capacitors to minimize

the voltage droop and overshoot during a 2A/μs transient.

The table optimizes total equivalent ESR and total bulk

capacitance to maximize transient performance.

Table 1. FB Resistor Table vs Various Output Voltages

V

0.8V

1.2V

10k

1.5V

1.8V

2.5V

3.3V

OUT

R

Open

5.76k

3.92k

2.37k

1.62k

FB

Input Capacitors

The LTM4614 module should be connected to a low AC

impedance DC source. One 4.7μF ceramic capacitor is

included inside the module for each regulator channel.

Additional input capacitors are needed if a large load step

is required up to the full 4A level and for RMS ripple cur-

rent requirements. A 47μF bulk capacitor can be used for

more input bulk capacitance. This 47μF capacitor is only

needed if the input source impedance is compromised by

long inductive leads or traces.

4614fa

9

LTM4614

APPLICATIONS INFORMATION

Fault Conditions: Current Limit and Overcurrent

where R and C are shown in the Block Diagram of

SS SS

Foldback

Figure 1, and 1.8V is the soft-start upper range. The

soft-start function can also be used to control the output

ramp-up time, so that another regulator can be easily

tracked to it.

The LTM4614 has current mode control, which inher-

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

in steady-state operation, but also in transient.

Along with foldback current limiting in the event of an

overload condition, the LTM4614 has overtemperature

shutdown protection that inhibits switching operation

around 150°C for each channel.

Output Voltage Tracking

Output voltage tracking can be programmed externally

using the TRACK pins. Either output can be tracked up

or down with another regulator. The master regulator’s

output is divided down with an external resistor divider

thatisthesameastheslaveregulator’sfeedbackdividerto

implement coincident tracking. The LTM4614 uses a very

accurate4.99kresistorfortheinternaltopfeedbackresistor.

Figure 2 shows an example of coincident tracking.

Run Enable and Soft-Start

The RUN/SS pins provide a dual function of enable and

soft-start control for each channel. The RUN/SS pins are

used to control turn on of the LTM4614. While each enable

pin is below 0.5V, the LTM4614 will be in a low quiescent

current state. At least a 0.8V level applied to the enable

pins will turn on the LTM4614 regulators. This pin can be

used to sequence the regulator channels. The soft-start

Equations:

⎛

⎞

R_FB1

4.99k +R

TRACK1=

•Master

⎜

⎟

⎝

⎠

FB1

control is provided by a 1M pull-up resistor (R ) and a

SS

⎛

⎞

1000pF capacitor (C ) as drawn in the Block Diagram for

4.99k

R_FB1

SS

Slave = 1+

• TRACK1

⎜

⎝

⎟

each channel. An external capacitor can be applied to the

RUN/SS pin to increase the soft-start time. A typical value

is 0.01μF. The approximate equation for soft-start:

⎠

⎛

⎞

V_IN

V –1.8V

t_SOFTSTART=In

•R_SS•C_SS

⎜

⎟

⎝

⎠

IN

V

3V TO 5.5V

IN

C1

22μF

6.3V

C2

22μF

6.3V

PGOOD1

PGOOD2

V

IN1

V

IN2

R3

10k

R4

10k

PGOOD1

PGOOD2

1.2V

4A

1.5V

4A

V

OUT1

OUT2

FB2

FB1

LTM4614

C7

100μF

6.3V

R

C4

TB

4.99k

22μF

COMP1

TRACK1

RUN/SS1

COMP2

TRACK2

RUN/SS2

1.5V

V

OR

IN

6.3V

C3

100μF

6.3V

C9

22μF

6.3V

CONTROL

RAMP

R

FB2

FB1

R

TA

5.76k

10k

GND1

GND2

C

SSEXT1

4614 F02

Figure 2. Dual Outputs (1.5V and 1.2V) with Tracking

4614fa

10

LTM4614

APPLICATIONS INFORMATION

TRACK1 is the track ramp applied to the slave’s track pin.

TRACK1appliesthetrackreferencefortheslaveoutputup

to the point of the programmed value at which TRACK1

proceeds beyond the 0.8V reference value. The TRACK1

pin must go beyond the 0.8V to ensure the slave output

has reached its ﬁnal value.

feedback resistor of the slave regulator in equal slew rate

or coincident tracking, then R is equal to R with V =

TA

FB

V

. Therefore R = 4.99k and R = 10k in Figure 2.

TRACK

TB TA

Figure 3 shows the output voltage tracking waveform for

coincident tracking.

Inratiometrictracking, adifferentslewratemaybedesired

Ratiometric tracking can be achieved by a few simple

calculationsandtheslewratevalueappliedtothemaster’s

TRACK pin. As mentioned above, the TRACK pin has a

control range from 0V to 0.8V. The control ramp slew rate

applied to the master’s TRACK pin is directly equal to the

master’s output slew rate in Volts/Time.

for the slave regulator. R can be solved for when SR is

TB

slower than MR. Make sure that the slave supply slew rate

ischosentobefastenoughsothattheslaveoutputvoltage

will reach it ﬁnal value before the master output.

For example, MR = 2.5V/ms and SR = 1.8V/1ms. Then

R = 6.98k. Solve for R to equal to 3.24k. The master

TB

TA

The equation:

output must be greater than the slave output for the

tracking to work. Output load current must be present

for tracking to operate properly during power down.

MR

SR

• 4.99k =R_TB

Power Good

where MR is the master’s output slew rate and SR is the

slave’s output slew rate in Volts/Time. When coincident

PGOOD1 and PGOOD2 are open-drain pins that can be

usedtomonitorvalidoutputvoltageregulation.Thesepins

monitor a 7.5% window around the regulation point.

tracking is desired, then MR and SR are equal, thus R

TB

is equal to 4.99k. R is derived from equation:

TA

0.8V

COMP Pin

R_TA

=

V_TRACK

R_TB

V_FB

4.99k R_FB

+

–

This pin is the external compensation pin. The module has

alreadybeeninternallycompensatedforalloutputvoltages.

Table 4 is provided for most application requirements.

The Linear Technology μModule Power Design Tool will

be provided for other control loop optimization.

where V is the feedback voltage reference of the regula-

FB

TRACK

tor, and V

is 0.8V. Since R is equal to the 4.99k top

TB

MASTER OUTPUT

SLAVE OUTPUT

TIME

4614 F03

Figure 3. Output Voltage Coincident Tracking

4614fa

11

LTM4614

APPLICATIONS INFORMATION

Parallel Switching Regulator Operation

and airﬂow conditions. Both of the LTM4614 outputs

are at full 4A load current, and the power loss curves in

Figures 5 and 6 are combine power losses plotted for both

output voltages up to 4A each. The 4A output voltages are

1.2V and 3.3V. These voltages are chosen to include the

lower and higher output voltage ranges for correlating

the thermal resistance. Thermal models are derived from

several temperature measurements in a controlled tem-

perature chamber along with thermal modeling analysis.

The junction temperatures are monitored while ambient

temperature is increased with and without airﬂow. The

junctions are maintained at ~120°C while lowering output

current or power while increasing ambient temperature.

The 120°C is chosen to allow for a 5°C margin window

relative to the maximum 125°C. The decreased output

current will decrease the internal module loss as ambi-

ent temperature is increased. The power loss curves in

Figures 5 and 6 show this amount of power loss as a

function of load current that is speciﬁed for both chan-

nels The monitored junction temperature of 120°C minus

the ambient operating temperature speciﬁes how much

The LTM4614 switching regulators are inherently current

mode control. Paralleling will have very good current

sharing. This will balance the thermals on the design.

Figure 13 shows a schematic of a parallel design. The

voltage feedback equation changes with the variable N

as channels are paralleled.

The equation:

4.99k

+R_FB

N

V_OUT= 0.8V •

R_FB

N is the number of paralleled channels.

Thermal Considerations and Output Current Derating

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

in coordination with the load current de-rating curves in

Figures 7 to 10 for calculating an approximate θ thermal

resistance for the LTM4614 with various heat sinking

JA

2.5

2.0

1.5

1.0

0.5

3.0

2.5

2.0

1.5

1.0

0.5

V

= 5V

V

= 5V

IN

0

1

2

3

4

0

1

2

3

4

LOAD CURRENT (A)

4614 F05

4614 F06

Figure 5. 1.2V Power Loss

Figure 6. 3.3V Power Loss

4614fa

12

LTM4614

APPLICATIONS INFORMATION

module temperature rise can be allowed. As an example in

Figure 7 the load current is de-rated to 3A for each chan-

nel with 0LFM at ~ 90°C and the power loss for both

channels at 5V to 1.2V at 3A output are ~1.5 watts. If the

90°C ambient temperature is subtracted from the 120°C

maximum junction temperature, then the difference of

30°C divided 1.5W equals a 20°C/W thermal resistance.

Table 2 speciﬁes a 15°C/W value which is close. Table 2

and Table 3 provide equivalent thermal resistances for

1.2V and 3.3V outputs with and without air ﬂow and

heat sinking. The combine power loss for the two 4A

outputs can be summed together and multiplied by the

thermal resistance values in Tables 2 and 3 for module

temperature rise under the speciﬁed conditions. The

printed circuit board is a 1.6mm thick four layer board

with 2 ounce copper for the two outer layers and 1 ounce

copper for the two inner layers. The PCB dimensions are

95mm × 76mm. The data sheet list the θ (junction to

JP

pin) and θ (junction to case) thermal resistances under

JC

the Pin Conﬁguration diagram.

4.5

4.0

3.5

4.5

4.0

3.5

200LFM NO HEAT SINK

3.0

200LFM HEAT SINK

2.5

400LFM HEAT SINK

400LFM NO HEAT SINK

2.0

1.5

0LFM NO HEAT SINK

1.0

0.5

0LFM HEAT SINK

0.5

0

40 50 60 70 80 90 100 110 120

AMBIENT TEMPERATURE (°C)

4614 F08

4614 F07

Figure 7. 1.2V No Heat Sink (V_IN= 5V)

Figure 8. 1.2V Heat Sink (V_IN= 5V)

4.5

4.0

3.5

4.5

4.0

3.5

3.0

200LFM NO HEAT SINK

2.5

400LFM HEAT SINK

2.5

400LFM NO HEAT SINK

200LFM HEAT SINK

2.0

0LFM HEAT SINK

1.5

0LFM NO HEAT SINK

1.0

0.5

0

40 50 60 70 80 90 100 110 120

AMBIENT TEMPERATURE (°C)

4614 F09

4614 F10

Figure 9. 3.3V No Heat Sink (V_IN= 5V)

Figure 10. 3.3V Heat Sink (V_IN= 5V)

4614fa

13

LTM4614

APPLICATIONS INFORMATION

Table 2. 1.2V Output

DERATING CURVE

Figure 7

V

IN

(V)

POWER LOSS CURVE

Figure 5

AIRFLOW (LFM)

HEAT SINK

None

θ

JA

(°C/W)

15

5

0

Figure 7

5

Figure 5

200

400

0

None

12

Figure 7

Figure 5

None

10

Figure 8

Figure 5

BGA Heat Sink

12

Figure 8

Figure 5

200

400

9

Figure 8

Figure 5

7

Table 3. 3.3V Output

DERATING CURVE

Figure 9

V

IN

(V)

POWER LOSS CURVE

Figure 6

AIRFLOW (LFM)

HEAT SINK

None

θ

JA

(°C/W)

15

5

0

Figure 9

Figure 6

200

400

0

None

12

Figure 9

Figure 6

None

10

Figure 10

Figure 6

BGA Heat Sink

12

Figure 10

Figure 6

200

400

9

Figure 10

Figure 6

7

HEAT SINK MANUFACTURER

PART NUMBER

PHONE NUMBER

Aavid

375424b00034G

603-635-2800

4614fa

14

LTM4614

APPLICATIONS INFORMATION

Safety Considerations

• Place high frequency ceramic input and output capaci-

tors next to the V , GND and V

pins to minimize

IN

OUT

TheLTM4614modulesdonotprovideisolationfromV to

IN

high frequency noise.

V

.Thereisnointernalfuse.Ifrequired,aslowblowfuse

OUT

with a rating twice the maximum input current needs to be

• Place a dedicated power ground layer underneath the

unit.

provided to protect each unit from catastrophic failure.

• Tominimizetheviaconductionlossandreducemodule

thermal stress, use multiple vias for interconnection

between the top layer and other power layers.

Layout Checklist/Example

The high integration of LTM4614 makes the PCB board

layoutverysimpleandeasy.However,tooptimizeitselectri-

cal and thermal performance, some layout considerations

are still necessary.

• Do not put via directly on pads unless the via is

capped.

Figure 11 gives a good example of the recommended

layout.

• Use large PCB copper areas for high current path,

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

IN

OUT

PCB conduction loss and thermal stress.

I/O PINS

V

GND1

OUT1

GND1

M

L

V

OUT1

C

IN1

C

OUT1 OUT2

K

J

V

IN1

H

G

F

GND1

GND2

GND1

V

OUT2

C

IN2

E

C

OUT3 OUT4

D

C

B

A

V

IN2

GND2

1

2

3

4

5

6

7

8

9

10 11 12

GND2

4614 F11

GND2

I/O PINS

Figure 11. Recommended PCB Layout

4614fa

15

LTM4614

APPLICATIONS INFORMATION

V

2.375V TO 5.5V

IN

C2

C1

22μF

6.3V

22μF

6.3V

X5R OR X7R

V

IN1

V

IN2

PGOOD1

PGOOD2

1V

4A

1.2V

4A

V

OUT1

OUT2

FB2

FB1

LTM4614

C5

100μF

6.3V

C4

100μF

6.3V

COMP1

COMP2

TRACK2

RUN/SS2

+

C6

22μF

6.3V

R2

10k

V

IN

C3

470μF

TRACK1

IN

R1

20k

RUN/SS1

C

SSEXT1

GND1

GND2

0.1μF

4614 F12

Figure 12. Typical 2.375V_INto 5.5V_IN, 1.2V and 1V at 4A

Table 4. Output Voltage Response vs Component Matrix (Refer to Figure 12) 0A to 2.5A Load Step Typical Measured Values

C

AND C

CERAMIC VENDORS VALUE

PART NUMBER

C

AND C BULK VENDORS VALUE

PART NUMBER

150μF 10V 10TPD150M

OUT1

OUT2

OUT1

OUT2

TDK

22μF 6.3V

22μF 16V

C3216X7SOJ226M

Sanyo POSCAP

Murata

TDK

GRM31CR61C226KE15L Sanyo POSCAP

220μF 4V

4TPE220MF

100μF 6.3V C4532X5R0J107MZ

100μF 6.3V GRM32ER60J107M

C

IN

BULK VENDORS

VALUE

PART NUMBER

Murata

Sanyo POSCAP

100μF 10V 10CE100FH

V

C

AND C

C

AND C

V

DROOP PEAK-TO-PEAK RECOVERY LOAD STEP

R

FB

(kΩ)

10

OUT

IN

OUT1

OUT2

OUT1

OUT2

IN

(V)

1.2

1.5

1.8

2.5

3.3

(CERAMIC) (BULK)*

(CER) EACH

(POSCAP) EACH

I

(V)

(mV)

33

25

33

25

30

28

30

27

34

30

50

33

50

DEVIATION

TIME (μs)

(A/μs)

2.5

TH

100μF

None

220μF

None

220μF

None

220μF

None

220μF

None

220μF

None

150μF

None

5

3.3

5

68

50

68

50

60

56

68

60

90

60

95

90

11

9

8

10μF ×2

100μF, 22μF ×2

22μF ×1

100μF, 22μF ×2

22μF ×1

100μF, 22μF ×2

22μF ×1

100μF, 22μF ×2

22μF ×1

10

11

10

12

10

12

10

5.76

3.92

3.09

1.62

5

3.3

5

3.3

5

3.3

5

100μF, 22μF ×2

22μF ×1

100μF

22μF ×1

*Bulk capacitance is optional if V has very low input impedance.

IN

4614fa

16

LTM4614

APPLICATIONS INFORMATION

V

3V TO 5.5V

IN

C2

C1

22μF

6.3V

22μF

6.3V

X5R OR X7R

R2

5k

V

IN1

V

IN2

PGOOD

PGOOD1

PGOOD2

1.2V

8A

V

OUT1

OUT2

FB2

FB1

C5

100μF

6.3V

C4

LTM4614

100μF

6.3V

COMP1

TRACK1

RUN/SS1

COMP2

TRACK2

RUN/SS2

X5R OR X7R

R1

V

IN

4.99k

C

SSEXT1

GND1

GND2

0.01μF

4614 F13

Figure 13. LTM4614 Parallel 1.2V at 8A Design (Also, See the LTM4608A)

V

2.375V TO 5.5V

IN

C1

22μF

6.3V

C2

22μF

6.3V

X5R OR X7R

R3

10k

R4

10k

V

IN1

V

IN2

PGOOD1

PGOOD2

1.8V

4A

1.5V

4A

V

OUT1

OUT2

FB2

FB1

LTM4614

C5

22μF

6.3V

C4

22μF

6.3V

1.8V

4.99k

COMP1

TRACK1

RUN/SS1

COMP2

TRACK2

RUN/SS2

C6

100μF

6.3V

V

IN

C3

100μF

6.3V

R1

4.02k

R2

5.76k

C

SSEXT

0.01μF

GND1

GND2

5.76k

X5R OR X7R

REFER TO TABLE 4

X5R OR X7R

REFER TO TABLE 4

4614 F14

Figure 14. 1.8V and 1.5V at 4A with Output Voltage Tracking Design

4614fa

17

LTM4614

PACKAGE DESCRIPTION

Z

b b b

Z

6 . 9 8 5 0

5 . 7 1 5 0

4 . 4 4 5 0

3 . 1 7 5 0

1 . 9 0 5 0

0 . 6 3 5 0

0 . 0 0 0 0

0 . 6 3 5 0

1 . 9 0 5 0

3 . 1 7 5 0

4 . 4 4 5 0

5 . 7 1 5 0

6 . 9 8 5 0

4614fa

18

LTM4614

PACKAGE DESCRIPTION

LTM4614 Component LGA Pinout

PIN ID

A1

FUNCTION

GND2

PIN ID

B1

FUNCTION

GND2

SW2

PIN ID

C1

FUNCTION

PIN ID

D1

FUNCTION

PIN ID

E1

FUNCTION

GND2

PIN ID

F1

FUNCTION

GND2

V

IN2

A2

B2

C2

D2

E2

RUN/SS2

TRACK2

PGOOD2

COMP2

FB2

F2

A3

B3

SW2

C3

D3

E3

F3

A4

B4

SW2

C4

D4

E4

F4

A5

B5

SW2

C5

D5

E5

F5

A6

B6

SW2

C6

D6

E6

F6

A7

B7

GND2

C7

GND2

D7

GND2

E7

GND2

F7

A8

B8

C8

D8

E8

GND2

F8

A9

B9

C9

V

D9

V

E9

V

F9

V

OUT2

A10

A11

A12

B10

B11

B12

C10

C11

C12

D10

D11

D12

E10

E11

E12

F10

F11

F12

PIN ID

G1

FUNCTION

GND1

PIN ID

H1

FUNCTION

GND1

SW1

PIN ID

J1

FUNCTION

PIN ID

K1

FUNCTION

PIN ID

L1

FUNCTION

GND1

PIN ID

M1

FUNCTION

GND1

V

IN1

G2

H2

J2

K2

L2

RUN/SS1

TRACK1

PGOOD1

COMP1

FB1

M2

G3

H3

SW1

J3

K3

L3

M3

G4

H4

SW1

J4

K4

L4

M4

G5

H5

SW1

J5

K5

L5

M5

G6

H6

SW1

J6

K6

L6

M6

G7

H7

GND1

J7

GND1

K7

GND1

L7

GND1

M7

G8

H8

J8

K8

L8

GND1

M8

G9

H9

J9

V

K9

V

L9

V

M9

V

OUT1

G10

G11

G12

H10

H11

H12

J10

J11

J12

K10

K11

K12

L10

L11

L12

M10

M11

M12

4614fa

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.

19

LTM4614

PACKAGE PHOTOGRAPH

RELATED PARTS

PART NUMBER

LTC^®2900

DESCRIPTION

COMMENTS

Quad Supply Monitor with Adjustable Reset Timer

Power Supply Tracking Controller

10A DC/DC μModule

Monitors Four Supplies, Adjustable Reset Timer

Tracks Both Up and Down, Power Supply Sequencing

LTC2923

LTM4600HV

LTM4600HVMP

LTM4601A

4.5V ≤ V ≤ 28V, 0.6V ≤ V

≤ 5V, LGA Package

OUT

IN

Wide Temperature Range 10A DC/DC μModule

12A DC/DC μModule with PLL, Output Tracking/Margining Synchronizable PolyPhase^®Operation, LTM4601-1/LTM4601A-1

and Remote Sensing

Guaranteed Operation from –55°C to 125°C Ambient, LGA Package

Version Has No Remote Sensing, LGA Package

LTM4602

LTM4603

6A DC/DC μModule

Pin Compatible with the LTM4600, LGA Package

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

Margining and Remote Sensing

Synchronizable, PolyPhase Operation, LTM4603-1 Version Has No

Remote Sensing, Pin Compatible with the LTM4601, LGA Package

LTM4604A

LTM4605

LTM4607

LTM4608A

Low V 4A DC/DC μModule

2.375V ≤ V ≤ 5.5V, 0.8V ≤ V

≤ 5V, 9mm × 15mm × 2.3mm

IN

OUT

LGA Package

5A to 12A Buck-Boost μModule

4.5V ≤ V ≤ 20V, 0.8V ≤ V

≤ 16V, 15mm × 15mm × 2.8mm

≤ 25V, 15mm × 15mm × 2.8mm

≤ 5V, 9mm × 15mm × 2.8mm

IN

OUT

LGA Package

4.5V ≤ V ≤ 36V, 0.8V ≤ V

IN

LGA Package

Low V 8A DC/DC Step-Down μModule

2.7V ≤ V ≤ 5.5V, 0.6V ≤ V

IN

OUT

LGA Package

LTM4615

LTM4616

LTM8020

Triple Low V DC/DC μModule

Two 4A Outputs and One 1.5A Output; 15mm × 15mm × 2.8mm

Current Share Inputs or Outputs; 15mm × 15mm × 2.8mm

IN

Dual 8A DC/DC μModule

High V 0.2A DC/DC Step-Down μModule

4V ≤ V ≤ 36V, 1.25V ≤ V

≤ 5V, 6.25mm × 6.25mm × 2.3mm

IN

OUT

LGA Package

LTM8021

LTM8022

LTM8023

High V 0.5A DC/DC Step-Down μModule

3V ≤ V ≤ 36V, 0.4V ≤ V

≤ 5V, 6.25mm × 11.25mm × 2.8mm

≤ 10V, 11.25mm × 9mm × 2.8mm

OUT

IN

OUT

LGA Package

High V 1A DC/DC Step-Down μModule

3.6V ≤ V ≤ 36V, 0.8V ≤ V

IN

LGA Package

High V 2A DC/DC Step-Down μModule

3.6V ≤ V ≤ 36V, 0.8V ≤ V

≤ 10V, 11.25mm × 9mm × 2.8mm

OUT

IN

LGA Package

PolyPhase is a registered trademark of Linear Technology Corporation.

4614fa

LT 0809 REV A • PRINTED IN USA

LinearTechnology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

20

●

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


型号：	LTM4614
厂家：	Linear
描述：	Dual 4A per Channel Low VIN DC/DC μModule Regulator 每通道低输入电压DC / DCμModule稳压器双4A 稳压器
文件：	总20页 (文件大小：347K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

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