2R5TPE470M9 [Linear]
10A High Effi ciency DC/DC μModule; 10A高艾菲效率DC / DC微型模块型号: | 2R5TPE470M9 |
厂家: | Linear |
描述: | 10A High Effi ciency DC/DC μModule |
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 |
LTM4600
10A High Efficiency
DC/DC µModule
FEATURES
n
DESCRIPTION
TheLTM®4600isacomplete10A,DC/DCstepdownpower
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
LTM4600 supports an output voltage range of 0.6V to 5V,
setbyasingleresistor. Thishighefficiency design delivers
10Acontinuouscurrent(14Apeak), needingnoheatsinks
or airflow to meet power specifications. Only bulk input
and output capacitors are needed to finish the design.
n
Complete Switch Mode Power Supply
Wide Input Voltage Range: 4.5V to 20V
n
10A DC, 14A Peak Output Current
n
Parallel Two μModule™ DC/DC Converters for 20A
Output Current
0.6V to 5V Output Voltage
n
n
1.5% Output Voltage Regulation
n
Ultrafast Transient Response
n
Current Mode Control
n
Pb-Free (e4) RoHS Compliant Package with Gold-
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.
Pad Finish
Up to 92% Efficiency
Programmable Soft-Start
Output Overvoltage Protection
n
n
n
n
Optional Short-Circuit Shutdown Timer
n
Small Footprint, Low Profile (15mm × 15mm ×
2.8mm) Surface Mount LGA Package
APPLICATIONS
TheLTM4600ispackagedinathermallyenhanced,compact
(15mm × 15mm) and low profile (2.8mm) over-molded
Land Grid Array (LGA) package suitable for automated
assembly by standard surface mount equipment. The
LTM4600 is Pb-free and RoHS compliant.
n
Telecom and Networking Equipment
n
Servers
n
Industrial Equipment
Point of Load Regulation
n
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
TYPICAL APPLICATION
with 12VIN (FCB = 0)
100
10A μModule Power Supply with 4.5V to 20V Input
90
80
70
V
1.5V
10A
OUT
V
IN
4.5V TO 20V
V
IN
V
OUT
C
IN
C
OUT
LTM4600
60
50
V
OSET
PGND SGND
66.5k
40
30
20
1.2V
1.5V
2.5V
3.3V
OUT
OUT
OUT
OUT
4600 TA01a
2
4
8
0
10
6
LOAD CURRENT (A)
4600 TA01b
4600fc
1
LTM4600
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
V
IN ADJ
COMP
SGND
RUN/SS
FCB
, COMP............................................. –0.3V to 2.7V
OSET
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,
JA JC
JMAX
θ
DERIVED FROM 95mm × 76mm PCB WITH 4 LAYERS
JA
WEIGHT = 1.7g
ORDER INFORMATION
LEAD FREE FINISH
LTM4600EV#PBF
LTM4600IV#PBF
PART MARKING
LTM4600EV
PACKAGE DESCRIPTION
TEMPERATURE RANGE
104-Lead (15mm × 15mm × 2.8mm) LGA
104-Lead (15mm × 15mm × 2.8mm) LGA
–40°C to 85°C
–40°C to 85°C
LTM4600IV
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the –40°C to 85°C
temperature range, otherwise specifications are at TA = 25°C, VIN = 12V. External CIN = 120μF, COUT = 200μF/Ceramic per typical
application (front page) configuration.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
l
V
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
1.50
1.522
1.530
V
V
IN
OUT
Input Specifications
V
Under Voltage Lockout Threshold
Input Inrush Current at Startup
I
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
A
IN
IN
V
I
Input Supply Bias Current
I
= 0A, EXTV Open
Q(VIN)
OUT CC
V
= 12V, V
= 12V, V
= 1.5V, FCB = 5V
1.2
42
mA
mA
mA
mA
μA
IN
IN
IN
IN
OUT
OUT
V
V
V
= 1.5V, FCB = 0V
= 5V, V
= 5V, V
= 1.5V, FCB = 5V
= 1.5V, FCB = 0V
1.0
52
OUT
OUT
Shutdown, RUN = 0.8V, V = 12V
35
75
IN
4600fc
2
LTM4600
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the –40°C to 85°C
temperature range, otherwise specifications are at TA = 25°C, VIN = 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
= 12V, V
= 1.5V, I
= 3.3V, I
= 10A
= 10A
1.52
3.13
3.64
A
A
A
S(VIN)
OUT
OUT
OUT
OUT
= 5V, V
= 1.5V, I
= 10A
OUT
OUT
Output Specifications
I
Output Continuous Current Range
V
= 12V, V = 1.5V
OUT
0
10
A
OUTDC
IN
(See Output Current Derating Curves for
Different V , V
and T )
A
IN OUT
l
l
ΔV
ΔV
Line Regulation Accuracy
V
V
= 1.5V, I = 0A, FCB = 0V,
OUT
0.15
0.3
%
OUT(LINE)
OUT
IN
= 4.5V to 20V
V
OUT
OUT(LOAD)
Load Regulation Accuracy
V
OUT
= 1.5V, I
= 5V
= 0A to 10A, FCB = 0V
OUT
V
V
1
1.5
%
%
IN
IN
V
OUT
= 12V (Notes 3, 4)
V
Output Ripple Voltage
Output Ripple Voltage Frequency
Turn-On Time
V
V
V
= 12V, V
= 1.5V, I
= 0A, FCB = 0V
10
15
mV
P-P
OUT(AC)
IN
OUT
OUT
fs
= 1.5V, I
= 5A, FCB = 0V
= 1A
850
kHz
OUT
OUT
OUT
t
= 1.5V, I
IN
IN
START
OUT
V
= 12V
= 5V
0.5
0.7
ms
ms
V
ΔV
Voltage Drop for Dynamic Load Step
V
C
= 1.5V, Load Step: 0A/μs to 5A/μs
= 3 • 22μF 6.3V, 470μF 4V POSCAP,
36
mV
OUTLS
OUT
OUT
See Table 2
t
I
Settling Time for Dynamic Load Step
Output Current Limit
Load: 10% to 90% to 10% of Full Load
25
μs
SETTLE
Output Voltage in Foldback
OUTPK
V
IN
V
IN
= 12V, V
= 1.5V
OUT
14
14
A
A
= 5V, V
= 1.5V
OUT
Control Stage
l
V
Voltage at V
Pin
I
= 0A, V = 1.5V
OUT
0.591
0.594
0.6
0.6
0.609
0.606
V
V
OSET
OSET
OUT
V
RUN ON/OFF Threshold
0.8
–0.5
0.8
1.5
–1.2
1.8
2
–3
3
V
μA
RUN/SS
I
I
Soft-Start Charging Current
Soft-Start Discharging Current
V
V
= 0V
= 4V
RUN(C)/SS
RUN(D)/SS
RUN/SS
μA
RUN/SS
V
– SV
EXTV = 0V, FCB = 0V
100
16
mV
mA
IN
IN
CC
I
Current into EXTV Pin
EXTV = 5V, FCB = 0V, V
= 1.5V,
EXTVCC
CC
CC
= 0A
OUT
I
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
= 0.6V
μA
FCB
FCB
PGOOD Output
ΔV
ΔV
ΔV
PGOOD Upper Threshold
PGOOD Lower Threshold
PGOOD Hysteresis
V
V
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.
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTM4600I is guaranteed over the
–40°C to 85°C temperature range.
Note 3: Test assumes current derating versus temperature.
Note 4: Guaranteed by correlation.
Note 2: The LTM4600E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
4600fc
3
LTM4600
TYPICAL PERFORMANCE CHARACTERISTICS
(See Figure 18 for all curves)
Efficiency vs Load Current
with 18VIN (FCB = 0)
Efficiency vs Load Current
with 5VIN (FCB = 0)
Efficiency vs Load Current
with 12V(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
0.6V
1.2V
1.5V
2.5V
3.3V
OUT
OUT
OUT
OUT
OUT
1.5V
1.8V
2.5V
3.3V
0.6V
1.2V
1.5V
2.5V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
8
10
2
4
8
0
2
4
6
0
10
6
2
4
8
0
10
6
LOAD CURRENT (A)
LOAD CURRENT (A)
LOAD CURRENT (A)
4600 G01
4600 G02
4600 G03
Efficiency vs Load Current
with Different FCB Settings
1.2V Transient Response
1.5V Transient Response
90
80
70
60
50
40
30
20
FCB > 0.7V
V
OUT
= 50mV/DIV
FCB = GND
I
= 5A/DIV
OUT
4600 G05
4600 G06
25μs/DIV
1.2V AT 5A/μs LOAD STEP
= 3 • 22μF 6.3V CERAMICS
25μs/DIV
V
V
= 12V
IN
OUT
1.5V AT 5A/μs LOAD STEP
= 1.5V
C
OUT
C
OUT
= 3 • 22μF 6.3V CERAMICS
470μF 4V SANYO POSCAP
C3 = 100pF
470μF 4V SANYO POSCAP
C3 = 100pF
0.1
10
1
LOAD CURRENT (A)
4600 G04
1.8V Transient Response
2.5V Transient Response
3.3V Transient Response
4600 G07
4600 G08
4600 G09
25μs/DIV
25μs/DIV
25μs/DIV
1.8V AT 5A/μs LOAD STEP
OUT
2.5V AT 5A/μs LOAD STEP
OUT
3.3V AT 5A/μs LOAD STEP
OUT
C
= 3 • 22μF 6.3V CERAMICS
470μF 4V SANYO POSCAP
C3 = 100pF
C
= 3 • 22μF 6.3V CERAMICS
470μF 4V SANYO POSCAP
C3 = 100pF
C
= 3 • 22μF 6.3V CERAMICS
470μF 4V SANYO POSCAP
C3 = 100pF
4600fc
4
LTM4600
TYPICAL PERFORMANCE CHARACTERISTICS (See Figure 18 for all curves)
Short-Circuit Protection,
IOUT = 0A
Start-Up, IOUT = 10A
(Resistive Load)
Start-Up, IOUT = 0A
V
V
OUT
(0.5V/DIV)
OUT
(0.5V/DIV)
V
OUT
(0.5V/DIV)
I
I
IN
IN
I
IN
(0.5A/DIV)
(0.5A/DIV)
(0.2A/DIV)
4600 G11
4600 G12
4600 G10
200μs/DIV
20μs/DIV
200μs/DIV
V
V
C
= 12V
V
V
C
= 12V
OUT
OUT
V
V
C
= 12V
IN
IN
IN
= 1.5V
= 1.5V
= 1.5V
OUT
OUT
= 200μF
= 2× 200μF/X5R
NO EXTERNAL SOFT-START CAPACITOR
= 200μF
OUT
OUT
NO EXTERNAL SOFT-START CAPACITOR
NO EXTERNAL SOFT-START CAPACITOR
12V Input Load Regulation vs
Temperature
Short-Circuit Protection,
I= 10A
VIN to VOUT Step-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
0.00
–0.05
–0.10
–0.15
–0.20
–0.25
–0.30
–0.35
–0.40
–0.45
f
= OPEN
5V
ADJ
V
OUT
(0.5V/DIV)
3.3V
I
IN
(0.5A/DIV)
2.5V
1.8V
25°C
100°C
4600 G13
20μs/DIV
1.5V
V
V
C
= 12V
OUT
OUT
IN
= 1.5V
1.2V
= 2× 200μF/X5R
NO EXTERNAL SOFT-START CAPACITOR
–45°C
0.6V
10
(V)
20
0
5
15
0
5
10
LOAD CURRENT
V
IN
4600 G15
SEE FREQUENCY ADJUSTMENT DISCUSSION
FOR 12V TO 5V
AND 5V TO 3.3V
IN
OUT
IN OUT
CONVERSION
4600 G14
4600fc
5
LTM4600
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 LTM4600 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
4600 PN01
4600fc
6
LTM4600
SIMPLIFIED BLOCK DIAGRAM
SV
IN
RUN/SS
LTM4600
V
V
4.5V TO 20V
IN
1000pF
C
1.5μF
IN
PGOOD
Q1
COMP
FCB
INT
COMP
1.5V/10A MAX
OUT
C
OUT
4.75k
15μF
6.3V
CONTROLLER
f
ADJ
PGND
Q2
10Ω
SGND
EXTV
CC
100k
0.5%
V
OSET
R6
66.5k
4600 F01
Figure 1. Simplified LTM4600 Block Diagram
DECOUPLING REQUIREMENTS TA = 25°C, VIN = 12V. Use Figure 1 configuration.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
C
External Input Capacitor Requirement
I
= 10A
20
μF
IN
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
= 10A, Refer to Table 2 in the
100
200
μF
OUT
Applications Information Section
IN
OUT
4600fc
7
LTM4600
OPERATION
μModule Description
a 10%windowaroundtheregulationpoint.Furthermore,
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 LTM4600 is a standalone non-isolated synchronous
switching DC/DC power supply. It can deliver up to 10A 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 softstart 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
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 18.
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
TheLTM4600containsanintegratedLTCconstanton-time
current-mode regulator, ultra-low 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 LTM4600 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-
Current mode control provides cycle-by-cycle fast current
limit. In addition, foldback current limiting is provided in
an over-current condition while V
LTM4600 has defeatable short circuit latch off. Internal
overvoltage and undervoltage comparators pull the open-
drainPGOODoutputlowiftheoutputfeedbackvoltageexits
plied on the EXTV pin, the internal regulator is turned
CC
off, and an internal switch connects EXTV to the gate
CC
drops. Also, the
driver voltage. This eliminates the linear regulator power
OSET
loss with high input voltage, reducing the thermal stress
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
4600fc
8
LTM4600
APPLICATIONS INFORMATION
The typical LTM4600 application circuit is shown in Figure
18. External component selection is primarily determined
by the maximum load current and output voltage.
down when Q
is on and Q is off. If the output
UP
DOWN
voltage V needs to be margined up/down by M%, the
O
resistor values of R and R
the following equations:
can be calculated from
UP
DOWN
Output Voltage Programming and Margining
(RSET RUP)• VO •(1+M%)
(RSET RUP)+100kꢀ
The PWM controller of the LTM4600 has an internal
0.6V 1% reference voltage. As shown in the block dia-
gram, a 100k/0.5% internal feedback resistor connects
= 0.6V
RSET • VO •(1–M%)
V
and V
pins. Adding a resistor R from V
OUT
OSET SET OSET
= 0.6V
pin to SGND pin programs the output voltage:
R
SET +(100kꢀ RDOWN
)
100k +RSET
VO = 0.6V •
Input Capacitors
RSET
The LTM4600 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
resistor
SET
for typical output voltages:
ule. In Figure 18, the bulk input capacitor C is selected
Table 1.
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:
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
(V)
O
VO
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 LTM4600. In addition to the feedback
D=
V
IN
Without considering the inductor current ripple, the RMS
current of the input capacitor can be estimated as:
IO(MAX)
ICIN(RMS)
=
• D•(1ꢁD)
resistor R , several external components are added.
SET
ꢀ%
Turn off both transistor Q and Q
margining. When Q is on and Q
voltage is margined up. The output voltage is margined
to disable the
UP
DOWN
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.
is off, the output
UP
DOWN
V
OUT
LTM4600
R
DOWN
Q
100k
DOWN
2N7002
V
OSET
PGND
SGND
R
R
UP
SET
In Figure 18, the input capacitors are used as high fre-
quency input decoupling capacitors. In a typical 10A
output application, 1-2 pieces of very low ESR X5R or
X7R, 10μF ceramic capacitors are recommended. This
decoupling capacitor should be placed directly adjacent
Q
UP
2N7002
4600 F02
Figure 2. LTM4600 Margining Implementation
4600fc
9
LTM4600
APPLICATIONS INFORMATION
the module input pins in the PCB layout to minimize the
trace inductance and high frequency AC noise.
Soft-Start and Latchoff with the RUN/SS pin
The RUN/SS pin provides a means to shut down the
LTM4600 as well as a timer for soft-start and over-cur-
rent latchoff. Pulling the RUN/SS pin below 0.8V puts
Output Capacitors
TheLTM4600isdesignedforlowoutputvoltageripple.The
the LTM4600 into a low quiescent current shutdown (I
Q
bulk output capacitors C
is chosen with low enough
≤ 75μA). Releasing the pin allows an internal 1.2μA cur-
OUT
effectiveseriesresistance(ESR)tomeettheoutputvoltage
ripple and transient requirements. C can be low ESR
rent source to charge up the timing capacitor C . Inside
SS
LTM4600, thereisaninternal1000pFcapacitorfromRUN/
OUT
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 5A/μs transient with
a specific output capacitance.
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
tDELAY
=
•(CSS_EXT +1000pF)
WhenthevoltageonRUN/SSpinreaches1.5V,theLTM4600
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 Over current
Foldback
V to V
Step-Down Ratios
IN
OUT
There are restrictions in the maximum V to V
step
IN
OUT
The LTM4600 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.
down ratio that can be achieved for a given input voltage.
These contraints are shown in the Typical Performance
Characteristics curves labeled “V to V
Step-Down
IN
OUT
To further limit current in the event of an over load condi-
tion,theLTM4600providesfoldbackcurrentlimiting.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.
Ratio”.Notethatadditionalthermalderatingmayapply.See
the Thermal Considerations and Output Current Derating
sections of this data sheet.
After the controller has been started and given adequate
4600fc
10
LTM4600
APPLICATIONS INFORMATION
Table 2. Output Voltage Response Versus Component Matrix (Refer to Figure 18)
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
SANYO POSCAP
SANYO POSCAP
6TPE330MIL (330μF, 6.3V)
2R5TPE470M9 (470μF, 2.5V)
4TPE470MCL (470μF, 4V)
TAIYO YUDEN
TAIYO YUDEN
V
C
C
C
C
C
C3
V
IN
(V)
DROOP
(mV)
PEAK TO PEAK
RECOVERY TIME
(μs)
LOAD STEP
(A/μs)
OUT
IN
IN
OUT1
OUT2
COMP
(V)
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.2
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.5
1.8
1.8
1.8
1.8
1.8
1.8
1.8
1.8
2.5
2.5
2.5
2.5
2.5
2.5
2.5
2.5
3.3
3.3
3.3
3.3
3.3
3.3
3.3
3.3
5
(CERAMIC)
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
2 × 10μF 25V
(BULK)
(CERAMIC)
(BULK)
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
(mV)
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
150μF 35V
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
4 × 100μF 6.3V
4 × 100μF 6.3V
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
NONE 100pF
5
35
35
40
49
35
35
40
49
36
37
44
61
36
37
44
54
40
44
46
62
40
44
44
62
48
56
57
60
48
51
56
70
64
66
82
100
52
64
64
76
188
159
68
25
20
20
20
25
20
20
20
25
20
20
20
25
20
20
20
30
20
20
20
30
20
20
20
30
30
30
25
30
30
30
25
30
30
35
25
30
35
30
25
25
25
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
70
5
80
5
98
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
12
12
12
12
5
68
70
80
98
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
75
5
79
5
84
5
118
75
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
12
12
12
12
5
79
89
108
81
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
5
88
5
91
5
128
81
470μF 4V
470μF 2.5V
330μF 6.3V
NONE
12
12
12
12
5
85
91
125
103
113
116
115
103
102
113
159
126
132
166
200
106
129
126
144
375
320
470μF 4V
330μF 6.3V
470μF 4V
NONE
5
5
5
470μF 4V
470μF 4V
330μF 6.3V
NONE
12
12
12
12
7
330μF 6.3V
470μF 4V
470μF 4V
NONE
7
7
7
470μF 4V
470μF 4V
330μF 6.3V
NONE
12
12
12
12
15
20
NONE
5
NONE
4600fc
11
LTM4600
APPLICATIONS INFORMATION
time to charge up the output capacitor, C is used as a
SS
V
RUN/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
4V
3.5V
3V
beginsdischargingC . Ifthefaultconditionpersistsuntil
SS
1.5V
SHORT-CIRCUIT
LATCH ARMED
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.
t
SOFT-START
CLAMPING
OF I RELEASED
SHORT-CIRCUIT
LATCHOFF
OUTPUT
OVERLOAD
HAPPENS
L
The over-current protection timer requires the soft-start
V
O
timing capacitor C be made large enough to guarantee
SS
75%V
O
that the output is in regulation by the time C has reached
SS
the 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:
t
SWITCHING
STARTS
4600 F03
Figure 3. RUN/SS Pin Voltage During Startup and
Short-Circuit Protection
C
SS EXT +1000pF >COUT • VOUT(10–3[F / VS])
V
V
IN
IN
Generally 0.1μF is more than sufficient.
R
LTM4600
RUN/SS
RUN/SS
Since the load current is already limited by the current
mode control and current foldback circuitry during a
shortcircuit, over-currentlatchoffoperationisNOTalways
needed or desired, especially if the output has a large
amount of capacitance or the load draws huge currents
during start up. The latchoff feature can be overridden
by a pull-up current greater than 5μA but less than 80μA
to the RUN/SS pin. The additional currents prevents the
PGND SGND
4600 F04
RECOMMENDED VALUES FOR R
RUN/SS
V
R
RUN/SS
IN
4.5V TO 5.5V
10.8V TO 13.8V
16V TO 20V
50k
150k
330k
Figure 4. Defeat Short-Circuit Latchoff with a Pull-Up
Resistor to VIN
discharge of C during a fault and also shortens the soft-
SS
start period. Using a resistor from RUN/SS pin to V is
IN
a simple solution to defeat latchoff. Any pull-up network
must be able to maintain RUN/SS above 4V maximum
latchoff threshold and overcome the 4μA maximum dis-
charge current. Figure 3 shows a conceptual drawing of
Enable
The RUN/SS pin can be driven from logic as shown in
Figure 5. This function allows the LTM4600 to be turned
on or off remotely. The ON signal can also control the
sequence of the output voltage.
V
during startup and short circuit.
RUN
RUN/SS
LTM4600
ON
PGND SGND
2N7002
4600 F05
Figure 5. Enable Circuit with External Logic
4600fc
12
LTM4600
APPLICATIONS INFORMATION
Output Voltage Tracking
1. EXTV grounded. Internal 5V LDO is always powered
CC
from the internal 5V regulator.
For the applications that require output voltage tracking,
several LTM4600 modules can be programmed by the
power supply tracking controller such as the LTC2923.
Figure 6 shows a typical schematic with LTC2923. Coin-
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
cident, ratiometric and offset tracking for V rising and
O
falling can be implemented with different sets of resistor
required that the EXTV voltage can not be higher than
CC
values. See the LTC2923 data sheet for more details.
V pin voltage.
IN
Discontinuous Operation and FCB Pin
Q1
V
IN
5V
DC/DC
3.3V
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.
V
V
IN
IN
R
V
GATE
RAMP
FB1
ONB
CC
LTM4600
V
V
1.8V
ON
OSET
OUT
R
ONA
49.9k
LTC2923
STATUS
SDO
RAMPBUF
TRACK1
TRACK2
V
V
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-
tionlossisminimizedandlightloadefficiencyisimproved.
The penalty is that the controller may skip cycle and the
output voltage ripple increases at light load.
IN
R
TB1
IN
R
TB2
R
LTM4600
V
TA1
V
FB2
1.5V
OSET
OUT
GND
R
66.5k
TA2
4600 F06
Figure 6. Output Voltage Tracking with the LTC2923 Controller
Paralleling Operation with Load Sharing
EXTV Connection
CC
TwoormoreLTM4600modulescanbeparalleledtoprovide
higher than 10A 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 LTM4600s
in parallel is:
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 LTM4600 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:
P
= 18mA • (V – 5V)
IN
LDO_LOSS
100k
+RSET
N
The LTM4600 also provides an external gate driver volt-
age pin EXTV . If there is a 5V rail in the system, it is
CC
VOUT = 0.6V •
RSET
recommended to connect EXTV pin to the external 5V
CC
rail. Whenever the EXTV pin is above 4.7V, the internal
CC
where N is the number of LTM4600s in parallel.
5V LDO is shut off and an internal 50mA P-channel switch
connects the EXTV to internal 5V. Internal 5V is supplied
CC
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
from EXTV until this pin drops below 4.5V. Do not apply
CC
more than 6V to the EXTV pin and ensure that EXTV
CC
CC
< V . The following list summaries the possible connec-
IN
tions for EXTV :
CC
4600fc
13
LTM4600
APPLICATIONS INFORMATION
temperature measurements at the bench, and thermal
modelinganalysis.ApplicationNote103providesadetailed
explanationoftheanalysisforthethermalmodels, andthe
derating curves. Tables 3 and 4 provide a summary of the
V
IN
V
V
V
IN
OUT
OUT
(20A
)
MAX
LTM4600
PGND COMP
V
SGND
OSET
R
SET
equivalent θ for the noted conditions. These equivalent
JA
θ parametersarecorrelatedtothemeasuredvalues, and
JA
COMP
V
SGND
OSET
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 heatsinking, and 2W power dissipation
V
LTM4600
V
OUT
IN
PGND
4600 F07
through the top of the module with an approximate θ
JC
Figure 7. Parallel Two μModules with Load Sharing
between 6°C/W to 9°C/W. This equates to a total of 124°C
at the junction of the device.
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
TheLTM4600modulesdonotprovideisolationfromV to
IN
V
.Thereisnointernalfuse.Ifrequired,aslowblowfuse
OUT
approximate θ for the module with various heatsink-
JA
with a rating twice the maximum input current should be
ing methods. Thermal models are derived from several
provided to protect each unit from catastrophic failure.
Table 3. 1.5V Output
DERATING CURVE
Figures 9, 11
Figures 9, 11
Figures 9, 11
Figures 10, 12
Figures 10, 12
Figures 10, 12
V
(V)
POWER LOSS CURVE
Figure 8
AIR FLOW (LFM)
HEATSINK
None
θ
JA
(°C/W)
IN
5, 12
5, 12
5, 12
5, 12
5, 12
5, 12
0
15.2
14
Figure 8
200
400
0
None
Figure 8
None
12
Figure 8
BGA Heatsink
BGA Heatsink
BGA Heatsink
13.9
11.3
10.25
Figure 8
200
400
Figure 8
Table 4. 3.3V Output
DERATING CURVE
Figure 14
V
IN
(V)
POWER LOSS CURVE
Figure 13
AIR FLOW (LFM)
HEATSINK
None
θ
JA
(°C/W)
12
0
15.2
14.6
13.4
13.9
11.1
10.5
Figure 14
12
12
12
12
12
Figure 13
200
400
0
None
Figure 14
Figure 13
None
Figure 15
Figure 13
BGA Heatsink
BGA Heatsink
BGA Heatsink
Figure 15
Figure 13
200
400
Figure 15
Figure 13
4600fc
14
LTM4600
APPLICATIONS INFORMATION
10
10
9
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
= 1.5V
V
V
= 5V
OUT
IN
O
V
V
= 5V
IN
O
= 1.5V
= 1.5V
9
8
8
7
7
12V LOSS
6
5V LOSS
6
0LFM
200LFM
400LFM
5
0 LFM
200 LFM
400 LFM
5
4
0
2
4
6
8
10
50
60
70
80
90
50
60
70
80
90
100
OUTPUT CURRENT (A)
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
4600 F08
4600 F09
4600 G10
Figure 8. Power Loss vs Load Current
Figure 9. No Heatsink
Figure 10. BGA Heatsink
10
9
10
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
V
V
= 12V
IN
V
V
= 12V
V
= 12V
IN
O
IN
O
= 3.3V
OUT
= 1.5V
V
= 1.5V
9
8
7
6
5
4
8
7
6
0LFM
200LFM
400LFM
0 LFM
200 LFM
400 LFM
5
50
60
70
80
90
100
50 55 60 65 70 75 80 85 90
AMBIENT TEMPERATURE (°C)
4600 F11
0
2
4
6
8
10
AMBIENT TEMPERATURE (°C)
OUTPUT CURRENT (A)
4600 G12
4600 F13
Figure 11. No Heatsink
Figure 12. BGA Heatsink
Figure 13. Power Loss vs Load Current
10
9
10
9
V
V
= 12V
= 3.3V
IN
O
V
V
= 12V
= 3.3V
IN
O
8
7
8
6
5
7
4
3
6
0LFM
200LFM
400LFM
2
0 LFM
200 LFM
400 LFM
1
0
5
40
60
80
100
40
50
60
70
80
90
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
4600 G15
4600 F14
Figure 14. No Heatsink
Figure 15. BGA Heatsink
4600fc
15
LTM4600
APPLICATIONS INFORMATION
Layout Checklist/Example
LTM4600 Frequency Adjustment
The high integration of the LTM4600 makes the PCB board
layoutverysimpleandeasy.However,tooptimizeitselectri-
cal and thermal performance, some layout considerations
are still necessary.
The LTM4600 is designed to typically operate at 850kHz
across most input and output conditions. The control ar-
chitectureisconstantontimevalleymodecurrentcontrol.
The f
pin is typically left open or decoupled with an
ADJ
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
• Use large PCB copper areas for high current path, in-
cluding V , PGND and V . It helps to minimize the
IN
OUT
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
high frequency noise
voltage up to a 2.4V clamp. This I current is equal to:
ON
• Place a dedicated power ground layer underneath
the unit
I
= (V – 0.7V)/110k, with the 110k onboard resistor
ON
IN
IN
from V to f . The on time is equal to t = (V /I )
ADJ
OFF
ON
OUT ON
• To minimize the via conduction loss and reduce module
thermal stress, use multiple vias for interconnection
between top layer and other power layers
• 10pF and t = t – t . The frequency is equal to: Freq.
s
ON
= DC/t . The I current is proportional to V , and the
ON
ON
IN
regulator duty cycle is inversely proportional to V , there-
IN
forethestep-downregulatorwillremainrelativelyconstant
• Do not put a via directly on pad unless it is capped
frequency as the duty cycle adjustment takes place with
• Use a separated SGND ground copper area for com-
ponents connected to signal pins. Connect the SGND
to PGND underneath the unit
lowering V . The on time is proportional to V
up to a
IN
OUT
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 17.
Figure 16 gives a good example of the recommended
layout.
V
IN
C
IN
PGND
V
OUT
4600 F16
LOAD
TOP LAYER
Figure 16. Recommended PCB Layout
4600fc
16
LTM4600
APPLICATIONS INFORMATION
t
ON
(DC) DUTY CYCLE =
t
t
= 0.41 • 1μs ≅ 410ns
ON
t
s
t
V
OUT
ON
DC =
=
t
s
V
IN
= 1μs – 410ns ≅ 590ns
OFF
DC
FREQ =
t
ON
t
t
ON
OFF
t
and t are above the minimums with adequate guard
OFF
ON
band.
4600 F21
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
ON
Figure 17. LTM4600 Switching Period
calculated from 12V input was 103μA, so a resistor from
f
to ground = (0.7V/15k) = 46μA. 103μA – 46μA =
TheLTM4600hasaminimum(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
to ~1.2MHz for 3.3V, and ~1.7MHz for 5V outputs due
Equations for setting frequency for 5V to 3.3V:
I
ON
= (V – 0.7V)/110k; I = 39μA
IN ON
to Frequency = (DC/t ) When the switching frequency
ON
increases to 1.2MHz, then the time period t is reduced
S
frequency = (I /[2.4V • 10pF]) • DC = 1.07MHz;
ON
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
DC = duty cycle, duty cycle is (V /V )
OUT IN
t = t + t , t = DC • t , t = off-time of the
OFF
S
ON
OFF ON
S
switching period; t = 1/frequency
S
t
must be greater than 400ns, or t – t > 400ns.
S ON
OFF
off time. Since the total switching period is t = t + t
,
S
ON OFF
The ~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.
t
will be below the 400ns minimum off time. A resistor
OFF
from the f
pin to ground can shunt current away from
ADJ
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.
t
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.
Equations for setting frequency for 12V to 5V:
Using the frequency = (I /[2.4V • 10pF]) • DC, solve for
ON
I
ON
= (V – 0.7V)/110k; I = 103μA
IN ON
I
ON
= (450kHz • 2.4V • 10pF) • (1/0.66) ≅ 16μA. I current
ON
calculated from 5V input was 39μA, so a resistor from f
frequency = (I /[2.4V • 10pF]) • DC = 1.79MHz;
ADJ
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
t = t + t , t = on-time, t = off-time of the
OFF
S
ON
OFF ON
for the higher duty cycle conversion of 5V to 3.3V. Input
switching period; t = 1/frequency
S
voltagerangeislimitedto4.5Vto7V.Higherinputvoltages
t
must be greater than 400ns, or t – t > 400ns.
S ON
can be used without the 30.1k on f . The inductor ripple
OFF
ADJ
current gets too high above 7V, and the 400ns minimum
t
= DC • t
S
ON
off-time is limited below 4.5V.
1MHz frequency or 1μs period is chosen for 12V to 5V.
4600fc
17
LTM4600
APPLICATIONS INFORMATION
5V to 3.3V at 8A
R1
30.1k
4.5V TO 7V
C5
100pF
C3
10μF
25V
C1
10μF
25V
V
f
ADJ
IN
3.3V AT 8A EFFICIENCY = 93%
EXTV
FCB
V
CC
OUT
+
C2
22μF
C4
330μF
6.3V
V
OSET
R2
22.1k
1%
LTM4600
RUN/SOFT-START
RUN/SS
COMP
SV
IN
PGOOD
PGND
OPEN DRAIN
SGND
4600 F18
5V TO 3.3V AT 8A WITH f
= 30.1k
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POS CAP, 6TPE330MIL
ADJ
12V to 5V at 8A
R1
15k
9V TO 16V
C5
100pF
C3
10μF
25V
C1
10μF
25V
V
IN
f
ADJ
5V AT 8A
EFFICIENCY = 94%
EXTV
V
CC
OUT
C4
+
C2
22μF
330μF
FCB
V
OSET
6.3V
R2
13.7k
1%
LTM4600
RUN/SOFT-START
RUN/SS
COMP
SV
IN
PGOOD
PGND
OPEN DRAIN
SGND
4600 F19
12V TO 5V AT 8A WITH f
= 15k
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POSCAP, 6TPE330MIL
ADJ
VIN to VOUT Step-Down Ratio for
12VIN to 5VOUT and 5VIN to 3.3VOUT
5.0
3.3V: f
= 30.1k
ADJ
4.5 5V: f
= 15k
ADJ
4.0
3.5
3.0
2.5
2.0
1.5
1.0
3.3V AT 8A
5V AT 8A
0.5
0
1
3
5
7
9
11 13 15 17
V
(V)
IN
4600 F20
4600fc
18
LTM4600
TYPICAL APPLICATION
V
IN
+
C
(BULK)
C
(CER)
IN
IN
5V TO 20V
GND
150μF
10μF
V
IN
2x
(MULTIPLE PINS)
EXTV
V
V
OUT
CC
OUT
(MULTIPLE PINS)
C3
100pF
SV
IN
C
+
OUT1
C
OUT2
22μF
6.3V
×3
f
ADJ
470μF
V
REFER TO
TABLE 2
V
OSET
OUT
LTM4600
COMP
FCB
REFER TO
TABLE 2
RUN/SS
PGOOD
0.6V TO 5V
SGND
REFER TO STEP-DOWN
RATIO GRAPH
PGND
(MULTIPLE PINS)
C4
OPT
R1
66.5k
REFER TO
TABLE 1
GND
4600 F17
Figure 18. Typical Application, 5V to 20V Input, 0.6V to 5V Output, 10A Max
4600fc
19
LTM4600
TYPICAL APPLICATION
Parallel Operation and Load Sharing
4.5V TO 20V
V
= 0.6V • ([100k/N] + R )/R
SET SET
OUT
WHERE N = 2
C8
10μF
25V
C7
10μF
25V
V
f
ADJ
IN
2.5V
EXTV
FCB
V
CC
OUT
+
C9
C10
470μF
4V
V
OSET
22μF
x3
LTM4600
R4
15.8k
1%
RUN
SV
IN
COMP
PGOOD
PGND
SGND
2.5V AT 20A
RUN/SOFT-START
C4
220pF
C3
10μF
25V
C1
10μF
V
f
ADJ
IN
25V
2.5V
R1
EXTV
V
CC
OUT
+
C2
22μF
x3
C5
470μF
4V
FCB
V
OSET
LTM4600
RUN
SV
IN
100k
COMP
PGOOD
PGND
SGND
C1, C3, C7, C8: TDK C3216X5R1E106MT
C2, C9: TAIYO YUDEN, JMK316BJ226ML-T501
C5, C10: SANYO POSCAP, 4TPE470MCL
4600 TA02
Current Sharing Between Two
LTM4600 Modules
12
10
8
12V
IN
2.5V
OUT
MAX
20A
6
I
OUT2
I
OUT1
4
2
0
0
10
TOTAL LOAD
15
20
5
4600 TA03
4600fc
20
LTM4600
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 . 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
4600fc
21
LTM4600
PACKAGE DESCRIPTION
Pin Assignment Tables
(Arranged by Pin Number)
PIN NAME
PIN NAME
PIN NAME
C1
PIN NAME
PIN NAME
E1
PIN NAME
PIN NAME
PIN NAME
A1
-
B1
V
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
V
-
V
-
V
-
-
-
-
-
-
-
-
-
D1
V
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
V
-
V
-
V
-
-
-
-
-
-
-
-
-
F1
V
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
G1 PGND
H1
-
-
-
-
-
-
IN
IN
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
IN
IN
IN
IN
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
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
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
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
-
-
4600fc
22
LTM4600
PACKAGE DESCRIPTION
Pin Assignment Tables
(Arranged by Pin Number)
PIN NAME
PIN NAME
PIN NAME
PIN NAME
G1
PGND
P2
V
A3
V
V
V
V
V
V
A15
A17
A19
A21
B23
D23
F23
G23
J23
f
ADJ
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
IN
IN
IN
IN
IN
IN
P4
V
V
V
V
V
V
V
V
V
V
A5
H7
H9
H11
H13
H15
H17
PGND
PGND
PGND
PGND
PGND
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
PGND
PGND
PGND
PGND
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
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
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
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
M4
M6
M8
M10
M12
M14
M16
M18
M20
M22
N2
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
N4
N6
N8
N10
N12
N14
N16
N18
N20
N22
4600fc
InformationfurnishedbyLinearTechnologyCorporationisbelievedtobeaccurateandreliable.However,
no responsibility is assumed for its use. Linear Technology Corporation makes no representation that
the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTM4600
TYPICAL APPLICATION
1.8V, 10A Regulator
4.5V AT 20V
C5
100pF
C2
10μF
25V
C1
10μF
V
f
ADJ
IN
25V
1.8V AT 10A
EXTV
FCB
V
CC
OUT
+
C3
22μF
x3
C4
470μF
4V
V
OSET
R1
100k
LTM4600
RUN
SV
IN
COMP
PGOOD
PGND
PGOOD
R2
49.9k
1%
SGND
C1, C2: TDK C3216X5R1E106MT
C3: TAIYO YUDEN, JMK316BJ226ML-T501
C4: SANYO POSCAP, 4TPE470MCL
4600 TA04
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2900
Quad Supply Monitor with Adjustable Reset Timer
Power Supply Tracking Controller
Monitors Four Supplies; Adjustable Reset Timer
LTC2923
Tracks Both Up and Down; Power Supply Sequencing
No Optocoupler Required; 3.3V, 12A Output; Simple Design
LT3825/LT3837
LTM4601
Synchronous Isolated Flyback Controllers
12A DC/DC μModule with PLL, Output Tracking/
Margining and Remote Sensing
Synchronizable, PolyPhase Operation, 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 Outpupt Tracking/ Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote
Margining and Remote Sensing
Sensing, Pin Compatible with the LTM4601
®
This product contains technology licensed from Silicon Semiconductor Corporation.
4600fc
LT 0807 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
●
●
© LINEAR TECHNOLOGY CORPORATION 2006
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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