LTM4608AMPV#PBF [Linear]
LTM4608A - Low VIN, 8A DC/DC µModule (Power Module) with Tracking, Margining, and Frequency Synchronization; Package: LGA; Pins: 68; Temperature Range: -55°C to 125°C;
| 型号： | LTM4608AMPV#PBF |
| 厂家： | 
Linear |
| 描述： | LTM4608A - Low VIN, 8A DC/DC µModule (Power Module) with Tracking, Margining, and Frequency Synchronization; Package: LGA; Pins: 68; Temperature Range: -55°C to 125°C 开关 |
| 文件： | 总26页 (文件大小：343K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTM4608
Low V , 8A DC/DC µModule
IN
Regulator with Tracking, Margining,
and Frequency Synchronization
FeaTures
DescripTion
The LTM®4608 is a complete 8A switch mode DC/DC
power supply. Included in the package are the switching
controller, power FETs, inductor and all support compo-
nents. Operating over an input voltage range of 2.7V to
5.5V, the LTM4608 supports an output voltage range of
0.6V to 5V, set by a single external resistor. This high ef-
ficiency design delivers up to 8A continuous current (10A
peak). Only bulk input and output capacitors are needed.
n
Complete Standalone Power Supply
n
1.5% Output Voltage Regulation
n
2.7V to 5.5V Input Voltage Range
n
8A DC, 10A Peak Output Current
0.6V Up to 5V Output
Output Voltage Tracking and Margining
Power Good Tracking and Margining
n
n
n
n
Multiphase Operation
Parallel Current Sharing
n
The low profile package (2.82mm) enables utilization
of unused space on the back side of PC boards for high
density point-of-load regulation. The high switching
frequency and a current mode architecture enable a very
fast transient response to line and load changes without
sacrificing stability. The device supports frequency syn-
chronization, programmable multiphase and/or spread
spectrum operation, output voltage tracking for supply
rail sequencing and voltage margining.
n
Onboard Frequency Synchronization
n
Spread Spectrum Frequency Modulation
n
Overcurrent/Thermal Shutdown Protection
n
Small Surface Mount Footprint, Low Profile
(9mm × 15mm × 2.82mm) LGA Package
applicaTions
n
Telecom, Networking and Industrial Equipment
Storage Systems
Point of Load Regulation
n
n
Fault protection features include overvoltage protection,
overcurrent protection and thermal shutdown. The power
module is offered in a compact and thermally enhanced
9mm × 15mm × 2.82mm LGA package. The LTM4608 is
RoHS compliant with Pb-free finish.
For easier board layout and PCB assembly due to in-
creased spacing between land grid pads, please refer
to the LTM4608A.
L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule, Burst Mode and PolyPhase are
registered trademarks and LTpowerCAD is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Typical applicaTion
2.7V to 5.5V Input to 1.8V Output DC/DC µModule® Regulator
Efficiency vs Load Current
100
CLKIN
95
CLKIN
V
V
OUT
V
= 3.3V
IN
IN
V
V
IN
OUT
2.7V TO 5.5V
1.8V
90
85
SV
FB
IN
10µF
100µF
V
IN
= 5V
4.87k
SW
I
TH
LTM4608
RUN
I
THM
80
75
70
PGOOD
PLLLPF
TRACK
PGOOD
MGN
CLKOUT GND SGND
4608 TA01a
V
= 1.8V
OUT
8
0
2
4
6
10
LOAD CURRENT (A)
4608 TA01b
4608fd
1
LTM4608
absoluTe MaxiMuM raTings
pin conFiguraTion
(Note 1)
V , SV ......................................................–0.3V to 6V
TOP VIEW
IN
IN
A
B
C
D
E
F
G
CLKOUT .......................................................–0.3V to 2V
GND
V
CNTRL GND
IN
PGOOD, PLLLPF, CLKIN, PHMODE, MODE.. –0.3V to V
TH THM
IN
IN
1
2
I , I
, RUN, FB, TRACK, MGN, BSEL..... –0.3V to V
SW
V
, V ..................................... –0.3V to (V + 0.3V)
OUT SW
IN
3
Operating Temperature Range (Note 2)....–40°C to 85°C
Junction Temperature ........................................... 125°C
Storage Temperature Range ..................–55°C to 125°C
4
5
6
CNTRL
7
8
9
10
11
GND
V
OUT
For easier board layout and PCB assembly due to in-
creased spacing between land grid pads, please refer
to the LTM4608A.
LGA PACKAGE
68-LEAD (15mm × 9mm × 2.82mm)
T
= 125°C, θ = 25°C/W, θ = 7°C/W, θ = 50°C/W, WEIGHT = 1.0g
JMAX
JA
JCbottom
JCtop
orDer inForMaTion
LEAD FREE FINISH
LTM4608EV#PBF
LTM4608IV#PBF
PART MARKING*
LTM4608V
PACKAGE DESCRIPTION
TEMPERATURE RANGE (NOTE 2)
–40°C to 85°C
68-Lead (15mm × 9mm × 2.82mm) LGA
68-Lead (15mm × 9mm × 2.82mm) LGA
LTM4608V
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
elecTrical characTerisTics The l denotes the specifications which apply over the full operating
temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 1.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
V
V
Input DC Voltage
Output Voltage
2.7
5.5
V
IN(DC)
C
= 10µF × 1, C
= 100µF Ceramic,
OUT(DC)
IN
OUT
FB
100µF POSCAP, R = 6.65k, MODE = 0V
1.475
1.468
1.49
1.49
1.505
1.512
V
V
V
IN
= 2.7V to 5.5V, V
= 1.5V, I
= 0A
OUT
OUT
l
Input Specifications
V
Undervoltage Lockout Threshold SV Rising
2.05
1.85
2.2
2.0
2.35
2.15
V
V
IN(UVLO)
IN
SV Falling
IN
4608fd
2
LTM4608
elecTrical characTerisTics The l denotes the specifications which apply over the full operating
temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 1.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
I
Input Supply Bias Current
V
IN
V
IN
V
IN
= 3.3V, V
= 3.3V, V
= 3.3V, V
= 1.5V, No Switching, MODE = V
IN
= 1.5V, No Switching, MODE = 0V
= 1.5V, Switching Continuous
400
1.15
55
µA
mA
mA
Q(VIN)
OUT
OUT
OUT
V
V
V
= 5V, V
= 5V, V
= 5V, V
= 1.5V, No Switching, MODE = V
IN
= 1.5V, No Switching, MODE = 0V
= 1.5V, Switching Continuous
450
1.3
75
µA
mA
mA
IN
IN
IN
OUT
OUT
OUT
Shutdown, RUN = 0, V = 5V
1
µA
IN
I
Input Supply Current
V
IN
V
IN
= 3.3V, V
= 1.5V, I = 8A
OUT
4.5
2.93
A
A
S(VIN)
OUT
= 5V, V
= 1.5V, I
= 8A
OUT
OUT
Output Specifications
I
Output Continuous Current Range V
(See Output Current Derating
= 1.5V
OUT(DC)
OUT
V
= 3.3V, 5.5V
0
0
8
5
A
A
IN
IN
Curves for Different V , V
V
= 2.7V
IN OUT
and T )
A
l
ΔV
Line Regulation Accuracy
Load Regulation Accuracy
V
V
= 1.5V, V from 2.7V to 5.5V, I
= 0A
0.1
0.2
%/V
OUT(LINE)
OUT
IN
OUT
V
OUT
ΔV
= 1.5V
OUT(LOAD)
OUT
V
V
l
l
= 3.3V, 5.5V, I
= 0A to 8A
LOAD
0.3
0.3
0.75
0.75
%
%
IN
IN
V
OUT
= 2.7V, I
= 0A to 5A
LOAD
V
Output Ripple Voltage
I
= 0A, C
= 1.5V
= 100µF/X5R/Ceramic, V = 5V,
OUT IN
OUT(AC)
OUT
OUT
V
10
mV
P-P
f
f
Switching Frequency
SYNC Capture Range
Turn-On Overshoot
I
= 8A, V = 5V, V = 1.5V
OUT
1.3
1.5
1.7
MHz
MHz
S
OUT
IN
0.75
2.25
SYNC
ΔV
C
= 100µF, V
= 1.5V, I
= 0A
OUT
OUT(START)
OUT
V
OUT
= 3.3V
= 5V
10
10
mV
mV
IN
IN
V
t
Turn-On Time
C
= 100µF, V
= 1.5V, V = 5V
IN
START
OUT
OUT
OUT
I
=1A Resistive Load, Track = V
100
15
µs
IN
ΔV
Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load,
mV
OUT(LS)
C
V
= 100µF Ceramic, 100µF POSCAP,
OUT
IN
= 5V, V
= 1.5V
OUT
t
I
Settling Time for Dynamic Load
Step
Load: 0% to 50% to 0% of Full Load, V = 5V,
OUT
10
µs
SETTLE
IN
V
= 1.5V, C
= 100µF
OUT
Output Current Limit
C
= 100µF
OUT(PK)
OUT
V
= 2.7V, V
= 3.3V, V
= 1.5V
= 1.5V
8
11
13
A
A
A
IN
IN
IN
OUT
OUT
V
V
= 5V, V
= 1.5V
OUT
Control Section
V
Voltage at FB Pin
I
= 0A, V
= 1.5V, V = 2.7V to 5.5V
0.592
0.589
0.596
0.596
0.600
0.603
V
V
FB
OUT
OUT
IN
l
SS Delay
Internal Soft-Start Delay
90
µs
I
0.2
µA
FB
V
RUN Pin On/Off Threshold
RUN Rising
RUN Falling
1.4
1.3
1.55
1.4
1.7
1.5
V
V
RUN
4608fd
3
LTM4608
elecTrical characTerisTics The l denotes the specifications which apply over the full operating
temperature range (Note 2), otherwise specifications are at TA = 25°C. VIN = 5V unless otherwise noted. See Figure 1.
SYMBOL
PARAMETER
CONDITIONS
RUN = V
MIN
TYP
MAX
UNITS
TRACK
Tracking Threshold (Rising)
Tracking Threshold (Falling)
Tracking Disable Threshold
0.57
0.18
V
V
V
IN
RUN = 0V
V
– 0.5
IN
R
Resistor Between V
and FB
OUT
9.95
10
10.05
kΩ
FBHI
Pins
ΔV
PGOOD
PGOOD Range
10
%
%Margining
Output Voltage Margining
Percentage
MGN = V , BSEL = 0V
4
9
14
–4
–9
–14
5
6
%
%
%
%
%
%
IN
MGN = V , BSEL = V
10
11
IN
IN
MGN = V , BSEL = Float
15
16
IN
MGN = 0V, BSEL = 0V
–5
–10
–15
–6
–11
–16
MGN = 0V, BSEL = V
IN
MGN = 0V, BSEL = Float
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 LTM4608E 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 LTM4608I is guaranteed over the
–40°C to 85°C temperature range.
4608fd
4
LTM4608
Typical perForMance characTerisTics
Efficiency vs Load Current
Efficiency vs Load Current
Efficiency vs Load Current
100
95
90
85
80
75
70
100
95
100
95
CONTINUOUS MODE
CONTINUOUS MODE
CONTINUOUS MODE
90
85
90
85
80
75
70
80
75
70
5V 1.2V
IN
OUT
OUT
OUT
OUT
OUT
3.3V 1.2V
IN
OUT
OUT
OUT
OUT
5V 1.5V
IN
2.7V 1.0V
3.3V 1.5V
IN
IN
OUT
OUT
OUT
5V 1.8V
IN
2.7V 1.5V
IN
3.3V 1.8V
IN
3.3V 2.5V
IN
5V 2.5V
IN
2.7V 1.8V
IN
5V 3.3V
IN
0
2
3
4
5
6
7
0
2
4
6
8
1
0
2
4
6
8
LOAD CURRENT (A)
LOAD CURRENT
LOAD CURRENT
4608 G03
4608 G02
4608 G01
Burst Mode Efficiency with
5V Input
VIN to VOUT Step-Down Ratio
VIN to VOUT Step-Down Ratio
100
90
80
70
60
50
40
4.0
3.5
3.0
2.5
4.0
3.5
3.0
2.5
2.0
1.5
2.0
1.5
1.0
0.5
0
1.0
0.5
0
I
V
V
= 8A
OUT
OUT
OUT
V
V
V
= 1.8V
= 2.5V
= 3.3V
V
V
V
= 1.5V
= 2.5V
= 3.3V
I
V
V
= 6A
V
V
V
= 1.8V
= 2.5V
= 3.3V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
= 1.2V
= 1.5V
= 1.2V
= 1.5V
OUT
OUT
0
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1
LOAD CURRENT (A)
4
2
3
4
5
6
2
5
6
3
V
(V)
V
(V)
IN
IN
4608 G04
4608 G05
4608 G06
Supply Current vs VIN
Load Transient Response
Load Transient Response
1.6
1.4
1.2
1
1A/DIV
V
= 1.2V PULSE-SKIPPING MODE
2A/DIV
O
V
20mV/DIV
20mV/DIV
0.8
0.6
0.4
0.2
0
= 1.2V BURST MODE
O
4608 G08
4608 G09
V
V
= 5V
20µs/DIV
V
V
= 5V
20µs/DIV
IN
OUT
IN
OUT
= 3.3V
= 2.5V
2A/µs STEP
= 100µF X5R
2.5A/µs STEP
= 100µF X5R
C
C
OUT
OUT
C1 = 100pF, C3 = 22pF FROM FIGURE 18
C1 = 120pF, C3 = 47pF FROM FIGURE 18
2.5
3
3.5
4
4.5
5
5.5
INPUT VOLTAGE (V)
4608 G07
4608fd
5
LTM4608
Typical perForMance characTerisTics
Load Transient Response
Load Transient Response
Load Transient Response
2A/DIV
2A/DIV
2A/DIV
20mV/DIV
20mV/DIV
20mV/DIV
4608 G10
4608 G11
4608 G12
V
V
= 5V
20µs/DIV
V
V
= 5V
20µs/DIV
V
V
= 5V
20µs/DIV
IN
OUT
IN
OUT
IN
OUT
= 1.8V
= 1.5V
= 1.2V
2.5A/µs STEP
= 100µF X5R
2.5A/µs STEP
= 100µF X5R
2.5A/µs STEP
= 2 × 100µF
C
C
C
OUT
OUT
OUT
C1 = NONE, C3 = NONE FROM FIGURE 18
C1 = NONE, C3 = NONE FROM FIGURE 18
C1 = 100pF, C3 = NONE FROM FIGURE 18
Start-Up
VFB vs Temperature
Load Regulation vs Current
602
600
598
596
594
592
590
0
–0.1
–0.2
–0.3
–0.4
V
OUT
V
V
= 5.5V
IN
0.5V/DIV
V
= 3.3V
IN
V
IN
2V/DIV
= 2.7V
IN
4608 G13
V
V
C
= 5V
50µs/DIV
FC MODE
IN
–0.5
–0.6
= 1.5V
V
V
= 3.3V
OUT
OUT
IN
OUT
= 100µF NO LOAD AND 8A LOAD
= 1.5V
(DEFAULT 100µs SOFT-START)
–25
0
50
–50
75
100
25
0
2
4
6
8
TEMPERATURE (°C)
LOAD CURRENT (A)
4608 G14
4608 G15
Short-Circuit Protection
(2.5V Short, No Load)
Short-Circuit Protection
(2.5V Short, 4A Load)
2.5V Output Current
3.0
2.5
V
IN
5V/DIV
5V/DIV
2V/DIV
2V/DIV
V
V
IN
OUT
V
OUT
2.0
1.5
I
LOAD
OUT
5A/DIV
5A/DIV
I
OUT
1.0
0.5
0
4608 G17
4608 G18
V
V
= 5V
50µs/DIV
V
V
= 5V
50µs/DIV
IN
OUT
IN
OUT
= 2.5V
= 2.5V
0
5
10
15
20
OUTPUT CURRENT (A)
4608 G16
4608fd
6
LTM4608
pin FuncTions
PLLLPF (E3): Phase-Locked Loop Lowpass Filter. An in-
ternal lowpass filter is tied to this pin. In spread spectrum
mode, placing a capacitor here to SGND controls the slew
rate from one frequency to the next. Alternatively, floating
this pin allows normal running frequency at 1.5MHz, tying
V (C1, C8, C9, D1, D3-D5, D7-D9 and E8): Power Input
IN
Pins. Apply input voltage between these pins and GND
pins. Recommend placing input decoupling capacitance
directly between V pins and GND pins.
IN
V
OUT
(C10-C11, D10-D11, E9-E11, F9-F11, G9-G11):
this pin to SV forces the part to run at 1.33 times its
IN
Power Output Pins. Apply output load between these pins
and GND pins. Recommend placing output decoupling
capacitance directly between these pins and GND pins.
See Table 1.
normal frequency (2MHz), tying it to ground forces the
frequencytorunat0.67timesitsnormalfrequency(1MHz).
PHMODE (B4): Phase Selector Input. This pin determines
the phase relationship between the internal oscillator and
CLKOUT. Tie it high for 2-phase operation, tie it low for
GND (A1-A11, B1, B9-B11, F3, F7-F8, G1-G8): Power
Ground Pins for Both Input and Output Returns.
3-phase operation, and float or tie it to V /2 for 4-phase
IN
SV (F4): Signal Input Voltage. This pin is internally con-
operation.
IN
nected to V through a lowpass filter.
IN
MGN (B8): Margining Pin. Increases or decreases the
output voltage by the amount specified by the BSEL pin.
To disable margining, tie the MGN pin to a voltage divider
SGND (E1): Signal Ground Pin. Return ground path for all
analog and low power circuitry. Tie a single connection to
GND in the application.
with50kresistorsfromV toground.SeetheApplications
IN
Information section and Figure 20.
MODE(B5):ModeSelectInput.Tyingthispinhighenables
Burst Mode® operation. Tying this pin low enables forced
BSEL (B7): Margining Bit Select Pin. Tying BSEL low se-
continuous operation. Floating this pin or tying it to V /2
enables pulse-skipping operation.
lects 5%, tying it high selects 10%. Floating it or tying
IN
it to V /2 selects 15%.
IN
CLKIN (B3): External Synchronization Input to Phase
Detector. This pin is internally terminated to SGND with a
50k resistor. The phase-locked loop will force the internal
top power PMOS turn on to be synchronized with the
TRACK (E5): Output Voltage Tracking Pin. Voltage track-
ing is enabled when the TRACK voltage is below 0.57V.
If tracking is not desired, then connect the TRACK pin to
SV . If TRACK is not tied to SV , then the TRACK pin’s
IN
IN
rising edge of the CLKIN signal. Connect this pin to SV
voltage needs to be below 0.18V before the chip shuts
down even though RUN is already low. Do not float this
pin. A resistor divider and capacitor can be applied to the
TRACK pin to increase the soft-start time of the regulator.
See the Applications Information section. Can tie together
for parallel operation and tracking. Load current needs to
be present during track down.
IN
to enable spread spectrum modulation. During external
synchronization, make sure the PLLLPF pin is not tied to
V or GND.
IN
4608fd
7
LTM4608
pin FuncTions
PGOOD (C7): Output Voltage Power Good Indicator.
Open-drain logic output that is pulled to ground when the
output voltage is not within 10% of the regulation point.
Disabled during margining.
FB(E7):TheNegativeInputoftheErrorAmplifier.Internally,
this pin is connected to V
with a 10k precision resistor.
OUT
Different output voltages can be programmed with an ad-
ditional resistor between FB and GND pins. In PolyPhase®
operation, tie FB pins together for parallel operation. See
the Applications Information section for details.
RUN (F1): Run Control Pin. A voltage above 1.5V will turn
on the module.
I
(F6): Current Control Threshold and Error Amplifier
TH
SW (C3-C5): Switching Node of the Circuit is Used for
Testing Purposes. This can be connected to an electri-
cally open circuit copper pad on the board for improved
thermal performance.
Compensation Point. The current comparator threshold
increases with this control voltage. Tie together in parallel
operation.
I
(F5): Negative Input to the Internal I Differential
TH
THM
CLKOUT (F2): Output Clock Signal for PolyPhase Opera-
tion. The phase of CLKOUT is determined by the state of
the PHMODE pin.
Amplifier. Tie this pin to SGND for single phase operation.
For PolyPhase operation, tie the master’s I
while connecting all of the I
to SGND
THM
pins together.
THM
4608fd
8
LTM4608
siMpliFieD block DiagraM
SV
V
IN
IN
V
INTERNAL
FILTER
IN
2.7 TO 5.5V
+
TRACK
10µF
10µF
10µF
C
IN
MGN
BSEL
SW
M1
M2
PGOOD
MODE
0.22µH
V
1.5V
8A
OUT
V
OUT
POWER
CONTROL
RUN
CLKIN
CLKOUT
PHMODE
22µF
22pF
C
OUT
GND
FB
I
TH
10k
INTERNAL
COMP
PLLLPF
R
FB
INTERNAL
FILTER
6.65k
I
THM
SGND
4608 BD
Figure 1. Simplified LTM4608 Block Diagram
Table 1. Decoupling Requirements. TA = 25°C, Block Diagram Configuration.
SYMBOL
PARAMETER
CONDITIONS
MIN
10
TYP
MAX
UNITS
C
IN
External Input Capacitor Requirement
I
= 8A
µF
OUT
(V = 2.7V to 5.5V, V
= 1.5V)
OUT
IN
C
OUT
External Output Capacitor Requirement
(V = 2.7V to 5.5V, V = 1.5V)
I
= 8A
100
µF
OUT
IN
OUT
operaTion
1.5MHz. For switching noise sensitive applications, it can
be externally synchronized from 0.75MHz to 2.25MHz.
Even spread spectrum switching can be implemented in
the design to reduce noise.
The LTM4608 is a standalone nonisolated switch mode
DC/DC power supply. It can deliver up to 8A of DC output
current with few external input and output capacitors.
This module provides precisely regulated output voltage
programmable via one external resistor from 0.6V DC to
5.0V DC over a 2.7V to 5.5V input voltage. The typical
application schematic is shown in Figure 18.
With current mode control and internal feedback loop
compensation, the LTM4608 module has sufficient stabil-
ity margins and good transient performance with a wide
range of output capacitors, even with all ceramic output
capacitors.
TheLTM4608hasanintegratedconstantfrequencycurrent
mode regulator and built-in power MOSFET devices with
fast switching speed. The typical switching frequency is
4608fd
9
LTM4608
operaTion
Currentmodecontrolprovidescycle-by-cyclefastcurrent
limit and thermal shutdown in an overcurrent condition.
Internal overvoltage and undervoltage comparators pull
the open-drain PGOOD output low if the output feedback
voltage exits a 10% window around the regulation point.
The FB pin is used to program the output voltage with a
single external resistor to ground.
Multiphase operation can be easily employed with the
synchronizationandphasemodecontrols.Upto12phases
can be cascaded to run simultaneously with respect to
each other by programming the PHMODE pin to different
levels. The LTM4608 has clock in and clock out for poly
phasing multiple devices or frequency synchronization.
Pulling the RUN pin below 1.3V forces the controller into
its shutdown state, by turning off both M1 and M2 at low
load current. The TRACK pin is used for programming the
output voltage ramp and voltage tracking during start-up.
See Applications Information.
High efficiency at light loads can be accomplished with
selectableBurstModeoperationusingtheMODEpin.These
light load features will accommodate battery operation.
Efficiency graphs are provided for light load operation in
the Typial Performance Characteristics.
The LTM4608 is internally compensated to be stable over
all operating conditions. Table 3 provides a guideline
for input and output capacitances for several operating
conditions. The Linear Technology µModule Power De-
sign Tool is provided for transient and stability analysis.
Output voltage margining is supported, and can be pro-
gramedfrom 5%to 15%usingtheMGNandBSELpins.
The PGOOD pin is disabled during margining.
applicaTions inForMaTion
Table 2. RFB Resistor vs Output Voltage
The typical LTM4608 application circuit is shown in Fig-
ure 18. External component selection is primarily deter-
mined by the maximum load current and output voltage.
RefertoTable3forspecificexternalcapacitorrequirements
for a particular application.
V
0.596V
Open
1.2V
10k
1.5V
1.8V
2.5V
3.3V
OUT
R
6.65k
4.87k
3.09k
2.21k
FB
Input Capacitors
The LTM4608 module should be connected to a low AC
impedance DC source. Three 10µF ceramic capacitors
are included inside the module. Additional input capaci-
tors are only needed if a large load step is required up to
the 4A level. A 47µF to 100µF surface mount aluminum
electrolytic bulk capacitor can be used for more input bulk
capacitance. This bulk input capacitor is only needed if
the input source impedance is compromised by long in-
ductive leads, traces or not enough source capacitance.
If low impedance power planes are used, then this 47µF
capacitor is not needed.
V to V
Step-Down Ratios
IN
OUT
There are restrictions in the maximum V to V
down ratio that can be achieved for a given input voltage.
The LTM4608 is 100% duty cycle, but the V to V
minimum dropout is a function of its load current. Please
refer to the curves in the Typical Performance Charac-
teristics section of this data sheet for more information.
step-
IN
OUT
IN
OUT
Output Voltage Programming
The PWM controller has an internal 0.596V reference
voltage. As shown in the Block Diagram, a 10k/0.5%
For a buck converter, the switching duty-cycle can be
estimated as:
internal feedback resistor connects V
and FB pins
OUT
together. The output voltage will default to 0.596V with
VOUT
no feedback resistor. Adding a resistor R from FB pin
FB
D=
V
to GND programs the output voltage:
IN
10k + RFB
VOUT = 0.596V •
RFB
4608fd
10
LTM4608
applicaTions inForMaTion
Without considering the inductor current ripple, the RMS
current of the input capacitor can be estimated as:
Burst Mode Operation
The LTM4608 is capable of Burst Mode operation in which
the power MOSFETs operate intermittently based on load
demand, thus saving quiescent current. For applications
where maximizing the efficiency at very light loads is a
high priority, Burst Mode operation should be applied. To
enable Burst Mode operation, simply tie the MODE pin to
IOUT(MAX)
ICIN(RMS)
=
• D• 1–D
(
)
η%
In the above equation, η% is the estimated efficiency of
the power module. The bulk capacitor can be a switcher-
rated electrolytic aluminum capacitor, polymer capacitor
for bulk input capacitance due to high inductance traces
or leads. If a low inductance plane is used to power the
device, then only one 10µF ceramic is required. The three
internal 10µF ceramics are typically rated for 2A of RMS
ripple current, so the ripple current at the worse case for
8A maximum current is 4A or less.
V . Duringthisoperation, thepeakcurrentoftheinductor
IN
is set to approximately 20% of the maximum peak current
value in normal operation even though the voltage at the
I
pin indicates a lower value. The voltage at the I pin
TH
TH
drops when the inductor’s average current is greater than
the load requirement. As the I voltage drops below 0.2V,
TH
the BURST comparator trips, causing the internal sleep
line to go high and turn off both power MOSFETs.
Output Capacitors
In sleep mode, the internal circuitry is partially turned off,
reducingthequiescentcurrenttoabout450µA.Theloadcur-
rentisnowbeingsuppliedfromtheoutputcapacitor.When
The LTM4608 is designed for low output voltage ripple
noise. The bulk output capacitors defined as C
are
OUT
chosen with low enough effective series resistance (ESR)
to meet the output voltage ripple and transient require-
the output voltage drops, causing I to rise above 0.25V,
TH
the internal sleep line goes low, and the LTM4608 resumes
normal operation. The next oscillator cycle will turn on the
toppowerMOSFETandtheswitchingcyclerepeats.
ments. C
can be a low ESR tantalum capacitor, a low
OUT
ESR polymer capacitor or ceramic capacitor. The typical
outputcapacitancerangeisfrom47µFto220µF.Additional
output filtering may be required by the system designer,
if further reduction of output ripple or dynamic transient
spikesisdesired.Table3showsamatrixofdifferentoutput
voltages and output capacitors to minimize the voltage
droop and overshoot during a 3A/µs transient. The table
optimizes total equivalent ESR and total bulk capacitance
tooptimizethetransientperformance.Stabilitycriteriaare
consideredintheTable3matrix,andtheLinearTechnology
LTpowerCAD™DesignToolisavailableforstabilityanalysis.
Multiphase operation will reduce effective output ripple as
a function of the number of phases. Application Note 77
discusses this noise reduction versus output ripple cur-
rent cancellation, but the output capacitance will be more
a function of stability and transient response. The Linear
Technology LTpowerCAD Design Tool will calculate the
outputripplereductionasthenumberphasesimplemented
increases by N times.
Pulse-Skipping Mode Operation
Inapplicationswherelowoutputrippleandhighefficiency
atintermediatecurrentsaredesired, pulse-skippingmode
should be used. Pulse-skipping operation allows the
LTM4608toskipcyclesatlowoutputloads,thusincreasing
efficiency by reducing switching loss. Floating the MODE
pin or tying it to V /2 enables pulse-skipping operation.
IN
Thisallowsdiscontinuousconductionmode(DCM)opera-
tion down to near the limit defined by the chip’s minimum
on-time (about 100ns). Below this output current level,
the converter will begin to skip cycles in order to main-
tain output regulation. Increasing the output load current
slightly, above the minimum required for discontinuous
conduction mode, allows constant frequency PWM.
4608fd
11
LTM4608
applicaTions inForMaTion
Table 3. Output Voltage Response Versus Component Matrix (Refer to Figure 18) 0A to 3A Load Step
TYPICAL MEASURED VALUES
C
VENDORS
VALUE
PART NUMBER
C
VENDORS
OUT2
VALUE
PART NUMBER
10TPD150M
PART NUMBER
10CE100FH
OUT1
TDK
22µF, 6.3V
22µF, 16V
100µF, 6.3V
100µF, 6.3V
C3216X7S0J226M
GRM31CR61C226KE15L
C4532X5R0J107MZ
GRM32ER60J107M
Sanyo POSCAP
150µF, 10V
Murata
TDK
C (BULK) VENDORS VALUE
IN
Sanyo
100µF, 10V
Murata
V
C
C
C
C
V
(V)
DROOP PEAK-TO- PEAK
RECOVERY
TIME (µs)
LOAD STEP
(A/µs)
R
FB
OUT
IN
IN
OUT1
OUT2
IN
(V)
1.0
1.0
1.0
1.0
1.0
1.0
1.2
1.2
1.2
1.2
1.2
1.2
1.5
1.5
1.5
1.5
1.5
1.5
1.8
1.8
1.8
1.8
1.8
1.8
2.5
2.5
2.5
2.5
3.3
3.3
(CERAMIC) (BULK)* (CERAMIC)
(BULK)
I
C1
C3
(mV)
13
17
13
17
13
17
16
20
16
20
16
16
18
20
16
20
18
20
22
21
21
21
22
21
28
33
30
21
38
39
DEVIATION (mV)
(kΩ)
14.7
14.7
14.7
14.7
14.7
14.7
10
TH
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
10µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 1
22µF × 1
100µF × 2
22µF × 1
100µF × 2
22µF × 1
100µF × 1
22µF × 1
100µF × 1
22µF × 1
100µF × 1
22µF × 1
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
None
100pF
None
68pF
None
100pF
None
100pF
None
100pF
None
100pF
None
100pF
None
None
None
47pF
None
47pF
None
None
None
47pF
None
47pF
None
None
None
None
None
None
None
None
5
26
34
26
34
26
34
32
41
32
41
32
32
36
41
32
41
36
41
42
42
43
41
44
42
42
60
60
41
74
75
7
3
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 2
150µF × 1
150µF × 1
150µF × 1
None
68pF
5
8
3
3.3
3.3
2.7
2.7
5
7
3
None
68pF
10
7
3
3
None
100pF
None
100pF
None
100pF
47pF
8
3
8
3
5
10
8
3
10
3.3
3.3
2.7
2.7
5
3
10
10
10
8
3
10
3
10
3
10
100pF
None
100pF
None
100pF
None
47pF
8
3
6.65
6.65
6.65
6.65
6.65
6.65
4.87
4.87
4.87
4.87
4.87
4.87
3.09
3.09
3.09
3.09
2.21
2.21
5
12
10
12
10
12
8
3
3.3
3.3
2.7
2.7
5
3
3
3
3
3
None
120pF
None
120pF
None
100pF
22pF
5
12
12
12
12
14
10
10
10
10
10
12
3
3.3
3.3
2.7
2.7
5
3
3
3
3
3
5
3
100pF
22pF
3.3
3.3
5
3
3
22pF
3
None
5
3
*Bulk capacitance is optional if V has very low input impedance.
IN
Forced Continuous Operation
throughout,andthetopMOSFETalwaysturnsonwitheach
oscillator pulse. During start-up, forced continuous mode
is disabled and inductor current is prevented from revers-
ing until the LTM4608’s output voltage is in regulation.
In applications where fixed frequency operation is more
critical than low current efficiency, and where the lowest
outputrippleisdesired,forcedcontinuousoperationshould
be used. Forced continuous operation can be enabled by
tying the MODE pin to GND. In this mode, inductor cur-
rent is allowed to reverse during low output loads, the I
voltage is in control of the current comparator threshold
Multiphase Operation
For output loads that demand more than 8A of current,
multiple LTM4608s can be cascaded to run out of phase to
TH
4608fd
12
LTM4608
applicaTions inForMaTion
provide more output current without increasing input and
output voltage ripple. The CLKIN pin allows the LTC4608
to synchronize to an external clock (between 0.75MHz
and 2.25MHz) and the internal phase-locked loop allows
the LTM4608 to lock onto CLKIN’s phase as well. The
CLKOUT signal can be connected to the CLKIN pin of the
following LTM4608 stage to line up both the frequency
and the phase of the entire system. Tying the PHMODE
which then can generate a CLKOUT signal that’s 420°,
or 60° (PHMODE = SV ) for the 4th stage. With the 60°
IN
CLKIN input, the next two stages can shift 120° (PHMODE
= 0) for each to generate a 300° signal for the 6th stage.
Finally, the signal with a 60° phase shift on the 6th stage
(PHMODE is floating) goes back to the 1st stage. Figure 3
shows the configuration for a 12 phase configuration
A multiphase power supply significantly reduces the
amount of ripple current in both the input and output
capacitors. The RMS input ripple current is reduced by,
and the effective ripple frequency is multiplied by, the
number of phases used (assuming that the input voltage
isgreaterthanthenumberofphasesusedtimestheoutput
voltage). The output ripple amplitude is also reduced by
the number of phases used.
pin to SV , SGND or SV /2 (floating) generates a phase
IN
IN
difference (between CLKIN and CLKOUT) of 180°, 120° or
90°respectively,whichcorrespondstoa2-phase,3-phase
or 4-phase operation. A total of 6 phases can be cascaded
to run simultaneously with respect to each other by pro-
gramming the PHMODE pin of each LTM4608 to different
levels. For a 6-phase example in Figure 2, the 2nd stage
that is 120° out of phase from the 1st stage can generate
a 240° (PHMODE = 0) CLKOUT signal for the 3rd stage,
(420)
60
0
120
240
180
300
+120
+120
+180
+120
+120
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
PHMODE
PHASE 1
PHMODE
PHASE 3
S
VIN
PHMODE
PHASE 5
PHMODE
PHASE 2
PHMODE
PHASE 4
PHMODE
PHASE 6
4608 F02
Figure 2. 6-Phase Operation
(420)
60
0
120
240
180
300
+120
+120
+180
+120
+120
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
PHMODE
PHASE 1
PHMODE
PHASE 5
S
VIN
PHMODE
PHASE 9
PHMODE
PHASE 3
PHMODE
PHASE 7
PHMODE
PHASE 11
4608 F02
+
V
OUT1
LTC6908-2
OUT2
(510)
150
(390)
30
90
210
330
270
+120
+120
+180
+120
+120
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
CLKIN CLKOUT
PHMODE
PHASE 4
PHMODE
PHASE 8
S
VIN
PHMODE
PHASE 12
PHMODE
PHASE 6
PHMODE
PHASE 10
PHMODE
PHASE 2
4608 F03
Figure 3. 12-Phase Operation
4608fd
13
LTM4608
applicaTions inForMaTion
The LTM4608 device is an inherently current mode con-
trolleddevice.Parallelmoduleswillhaveverygoodcurrent
sharing. This will balance the thermals on the design. Tie
Spread Spectrum Operation
Switching regulators can be particularly troublesome
where electromagnetic interference (EMI) is concerned.
the I pins of each LTM4608 together to share the current
TH
Switching regulators operate on a cycle-by-cycle basis to
transfer power to an output. In most cases, the frequency
ofoperationisfixedbasedontheoutputload.Thismethod
of conversion creates large components of noise at the
frequency of operation (fundamental) and multiples of the
operating frequency (harmonics).
evenly. To reduce ground potential noise, tie the I
pins
THM
of all LTM4608s together and then connect to the SGND at
onlyonepoint. Figure19showsaschematicoftheparallel
design.TheFBpinsoftheparallelmodulearetiedtogether.
With parallel operation, input and output capacitors may
be reduced in part according to the operating duty cycle.
To reduce this noise, the LTM4608 can run in spread
Input RMS Ripple Current Cancellation
spectrum operation by tying the CLKIN pin to SV .
IN
In spread spectrum operation, the LTM4608’s internal
oscillator is designed to produce a clock pulse whose
period is random on a cycle-by-cycle basis but fixed
between 70% and 130% of the nominal frequency. This
has the benefit of spreading the switching noise over
a range of frequencies, thus significantly reducing the
Application Note 77 provides a detailed explanation of
multiphase operation. The input RMS ripple current can-
cellation mathematical derivations are presented, and a
graph is displayed representing the RMS ripple current
reductionasafunctionofthenumberofinterleavedphases.
Figure 4 shows this graph.
0.60
1-PHASE
2-PHASE
3-PHASE
4-PHASE
6-PHASE
0.55
0.50
0.45
0.40
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9
DUTY FACTOR (V /V
)
IN
O
4608 F04
Figure 4. Normalized Input RMS Ripple Current vs Duty Factor for One to Six Modules (Phases)
4608fd
14
LTM4608
applicaTions inForMaTion
peak noise. Spread spectrum operation is disabled if
CLKIN is tied to ground or if it’s driven by an external
frequency synchronization signal. A capacitor value of
0.01µF must be placed from the PLLLPF pin to ground to
control the slew rate of the spread spectrum frequency
sameastheslaveregulator’sfeedbackdividertoimplement
coincident tracking. The LTM4608 uses an accurate 10k
resistor internally for the top feedback resistor. Figure 5
shows an example of coincident tracking:
10k
change. Add a control ramp on the TRACK pin with R
SR
Slave = 1+
• V
TRACK
and C referenced to V . Figure 21 shows an example
R
FB4
SR
IN
for spread spectrum operation.
V
V
is the track ramp applied to the slave’s track pin.
has a control range of 0V to 0.596V, or the internal
TRACK
TRACK
1
RSR
≥
SR
0.592
referencevoltage.Whenthemaster’soutputisdivideddown
withthesameresistorvaluesusedtosettheslave’soutput,
this resistor divider is connected to the slave’s track pin.
The slave will then coincident track with the master until it
reaches its final value. The master will continue to its final
value from the slave’s regulation point. Voltage tracking
− ln 1−
• 500 • C
V
IN
Output Voltage Tracking
Output voltage tracking can be programmed externally
using the TRACK pin. The output can be tracked up and
downwithanotherregulator.Themasterregulator’soutput
is divided down with an external resistor divider that is the
is disabled when V
Figure 5 will be equal to R for coincident tracking.
is more than 0.596V. R
in
TRACK
FB4
FB2
MASTER
3.3V
7A
CLKIN
V
IN
V
V
IN
OUT
FB
5V
C2
100µF
SV
IN
100pF
SW
TIE TO V
IN
LTM4608
C3
R
FB1
2.21k
FOR DISABLE
AND DEFAULT
RUN
RUN
I
TH
22pF
PLLLPF
TRACK
MODE
I
100µs SOFT-START
THM
TRACK
V
IN
PGOOD
R
C
SR
SR
50k
BSEL
MGN
PHMODE
APPLY A CONTROL
RAMP WITH R AND
CLKOUT GND SGND
SR
50k
C
TIED TO V WHERE
SR
IN
t = –(ln (1 – 0.596/V ) • R • C )
SR
IN
SR
OR APPLY AN EXTERNAL TRACKING RAMP
SLAVE
1.5V
8A
CLKIN
V
V
IN
OUT
+
C4
100µF
POSCAP
C1
100µF
SV
IN
SW
FB
MASTER
LTM4608
3.3V
R
FB2
6.65k
RUN
RUN
I
TH
R
FB3
PLLLPF
TRACK
MODE
I
THM
10k
V
TRACK
IN
PGOOD
BSEL
R
FB4
50k
6.65k
PHMODE
MGN
CLKOUT GND SGND
50k
4608 F05
Figure 5. Dual Outputs (3.3V and 1.5V) with Tracking
4608fd
15
LTM4608
applicaTions inForMaTion
Thetrackpinofthemastercanbecontrolledbyanexternal
ramp or by R and C in Figure 5 referenced to V . The
SR
SR
IN
RC ramp time can be programmed using equation:
MASTER OUTPUT
SLAVE OUTPUT
0.596V
t = –ln 1–
•R • CSR
SR
V
IN
Ratiometric tracking can be achieved by a few simple
calculations and the slew rate value applied to the mas-
ter’s track pin. As mentioned above, the TRACK pin has
a control range from 0V to 0.596V. The master’s TRACK
pin slew rate is directly equal to the master’s output slew
rate in Volts/Time:
TIME
4608 F06
Figure 6. Output Voltage Coincident Tracking
MR
SR
•10k = RFB3
For example: MR = 3.3V/ms and SR = 1.5V/ms. Then
where MR is the master’s output slew rate and SR is the
slave’s output slew rate in Volts/Time. When coincident
R
= 22.1k. Solve for R to equal to 4.87k.
FB3
FB4
Forapplicationsthatdonotrequiretrackingorsequencing,
tracking is desired, then MR and SR are equal, thus R
FB3
simply tie the TRACK pin to SV to let RUN control the
IN
is equal the 10k. R is derived from equation:
FB4
turn on/off. Connecting TRACK to SV also enables the
IN
0.596V
~100µs of internal soft-start during start-up. Load current
RFB4
=
VTRACK
V
V
FB
FB
needs to be present during track down.
+
–
10k RFB2
RFB3
Power Good
where V is the feedback voltage reference of the regula-
FB
The PGOOD pin is an open-drain pin that can be used to
monitor valid output voltage regulation. This pin monitors
a 10% window around the regulation point. As shown
in Figure 20, the sequencing function can be realized in a
dualoutputapplicationbycontrollingtheRUNpinsandthe
PGOOD signals from each other. The 1.5V output begins
its soft starting after the PGOOD signal of 3.3V output
becomes high, and 3.3V output starts its shutdown after
the PGOOD signal of 1.5V output becomes low. This can
be applied to systems that require voltage sequencing
between the core and sub-power supplies.
tor and V
is 0.596V. Since R is equal to the 10k
TRACK
FB3
top feedback resistor of the slave regulator in equal slew
rate or coincident tracking, then R is equal to R with
FB4
FB2
V
= V
. Therefore R = 10k and R = 6.65k in
TRACK FB3 FB4
FB
Figure 5.
Inratiometrictracking, adifferentslewratemaybedesired
for the slave regulator. R can be solved for when SR
FB3
is slower than MR. Make sure that the slave supply slew
rate is chosen to be fast enough so that the slave output
voltage will reach it final value before the master output.
4608fd
16
LTM4608
applicaTions inForMaTion
Slope Compensation
determined by the BSEL pin. When BSEL is low, it is 5%.
When BSEL is high, it is 10%. When BSEL is floating,
it is 15%. When margining is active, the internal output
overvoltage and undervoltage comparators are disabled
and PGOOD remains high. Margining is disabled by tying
the MGN pin to a voltage divider as shown in Figure 20.
The module has already been internally compensated for
alloutputvoltages.Table3isprovidedformostapplication
requirements. A spice model will be provided for other
control loop optimization. For single module operation,
connect I
pin to SGND. For parallel operation, tie I
THM
THM
pins together and then connect to SGND at one point. Tie
Thermal Considerations and Output Current Derating
I
TH
pins together to share currents evenly for all phases.
The power loss curves in Figures 7 and 8 can be used
in coordination with the load current derating curves in
Output Margining
Figures 9 to 16 for calculating an approximate θ for the
JA
For a convenient system stress test on the LTM4608’s
output, the user can program the LTM4608’s output to
5%, 10% or 15% of its normal operational voltage.
The margin pin with a voltage divider is driven with a
small three-state gate as shown in Figure 18, for the three
margin states (high, low, no margin). When the MGN
pin is <0.3V, it forces negative margining in which the
output voltage is below the regulation point. When MGN is
modulewithvariousheatsinkingmethods.Thermalmodels
are derived from several temperature measurements at
the bench, and thermal modeling analysis. Thermal Ap-
plication Note 103 provides a detailed explanation of the
analysis for the thermal models and the derating curves.
Tables 4 and 5 provide a summary of the equivalent θ
JA
for the noted conditions. These equivalent θ parameters
JA
are correlated to the measured values and improve with
air flow. The junction temperature is maintained at 125°C
or below for the derating curves.
>V – 0.3V, the output voltage is forced above the regu-
IN
lation point. The amount of output voltage margining is
4.0
3.5
3.0
2.5
2.0
1.5
1.0
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.5
5V 1.5V
3.3V 1.5V
IN
OUT
OUT
IN
OUT
OUT
5V 3.3V
IN
3.3V 2.5V
IN
0
0
4
0
2
6
8
4
0
2
6
8
LOAD CURRENT (A)
LOAD CURRENT (A)
4608 F08
4608 F07
Figure 7. 3.3VIN, 2.5V and 1.5VOUT Power Loss
Figure 8. 5VIN, 3.3V and 1.5VOUT Power Loss
4608fd
17
LTM4608
applicaTions inForMaTion
9
8
7
6
5
4
3
9
8
7
6
5
4
3
2
1
0
2
400LFM
200LFM
0LFM
400LFM
200LFM
0LFM
1
0
80 90
80 90
40 50 60 70
100 110 120
40 50 60 70
100 110 120
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
4608 F09
4608 F10
Figure 9. No Heat Sink with 3.3VIN to 1.5VOUT
Figure 10. BGA Heat Sink with 3.3VIN to 1.5VOUT
9
8
7
6
5
4
3
9
8
7
6
5
4
3
2
2
400LFM
200LFM
0LFM
400LFM
200LFM
0LFM
1
0
1
0
80 90
80 90
40 50 60 70
100 110 120
40 50 60 70
100 110 120
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
4608 F11
4608 F12
Figure 11. No Heat Sink with 5VIN to 1.5VOUT
Figure 12. BGA Heat Sink with 5VIN to 1.5VOUT
9
8
7
6
5
4
3
9
8
7
6
5
4
3
2
2
400LFM
200LFM
0LFM
400LFM
200LFM
0LFM
1
0
1
0
80 90
40 50 60 70 80 90 100 110 120
AMBIENT TEMPERATURE (°C)
4608 F14
40 50 60 70
100 110 120
AMBIENT TEMPERATURE (°C)
4608 F13
Figure 13. No Heat Sink with 3.3VIN to 2.5VOUT
Figure 14. BGA Heat Sink with 3.3VIN to 2.5VOUT
4608fd
18
LTM4608
applicaTions inForMaTion
9
8
7
6
5
4
3
9
8
7
6
5
4
3
2
1
0
2
400LFM
400LFM
200LFM
0LFM
1
200LFM
0LFM
0
80 90
40 50 60 70
AMBIENT TEMPERATURE (°C)
100 110 120
80 90
40 50 60 70
100 110 120
AMBIENT TEMPERATURE (°C)
4608 F15
4608 F16
Figure 16. BGA Heat Sink with 5VIN to 3.3VOUT
Figure 15. No Heat Sink with 5VIN to 3.3VOUT
Table 4. 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
Figures 7, 8
AIR FLOW (LFM)
HEAT SINK
None
θ
JA
(°C/W)
25
IN
3.3, 5
3.3, 5
3.3, 5
3.3, 5
3.3, 5
3.3, 5
0
Figures 7, 8
200
400
0
None
21
Figures 7, 8
None
20
Figures 7, 8
BGA Heat Sink
BGA Heat Sink
BGA Heat Sink
23.5
22
Figures 7, 8
200
400
Figures 7, 8
22
Table 5. 3.3V Output
DERATING CURVE
Figure 15
V
(V)
POWER LOSS CURVE
Figure 8
AIR FLOW (LFM)
HEAT SINK
None
θ
(°C/W)
IN
JA
5
0
25
21
Figure 15
5
5
5
5
5
Figure 8
200
400
0
None
Figure 15
Figure 8
None
20
Figure 16
Figure 8
BGA Heat Sink
BGA Heat Sink
BGA Heat Sink
23.5
22
Figure 16
Figure 8
200
400
Figure 16
Figure 8
22
4608fd
19
LTM4608
applicaTions inForMaTion
Safety Considerations
•ꢀ Placeꢀhighꢀfrequencyꢀceramicꢀinputꢀandꢀoutputꢀcapaci-
tors next to the V , GND and V
pins to minimize
IN
OUT
The LTM4608 modules do not provide isolation from V
IN
high frequency noise.
to V . There is no internal fuse. If required, a slow blow
OUT
fuse with a rating twice the maximum input current needs
tobeprovidedtoprotecteachunitfromcatastrophicfailure.
•ꢀ Placeꢀaꢀdedicatedꢀpowerꢀgroundꢀlayerꢀunderneathꢀtheꢀ
unit.
•ꢀ Toꢀminimizeꢀtheꢀviaꢀconductionꢀlossꢀandꢀreduceꢀmoduleꢀ
thermal stress, use multiple vias for interconnection
between top layer and other power layers.
Layout Checklist/Example
The high integration of LTM4608 makes the PCB board
layout very simple and easy. However, to optimize its
electrical and thermal performance, some layout consid-
erations are still necessary.
•ꢀ Doꢀnotꢀputꢀviasꢀdirectlyꢀonꢀtheꢀpads,ꢀunlessꢀtheyꢀareꢀ
capped.
•ꢀ UseꢀaꢀseparatedꢀSGNDꢀgroundꢀcopperꢀareaꢀforꢀcom-
ponents connected to signal pins. Connect the SGND
to GND underneath the unit.
•ꢀ Useꢀ largeꢀ PCBꢀ copperꢀ areasꢀ forꢀ highꢀ currentꢀ path,ꢀ
including V , GND and V . It helps to minimize the
IN
OUT
PCB conduction loss and thermal stress.
Figure17givesagoodexampleoftherecommendedlayout.
GND
V
OUT
C
OUT
OUT
OUT
C
GND
C
C
IN
V
IN
C
IN
GND
4608 F17
Figure 17. Recommended PCB Layout
For easier board layout and PCB assembly due to increased
spacing between land grid pads, please refer to the LTM4608A.
4608fd
20
LTM4608
Typical applicaTions
CLKIN
CLKIN
V
2.5V
8A
8A AT 5V INPUT
6A AT 3.3V INPUT
OUT
V
IN
V
V
I
IN
OUT
3V TO 5.5V
C
C1
C
OUT
IN
SV
IN
10µF
220pF
100µF
SW
FB
LTM4608
C3
47pF
R
V
IN
FB
3.09k
RUN
I
TH
PLLLPF
TRACK
MODE
100k
THM
PGOOD
PGOOD
V
(HIGH = 10%)
(FLOAT = 15%)
(LOW = 5%)
BSEL
50k
IN
BSEL
MGN
MODE
PHMODE
OE
PHMODE
1
50k
5
Y
OUT
2
4
CLKOUT GND SGND
U1
A
IN
U1: PERICOM PI74ST1G126CEX
OR TOSHIBA TC7SZ126AFE
3
4608 F18
OE
A
Y
MGN
MARGIN VALUE
IN OUT
H
H
L
H
H
L
Z
H
L
IN
+ OF BSEL SELECTION
– OF BSEL SELECTION
NO MARGIN
L
X
V
/2
Figure 18. Typical 3V to 5.5VIN, 2.5V at 8A Design
V
1.5V
16A
OUT
CLKIN
V
IN
V
V
IN
OUT
3V TO 5.5V
C4
100pF
100µF
6.3V
X5R
10µF
SV
IN
SW
FB
LTM4608
3.32k
RUN
RUN
I
TH
PLLLPF
TRACK
MODE
I
THM
TRACK
PGOOD
BSEL
C3
V
IN
PHMODE
MGN
100µF
6.3V
X5R
CLKOUT GND SGND
50k
50k
CLKIN
V
IN
V
OUT
C2
10µF
C1
SV
IN
100µF
6.3V
X5R
SW
FB
LTM4608
RUN
I
TH
PLLLPF
TRACK
MODE
I
THM
PGOOD
BSEL
PHMODE
MGN
CLKOUT GND SGND
4608 F19
Figure 19. Two LTM4608s in Parallel, 1.5V at 16A Design.
See Also Dual 8A per Channel LTM4616
4608fd
21
LTM4608
Typical applicaTions
CLKIN
CLKIN
V
3.3V
7A
OUT2
V
IN
V
V
IN
OUT
5V
100µF
6.3V
X5R
C2
SV
IN
100pF
D1
MMSD4148
SW
FB
LTM4608
R
C3
22pF
FB1
2.21k
SHDN
RUN
I
TH
PLLLPF
TRACK
MODE
I
THM
100k
PGOOD
BSEL
V
IN
SHDN
3.3V
50k
50k
PHMODE
MGN
CLKOUT GND SGND
R1
100k
R2
100k
1.5V
V
1.5V
8A
OUT1
CLKIN
V
V
IN
OUT
C1
C4
+
SV
FB
IN
100µF
6.3V
X5R
100µF
SANYO
POSCAP
10mΩ
D2
R
FB2
MMSD4148
SW
I
TH
6.65k
LTM4608
SHDN
RUN
I
THM
PLLLPF
TRACK
MODE
100k
PGOOD
BSEL
PHMODE
MGN
CLKOUT GND SGND
4608 F20
Figure 20. Dual LTM4608 Output Sequencing Application
See Also Dual 8A per Channel LTM4616
SV
IN
V
OUT
CLKIN
V
1.2V/8A
5A AT
IN
V
V
IN
OUT
2.7V TO 5.5V
C2
C1
10µF
100pF
2.7V INPUT
SV
IN
100µF
6.3V
X5R
100µF
6.3V
X5R
R
SR
SW
FB
LTM4608
180k
10k
RUN
I
TH
PLLLPF
TRACK
MODE
I
THM
V
IN
PGOOD
BSEL
PGOOD
BSEL
0.01µF
C
SR
MODE
PHMODE
50k
0.22µF
PHMODE
MGN
CLKOUT GND SGND
50k
4608 F21
Figure 21. 2.7V to 5.5VIN, 1.2VOUT Design in Spread Spectrum Operation
4608fd
22
LTM4608
Typical applicaTions
4608fd
23
LTM4608
package DescripTion
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
Z
b b b
Z
6 . 3 5 0
5 . 0 8 0
3 . 8 1 0
2 . 5 4 0
1 . 2 7 0
0 . 3 8 1
0 . 0 0 0
0 . 3 8 1
1 . 2 7 0
2 . 5 4 0
3 . 8 1 0
5 . 0 8 0
6 . 3 5 0
a a a
Z
4608fd
24
LTM4608
revision hisTory (Revision history begins at Rev B)
REV
DATE
DESCRIPTION
PAGE NUMBER
B
12/10 Voltage changed in the Typical Application drawing.
Note added to the Absolute Maximum Ratings section.
Note 2 added to the Electrical Characteristics section.
Replaced graphs G05 and G06 in the Typical Performance Characteristics section.
Updated MGN (B8) in the Pin Functions section.
Changes made to Figure 1.
1
2
2, 3, 4
5
7
9
Text changes made to the Applications Information section.
Changes made to Figure 5.
11, 14, 19
15
Note added to Figure 17.
20
Changes made to Figures 18, 21, 22.
21, 22, 23
Updated the Related Parts table.
26
8
C
D
3/11
3/12
Removed Pin Configuration drawing from Pin Functions
Added value of 0.22µH to Inductor in Figure 1
Updated Figure 3
9
13
1
Revised the Typical Application circuit.
Changed the format of the Pin Assignment Table.
26
4608fd
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
25
LTM4608
package DescripTion
Pin Assignment Table
(Arranged by Pin Number)
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
PIN
NAME FUNCTION NAME FUNCTION NAME FUNCTION NAME FUNCTION NAME FUNCTION NAME FUNCTION NAME FUNCTION
A1
A2
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
B1
B2
GND
–
C1
C2
V
D1
D2
V
E1
E2
SGND
F1
F2
RUN
CLKOUT
GND
G1
G2
GND
GND
GND
GND
GND
GND
GND
GND
IN
IN
–
–
–
PLLLPF
–
A3
B3
CLKIN
PHMODE
MODE
–
C3
SW
SW
D3
V
V
V
E3
F3
G3
IN
IN
IN
A4
B4
C4
D4
E4
F4
SV
G4
IN
A5
B5
C5
SW
D5
E5
TRACK
–
F5
I
G5
THM
A6
B6
C6
–
D6
–
E6
F6
I
G6
TH
A7
B7
BSEL
MGN
GND
GND
GND
C7
PGOOD
D7
V
V
V
E7
FB
F7
GND
GND
G7
IN
IN
IN
A8
B8
C8
V
V
D8
E8
V
F8
G8
IN
IN
IN
A9
B9
C9
D9
E9
V
V
V
F9
V
V
V
G9
V
OUT
V
OUT
V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
A10
A11
B10
B11
C10
C11
V
V
D10
D11
V
V
E10
E11
F10
F11
G10
G11
OUT
OUT
OUT
OUT
relaTeD parTs
PART NUMBER DESCRIPTION
COMMENTS
Monitors Four Supplies; Adjustable Reset Timer
LTC2900
LTC2923
Quad Supply Monitor with Adjustable Reset Timer
Power Supply Tracking Controller
Tracks Both Up and Down; Power Supply Sequencing
LT3825/LT3837 Synchronous Isolated Flyback Controllers
No Optocoupler Required; 3.3V, 12A Output; Simple Design
LTM4616
LTM4628
Low V Dual 8A DC/DC Step-Down µModule Regulator
2.7V ≤ V ≤ 5.5V, 0.6V ≤ V
≤ 5V, 15mm × 15mm × 2.82mm LGA Package
OUT
IN
IN
Dual 8A, 26V, DC/DC Step-Down µModule Regulator
4.5V ≤ V ≤ 26.5V, 0.6V ≤ V
≤ 5.5V, Remote Sense Amplifier, Internal
IN
OUT
Temperature Sensing Output, 15mm × 15mm × 4.32mm LGA Package
LTM4601/
LTM4601A
12A DC/DC µModule Regulator with PLL, Output
Tracking/ Margining and Remote Sensing
Synchronizable, PolyPhase Operation, LTM4601-1/LTM4601A-1 Version Has
No Remote Sensing, LGA and BGA Packages
LTM4602
LTM4618
6A DC/DC µModule Regulator
Pin Compatible with the LTM4600, LGA Package
Synchronizable, PolyPhase Operation
6A DC/DC µModule Regulator with PLL and Outpupt
Tracking/Margining and Remote Sensing
LTM4604A
Low V 4A DC/DC µModule Regulator
2.375V ≤ V ≤ 5.5V, 0.8V ≤ V
≤ 5V, 9mm × 15mm × 2.32mm LGA Package
OUT
IN
IN
4608fd
LT 0312 REV D • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
26
l
l
LINEAR TECHNOLOGY CORPORATION 2007
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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