Linear Technology LTM4612 User manual

LTM4612
1
4612fc
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TYPICAL APPLICATION
FEATURES
APPLICATIONS
DESCRIPTION
EN55022B Compliant
36VIN, 15VOUT, 5A,
DC/DC
µ Module Regulator
The LT M
®
4612 is a EN55022 Class B certified high voltage
inputandoutput,5AswitchingmodeDC/DCpowersupply.
Includedin the package are the switching controller,power
FETs, inductor and all support components. Operating
over an input voltage range of 5V to 36V, the LTM4612
supports an output voltage range of 3.3V to 15V, set by a
single resistor. Only bulk input and output capacitors are
needed to finish the design.
High switching frequency and an adaptive on-time current
mode architecture enables a very fast transient response
to line and load changes without sacrificing stability.
The onboard input filter and noise cancellation circuits
achieve low noise coupling, thus effectively reducing the
electromagnetic interference (EMI)—see Figures 4 and 8.
Furthermore, the DC/DC µModule
®
regulator can be syn-
chronized with an external clock to reduce undesirable
frequency harmonics and allow PolyPhase
®
operation for
high load currents.
The LTM4612 is offered in a space saving and thermally
enhanced 15mm ×15mm ×2.8mm LGA package, which
enables utilization of unused space on the bottom of PC
boards for high density point-of-load regulation. The
LTM4612 is Pb-free and RoHS compliant.
L, LT, LTC, LTM, Linear Technology, the Linear logo, PolyPhase and µModule are registered
trademarks and LTpowerCAD is a trademark of Linear Technology Corporation. All other
trademarks are the property of their respective owners.
5V/5A Ultralow Noise µModule with 7V to 36V Input
nComplete Low EMI Switch Mode Power Supply
nEN55022 Class B Compliant
nWide Input Voltage Range: 5V to 36V
n3.3V to 15V Output Voltage Range
n5A DC, 7A Peak Output Current
nLow Input and Output Referred Noise
nOutput Voltage Tracking and Margining
nPower Good Tracks with Margining
nPLL Frequency Synchronization
n±1.5% Set Point Accuracy
nCurrent Foldback Protection (Disabled at Start-Up)
nParallel/Current Sharing
nUltrafast Transient Response
nCurrent Mode Control
nProgrammable Soft-Start
nOutput Overvoltage Protection
n–55°C to 125°C Operating Temperature Range
(LTM4612MPV)
nSmall Surface Mount Footprint, Low Profile
(15mm ×15mm ×2.8mm) LGA Package
nTelecom and Networking Equipment
nIndustrial and Avionic Equipment
nRF Systems
Radiated Emission Scan at 24VIN, 5VOUT/5A
FREQUENCY (MHz)
30
dBµV/m
30
70
128.1
226.2
324.3
10
60
20
0
–10
50
40
422.4
520.5
618.6
716.7
814.8
912.9
1010
EN55022 CLASS B LIMIT
4612 TA01b
PGOOD
RUN
COMP
INTVCC
DRVCC
fSET
TRACK/SS
FCB
MARG0
MARG1
MPGM
VOUT
VFB
VIN
0.01µF
10µF
100pF COUT
VOUT
5V
5A
CIN
VIN
7V
TO 36V PLLIN
CLOCK SYNC
LTM4612
SGND
VD
PGND
MARGIN
CONTROL
100k
2M
13.7k
392k
5% MARGIN
4612 TA01

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PIN CONFIGURATIONABSOLUTE MAXIMUM RATINGS
INTVCC, DRVCC............................................. –0.3V to 6V
VOUT........................................................... –0.3V to 16V
PLLIN, FCB, TRACK/SS, MPGM, MARG0,
MARG1, PGOOD ....................–0.3V to INTVCC + 0.3V
RUN ............................................................. –0.3V to 5V
VFB, COMP ................................................ –0.3V to 2.7V
VIN, VD....................................................... –0.3V to 36V
Internal Operating Temperature Range (Note 2)
E and I Grades ................................... –40°C to 125°C
MP Grade........................................... –55°C to 125°C
Junction Temperature ........................................... 125°C
Storage Temperature Range .................. –55°C to 125°C
(Note 1)
MARG1
DRVCC
VFB
PGOOD
SGND
NC
NC
NC
FCB
VIN
BANK 1 VD
PGND
BANK 2
VOUT
BANK 3
fSET
MARG0
RUN COMP MPGM PLLIN INTVCC TRACK/SS
LGA PACKAGE
133-LEAD (15mm × 15mm × 2.8mm)
TOP VIEW
SGND
1221 43 5 6 98 10 117
A
B
C
D
E
F
G
H
J
K
L
M
TJMAX = 125°C, θJA = 15°C/W, θJC = 6°C/W
θJA DERIVED FROM 95mm ×76mm PCB WITH 4 LAYERS
WEIGHT = 1.7g
ORDER INFORMATION
LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTM4612EV#PBF LTM4612EV#PBF LTM4612V 133-Lead (15mm ×15mm ×2.8mm) LGA –40°C to 125°C
LTM4612IV#PBF LTM4612IV#PBF LTM4612V 133-Lead (15mm ×15mm ×2.8mm) LGA –40°C to 125°C
LTM4612MPV#PBF LTM4612MPV#PBF LTM4612MPV 133-Lead (15mm ×15mm ×2.8mm) LGA –55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://www.linear.com/packaging/
ELECTRICAL CHARACTERISTICS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN(DC) Input DC Voltage l5 36 V
VOUT(DC) Output Voltage CIN = 10µF ×3, COUT = 300µF; FCB = 0
VIN = 24V, VOUT = 12V, IOUT = 0A
VIN = 36V, VOUT=12V, IOUT = 0A
l
l
11.83
11.83
12.07
12.07
12.31
12.31
V
V
Input Specifications
VIN(UVLO) Undervoltage Lockout Threshold IOUT = 0A 3.2 4.8 V
IINRUSH(VIN) Input Inrush Current at Start-Up IOUT = 0A; CIN = 10µF ×2, COUT = 200µF;
VOUT = 12V
VIN = 24V
VIN = 36V
0.6
0.7
A
A
The ldenotes the specifications which apply over the specified internal
operating temperature range, otherwise specifications are at TA= 25°C, VIN = 24V, unless otherwise noted (Note 2). Per Typical
Application (front page) configuration.
http://www.linear.com/product/LTM4612#orderinfo

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ELECTRICAL CHARACTERISTICS
The ldenotes the specifications which apply over the specified internal
operating temperature range, otherwise specifications are at TA= 25°C, VIN = 24V, unless otherwise noted (Note 2). Per Typical
Application (front page) configuration.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
IQ(VIN) Input Supply Bias Current VIN = 36V, VOUT = 12V, Switching Continuous
VIN = 24V, VOUT = 12V, Switching Continuous
Shutdown, RUN = 0, VIN = 36V
57
48
50
mA
mA
µA
IS(VIN) Input Supply Current VIN = 36V, VOUT = 12V, IOUT = 5A
VIN = 24V, VOUT = 12V, IOUT = 5A
1.85
2.72
A
A
VINTVCC Internal VCC Voltage VIN = 36V, RUN > 2V, IOUT = 0A 4.7 5 5.5 V
Output Specifications
IOUT(DC) Output Continuous Current Range VIN = 24V, VOUT = 12V (Note 4) 0 5 A
DVOUT(LINE)
VOUT
Line Regulation Accuracy VOUT = 12V, FCB = 0V, VIN = 22V to 36V,
IOUT = 0A
l
0.05 0.3 %
DVOUT(LOAD)
VOUT
Load Regulation Accuracy VOUT = 12V, FCB = 0V, IOUT = 0A to 5A (Note 4)
VIN = 36V
VIN = 24V
l
l
0.3
0.3
0.6
0.6
%
%
VIN(AC) Input Ripple Voltage IOUT = 0A,
CIN = 2 ×10µF X5R Ceramic and 1 ×100µF
Electrolytic, 1 ×10µF X5R Ceramic on VDPins
VIN = 24V, VOUT = 5V
VIN = 24V, VOUT = 12V
7.2
3.4
mVP-P
mVP-P
VOUT(AC) Output Ripple Voltage IOUT = 0A,
COUT = 2 ×22µF, 2 ×47µF X5R Ceramic
VIN = 24V, VOUT = 5V
VIN = 24V, VOUT = 12V
17.5
12.5
mVP-P
mVP-P
fSOutput Ripple Voltage Frequency IOUT = 1A, VIN = 24V, VOUT = 12V 940 kHz
DVOUT(START) Turn-On Overshoot,
TRACK/SS = 10nF
COUT = 200µF, VOUT = 12V, IOUT = 0A
VIN = 36V
VIN = 24V
20
20
mV
mV
tSTART Turn-On Time, TRACK/SS = Open COUT = 300µF, VOUT = 12V, IOUT = 1A
Resistive Load
VIN = 36V
VIN = 24V
0.5
0.5
ms
ms
DVOUT(LS) Peak Deviation for Dynamic Load Load: 0% to 50% to 0% of Full Load
COUT = 2 ×22µF Ceramic, 150µF Bulk
VIN = 24V, VOUT = 12V
153 mV
tSETTLE Settling Time for Dynamic Load Step Load: 0% to 50% to 0% of Full Load, VIN = 24V 37 µs
IOUT(PK) Output Current Limit COUT = 200µF
VIN = 36V, VOUT = 12V
VIN = 24V, VOUT = 12V
9
9
A
A
Control Section
VFB Voltage at VFB Pin IOUT = 0A, VOUT = 12V l0.591 0.6 0.609 V
VRUN RUN Pin On/Off Threshold 1 1.5 1.9 V
ISS / TRACK Soft-Start Charging Current VSS/TRACK = 0V –1 –1.5 –2 µA
VFCB Forced Continuous Threshold 0.57 0.6 0.63 V
IFCB Forced Continuous Pin Current VFCB = 0V –1 –2 µA
tON(MIN) Minimum On-Time (Note 3) 50 100 ns
tOFF(MIN) Minimum Off-Time (Note 3) 250 400 ns
RPLLIN PLLIN Input Resistor 50 kW

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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 LTM4612E is guaranteed to meet performance specifications
over the 0°C to 125°C internal operating temperature range. Specifications
over the –40°C to 125°C internal operating temperature range are assured
by design, characterization and correlation with statistical process
controls. The LTM4612I is guaranteed to meet specifications over the
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
IDRVCC Current into DRVCC Pin VOUT = 12V, IOUT = 1A 22 30 mA
RFBHI Resistor Between VOUT and VFB Pins 99.5 100 100.5 kW
VMPGM Margin Reference Voltage 1.18 V
VMARG0, VMARG1 MARG0, MARG1 Voltage Thresholds 1.4 V
PGOOD
DVFBH PGOOD Upper Threshold VFB Rising 7 10 13 %
DVFBL PGOOD Lower Threshold VFB Falling –7 –10 –13 %
DVFB(HYS) PGOOD Hysteresis VFB Returning 1.5 %
VPGL PGOOD Low Voltage IPGOOD = 5mA 0.15 0.4 V
ELECTRICAL CHARACTERISTICS
The ldenotes the specifications which apply over the specified internal
operating temperature range, otherwise specifications are at TA= 25°C, VIN = 24V, unless otherwise noted (Note 2). Per Typical
Application (front page) configuration.
–40°C to 125°C internal operating temperature range. The LTM4612MP
is guaranteed and tested over the full –55°C to 125°C internal operating
temperature range. Note that the maximum ambient temperature
consistent with these specifications is determined by specific operating
conditions in conjunction with board layout, the rated package thermal
resistance and other environmental factors.
Note 3: 100% tested at die level only.
Note 4: See the Output Current Derating curves for different VIN, VOUT
and TA.

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TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current with
3.3VOUT (FCB = 0)
Efficiency vs Load Current with
5VOUT (FCB = 0)
Efficiency vs Load Current with
12VOUT (FCB = 0)
Efficiency vs Load Current with
15VOUT (FCB = 0, Refer to Figure 20)
Transient Response from 12VIN
to 3.3VOUT
Transient Response from 12VIN
to 5VOUT
Transient Response from 24VIN
to 12VOUT
Start-Up with 24VIN to 12VOUT
at IOUT = 0A
Start-Up with 24VIN to 12VOUT at
IOUT = 5A
(Refer to Figure 18)
LOAD CURRENT (A)
0
EFFICIENCY (%)
70
95
100
123
60
85
65
90
55
50
80
75
45
4612 G01
5VIN 3.3VOUT
12VIN 3.3VOUT
24VIN 3.3VOUT
36VIN 3.3VOUT
LOAD CURRENT (A)
0
EFFICIENCY (%)
70
95
123
60
85
65
90
55
50
80
75
45
4612 G02
12VIN 5VOUT
24VIN 5VOUT
36VIN 5VOUT
LOAD CURRENT (A)
0
EFFICIENCY (%)
70
95
100
123
60
85
65
90
55
50
80
75
45
4612 G03
20VIN 12VOUT
24VIN 12VOUT
28VIN 12VOUT
36VIN 12VOUT
LOAD CURRENT (A)
0
EFFICIENCY (%)
70
100
95
123
60
85
65
90
80
75
45
4612 G04
28VIN 15VOUT
32VIN 15VOUT
36VIN 15VOUT
50µs/DIV
2A/DIV
100mV/DIV
4612 G05
LOAD STEP: 0A to 3A
COUT = 2 ×22µF CERAMIC CAPACITORS AND
2 ×47µF CERAMIC CAPACITORS
50µs/DIV
2A/DIV
100mV/DIV
4612 G06
LOAD STEP: 0A to 3A
COUT = 2 ×22µF CERAMIC CAPACITORS AND
2 ×47µF CERAMIC CAPACITORS
50µs/DIV
2A/DIV
200mV/
DIV
4612 G07
LOAD STEP: 0A to 3A
COUT = 2 ×22µF CERAMIC CAPACITORS AND
2 ×47µF CERAMIC CAPACITORS
500µs/DIV
IIN
0.2A/DIV
VOUT
5V/DIV
4612 G08
SOFT-START CAPACITOR: 3.9nF
CIN = 3 ×10µF CERAMIC CAPACITORS AND
1 ×47µF OSCON CAPACITOR
500µs/DIV
IIN
1A/DIV
VOUT
5V/DIV
4612 G09
SOFT-START CAPACITOR: 3.9nF
CIN = 3 ×10µF CERAMIC CAPACITORS AND
1 ×47µF OSCON CAPACITOR

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TYPICAL PERFORMANCE CHARACTERISTICS
Start-Up with 24VIN to 12VOUT at
IOUT = 5A, TA= –55°C
Short-Circuit with 24VIN to 12VOUT
at IOUT = 0A
Short-Circuit with 24VIN to 12VOUT
at IOUT = 5A
VIN to VOUT Step-Down Ratio
Input Ripple Output Ripple
500µs/DIV
IIN
1A/DIV
VOUT
5V/DIV
4612 G10
SOFT-START CAPACITOR: 3.9nF
CIN = 3 ×10µF CERAMIC CAPACITORS AND
1 ×47µF OSCON CAPACITOR
50µs/DIV
IIN
0.2A/DIV
VOUT
5V/DIV
4612 G11
COUT = 2 ×22µF CERAMIC CAPACITORS AND
2 ×47µF CERAMIC CAPACITORS
20µs/DIV
IIN
2A/DIV
VOUT
5V/DIV
4612 G12
COUT = 2 ×22µF CERAMIC CAPACITORS AND
2 ×47µF CERAMIC CAPACITORS
3.3
24
30
18
12
6 10
4
8 12 14 15
6
0
36
4612 G13
SEE FREQUENCY ADJUSTMENT SECTION
FOR OPERATIONS OUTSIDE THIS REGION
OPERATING REGION
WITH DEFAULT FREQUENCY
VOUT (V)
V
IN
(V)
1µs/DIV
50mV/DIV
4612 G14
VIN = 24V
VOUT = 12V AT 5A RESISTIVE LOAD
CIN = 3 ×10µF 50V CERAMIC 1 ×100µF BULK
1µs/DIV
10mV/DIV
4612 G15
VIN = 24V
VOUT = 12V AT 5A RESISTIVE LOAD
COUT = 2 ×22µF 16V CERAMIC AND
2 ×47µF 16V CERAMIC

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PIN FUNCTIONS
VIN (Bank 1): Power Input Pins. Apply input voltage be-
tween these pins and PGND pins. Recommend placing
input decoupling capacitance directly between VIN pins
and PGND pins.
PGND (Bank 2): Power Ground Pins for Both Input and
Output Returns.
VOUT (Bank 3): Power Output Pins. Apply output load
betweenthesepinsandPGNDpins.Recommendplacingout-
put decoupling capacitance directly between these pins and
GND pins (see the L
TM4612 Pin Configuration below).
VD(Pins B7, C7): Top FET Drain Pins. Add more capa-
citors between VDand ground to handle the input RMS
current and reduce the input ripple further.
DRVCC (Pins C10, E11, E12): These pins normally connect
to INTVCC for powering the internal MOSFET drivers. They
can be biased up to 6V from an external supply with about
50mA capability. This improves efficiency at higher input
voltages by reducing power dissipation in the module.
INTVCC (Pin A7): This pin is for additional decoupling of
the 5V internal regulator.
PLLIN(PinA8):ExternalClock Synchronization Inputtothe
Phase Detector. This pin is internally terminated to SGND
with a 50k resistor. Apply a clock above 2V and below
INTVCC. See the Applications Information section.
FCB (Pin M12): Forced Continuous Input. Connect this pin
to SGND to force continuous synchronization operation at
low load, to INTVCC to enable discontinuous mode opera-
tion at low load or to a resistive divider from a secondary
output when using a secondary winding.
TRACK/SS(PinA9):OutputVoltageTrackingand Soft-Start
Pin. When the module is configured as a master output,
then a soft-start capacitor is placed on this pin to ground
to control the master ramp rate. A soft-start capacitor can
be used for soft-start turn-on as a standalone regulator.
Slave operation is performed by putting a resistor divider
from the master output to the ground, and connecting the
center point of the divider to this pin. See the Applications
Information section.
MPGM (Pins A12, B11): Programmable Margining In-
put. A resistor from these pins to ground sets a current
that is equal to 1.18V/R. This current multiplied by 10k
will equal a value in millivolts that is a percentage of the
0.6V reference voltage. May be left open if margining is
not desired. See the Applications Information section. To
parallel LTM4612s, each requires an individual MPGM
resistor. Do not tie MPGM pins together.
fSET (Pin B12): Frequency Set Internally to ~850kHz to
900kHz at 12V Output. An external resistor can be placed
from this pin to ground to increase frequency. See the
ApplicationsInformationsectionforfrequency adjustment.
LTM4612 Pin Configuration
(See Package Description for Pin Assignments)
MARG1
DRVCC
VFB
PGOOD
SGND
NC
NC
NC
FCB
VIN
BANK 1 VD
PGND
BANK 2
VOUT
BANK 3
fSET
MARG0
RUN COMP MPGM PLLIN INTVCC TRACK/SS
LGA PACKAGE
133-LEAD (15mm × 15mm × 2.8mm)
TOP VIEW
SGND
1221 43 5 6 98 10 117
A
B
C
D
E
F
G
H
J
K
L
M

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VFB (Pin F12): The Negative Input of the Error Ampli-
fier. Internally, this pin is connected to VOUT with a 100k
0.5% precision resistor. Different output voltages can be
programmed with an additional resistor between the VFB
and SGND pins. See the Applications Information section.
MARG0 (Pin C12): LSB Logic Input for the Margining
Function. Together with the MARG1 pin, the MARG0 pin
will determine if a margin high, margin low, or no margin
state is applied. The pin has an internal pull-down resistor
of 50k. See the Applications Information section.
MARG1 (Pins C11, D12): MSB Logic Input for the Margin-
ingFunction. Togetherwith theMARG0pin, theMARG1pin
will determine if a margin high, margin low, or no margin
stateis applied.Thepins have aninternalpull-down resistor
of 50k. See the Applications Information section.
SGND (Pins D9, H12): Signal Ground Pins. These pins
connect to PGND at output capacitor point.
COMP (Pins A11, D11): Current Control Threshold and
Error Amplifier Compensation Point. The current com-
parator threshold increases with this control voltage. The
voltage ranges from 0V to 2.4V with 0.7V corresponding
to zero sense voltage (zero current).
PGOOD (Pin G12): Output Voltage Power Good Indicator.
Open-drain logic output that is pulled to ground when the
output voltage is not within ±10% of the regulation point,
after a 25µs power bad mask timer expires.
RUN (Pins A10, B9): Run Control Pins. A voltage above
1.9V will turn on the module, and below 1V will turn off
the module. A programmable UVLO function can be ac-
complished with a resistor from VIN to this pin that is has
a 5.1V zener to ground. Maximum pin voltage is 5V.
NC (Pins J12, K12, L12): No Connect Pins. Leave floating.
PIN FUNCTIONS

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BLOCK DIAGRAM
DECOUPLING REQUIREMENTS
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
CIN External Input Capacitor Requirement
(VIN = 20V to 36V, VOUT = 12V)
IOUT = 4A 20 µF
COUT External Output Capacitor Requirement
(VIN = 20V to 36V, VOUT = 12V)
IOUT = 4A 100 150 µF
Specifications are at TA= 25°C. Use Figure 1 configuration.
+
INTERNAL
COMP
SGND
COMP
PGOOD
RUN
> 1.9V = ON
< 1V = OFF
MAX = 5V
MARG1
MARG0
MPGM
FCB
PLLIN
CSS
INTVCC
DRVCC
TRACK/SS
VFB
fSET
50k
93.1k
RFB
5.23k
50k
100k
VOUT
5.1V
ZENER
POWER CONTROL M1
VIN
20V TO 36V
VD
VOUT
12V
AT 4A
M2
50k
10µF
1µF CIN
+
COUT
PGND
4612 F01
CD
10k
4.7µF
INPUT
FILTER
2.7µH
NOISE
CANCEL-
LATION
Figure 1. Simplified Block Diagram

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OPERATION
Power Module Description
The LTM4612 is a standalone nonisolated switching mode
DC/DC power supply. It can deliver 5A of DC output
current with some external input and output capacitors.
This module provides precisely regulated output voltage
programmable via one external resistor from 3.3VDC to
15VDC over a 5V to 36V wide input voltage. The typical
application schematic is shown in Figure 18.
The LTM4612 has an integrated constant on-time current
mode regulator, ultralow RDS(ON) FETs with fast switching
speedandintegratedSchottky diodes.The typicalswitching
frequencyis850kHzat full load at 12V output. With current
mode control and internal feedback loop compensation,
the LTM4612 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.
Current mode control provides cycle-by-cycle fast current
limiting. Moreover, foldback current limiting is provided in
an overcurrent condition while VFB drops. Internal over-
voltageandundervoltage comparators pull the open-drain
PGOOD output low if the output feedback voltage exits a
±10% window around the regulation point. Furthermore,
in an overvoltage condition, internal top FET M1 is turned
off and bottom FET M2 is turned on and held on until the
overvoltage condition clears.
Inputfilter and noise cancellation circuitry reduce thenoise
coupling to I/O sides, and ensure the electromagnetic
interference (EMI) meets the limits of EN55022 Class B.
Pulling the RUN pin below 1V forces the controller into
its shutdown state, turning off both M1 and M2. At light
load currents, discontinuous mode (DCM) operation can
be enabled to achieve higher efficiency compared to con-
tinuous mode (CCM) by setting FCB pin higher than 0.6V.
When the DRVCC pin is connected to INTVCC, an integrated
5V linear regulator powers the internal gate drivers. If a
5V external bias supply is applied on DRVCC pin, then an
efficiencyimprovement willoccurdue tothereduced power
loss in the internal linear regulator. This is especially true
at higher input voltages.
The MPGM, MARG0, and MARG1 pins are used to sup-
port output voltage margining, where the percentage of
margin is programmed by the MPGM pin, and the MARG0
and MARG1 select margining. The PLLIN pin provides
frequency synchronization of the device to an external
clock. The TRACK/SS pin is used for power supply track-
ing and soft-start programming.
The typical L
TM4612 application circuit is shown in Figure
18. External component selection is primarily determined
by the maximum load current and output voltage. Refer
to Table 2 for specific external capacitor requirements for
a particular application.
APPLICATIONS INFORMATION
VIN to VOUT Stepdown Ratios
There are restrictions in the maximum VIN and VOUT step
down ratio that can be achieved for a given input voltage.
These constraints are shown in the Typical Performance
Characteristic curve labeled “VIN to VOUT Step-Down
Ratio.” Note that additional thermal derating may be ap-
plied. See the Thermal Considerations and Output Current
Derating section in this data sheet.