LTM4602
6A High Efficiency
DC/DC µModule
FEATURES
DESCRIPTION
n
The LTM®4602 is a complete 6A DC/DC step down power
supply. Included in the package are the switching controller, power FETs, inductor, and all support components.
Operating over an input voltage range of 4.5V to 20V, the
LTM4602 supports an output voltage range of 0.6V to 5V,
set by a single resistor. This high efficiency design delivers
6A continuous current (8A peak), needing no heat sinks or
airflow to meet power specifications. Only bulk input and
output capacitors are needed to finish the design.
n
n
n
n
n
n
n
n
n
n
n
n
n
n
Complete Switch Mode Power Supply
Wide Input Voltage Range: 4.5V to 20V
6A DC, 8A Peak Output Current
0.6V to 5V Output Voltage
1.5% Output Voltage Regulation
Ultrafast Transient Response
Current Mode Control
Pb-Free (e4) RoHS Compliant Package with GoldPad Finish
Pin Compatible with the LTM4600
Up to 92% Efficiency
Programmable Soft-Start
Output Overvoltage Protection
Optional Short-Circuit Shutdown Timer
See the LTM4602HV for Operation Up to 28VIN
Small Footprint, Low Profile (15mm × 15mm ×
2.8mm) Surface Mount LGA Package
APPLICATIONS
n
n
n
n
The low profile package (2.8mm) enables utilization of
unused space on the bottom of PC boards for high density
point of load regulation. High switching frequency and an
adaptive on-time current mode architecture enables a very
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.
The LTM4602 is packaged in a thermally enhanced, compact
(15mm × 15mm) and low profile (2.8mm) over-molded
Land Grid Array (LGA) package suitable for automated assembly by standard surface mount equipment. For the 4.5V
to 28V input range version, refer to the LTM4602HV.
Telecom and Networking Equipment
Servers
Industrial Equipment
Point of Load Regulation
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
μModule is a trademark of Linear Technology Corporation. All other trademarks are the property
of their respective owners. Protected by U.S. Patents including 5481178, 6100678, 6580258,
5847554, 6304066.
TYPICAL APPLICATION
Efficiency vs Load Current
with 12VIN (FCB = 0)
100
6A μModuleTM Power Supply with 4.5V to 20V Input
90
VIN
CIN
VOUT
1.5V
6A
VOUT
LTM4602
VOSET
PGND SGND
COUT
RSET
66.5k
4602 TA01a
EFFICIENCY (%)
80
VIN
4.5V TO 20V
70
60
0.8VOUT
1.2VOUT
1.5VOUT
1.8VOUT
2.5VOUT
3.3VOUT
3.3VOUT (950kHz)*
50
40
30
20
*950kHz INSTEAD OF 1.3MHz
INCREASES 3.3V EFFICIENCY 2%
10
0
0
2
4
6
LOAD CURRENT (A)
8
4602 TA01b
4602fa
1
LTM4602
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
fADJ
SVIN
EXTVCC
VOSET
FCB, EXTVCC, PGOOD, RUN/SS, VOUT .......... –0.3V to 6V
VIN, SVIN, fADJ ............................................ –0.3V to 20V
VOSET, COMP ............................................. –0.3V to 2.7V
Operating Temperature Range (Note 2).... –40°C to 85°C
Junction Temperature ........................................... 125°C
Storage Temperature Range................... –55°C to 125°C
COMP
SGND
RUN/SS
FCB
VIN
PGOOD
PGND
VOUT
LGA PACKAGE
104-LEAD (15mm × 15mm × 2.8mm)
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
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTM4602EV#PBF
LTM4602V
104-Lead (15mm × 15mm × 2.8mm) LGA
–40°C to 85°C
LTM4602IV#PBF
LTM4602V
104-Lead (15mm × 15mm × 2.8mm) LGA
–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.
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
VIN(DC)
Input DC Voltage
VOUT(DC)
Output Voltage
CONDITIONS
FCB = 0V
VIN = 5V or 12V, VOUT = 1.5V, IOUT = 0A
MIN
l
4.5
l
1.478
1.470
TYP
MAX
UNITS
20
V
1.50
1.50
1.522
1.530
V
4
V
Input Specifications
VIN(UVLO)
Under Voltage Lockout Threshold
IOUT = 0A
3.4
IINRUSH(VIN)
Input Inrush Current at Startup
IOUT = 0A. VOUT = 1.5V, FCB = 0
VIN = 5V
VIN = 12V
0.6
0.7
A
A
IOUT = 0A, EXTVCC Open
VIN = 12V, VOUT = 1.5V, FCB = 5V
VIN = 12V, VOUT = 1.5V, FCB = 0V
VIN = 5V, VOUT = 1.5V, FCB = 5V
VIN = 5V, VOUT = 1.5V, FCB = 0V
Shutdown, RUN = 0.8V, VIN = 12V
1.2
42
1.0
52
50
mA
mA
mA
mA
μA
IQ(VIN)
Input Supply Bias Current
100
4602fa
2
LTM4602
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the –40°C to 85°C
temperature range, otherwise specifications are at TA = 25°C, VIN = 12V. Per typical application (front page) configuration.
SYMBOL
PARAMETER
CONDITIONS
MIN
IS(VIN)
Input Supply Current
VIN = 12V, VOUT = 1.5V, IOUT = 6A
VIN = 12V, VOUT = 3.3V, IOUT = 6A
VIN = 5V, VOUT = 1.5V, IOUT = 6 A
TYP
MAX
0.88
1.80
2.08
UNITS
A
A
A
Output Specifications
IOUTDC
Output Continuous Current Range
VIN = 12V, VOUT = 1.5V
(See Output Current Derating Curves for
Different VIN, VOUT and TA)
ΔVOUT(LINE)
Line Regulation Accuracy
VOUT = 1.5V, IOUT = 0A, FCB = 0V,
VIN = 4.5V to 20V
Load Regulation Accuracy
VOUT = 1.5V, IOUT = 0A to 6A, FCB = 0V,
VIN = 5V, VIN = 12V (Note 3)
VOUT
ΔVOUT(LOAD)
VOUT
0
6
A
l
0.15
0.3
%
l
±0.25
±0.15
±0.5
±1.0
%
%
15
VOUT(AC)
Output Ripple Voltage
VIN = 12V, VOUT = 1.5V, IOUT = 0A, FCB = 0V
10
mVP-P
fs
Output Ripple Voltage Frequency
VOUT = 1.5V, IOUT = 6A, FCB = 0V
850
kHz
tSTART
Turn-On Time
VOUT = 1.5V, IOUT = 1A
VIN = 12V
VIN = 5V
0.5
0.7
ms
ms
ΔVOUTLS
Voltage Drop for Dynamic Load Step
VOUT = 1.5V, Load Step: 0A/μs to 3A/μs
COUT = 22μF 6.3V, 330μF 4V POSCAP,
See Table 2
30
mV
tSETTLE
Settling Time for Dynamic Load Step
Load: 10% to 50% to 10% of Full Load
25
μs
IOUTPK
Output Current Limit
Output Voltage in Foldback
VIN = 12V, VOUT = 1.5V
VIN = 5V, VOUT = 1.5V
9
9
A
A
Control Stage
VOSET
Voltage at VOSET Pin
VRUN/SS
RUN ON/OFF Threshold
IRUN(C)/SS
Soft-Start Charging Current
IRUN(D)/SS
Soft-Start Discharging Current
VIN – SVIN
IOUT = 0A, VOUT = 1.5V
l
0.591
0.6
0.609
V
0.8
1.5
2
V
VRUN/SS = 0V
–0.5
–1.2
–3
μA
VRUN/SS = 4V
0.8
1.8
3
μA
EXTVCC = 0V, FCB = 0V
100
mV
EXTVCC = 5V, FCB = 0V, VOUT = 1.5V,
IOUT = 0A
16
mA
100
kΩ
IEXTVCC
Current into EXTVCC Pin
RFBHI
Resistor Between VOUT and VOSET Pins
VFCB
Forced Continuous Threshold
IFCB
Forced Continuous Pin Current
VFCB = 0.6V
0.57
0.6
0.63
V
–1
–2
μA
PGOOD Output
ΔVOSETH
PGOOD Upper Threshold
VOSET Rising
7.5
10
12.5
%
ΔVOSETL
PGOOD Lower Threshold
VOSET Falling
–7.5
–10
–12.5
%
ΔVOSET(HYS)
PGOOD Hysteresis
VOSET Returning
VPGL
PGOOD Low Voltage
IPGOOD = 5mA
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.
2
0.15
%
0.4
V
Note 2: The LTM4602E is guaranteed to meet performance specifications
from 0°C to 85°C. Specifications over the –40°C to 85°C operating
temperature range are assured by design, characterization and correlation
with statistical process controls. The LTM4602I is guaranteed over the
–40°C to 85°C temperature range.
Note 3: Test assumes current derating versus temperature.
4602fa
3
LTM4602
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Load Current
with 20VIN (FCB = 0)
Efficiency vs Load Current
with 12VIN (FCB = 0)
100
100
90
90
90
80
80
80
70
0.8VOUT
1.2VOUT
1.5VOUT
1.8VOUT
2.5VOUT
3.3VOUT*
*FOR 5V TO 3.3V CONVERSION,
SEE FREQUENCY ADJUSTMENT
IN APPLICATIONS INFORMATION
60
50
40
30
0
2
8
4
6
LOAD CURRENT (A)
70
0.8VOUT
1.2VOUT
1.5VOUT
1.8VOUT
2.5VOUT
3.3VOUT
3.3VOUT (950kHz)*
60
50
40
*950kHz INSTEAD OF 1.3MHz
INCREASES 3.3V EFFICIENCY 2%
30
0
2
4
6
LOAD CURRENT (A)
4602 G01
8
EFFICIENCY (%)
100
EFFICIENCY (%)
EFFICIENCY (%)
Efficiency vs Load Current
with 5VIN (FCB = 0)
(See Figure 21 for all curves)
70
60
1.2VOUT
1.5VOUT
1.8VOUT
2.5VOUT
3.3VOUT
50
40
30
0
2
4
6
4602 G02
Light Load Efficiency vs
Load Current with 12VIN
(FCB > 0.7V, COUT • VOUT (10 –3[F / VS ])
Generally 0.1μF is more than sufficient.
Since the load current is already limited by the current mode
control and current foldback circuitry during a short circuit,
overcurrent latchoff operation is NOT always needed or
desired, especially if the output has large capacitance or
the load draws high current during start up. The latchoff
feature can be overridden by a pull-up current greater than
5μA but less than 80μA to the RUN/SS pin. The additional
current prevents the discharge of CSS during a fault and
also shortens the soft-start period. Using a resistor from
RUN/SS pin to VIN is 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 discharge current. Figure 3 shows a conceptual
drawing of VRUN during start-up and short circuit.
VRUN/SS
4V
3.5V
3V
1.5V
SHORT-CIRCUIT
LATCH ARMED
t
SOFT-START
CLAMPING
OF IL RELEASED
OUTPUT
OVERLOAD
HAPPENS
SHORT-CIRCUIT
LATCHOFF
VOUT
75%VO
t
SWITCHING
STARTS
4602 F03
Figure 3. RUN/SS Pin Voltage During Startup and
Short-Circuit Protection
VIN
VIN
RRUN/SS
LTM4602
RUN/SS
PGND SGND
RECOMMENDED VALUES FOR RRUN/SS
VIN
RRUN/SS
4.5V TO 5.5V
10.8V TO 13.8V
16V TO 20V
50k
150k
330k
4602 F04
Figure 4. Defeat Short-Circuit Latchoff with a Pull-Up
Resistor to VIN
4602fa
12
LTM4602
APPLICATIONS INFORMATION
Enable
EXTVCC Connection
The RUN/SS pin can be driven from logic as shown in
Figure 5. This function allows the LTM4602 to be turned
on or off remotely. The ON signal can also control the
sequence of the output voltage.
An internal low dropout regulator produces an internal 5V
supply that powers the control circuitry and FET drivers.
Therefore, if the system does not have a 5V power rail,
the LTM4602 can be directly powered by VIN. The gate
driver current through LDO is about 18mA. The internal
LDO power dissipation can be calculated as:
RUN/SS
ON
PLDO_LOSS = 18mA • (VIN – 5V)
LTM4602
PGND SGND
2N7002
4602 F05
Figure 5. Enable Circuit with External Logic
Output Voltage Tracking
For the applications that require output voltage tracking,
several LTM4602 modules can be programmed by the
power supply tracking controller such as the LTC2923.
Figure 6 shows a typical schematic with LTC2923. Coincident, ratiometric and offset tracking for VOUT rising and
falling can be implemented with different sets of resistor
values. See the LTC2923 data sheet for more details.
Q1
VIN
5V
3.3V
DC/DC
VIN
VIN
RONB
VCC
RAMP
GATE
ON
RONA
LTM4602
VOSET
VOUT
FB1
RAMPBUF
STATUS
VIN
RTB1
TRACK1
RTA1
SDO
VIN
FB2
LTM4602
VOSET
VOUT
RTB2
TRACK2
RTA2
GND
1. EXTVCC grounded. Internal 5V LDO is always powered
from the internal 5V regulator.
2. EXTVCC connected to an external supply. Internal LDO
is shut off. A high efficiency supply compatible with the
MOSFET gate drive requirements (typically 5V) can improve overall efficiency. With this connection, it is always
required that the EXTVCC voltage can not be higher than
VIN pin voltage.
Discontinuous Operation and FCB Pin
1.8V
RSET
49.9k
LTC2923
The LTM4602 also provides an external gate driver voltage pin EXTVCC. If there is a 5V rail in the system, it is
recommended to connect EXTVCC pin to the external 5V
rail. Whenever the EXTVCC pin is above 4.7V, the internal 5V LDO is shut off and an internal 50mA P-channel
switch connects the EXTVCC to internal 5V. Internal 5V is
supplied from EXTVCC until this pin drops below 4.5V. Do
not apply more than 6V to the EXTVCC pin and ensure that
EXTVCC < VIN. The following list summaries the possible
connections for EXTVCC:
1.5V
RSET
66.5k
4602 F06
Figure 6. Output Voltage Tracking with the LTC2923 Controller
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.
In the application where the light load efficiency is important, tying the FCB pin above 0.6V threshold enables
discontinuous operation where the bottom MOSFET turns
off when inductor current reverses. Therefore, the conduc-
4602fa
13
LTM4602
APPLICATIONS INFORMATION
tion loss is minimized and light load efficiency is improved.
The penalty is that the controller may skip cycle and the
output voltage ripple increases at light load.
where N is the number of LTM4602s in parallel.
sinking methods. Thermal models are derived from
several temperature measurements at the bench,
and thermal modeling analysis. Application Note 103
provides a detailed explanation of the analysis for the
thermal models, and the derating curves. Tables 3
and 4 provide a summary of the equivalent θJA for the
noted conditions. These equivalent θJA parameters are
correlated to the measured values, and improve with
air-flow. The case temperature is maintained at 100°C
or below for the derating curves. This allows for 4W
maximum power dissipation in the total module with
top and bottom heat sinking, and 2W power dissipation
through the top of the module with an approximate
θJC between 6°C/W to 9°C/W. This equates to a total
of 124°C at the junction of the device. The θJA values
in Tables 3 and 4 can be used to derive the derating
curves for other output voltages.
Thermal Considerations and Output Current Derating
Safety Considerations
The power loss curves in Figures 8 and 13 can be used
in coordination with the load current derating curves
in Figures 9 to 12, and Figures 14 to 15 for calculating
an approximate θJA for the module with various heat
The LTM4602 modules do not provide isolation from VIN to
VOUT. There is no internal fuse. If required, a slow blow fuse
with a rating twice the maximum input current should be
provided to protect each unit from catastrophic failure.
Paralleling Operation with Load Sharing
Two or more LTM4602 modules can be paralleled to provide
higher than 6A output current. Figure 7 shows the necessary interconnection between two paralleled modules. The
OPTI-LOOP® current mode control ensures good current
sharing among modules to balance the thermal stress.
The new feedback equation for two or more LTM4602s
in parallel is:
100k
+ RSET
N
VOUT = 0.6V •
RSET
OPTI-LOOP is a registered trademark of Linear Technology Corporation.
VPULLUP
100k
PGOOD
VIN
VIN
LTM4602
VOUT
12A MAX
VOUT
PGND COMP VOSET SGND
RSET
PGOOD COMP VOSET SGND
VIN
PGND
LTM4602
VOUT
4602 F07
Figure 7. Parallel Two μModules with Load Sharing
4602fa
14
LTM4602
APPLICATIONS INFORMATION
2.0
1.8
7
7
6
6
5
5
12V TO 1.5V
LOSS
1.2
1.0
0.8
5V TO 1.5V
LOSS
0.6
0.4
CURRENT (A)
1.4
CURRENT (A)
POWER LOSS (W)
1.6
4
3
2
0LFM
200LFM
400LFM
1
0
0
1.0
3.1
4.1
2.1
CURRENT (A)
5.1
6.1
50
60
70
80
90
0LFM
200LFM
400LFM
1
0
100
6
6
3.5
5
5
2
4
3
2
0LFM
200LFM
400LFM
50
60
70
80
90
0
50
TEMPERATURE (°C)
60
70
80
90
2.5
2.0
1.5
0.5
0
0.5
100
1.0
2.1
4.1
3.1
CURRENT (A)
TEMPERATURE (°C)
4602 F11
5.1
Figure 12. 12v to 1.5V, BGA Heat Sink
7
6
6
5
5
CURRENT (A)
7
4
3
2
6.1
4601 F13
4602 F09
Figure 11. 12V to 1.5V, No Heat Sink
CURRENT (A)
5V TO 3.3V LOSS
12V TO 3.3V LOSS
12V TO 3.3V (950kHz) LOSS
1.0
0LFM
200LFM
400LFM
1
100
100
3.0
POWER LOSS (W)
CURRENT (A)
4.0
0
90
Figure 10. 5V to 1.5V, BGA Heat Sink
7
3
80
4602 F10
Figure 9. 5V to 1.5V, No Heat Sink
7
4
70
TEMPERATURE (°C)
4602 F09
Figure 8. 1.5V Power Loss vs Load Current
1
60
50
TEMPERATURE (°C)
4602 F08
CURRENT (A)
3
2
0.2
0.6
4
Figure 13. 3.3V Power Loss
vs Load Current
4
3
2
0LFM
200LFM
400LFM
1
0
50
60
70
80
90
100
TEMPERATURE (°C)
0LFM
200LFM
400LFM
1
0
50
60
70
80
90
100
TEMPERATURE (°C)
4602 F14
Figure 14. 5V to 3.3V, No Heat Sink
4602 F15
Figure 15. 5V to 3.3V, BGA Heat Sink
4602fa
15
LTM4602
7
7
6
6
5
5
CURRENT (A)
CURRENT (A)
APPLICATIONS INFORMATION
4
3
4
3
2
2
0LFM
200LFM
400LFM
1
0
50
60
0LFM
200LFM
400LFM
1
0
70
80
90
100
50
TEMPERATURE (°C)
60
70
80
90
100
TEMPERATURE (°C)
4602 F16
4602 F16
Figure 17. 12V to 3.3V, BGA Heat Sink
Figure 16. 12V to 3.3V, No Heat Sink
Table 3. 1.5V Output
Table 4. 3.3V Output
AIR FLOW (LFM)
HEAT SINK
θJA (°C/W)
AIR FLOW (LFM)
HEAT SINK
θJA (°C/W)
0
None
15.2
0
None
15.2
200
None
14
200
None
14.6
400
None
12
400
None
13.4
0
BGA Heat Sink
13.9
0
BGA Heat Sink
13.9
200
BGA Heat Sink
11.3
200
BGA Heat Sink
11.1
400
BGA Heat Sink
10.25
400
BGA Heat Sink
10.5
Layout Checklist/Example
The high integration of the LTM4602 makes the PCB board
layout very simple and easy. However, to optimize its electrical and thermal performance, some layout considerations
are still necessary.
• Use large PCB copper areas for high current path,
including VIN, PGND and VOUT. It helps to minimize the
PCB conduction loss and thermal stress.
• Place high frequency ceramic input and output capacitors next to the VIN, PGND and VOUT pins to minimize
high frequency noise.
• Place a dedicated power ground layer underneath
the unit.
• To minimize the via conduction loss and reduce module
thermal stress, use multiple vias for interconnection
between top layer and other power layers.
• Do not put vias directly on pads unless they are capped.
• Use a separated SGND ground copper area for components connected to signal pins. Connect the SGND
to PGND underneath the unit.
Figure 18 gives a good example of the recommended
layout.
LTM4602 Frequency Adjustment
The LTM4602 is designed to typically operate at 850kHz
across most input and output conditions. The control architecture is constant on time valley mode current control.
The fADJ pin is typically left open or decoupled with an
optional 1000pF capacitor. The switching frequency has
been optimized to maintain constant output ripple over the
operating conditions. The equations for setting the operating frequency are set around a programmable constant on
time. This on time is developed by a programmable current
into an on board 10pF capacitor that establishes a ramp
that is compared to a voltage threshold equal to the output
voltage up to a 2.4V clamp. This ION current is equal to:
ION = (VIN – 0.7V)/110k, with the 110k onboard resistor
4602fa
16
LTM4602
APPLICATIONS INFORMATION
VIN
CIN
PGND
VOUT
4600 F16
LOAD
TOP LAYER
Figure 18. Recommended PCB Layout
from VIN to fADJ. The on time is equal to tON = (VOUT/ION)
• 10pF and tOFF = ts – tON. The frequency is equal to: Freq.
= DC/tON. The ION current is proportional to VIN, and the
regulator duty cycle is inversely proportional to VIN, therefore the step-down regulator will remain relatively constant
frequency as the duty cycle adjustment takes place with
lowering VIN. The on time is proportional to VOUT up to a
2.4V clamp. This will hold frequency relatively constant
with different output voltages up to 2.4V. The regulator
switching period is comprised of the on time and off time
as depicted in Figure 19.
t
(DC) DUTY CYCLE = ON
ts
tOFF
tON
t
V
DC = ON = OUT
ts
VIN
DC
FREQ =
tON
4602 F19
PERIOD ts
Figure 19. LTM4602 Switching Period
The LTM4602 has a minimum (tON) on time of 100 nanoseconds and a minimum (tOFF) off time of 400 nanoseconds.
The 2.4V clamp on the ramp threshold as a function of
VOUT will cause the switching frequency to increase by the
ratio of VOUT/2.4V for 3.3V and 5V outputs. This is due to
the fact the on time will not increase as VOUT increases
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
to Frequency = (DC/tON) When the switching frequency
increases to 1.2MHz, then the time period tS is reduced
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
off time. Since the total switching period is tS = tON + tOFF,
tOFF will be below the 400ns minimum off time. A resistor
from the fADJ pin to ground can shunt current away from
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.
Equations for setting frequency for 12V to 5V:
ION = (VIN – 0.7V)/110k; ION = 103μA
frequency = (ION/[2.4V • 10pF]) • DC = 1.79MHz;
DC = duty cycle, duty cycle is (VOUT/VIN)
tS = tON + tOFF, tON = on-time, tOFF = off-time of the
switching period; tS = 1/frequency
tOFF must be greater than 400ns, or tS – tON > 400ns.
tON = DC • tS
1MHz frequency or 1μs period is chosen for 12V to 5V.
tON = 0.41 • 1μs ≅ 410ns
tOFF = 1μs – 410ns ≅ 590ns
tON and tOFF are above the minimums with adequate guard
band.
Using the frequency = (ION/[2.4V • 10pF]) • DC, solve for
ION = (1MHz • 2.4V • 10pF) • (1/0.41) ≅ 58μA. ION current
calculated from 12V input was 103μA, so a resistor from
fADJ to ground = (0.7V/15k) = 46μA. 103μA – 46μA =
57μA, sets the adequate ION current for proper frequency
range for the higher duty cycle conversion of 12V to
5V. Input voltage range is limited to 9V to 16V. Higher
input voltages can be used without the 15k on fADJ. The
inductor ripple current gets too high above 16V, and the
400ns minimum off-time is limited below 9V.
4602fa
17
LTM4602
APPLICATIONS INFORMATION
Equations for setting frequency for 5V to 3.3V:
ION = (VIN – 0.7V)/110k; ION = 39μA
frequency = (ION/[2.4V • 10pF]) • DC = 1.07MHz;
DC = duty cycle, duty cycle is (VOUT/VIN)
tS = tON + tOFF, tON = on-time, tOFF = off-time of the
switching period; tS = 1/frequency
tOFF must be greater than 400ns, or tS – tON > 400ns.
tON = DC • tS
~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.
tON = 0.66 • 2.22μs ≅ 1.46μs
tOFF = 2.22μs – 1.46μs ≅ 760ns
Using the frequency = (ION/[2.4V • 10pF]) • DC, solve for
ION = (450kHz • 2.4V • 10pF) • (1/0.66) ≅ 16μA. ION current
calculated from 5V input was 39μA, so a resistor from fADJ
to ground = (0.7V/30.1k) = 23μA. 39μA – 23μA = 16μA,
sets the adequate ION current for proper frequency range
for the higher duty cycle conversion of 5V to 3.3V. Input
voltage range is limited to 4.5V to 7V. Higher input voltages
can be used without the 30.1k on fADJ. The inductor ripple
current gets too high above 7V, and the 400ns minimum
off-time is limited below 4.5V.
In 12V to 3.3V applications, if a 35k resistor is added from
the fADJ pin to ground, then a 2% efficiency gain will be
achieved as shown in the 12V efficiency graph in the Typical Performance Characteristics. This is due to the lower
transition losses in the power MOSFETs after lowering the
switching frequency down from 1.3MHz to 950kHz.
tON and tOFF are above the minimums with adequate guard
band.
4602fa
18
LTM4602
APPLICATIONS INFORMATION
5V to 3.3V at 5A
R1
30.1k
VIN
4.5V TO 7V
C3
10μF
25V
C1
10μF
25V
C5
100pF
fADJ
VIN
EXTVCC
EFFICIENCY = 94%
AT 5A LOAD
VOUT
FCB
VOSET
RSET
22.1k
1%
LTM4602
RUN/SS
RUN/SOFT-START
VOUT
3.3V AT 5A
SVIN
PGOOD
COMP
SGND
C2
22μF
+
C4
330μF
6.3V
OPEN DRAIN
PGND
4602 F20a
5V TO 3.3V AT 5A WITH fADJ = 30.1k
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POSCAP, 6TPE330MIL
12V to 5V at 5A
R1
15k
VIN
7V TO 20V
C3
10μF
25V
C1
10μF
25V
VIN
C5
100pF
fADJ
EXTVCC
FCB
VOSET
RSET
13.7k
1%
LTM4602
RUN/SS
RUN/SOFT-START
VOUT
5V AT 5A
VOUT
SVIN
PGOOD
COMP
SGND
EFFICIENCY = 92.5%
AT 5A LOAD
C2
22μF
+
C4
330μF
6.3V
OPEN DRAIN
PGND
4602 F20b
7V TO 20V AT 5A WITH fADJ = 15k
C1, C3: TDK C3216X5R1E106MT
C2: TAIYO YUDEN, JMK316BJ226ML
C4: SANYO POSCAP, 6TPE330MIL
Figure 20. VIN to VOUT Step-Down Ratio for 12VIN to 5VOUT and 5VIN to 3.3VOUT
VIN
+
5V TO 20V
CIN
10μF
×2
CER
CIN
150μF
BULK
VIN
(MULTIPLE PINS)
GND
EXTVCC
C3
100pF
SVIN
VOUT
(MULTIPLE PINS)
fADJ
VOSET
VOUT
VOUT
6A
COUT1
REFER TO
TABLE 2
+
COUT2
REFER TO
TABLE 2
LTM4602
COMP
RSET
66.5k
REFER TO
TABLE 1
FCB
C4
OPT
RUN/SS
PGOOD
0.6V TO 5V
SGND
REFER TO STEP-DOWN
RATIO GRAPH
PGND
(MULTIPLE PINS)
GND
4602 F21
Figure 21. Typical Application, 5V to 20V Input, 0.6V to 5V Output, 6A Max
4602fa
19
LTM4602
TYPICAL APPLICATION
Parallel Operation and Load Sharing
VIN
4.5V TO 20V
VOUT = 0.6V • ([100k/N] + RSET)/RSET
WHERE N = 2
C7
10μF
25V
VIN
fADJ
EXTVCC
VOUT
FCB
VOSET
LTM4602
RUN
SVIN
C9
22μF
RSET
15.8k
1%
+
C10
330μF
4V
PGOOD
COMP
SGND
PGND
VOUT
2.5V
12A
RUN/SOFT-START
C1
10μF
25V
VIN
C4
220pF
fADJ
EXTVCC
VOUT
FCB
C2
22μF
VOSET
LTM4602
RUN
+
C5
330μF
4V
R1
100k
SVIN
PGOOD
COMP
SGND
PGND
4602 TA02
C1, C7: TDK C3216X5R1E106MT
C2, C9: TAIYO YUDEN, JMK316BJ226ML-T501
C5, C10: SANYO POSCAP, 4TPE330MI
Current Sharing Between Two
LTM4602 Modules
6
INDIVIDUAL SHARE
12VIN
2.5VOUT
12AMAX
4
IOUT2
IOUT1
2
0
0
6
TOTAL LOAD
12
4602 TA03
4602fa
20
5.7150
2.5400
0.3175
0.3175
2.7375
C(0.30)
PAD 1
13.97
BSC
0.11 – 0.27
6.9850
4.4450
1.2700
0.0000
1.4675
4.0075
6.9421
94
83
72
61
50
39
5.7158
43
89
78
67
56
45
15
11
100
36
29
7
99
88
77
66
55
44
14
10
98
87
76
65
54
35
28
6
1.9042
37
30
16
91
102
101
80
69
58
47
90
79
68
57
46
38
31
17
18
4.4442
33
1
1
8
3
5
6
7
4
8
13
10
9
11
6
28
35
14
44
55
13
13.93
BSC
12
10
7
29
36
15
45
56
67
78
89
100
14
11
15
16
30
37
BOTTOM VIEW
9
5
27
34
54
43
66
77
88
99
16
46
57
68
79
90
101
17
17
31
38
18
47
58
69
80
91
102
18
20
48
19
22
49
60
71
70
59
82
93
104
81
92
103
104
93
82
71
60
49
20
24
24
23
22
21
19
21
23
20
21
22
26
42
53
65
76
87
98
12.70
BSC
103
92
81
70
59
48
19
12
4
34
27
13
9
6.9865
23
2
3
41
52
40
51
50
86
97
64
85
96
63
61
1.9058
5
3.1742
SUGGESTED SOLDER PAD LAYOUT
TOP VIEW
62
73
72
97
86
75
64
53
42
75
84
83
96
85
74
63
52
41
33
26
4.4950
74
95
2
95
84
73
62
51
40
1.0900
94
39
4.4458
2.3600
3.1758
4
5.7142
25
32
32
25
12
6.3500
8
3.8100
0.0000
1.2700
5.2775
5.0800
0.6358
0.3175
0.3175
0.0000
5.7650
2.5400
0.6342
1.2700
3
2.5400
2
3.8100
1
5.0800
6.9888
6.3500
6.5475
A
C
E
G
J
L
M
N
P
R
B
D
F
H
K
DETAIL B
MOLD
CAP
LGA104 0206
DETAIL B
4
PAD 1
CORNER
aaa Z
DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PAD #1 IDENTIFIER IS A MARKED FEATURE OR A
NOTCHED BEVELED PAD
4
SYMBOL TOLERANCE
aaa
0.15
bbb
0.10
eee
0.15
6. THE TOTAL NUMBER OF PADS: 104
5. PRIMARY DATUM -Z- IS SEATING PLANE
LAND DESIGNATION PER JESD MO-222, SPP-010
3
2. ALL DIMENSIONS ARE IN MILLIMETERS
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
0.27 – 0.37
SUBSTRATE
2.72 – 2.92
(Reference LTM DWG # 05-05-1800)
eee M X Y
PADS
SEE NOTES
T
3
2.45 – 2.55
bbb Z
LGA Package
104-Lead (15mm × 15mm)
TOP VIEW
15
BSC
X
15
BSC
Y
aaa Z
LTM4602
PACKAGE DESCRIPTION
4602fa
21
Z
LTM4602
PACKAGE DESCRIPTION
Pin Assignment Tables
(Arranged by Pin Number)
PIN NAME
A1 A2 A3 VIN
A4 A5 VIN
A6 A7 VIN
A8 A9 VIN
A10 A11 VIN
A12 A13 VIN
A14 A15 fADJ
A16 A17 SVIN
A18 A19 EXTVCC
A20 A21 VOSET
A22 A23 -
PIN NAME
B1 VIN
B2 B3 B4 B5 B6 B7 B8 B9 B10 B11 B12 B13 B14 B15 B16 B17 B18 B19 B20 B21 B22 B23 COMP
PIN NAME
C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 VIN
C11 C12 VIN
C13 C14 VIN
C15 C16 C17 C18 C19 C20 C21 C22 C23 -
PIN NAME
D1 VIN
D2 D3 D4 D5 D6 D7 D8 D9 D10 D11 D12 D13 D14 D15 D16 D17 D18 D19 D20 D21 D22 D23 SGND
PIN NAME
E1 E2 E3 E4 E5 E6 E7 E8 E9 E10 VIN
E11 E12 VIN
E13 E14 VIN
E15 E16 E17 E18 E19 E20 E21 E22 E23 -
PIN NAME
F1 VIN
F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 F13 F14 F15 F16 F17 F18 F19 F20 F21 F22 F23 RUN/SS
PIN NAME
G1 PGND
G2 G3 G4 G5 G6 G7 G8 G9 G10 G11 G12 G13 G14 G15 G16 G17 G18 G19 G20 G21 G22 G23 FCB
PIN NAME
H1 H2 H3 H4 H5 H6 H7 PGND
H8 H9 PGND
H10 H11 PGND
H12 H13 PGND
H14 H15 PGND
H16 H17 PGND
H18 H19 H20 H21 H22 H23 -
PIN NAME
J1 PGND
J2 J3 J4 J5 J6 J7 J8 J9 J10 J11 J12 J13 J14 J15 J16 J17 J18 J19 J20 J21 J22 J23 PGOOD
PIN NAME
K1 K2 K3 K4 K5 K6 K7 PGND
K8
K9 PGND
K10
K11 PGND
K12 K13 PGND
K14 K15 PGND
K16 K17 PGND
K18 K19 K20 K21 K22 K23 -
PIN NAME
L1 L2 PGND
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 -
PIN NAME
M1 M2 PGND
M3 M4 PGND
M5 M6 PGND
M7 M8 PGND
M9 M10 PGND
M11 M12 PGND
M13 M14 PGND
M15 M16 PGND
M17 M18 PGND
M19 M20 PGND
M21 M22 PGND
M23 -
PIN NAME
N1 N2 PGND
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 -
PIN NAME
P1 P2 VOUT
P3 P4 VOUT
P5 P6 VOUT
P7 P8 VOUT
P9 P10 VOUT
P11 P12 VOUT
P13 P14 VOUT
P15 P16 VOUT
P17 P18 VOUT
P19 P20 VOUT
P21 P22 VOUT
P23 -
PIN NAME
R1 R2 VOUT
R3 R4 VOUT
R5 R6 VOUT
R7 R8 VOUT
R9 R10 VOUT
R11 R12 VOUT
R13 R14 VOUT
R15 R16 VOUT
R17 R18 VOUT
R19 R20 VOUT
R21 R22 VOUT
R23 -
PIN NAME
T1 T2 VOUT
T3 T4 VOUT
T5 T6 VOUT
T7 T8 VOUT
T9 T10 VOUT
T11 T12 VOUT
T13 T14 VOUT
T15 T16 VOUT
T17 T18 VOUT
T19 T20 VOUT
T21 T22 VOUT
T23 4602fa
22
LTM4602
PACKAGE DESCRIPTION
Pin Assignment Tables
(Arranged by Pin Number)
PIN NAME
G1
PGND
H7
H9
H11
H13
H15
H17
PGND
PGND
PGND
PGND
PGND
PGND
J1
PGND
K7
K9
K11
K13
K15
K17
PGND
PGND
PGND
PGND
PGND
PGND
L2
L4
L6
L8
L10
L12
L14
L16
L18
L20
L22
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
M2
M4
M6
M8
M10
M12
M14
M16
M18
M20
M22
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
N2
N4
N6
N8
N10
N12
N14
N16
N18
N20
N22
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PGND
PIN NAME
P2
P4
P6
P8
P10
P12
P14
P16
P18
P20
P22
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
R2
R4
R6
R8
R10
R12
R14
R16
R18
R20
R22
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
T2
T4
T6
T8
T10
T12
T14
T16
T18
T20
T22
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
VOUT
PIN NAME
A3
A5
A7
A9
A11
A13
VIN
VIN
VIN
VIN
VIN
VIN
B1
VIN
C10
C12
C14
VIN
VIN
VIN
D1
VIN
E10
E12
E14
VIN
VIN
VIN
F1
VIN
PIN NAME
A15
fADJ
A17
SVIN
A19
EXTVCC
A21
VOSET
B23
COMP
D23
SGND
F23
RUN/SS
G23
FCB
J23
PGOOD
4602fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
23
LTM4602
TYPICAL APPLICATION
1.8V, 6A Regulator
VIN
4.5V TO 20V
C2
10μF
25V
C1
10μF
25V
VIN
C5
100pF
fADJ
EXTVCC
VOUT
1.8V AT 6A
VOUT
FCB
VOSET
R1
100k
LTM4602
RUN
C3
22μF
+
C4
330μF
4V
SVIN
PGOOD
COMP
SGND
PGOOD
PGND
4602 TA04
RSET
49.9k
1%
C1, C2: TDK C3216X5R1E106MT
C3: TAIYO YUDEN, JMK316BJ226ML-T501
C4: SANYO POSCAP, 4TPE330MI
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2900
Quad Supply Monitor with Adjustable Reset Timer
Monitors Four Supplies; Adjustable Reset Timer
LTC2923
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
LTM4600
10A DC/DC μModule
10A Basic DC/DC Module
LTM4601
12A DC/DC μModule with PLL, Output Tracking/
Margining and Remote Sensing
Synchronizable, PolyPhase® Operation, LTM4601-1 Version has no Remote
Sensing, Fast Transient Response
LTM4603
6A DC/DC μModule with PLL and Output Tracking/
Margining and Remote Sensing
Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote
Sensing, Fast Transient Response
PolyPhase is a registered trademark of Linear Technology Corporation.
This product contains technology licensed from Silicon Semiconductor Corporation.
24 Linear Technology Corporation
®
4602fa
LT 0807 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2007
工商网监
湘ICP备2023018690号
