LTM8033
1
8033f
TYPICAL APPLICATION
FEATURES DESCRIPTION
Ultralow Noise EMC 36VIN,
3A DC/DC µModule
Regulator
The LTM
®
8033 is an electromagnetic compatible (EMC)
36V, 3A DC/DC Module
®
buck converter designed to
meet the radiated emissions requirements of EN55022.
Conducted emission requirements can be met by adding
standard filter components. Included in the package are the
switching controller, power switches, inductor, filters and
all support components. Operating over an input voltage
range of 3.6V to 36V, the LTM8033 supports an output
voltage range of 0.8V to 24V, and a switching frequency
range of 200kHz to 2.4MHz, each set by a single resistor.
Only the bulk input and output filter capacitors are needed
to finish the design.
The LTM8033 is packaged in a thermally enhanced, com-
pact (11.25mm × 15mm × 4.32mm) overmolded land grid
array (LGA) package suitable for automated assembly by
standard surface mount equipment.
L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule and Burst Mode are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
Ultralow Noise 12V/3A DC/DC μModule Regulator
APPLICATIONS
n Complete Step-Down Switch Mode Power Supply
n Wide Input Voltage Range: 3.6V to 36V
n 3A Output Current
n 0.8V to 24V Output Voltage
n EN55022 Class B Compliant
n Current Share Multiple LTM8033 Regulators for
More Than 3A Output
n Selectable Switching Frequency: 200kHz to 2.4MHz
n Current Mode Control
n (e4) RoHS Compliant Package with Gold Pad Finish
n Programmable Soft-Start
n Compact Package (11.25mm × 15mm × 4.32mm)
Surface Mount LGA
n Automotive Battery Regulation
n Power for Portable Products
n Distributed Supply Regulation
n Industrial Supplies
n Wall Transformer Regulation
EMI Performance
8033 TA01a
VIN
RUN/SS
FIN
SHARE
VIN*
20V TO 36V
VOUT
12V
3A
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
2.2µF
SYNC GND ADJ
1µF
f = 850kHz
41.2k 34.8k
47µF
* RUNNING VOLTAGE RANGE. PLEASE REFER TO THE
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS.
FREQUENCY (MHz)
30 814.8
716.7
618.6
520.5
226.2324.3422.4
0
10
30
20
60
50
40
70
80
912.91010
8033 TA01b
128.1
LTM8033
2
8033f
PIN CONFIGURATION ABSOLUTE MAXIMUM RATINGS
VIN, FIN, RUN/SS Voltage ........................................36V
ADJ, RT, SHARE Voltage ............................................6V
VOUT, AUX ................................................................25V
PGOOD, SYNC ..........................................................30V
BIAS .........................................................................25V
Maximum Junction Temperature (Note 2) .......... 125°C
Solder Temperature ............................................. 245°C
(Note 1)
LGA PACKAGE
76-LEAD (15mm s 11.25mm s 4.32mm)
TOP VIEW
FGH LJKEABCD
2
1
4
3
5
6
7
8
BIAS
RUN/SS
AUX
PGOOD
RT
ADJ
SYNC
GND
SHARE
BANK 4
BANK 3 FIN
BANK 2
GND
VIN
BANK 1
VOUT
TJMAX = 125°C, θJA = 15.4°C/W, θJCbottom = 5.2°C/W, θJB = 9.8°C/W, θJCtop = 16.7°C/W
θ VALUES DERIVED FROM A 4 LAYER 6.35cm × 6.35cm PCB
WEIGHT = 2.2g
ORDER INFORMATION
LEAD FREE FINISH TRAY PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE
LTM8033EV#PBF LTM8033EV#PBF 8033V 76-Lead (15mm × 11.25mm × 4.32mm) LGA –40°C to 125°C
LTM8033IV#PBF LTM8033IV#PBF 8033V 76-Lead (15mm × 11.25mm × 4.32mm) LGA –40°C to 125°C
LTM8033MPV#PBF LTM8033MPV#PBF 8033V 76-Lead (15mm × 11.25mm × 4.32mm) 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/
PARAMETER CONDITIONS MIN TYP MAX UNITS
Minimum Input Voltage l3.6 V
Output DC Voltage 0 < IOUT < 3A, RADJ Open, VIN = 24V
0 < IOUT < 3A, RADJ = 16.5k, VIN = 32V
0.8
24
V
V
Output DC Current VIN = 24V 0 3 A
Quiescent Current into VIN RUN/SS = 0V
Not Switching
BIAS = 0V, Not Switching
0.01
30
100
1
60
150
µA
µA
µA
Quiescent Current into BIAS RUN/SS = 0V
Not Switching
BIAS = 0V, Not Switching
0.01
75
0
0.5
120
5
µA
µA
µA
Line Regulation 5.5V < VIN < 36V 0.3 %
Load Regulation 0A < IOUT < 3A, VIN = 24V 0.4 %
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN/SS = 12V unless otherwise noted (Note 2).
LTM8033
3
8033f
ELECTRICAL CHARACTERISTICS
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 LTM8033E is guaranteed to meet performance specifications
from 0°C to 125°C internal. Specifications over the full –40°C to
125°C internal operating temperature range are assured by design,
characterization and correlation with statistical process controls. The
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.VIN = 12V, RUN/SS = 12V unless otherwise noted (Note 2).
PARAMETER CONDITIONS MIN TYP MAX UNITS
Output RMS Voltage Ripple VIN = 24V, 0A < IOUT < 3A 5 mV
Switching Frequency RT = 45.3k 780 kHz
Voltage at ADJ Pin l775 790 805 mV
Current Out of ADJ Pin ADJ = 1V, VOUT = 0V 2 µA
Minimum BIAS Voltage for Proper Operation 2 2.8 V
RUN/SS Pin Current RUN/SS = 2.5V 5 10 µA
RUN/SS Input High Voltage 2.5 V
RUN/SS Input Low Voltage 0.2 V
PGOOD Threshold (at ADJ) VOUT Rising 730 mV
PGOOD Leakage Current PGOOD = 30V, RUN/SS = 0V 0.1 1 µA
PGOOD Sink Current PGOOD = 0.4V 200 735 µA
SYNC Input Low Threshold fSYNC = 550kHz 0.5 V
SYNC Input High Threshold fSYNC = 550kHz 0.7 V
SYNC Bias Current SYNC = 0V 0.1 µA
500kHz Narrowband Conducted Emissions 24VIN, 3.3VOUT, IOUT = 3A, 5µH LISN 89
69
51
dBµV
dBµV
dBµV
1MHz Narrowband Conducted Emissions
3MHz Narrowband Conducted Emissions
LTM8033I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8033MP is
guaranteed to meet specifications over the full –55°C to 125°C internal
operating temperature range. Note that the maximum internal temperature
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
2.5VOUT Efficiency 3.3VOUT Efficiency 5VOUT Efficiency
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
95
2500 3000
8033 G01
500
5VIN
12VIN
24VIN
36VIN
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
2500 3000
8033 G02
500
5.5VIN 12VIN
36VIN 24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
95
2500 3000
8033 G03
500
12VIN
24VIN
36VIN
LTM8033
4
8033f
TYPICAL PERFORMANCE CHARACTERISTICS
Bias Current vs Load Current,
2.5VOUT
Bias Current vs Load Current,
3.3VOUT
Bias Current vs Load Current,
5VOUT
Bias Current vs Load Current,
8VOUT
Bias Current vs Load Current,
12VOUT
Bias Current vs Load Current,
18VOUT
8VOUT Efficiency 12VOUT Efficiency 18VOUT Efficiency
TA = 25°C, unless otherwise noted.
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
95
2500 3000
8033 G04
500
12VIN
36VIN 24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
95
2500 3000
8033 G05
500
24VIN
36VIN
OUTPUT CURRENT (mA)
0 20001000 1500
50
EFFICIENCY (%)
55
65
60
80
75
70
85
90
95
2500 3000
8033 G06
500
36VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
10
5
20
15
35
30
25
40
45
50
2500 3000
8033 G07
500
36VIN
5VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
20
10
40
30
60
50
70
80
2500 3000
8033 G08
500
36VIN
5VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
10
5
20
15
30
25
35
40
2500 3000
8033 G09
500
36VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
10
30
20
60
50
40
70
80
90
2500 3000
8033 G10
500
12VIN
24VIN
36VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
10
30
20
60
50
40
70
80
2500 3000
8033 G11
500
24VIN
36VIN
LOAD CURRENT (mA)
0 20001000 1500
0
BIAS CURRENT (mA)
10
30
20
60
50
40
70
80
90
2500 3000
8033 G12
500
36VIN
LTM8033
5
8033f
TYPICAL PERFORMANCE CHARACTERISTICS
Input Current vs Output Current
5VOUT
Input Current vs Output Current
8VOUT
Input Current vs Output Current
12VOUT
Input Current vs Output Current
18VOUT
Minimum Required Input Voltage
vs Output Voltage, IOUT = 3A
Minimum Required Input Voltage
vs Load Current, 2.5VOUT
Input Current vs Input Voltage
Output Shorted
Input Current vs Output Current
2.5VOUT
Input Current vs Output Current
3.3VOUT
TA = 25°C, unless otherwise noted.
INPUT VOLTAGE (V)
02010
0
INPUT CURRENT (mA)
100
300
200
600
500
400
700
800
1000
900
30 40
8033 G13
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
1000
500
1500
2000
2500
2500 3000
8033 G14
500
36VIN
5VIN
12VIN
24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
1000
500
1500
2000
2500
2500 3000
8033 G15
500
36VIN
5.5VIN
12VIN
24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
400
200
600
800
1400
1200
1000
1600
2500 3000
8033 G16
500
36VIN
12VIN
24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
500
2000
1500
1000
2500
2500 3000
8033 G17
500
36VIN
12VIN
24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
200
400
600
800
1600
1400
1200
1000
1800
2500 3000
8033 G18
500
36VIN
24VIN
OUTPUT CURRENT (mA)
0 20001000 1500
0
INPUT CURRENT (mA)
200
400
600
800
1600
1400
1200
1000
1800
2500 3000
8033 G19
500
36VIN
OUTPUT VOLTAGE (V)
010
0
INPUT VOLTAGE (V)
5
10
15
20
35
30
25
40
15
8033 G20
5
LOAD CURRENT (mA)
0 20001000 1500
3.0
INPUT VOLTAGE (V)
3.2
3.4
4.2
4.0
3.8
3.6
4.4
2500 3000
8033 G21
500
TO START, WITH RUN = VIN
TO RUN OR SS
CONTROLLED START
LTM8033
6
8033f
TYPICAL PERFORMANCE CHARACTERISTICS
Minimum Required Input Voltage
vs Load Current, 12VOUT
Minimum Required Input Voltage
vs Load Current, 18VOUT
Radiated Emissions, 36VIN,
24VOUT at 1.5A Load
Radiated Emissions, 36VIN,
1.2VOUT at 3A Load
Temperature Rise vs Load
Current, 2.5VOUT
Temperature Rise vs Load
Current, 3.3VOUT
Minimum Required Input Voltage
vs Load Current, 3.3VOUT
Minimum Required Input Voltage
vs Load Current, 5VOUT
Minimum Required Input Voltage
vs Load Current, 8VOUT
TA = 25°C, unless otherwise noted.
LOAD CURRENT (mA)
0 20001000 1500
3.0
INPUT VOLTAGE (V)
3.5
4.0
5.5
5.0
4.5
6.0
2500 3000
8033 G22
500
TO START, WITH RUN = VIN
TO RUN
RUN/SS CONTROLLED START
LOAD CURRENT (mA)
0 20001000 1500
3.0
INPUT VOLTAGE (V)
3.5
4.0
7.5
7.0
6.5
5.5
5.0
6.0
4.5
8.0
2500 3000
8033 G23
500
TO START, WITH RUN = VIN
TO RUN OR RUN/SS
CONTROLLED START
LOAD CURRENT (mA)
0 20001000 1500
8.0
INPUT VOLTAGE (V)
8.5
10.0
9.5
9.0
10.5
2500 3000
8033 G24
500
TO START, WITH RUN = VIN
TO RUN OR RUN/SS
CONTROLLED START
LOAD CURRENT (mA)
0 20001000 1500
TO RUN OR START
12
INPUT VOLTAGE (V)
13
19
15
16
17
18
14
20
2500 3000
8033 G25
500
LOAD CURRENT (mA)
0 20001000 1500
12
INPUT VOLTAGE (V)
14
28
18
22
20
24
26
16
30
2500 3000
8033 G26
500
TO START,
WITH RUN = VIN
TO RUN
RUN/SS CONTROLLED START
FREQUENCY (MHz)
30 814.8
716.7
618.6
520.5
226.2
324.3
422.4
0
10
30
20
60
50
40
70
80
912.9
1010
8033 G27
128.1
dBµV/m
FREQUENCY (MHz)
30 814.8
716.7
618.6
520.5
226.2
324.3
422.4
0
10
30
20
60
50
40
70
80
912.9
1010
8033 G28
128.1
dBµV/m
LOAD CURRENT (mA)
0 20001000 1500
0
TEMPERATURE RISE (°C)
35
10
20
15
25
30
5
40
2500 3000 3500
8033 G29
500
36VIN
5VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
TEMPERATURE RISE (°C)
35
10
20
15
25
30
5
40
2500 3000
8033 G30
500
36VIN
12VIN
24VIN
LTM8033
7
8033f
TYPICAL PERFORMANCE CHARACTERISTICS
Temperature Rise vs Load
Current, 18VOUT
Temperature Rise vs Load
Current, 5VOUT
Temperature Rise vs Load
Current, 8VOUT
Temperature Rise vs Load
Current, 12VOUT
TA = 25°C, unless otherwise noted.
LOAD CURRENT (mA)
0 20001000 1500
0
TEMPERATURE RISE (°C)
35
10
20
15
25
30
5
45
40
2500 3000
8033 G31
500
36VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
TEMPERATURE RISE (°C)
40
10
20
30
60
50
2500 3000
8033 G32
500
36VIN
12VIN
24VIN
LOAD CURRENT (mA)
0 20001000 1500
0
TEMPERATURE RISE (°C)
40
10
20
30
70
50
60
2500 3000
8033 G33
500
36VIN
24VIN
LOAD CURRENT (mA)
0 1000 1500
0
TEMPERATURE RISE (°C)
40
10
20
30
70
50
60
2000
8033 G34
500
36VIN
LTM8033
8
8033f
PIN FUNCTIONS
VOUT (Bank 1): Power Output Pins. Apply the output filter
capacitor and the output load between these pins and
GND pins.
GND (A8, Bank 2): Tie these GND pins to a local ground
plane below the LTM8033 and the circuit components.
Return the feedback divider (RADJ) to this net.
FIN (Bank 3): Filtered Input. This is the node after the input
EMI filter. Apply the capacitor recommended by Table 1.
Additional capacitance may be applied if there is a need
to modify the behavior of the integrated EMI filter; other-
wise, leave these pins unconnected. See the Applications
Information section for more details.
VIN (Bank 4): The VIN pin supplies current to the LTM8033’s
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor; see Table 1 for recommended values. Ensure
that VIN + BIAS is less than 56V.
SHARE (Pin A6): Tie this to the SHARE pin of another
LTM8033 when paralleling the outputs. Otherwise, do
not connect.
ADJ (Pin A7): The LTM8033 regulates its ADJ pin to 0.79V.
Connect the adjust resistor from this pin to ground. The
value of RADJ is given by the equation RADJ = 394.21/(VOUT
– 0.79), where RADJ is in kΩ.
RT (Pin B6): The RT pin is used to program the switching
frequency of the LTM8033 by connecting a resistor from
this pin to ground. The Applications Information section of
the data sheet includes a table to determine the resistance
value based on the desired switching frequency. Minimize
capacitance at this pin.
SYNC (Pin B8): This is the external clock synchronization
input. Ground this pin for low ripple Burst Mode
®
operation
at low output loads. Tie to a stable voltage source greater
than 0.7V to disable Burst Mode operation. Do not leave
this pin floating. Tie to a clock source for synchronization.
Clock edges should have rise and fall times faster than
1s. See the Synchronization section in the Applications
Information section.
PGOOD (Pin B7): The PGOOD pin is the open-collector
output of an internal comparator. PGOOD remains low
until the ADJ pin is greater than 90% of the final regulation
voltage. PGOOD output is valid when VIN is above 3.6V
and RUN/SS is high. If this function is not used, leave
this pin floating.
AUX (Pin G3): Low Current Voltage Source for BIAS.
In many designs, the BIAS pin is simply connected to
VOUT. The AUX pin is internally connected to VOUT and
is placed adjacent to the BIAS pin to ease printed circuit
board routing. Although this pin is internally connected
to VOUT, it is not intended to deliver a high current, so do
not connect this pin to the load. If this pin is not tied to
BIAS, leave it floating.
BIAS (Pin G4): The BIAS pin connects to the internal power
bus. Connect to a power source greater than 2.8V and less
than 25V. If the output is greater than 2.8V, connect this
pin there. If the output voltage is less, connect this to a
voltage source between 2.8V and 25V but ensure that VIN
+ BIAS is less than 56V.
RUN/SS (Pin G8): Pull the RUN/SS pin below 0.2V to
shut down the LTM8033. Tie to 2.5V or more for normal
operation. If the shutdown feature is not used, tie this pin
to the VIN pin. RUN/SS also provides a soft-start function;
see the Applications Information section.
LTM8033
9
8033f
BLOCK DIAGRAM
8033 BD
CURRENT
MODE
CONTROLLER
RUN/SS
SHARE
SYNC
FIN
VIN
499k
1µF
EMI
FILTER
15pF
GND RT PGOOD ADJ
BIAS
AUX
VOUT
8.2µH
LTM8033
10
8033f
OPERATION
The LTM8033 is a standalone nonisolated step-down
switching DC/DC power supply that can deliver up to 3A of
output current. It is an EMC product; its radiated emissions
are so quiet that it can pass the stringent requirements of
EN55022 class B as a stand alone product. This µModule
provides a precisely regulated output voltage program-
mable via one external resistor from 0.8V to 25V. The input
voltage range is 3.6V to 36V. Given that the LTM8033 is
a step-down converter, make sure that the input voltage
is high enough to support the desired output voltage and
load current.
As shown in the Block Diagram, the LTM8033 contains an
EMI filter, current mode controller, power switching ele-
ment, power inductor, power Schottky diode and a modest
amount of input and output capacitance. The LTM8033 is
a fixed frequency PWM regulator. The switching frequency
is set by simply connecting the appropriate resistor value
from the RT pin to GND.
An internal regulator provides power to the control cir-
cuitry. The bias regulator normally draws power from the
VIN pin, but if the BIAS pin is connected to an external
voltage higher than 2.8V, bias power will be drawn from
the external source (typically the regulated output voltage).
This improves efficiency. The RUN/SS pin is used to place
the LTM8033 in shutdown, disconnecting the output and
reducing the input current to less than 1A.
To further optimize efficiency, the LTM8033 automatically
switches to Burst Mode operation in light load situations.
Between bursts, all circuitry associated with controlling
the output switch is shut down reducing the input supply
current to 50A in a typical application.
The oscillator reduces the LTM8033’s operating frequency
when the voltage at the ADJ pin is low. This frequency
foldback helps to control the output current during start-
up and overload.
The LTM8033 contains a power good comparator which
trips when the ADJ pin is at roughly 90% of its regulated
value. The PGOOD output is an open-collector transistor
that is off when the output is in regulation, allowing an
external resistor to pull the PGOOD pin high. Power good
is valid when the LTM8033 is enabled and VIN is above
3.6V.
The LTM8033 is equipped with a thermal shutdown that
will inhibit power switching at high junction temperatures.
The activation threshold of this function, however, is above
125°C to avoid interfering with normal operation. Thus,
prolonged or repetitive operation under a condition in
which the thermal shutdown activates may damage or
impair the reliability of the device.
LTM8033
11
8033f
APPLICATIONS INFORMATION
For most applications, the design process is straight for-
ward, summarized as follows:
• Look at Table 1 and find the row that has the desired
input range and output voltage.
• Apply the recommended CIN, CFIN, COUT, RADJ and RT
values.
• Connect BIAS as indicated.
As the integrated input EMI filter may ring in response to
an application of a step input voltage, a bulk capacitance
may be applied between FIN and GND. See the Hot-Plug-
ging Safely section for details.
While these component combinations have been tested
for proper operation, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions. Bear in mind that the
maximum output current is limited by junction tempera-
ture, the relationship between the input and output voltage
magnitude and polarity and other factors. Please refer to
the graphs in the Typical Performance Characteristics
section for guidance.
The maximum frequency (and attendant RT value) at
which the LTM8033 should be allowed to switch is given
in Table 1 in the fMAX column, while the recommended
frequency (and RT value) for optimal efficiency over the
given input condition is given in the fOPTIMAL column.
There are additional conditions that must be satisfied if
the synchronization function is used. Please refer to the
Synchronization section for details.
Note: An input bulk capacitance is required at either VIN
or FIN. Refer to the Typical Performance Characteristics
section for load conditions.
Capacitor Selection Considerations
The CIN, CFIN and COUT capacitor values in Table 1 are the
minimum recommended values for the associated oper-
ating conditions. Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield improved dynamic response, if
it is necessary. Again, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions.
Ceramic capacitors are small, robust and have very low
ESR. However, not all ceramic capacitors are suitable.
X5R and X7R types are stable over temperature and ap-
plied voltage and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application cir-
cuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
Ceramic capacitors are also piezoelectric. In Burst Mode
operation, the LTM8033’s switching frequency depends
on the load current, and can excite a ceramic capacitor
at audio frequencies, generating audible noise. Since the
LTM8033 operates at a lower current limit during Burst
Mode operation, the noise is typically very quiet to a
casual ear.
If this audible noise is unacceptable, use a high perfor-
mance electrolytic capacitor at the output. It may also be
a parallel combination of a ceramic capacitor and a low
cost electrolytic capacitor.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8033. A
ceramic input capacitor combined with trace or cable
inductance forms a high Q (under damped) tank circuit.
If the LTM8033 circuit is plugged into a live supply, the
input voltage can ring to twice its nominal value, possibly
exceeding the device’s rating. This situation can be easily
avoided; see the Hot-Plugging Safely section.
LTM8033
12
8033f
APPLICATIONS INFORMATION
Table 1. Recommended Component Values and Configuration (TA = 25°C)
VIN VOUT CIN CFIN COUT BIAS RADJ fOPTIMAL RT(OPTIMAL) fMAX RT(MIN)
3.6V to 36V 0.8V 4.7µF, 50V, 1206 10µF, 50V, 1210 4 × 100µF, 6.3V, 1210 2.8V to 25V 30M 230kHz 182k 250kHz 169k
3.6V to 36V 1V 4.7µF, 50V, 1206 10µF, 50V, 1210 4 × 100µF, 6.3V, 1210 2.8V to 25V 1.87M 240kHz 174k 285kHz 147k
3.6V to 36V 1.2V 4.7µF, 50V, 1206 10µF, 50V, 1210 4 × 100µF, 6.3V, 1210 2.8V to 25V 953k 255kHz 162k 315kHz 130k
3.6V to 36V 1.5V 4.7µF, 50V, 1206 10µF, 50V, 1210 4 × 100µF, 6.3V, 1210 2.8V to 25V 549k 270kHz 154k 360kHz 113k
3.6V to 36V 1.8V 4.7µF, 50V, 1206 10µF, 50V, 1210 4 × 100µF, 6.3V, 1210 2.8V to 25V 383k 285kHz 147k 420kHz 95.3k
4.1V to 36V 2.5V 4.7µF, 50V, 1206 10µF, 50V, 1210 3 × 100µF, 6.3V, 1210 2.8V to 25V 226k 345kHz 118k 540kHz 71.5k
5.3V to 36V 3.3V 4.7µF, 50V, 1206 10µF, 50V, 1210 100µF, 6.3V, 1210 AUX 154k 425kHz 93.1k 675kHz 54.9k
7.5V to 36V 5V 4.7µF, 50V, 1206 4.7µF, 50V, 1206 100µF, 6.3V, 1210 AUX 93.1k 500kHz 76.8k 950kHz 36.5k
10.5V to 36V 8V 4.7µF, 50V, 1206 1µF, 50V, 1206 47µF, 16V, 1210 AUX 54.9k 700kHz 52.3k 1.45MHz 20.5k
20V to 36V 12V 2.2µF, 50V, 1206 1µF, 50V, 1206 47µF, 16V, 1210 AUX 34.8k 850kHz 41.2k 2.3MHz 9.09k
25.5V to 36V 18V 2.2µF, 50V, 1206 Open 22F, 25V, 1812 AUX 22.6k 1.1MHz 29.4k 2.4MHz 8.25k
32.5V to 36V 24V 1µF, 50V, 1206 Open 22F, 25V, 1812 2.8V to 20V 16.5k 1.2MHz 25.5k 2.4MHz 8.25k
3.6V to 15V 0.8V 4.7µF, 25V, 1206 10µF, 16V, 1210 4 × 100µF, 6.3V, 1210 VIN 30M 230kHz 182k 575kHz 66.5k
3.6V to 15V 1V 4.7µF, 25V, 1206 10µF, 16V, 1210 4 × 100µF, 6.3V, 1210 VIN 1.87M 240kHz 174k 660kHz 56.2k
3.6V to 15V 1.2V 4.7µF, 25V, 1206 10µF, 16V, 1210 4 × 100µF, 6.3V, 1210 VIN 953k 255kHz 162k 760kHz 47.5k
3.6V to 15V 1.5V 4.7µF, 25V, 1206 10µF, 16V, 1210 4 × 100µF, 6.3V, 1210 VIN 549k 270kHz 154k 840kHz 42.2k
3.6V to 15V 1.8V 4.7µF, 25V, 1206 10µF, 16V, 1210 4 × 100µF, 6.3V, 1210 VIN 383k 285kHz 147k 1.0MHz 34.0k
4.1V to 15V 2.5V 4.7µF, 16V, 1206 10µF, 16V, 1210 3 x 100µF, 6.3V, 1210 VIN 226k 345kHz 118k 1.3MHz 23.7k
5.3V to 15V 3.3V 4.7µF, 16V, 1206 10µF, 16V, 1210 100µF, 6.3V, 1210 AUX 154k 425kHz 93.1k 1.6MHz 17.8k
7.5V to 15V 5V 4.7µF, 16V, 1206 4.7µF, 50V, 1206 100µF, 6.3V, 1210 AUX 93.1k 500kHz 76.8k 2.4MHz 8.25k
10.5V to 15V 8V 2.2µF, 25V, 1206 Open 47µF, 16V, 1210 AUX 54.9k 700kHz 52.3k 2.4MHz 8.25k
9V to 24V 0.8V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 4 × 100µF, 6.3V, 1210 VIN 30M 270kHz 154k 360kHz 113k
9V to 24V 1V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 4 × 100µF, 6.3V, 1210 VIN 1.87M 285kHz 147k 410kHz 97.6k
9V to 24V 1.2V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 4 × 100µF, 6.3V, 1210 VIN 953k 295kHz 140k 475kHz 82.5k
9V to 24V 1.5V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 4 × 100µF, 6.3V, 1210 VIN 549k 310kHz 133k 550kHz 69.8k
9V to 24V 1.8V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 3 × 100µF, 6.3V, 1210 VIN 383k 330kHz 124k 620kHz 60.4k
9V to 24V 2.5V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 2 × 100µF, 6.3V, 1210 VIN 226k 345kHz 118k 800kHz 44.2k
9V to 24V 3.3V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 100µF, 6.3V, 1210 AUX 154k 425kHz 93.1k 1.0MHz 34.0k
9V to 24V 5V 4.7µF, 25V, 1206 4.7µF, 25V, 1206 100µF, 6.3V, 1210 AUX 93.1k 500kHz 76.8k 1.4MHz 21.5k
10.5V to 24V 8V 2.2µF, 25V, 1206 1µF, 25V, 1206 47µF, 16V, 1210 AUX 54.9k 700kHz 52.3k 2.2MHz 9.76k
20V to 24V 12V 2.2µF, 25V, 1206 1µF, 25V, 1206 47µF, 16V, 1210 AUX 34.8k 850kHz 41.2k 2.3MHz 9.09k
18V to 36V 0.8V 1µF, 50V, 1206 2.2µF, 50V, 1206 4 × 100µF, 6.3V, 1210 2.8V to 25V 30M 230kHz 182k 250kHz 169k
18V to 36V 1V 1µF, 50V, 1206 2.2µF, 50V, 1206 4 × 100µF, 6.3V, 1210 2.8V to 25V 1.87M 240kHz 174k 285kHz 147k
18V to 36V 1.2V 1µF, 50V, 1206 2.2µF, 50V, 1206 4 × 100µF, 6.3V, 1210 2.8V to 25V 953k 255kHz 162k 315kHz 130k
18V to 36V 1.5V 1µF, 50V, 1206 2.2µF, 50V, 1206 4 × 100µF, 6.3V, 1210 2.8V to 25V 549k 270kHz 154k 360kHz 113k
18V to 36V 1.8V 1µF, 50V, 1206 2.2µF, 50V, 1206 3 × 100µF, 6.3V, 1210 2.8V to 25V 383k 285kHz 147k 420kHz 95.3k
18V to 36V 2.5V 1µF, 50V, 1206 2.2µF, 50V, 1206 2 × 100µF, 6.3V, 1210 2.8V to 25V 226k 345kHz 118k 540kHz 71.5k
18V to 36V 3.3V 1µF, 50V, 1206 2.2µF, 50V, 1206 100µF, 6.3V, 1210 AUX 154k 425kHz 93.1k 675kHz 54.9k
18V to 36V 5V 1µF, 50V, 1206 1µF, 50V, 1206 47µF, 10V, 1210 AUX 93.1k 500kHz 76.8k 950kHz 36.5k
18V to 36V 8V 2.2µF, 50V, 1206 1µF, 50V, 1206 47µF, 16V, 1210 AUX 54.9k 700kHz 52.3k 1.45MHz 20.5k
Note: A bulk capacitor is required. Do not allow VIN + BIAS above 56V.
LTM8033
13
8033f
APPLICATIONS INFORMATION
Frequency Selection
The LTM8033 uses a constant frequency PWM architecture
that can be programmed to switch from 200kHz to 2.4MHz
by using a resistor tied from the RT pin to ground. Table 2
provides a list of RT resistor values and their resulting
frequencies.
Table 2. Switching Frequency vs RT Value
SWITCHING FREQUENCY (MHz) RT VALUE (kΩ)
0.2 215
0.3 137
0.4 100
0.5 76.8
0.6 63.4
0.7 52.3
0.8 44.2
0.9 38.3
134
1.2 25.5
1.4 21.5
1.6 17.8
1.8 14.7
2 12.1
2.2 9.76
2.4 8.25
Operating Frequency Trade-Offs
It is recommended that the user apply the optimal RT
value given in Table 1 for the input and output operating
condition. System level or other considerations, however,
may necessitate another operating frequency. While the
LTM8033 is flexible enough to accommodate a wide range
of operating frequencies, a haphazardly chosen one may
result in undesirable operation under certain operating or
fault conditions. A frequency that is too high can reduce
efficiency, generate excessive heat or even damage the
LTM8033 if the output is overloaded or short-circuited.
A frequency that is too low can result in a final design
that has too much output ripple or too large of an output
capacitor.
BIAS Pin Considerations
The BIAS pin is used to provide drive power for the internal
power switching stage and operate other internal circuitry.
For proper operation, it must be powered by at least 2.8V. If
the output voltage is programmed to 2.8V or higher, BIAS
may be simply tied to VOUT. If VOUT is less than 2.8V, BIAS
can be tied to VIN or some other voltage source. If the BIAS
pin voltage is too high, the efficiency of the LTM8033 may
suffer. The optimum BIAS voltage is dependent upon many
factors, such as load current, input voltage, output voltage
and switching frequency, but 4V to 5V works well in many
applications. In all cases, ensure that the maximum voltage
at the BIAS pin is less than 25V and that the sum of VIN
and BIAS is less than 56V. If BIAS power is applied from
a remote or noisy voltage source, it may be necessary to
apply a decoupling capacitor locally to the pin.
Load Sharing
Two or more LTM8033 may be paralleled to produce higher
currents. To do this, tie the VIN, ADJ, VOUT and SHARE
pins of all the paralleled LTM8033 together. To ensure that
paralleled modules start up together, the RUN/SS pins
may be tied together as well. If the RUN/SS pins are not
tied together, make sure that the same valued soft-start
capacitors are used for each module. Current sharing can
be improved by synchronizing the LTM8033s. An example
of two LTM8033 configured for load sharing is given in
the Typical Applications section.
Burst Mode Operation
To enhance efficiency at light loads, the LTM8033 auto-
matically switches to Burst Mode operation which keeps
the output capacitor charged to the proper voltage while
minimizing the input quiescent current. During Burst Mode
operation, the LTM8033 delivers single cycle bursts of
current to the output capacitor followed by sleep periods
where the output power is delivered to the load by the output
capacitor. In addition, VIN and BIAS quiescent currents are
reduced to typically 20A and 50A respectively during
the sleep time. As the load current decreases towards a
LTM8033
14
8033f
APPLICATIONS INFORMATION
no-load condition, the percentage of time that the LTM8033
operates in sleep mode increases and the average input
current is greatly reduced, resulting in higher efficiency.
Burst Mode operation is enabled by tying SYNC to GND. To
disable Burst Mode operation, tie SYNC to a stable voltage
above 0.7V. Do not leave the SYNC pin floating.
Minimum Input Voltage
The LTM8033 is a step-down converter, so a minimum
amount of headroom is required to keep the output in
regulation. In addition, the input voltage required to turn
on is higher than that required to run, and depends upon
BIAS power whether RUN/SS is used. If BIAS is available
before VOUT ramps up, the minimum VIN voltage to start
may be reduced. As shown in the Typical Performance
Characteristics section, the minimum input voltage to
run a 3.3V output at light load is only about 3.6V, but, if
RUN/SS is pulled up to VIN, it takes 5.6VIN to start. If the
LTM8033 is enabled with the RUN/SS pin, the minimum
voltage to start at light loads is lower, about 4.2V. Similar
curves detailing this behavior of the LTM8033 for other
outputs are also included in the Typical Performance
Characteristics section.
Soft-Start
The RUN/SS pin can be used to soft-start the LTM8033,
reducing the maximum input current during start-up. The
RUN/SS pin is driven through an external RC filter to cre-
ate a voltage ramp at this pin. Figure 2 shows the start-up
and shutdown waveforms with the soft-start circuit. By
choosing an appropriate RC time constant, the peak start-
up current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
of the resistor so that it can supply at least 20A when
the RUN/SS pin reaches 2.5V.
Frequency Foldback
The LTM8033 is equipped with frequency foldback which
acts to reduce the thermal and energy stress on the internal
power elements during a short-circuit or output overload
condition. If the LTM8033 detects that the output has fallen
out of regulation, the switching frequency is reduced as a
function of how far the output is below the target voltage.
This in turn limits the amount of energy that can be delivered
to the load under fault. During the start-up time, frequency
foldback is also active to limit the energy delivered to the
potentially large output capacitance of the load.
Figure 2. To Soft-Start the LTM8033, Add a Resistor and Capacitor to the RUN/SS Pin
VOUT
2V/DIV
INTERNAL
INDUCTOR
CURRENT
1A/DIV
VRUN/SS
2V/DIV
2ms/DIV 8033 F02
GND
RUN
RUN/SS
0.22µF
15k
LTM8033
15
8033f
Synchronization
The internal oscillator of the LTM8033 can be synchro-
nized by applying an external 250kHz to 2MHz clock to
the SYNC pin. Do not leave this pin floating. Ground the
SYNC pin if the synchronization function is not used.
When synchronizing the LTM8033, select an RT resistor
value that corresponds to an operating frequency 20%
lower than the intended synchronization frequency (see
the Frequency Selection section).
In addition to synchronization, the SYNC pin controls Burst
Mode behavior. If the SYNC pin is driven by an external
clock, or pulled up above 0.7V, the LTM8033 will not en-
ter Burst Mode operation, but will instead skip pulses to
maintain regulation instead.
APPLICATIONS INFORMATION
Figure 3. The Input Diode Prevents a Shorted Input from Discharging
a Backup Battery Tied to the Output. It Also Protects the Circuit from a
Reversed Input. The LTM8033 Runs Only When the Input is Present
8033 F03
VIN
RUN/SS
SHARE
VIN VOUT
VOUT
AUX
BIAS
ADJ
RT
LTM8033
SYNC GND
Shorted Input Protection
Care needs to be taken in systems where the output will be
held high when the input to the LTM8033 is absent. This
may occur in battery charging applications or in battery
backup systems where a battery or some other supply is
diode OR-ed with the LTM8033’s output. If the VIN pin is
allowed to float and the RUN/SS pin is held high (either
by a logic signal or because it is tied to VIN), then the
LTM8033’s internal circuitry will pull its quiescent current
through its internal power switch. This is fine if your system
can tolerate a few milliamps in this state. If you ground the
RUN/SS pin, the SW pin current will drop to essentially
zero. However, if the VIN pin is grounded while the output
is held high, then parasitic diodes inside the LTM8033 can
pull large currents from the output through the VIN pin.
Figure 3 shows a circuit that will run only when the input
voltage is present and that protects against a shorted or
reversed input.
LTM8033
16
8033f
APPLICATIONS INFORMATION
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8033. The LTM8033 is neverthe-
less a switching power supply, and care must be taken to
minimize EMI and ensure proper operation. Even with the
high level of integration, you may fail to achieve specified
operation with a haphazard or poor layout. See Figure 4
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
A few rules to keep in mind are:
1. Place the RADJ and RT resistors as close as possible to
their respective pins.
2. Place the CIN and CFIN capacitors as close as possible
to the VIN, FIN and GND connections of the LTM8033.
A haphazardly placed CFIN capacitor may impair EMI
performance.
3. Place the COUT capacitors as close as possible to the
VOUT and GND connection of the LTM8033.
Figure 4. Layout Showing Suggested External
Components, GND Plane and Thermal Vias
4. Place the CIN, CFIN and COUT capacitors such that their
ground currents flow directly adjacent or underneath
the LTM8033.
5. Connect all of the GND connections to as large a copper
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8033.
6. Use vias to connect the GND copper area to the board’s
internal ground planes. Liberally distribute these GND
vias to provide both a good ground connection and
thermal path to the internal planes of the printed circuit
board. Pay attention to the location and density of the
thermal vias in Figure 4. The LTM8033 can benefit from
the heat sinking afforded by vias that connect to internal
GND planes at these locations, due to their proximity
to internal power handling components. The optimum
number of thermal vias depends upon the printed
circuit board design. For example, a board might use
very small via holes. It should employ more thermal
vias than a board that uses larger holes.
PG
RADJ
RT
SYNC
GND
SHARE
FIN
RUN/SS
GND
VOUT GND VIN
COUT CIN
THERMAL VIAS TO GND
LTM8033
BIAS
AUX
CFIN
LTM8033
17
8033f
APPLICATIONS INFORMATION
Hot-Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8033. However, these capacitors
can cause problems if the LTM8033 is plugged into a live
supply (see Application Note 88 for a complete discus-
sion). The low loss ceramic capacitor combined with
stray inductance in series with the power source forms an
underdamped tank circuit, and the voltage at the VIN pin
of the LTM8033 can ring to more than twice the nominal
input voltage, possibly exceeding the LTM8033’s rating and
damaging the part. A similar phenomenon can occur inside
the LTM8032 module, at the output of the integrated EMI
filter (FIN), with the same potential of damaging the part.
If the input supply is poorly controlled or the user will be
plugging the LTM8033 into an energized supply, the input
network should be designed to prevent this overshoot.
This can be accomplished by installing a small resistor
in series to VIN, but the most popular method of control-
ling input voltage overshoot is adding an electrolytic bulk
capacitor to the VIN or FIN net. This capacitor’s relatively
high equivalent series resistance damps the circuit and
eliminates the voltage overshoot. The extra capacitor
improves low frequency ripple filtering and can slightly
improve the efficiency of the circuit, though it can be a
large component in the circuit.
Electromagnetic Compliance
The LTM8033 was evaluated by an independent nation-
ally recognized test lab and found to be compliant with
EN 55022 class B: 2006 by a wide margin. Sample graphs
of the LTM8033’s radiated EMC performance are given in the
Typical Performance Characteristics section, while further
data, operating conditions and test set-up are detailed in
the electromagnetic compatibility test report, available
on the Linear Technology website. Conducted emissions
requirements may be met by adding an appropriate input
power line filter. The proper implementation of this filter
depends upon the system operating and performance
conditions as a whole, of which the LTM8033 is typically
only a component, so conducted emissions are not ad-
dressed at this level.
Thermal Considerations
The LTM8033 output current may need to be derated if it
is required to operate in a high ambient temperature or
deliver a large amount of continuous power. The amount
of current derating is dependent upon the input voltage,
output power and ambient temperature. The temperature
rise curves given in the Typical Performance Charac-
teristics section can be used as a guide. These curves
were generated by an LTM8033 mounted to a 40cm2
4-layer FR4 printed circuit board. Boards of other sizes
and layer count can exhibit different thermal behavior, so
it is incumbent upon the user to verify proper operation
over the intended system’s line, load and environmental
operating conditions.
The thermal resistance numbers listed in the Pin Con-
figuration are based on modeling the µModule package
mounted on a test board specified per JESD51-9 “Test
Boards for Area Array Surface Mount Package Thermal
Measurements.” The thermal coefficients provided in this
page are based on JESD 51-12 “Guidelines for Reporting
and Using Electronic Package Thermal Information.”
For increased accuracy and fidelity to the actual application,
many designers use FEA to predict thermal performance.
To that end, the Pin Configuration typically gives four
thermal coefficients:
• θJA – Thermal resistance from junction to ambient.
• θJCBOTTOM – Thermal resistance from junction to the
bottom of the product case.
• θJCTOP – Thermal resistance from junction to top of
the product case.
• θJB – Thermal resistance from junction to the printed
circuit board.
LTM8033
18
8033f
While the meaning of each of these coefficients may seem
to be intuitive, JEDEC has defined each to avoid confu-
sion and inconsistency. These definitions are given in
JESD 51-12, and are quoted or paraphrased in the fol-
lowing:
• θJA is the natural convection junction-to-ambient air
thermal resistance measured in a one cubic foot sealed
enclosure. This environment is sometimes referred to as
“still air” although natural convection causes the air to
move. This value is determined with the part mounted to
a JESD 51-9 defined test board, which does not reflect
an actual application or viable operating condition.
• θJCBOTTOM is the junction-to-board thermal resistance
with all of the component power dissipation flowing
through the bottom of the package. In the typical
µModule, the bulk of the heat flows out the bottom
of the package, but there is always heat flow out into
the ambient environment. As a result, this thermal re-
sistance value may be useful for comparing packages
but the test conditions don’t generally match the user’s
application.
• θJCTOP is determined with nearly all of the component
power dissipation flowing through the top of the pack-
age. As the electrical connections of the typical µModule
are on the bottom of the package, it is rare for an ap-
plication to operate such that most of the heat flows
from the junction to the top of the part. As in the case
of θJCBOTTOM, this value may be useful for comparing
packages but the test conditions don’t generally match
the user’s application.
• θJB is the junction-to-board thermal resistance where
almost all of the heat flows through the bottom of the
µModule and into the board, and is really the sum of
the θJCBOTTOM and the thermal resistance of the bot-
tom of the part through the solder joints and through
a portion of the board. The board temperature is mea-
sured a specified distance from the package, using a
two sided, two layer board. This board is described in
JESD 51-9.
The most appropriate way to use the coefficients is when
running a detailed thermal analysis, such as FEA, which
considers all of the thermal resistances simultaneously.
None of them can be individually used to accurately pre-
dict the thermal performance of the product, so it would
be inappropriate to attempt to use any one coefficient to
correlate to the junction temperature versus load graphs
given in the LTM8033 data sheet.
A graphical representation of these thermal resistances
is given in Figure 5.
The blue resistances are contained within the µModule,
and the green are outside.
The die temperature of the LTM8033 must be lower than
the maximum rating of 125°C, so care should be taken
in the layout of the circuit to ensure good heat sinking
of the LTM8033. The bulk of the heat flow out of the
LTM8033 is through the bottom of the module and the LGA
pads into the printed circuit board. Consequently a poor
printed circuit board design can cause excessive heating,
APPLICATIONS INFORMATION
8033 F05
µMODULE REGULATOR
JUNCTION-TO-CASE (TOP)
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
CASE (TOP)-TO-AMBIENT
RESISTANCE
BOARD-TO-AMBIENT
RESISTANCE
JUNCTION-TO-CASE
(BOTTOM) RESISTANCE
JUNCTION At
CASE (BOTTOM)-TO-BOARD
RESISTANCE
Figure 5
LTM8033
19
8033f
resulting in impaired performance or reliability. Please
refer to the PCB Layout section for printed circuit board
design suggestions.
The LTM8033 is equipped with a thermal shutdown that
will inhibit power switching at high junction temperatures.
The activation threshold of this function, however, is above
125°C to avoid interfering with normal operation. Thus,
it follows that prolonged or repetitive operation under a
condition in which the thermal shutdown activates neces-
APPLICATIONS INFORMATION
sarily means that the internal components are subjected
to temperatures above the 125°C rating for prolonged
or repetitive intervals, which may damage or impair the
reliability of the device.
Finally, be aware that at high ambient temperatures the
internal Schottky diode will have significant leakage cur-
rent (see the Typical Performance Characteristics section)
increasing the quiescent current of the LTM8033.
TYPICAL APPLICATIONS
8033 TA02
VIN
BIAS
RUN/SS
FIN
SHARE
VIN
3.6V TO 15V
VOUT
0.8V
3A
VOUT
AUX
PGOOD
RT
LTM8033
4.7µF
SYNC GND ADJ
10µF
182k 30M
f = 230kHz
400µF
8033 TA03
VIN
BIAS
RUN/SS
FIN
SHARE
VIN
3.6V TO 36V
VOUT
1.8V
3A
VOUT
AUX
PGOOD
RT
LTM8033
4.7µF 2.8V TO 25V
SYNC GND ADJ
10µF
NOTE: DO NOT ALLOW VIN + BIAS TO BE GREATER THAN 56V.
f = 285kHz
147k 383k
400µF
0.8V Step-Down Converter
1.8V Step-Down Converter
LTM8033
20
8033f
TYPICAL APPLICATIONS
8033 TA05
VIN
SHARE
RUN/SS
FIN
VIN
7.5V TO 36VDC VOUT
5V
3A
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
4.7µF
f = 500kHz
SYNC GND ADJ
4.7µF
76.8k 93.1k
100µF
8033 TA04
VIN
SHARE
BIAS
RUN/SS
FIN
VIN*
4.1V TO 36V
VOUT
2.5V
3A
VOUT
AUX
PGOOD
RT
LTM8033
4.7µF
2.8V to 25V
SYNC GND ADJ
10µF
118k 226k
f = 345kHz
300µF
NOTE: DO NOT ALLOW VIN + BIAS TO BE GREATER THAN 56V.
* RUNNING VOLTAGE RANGE. PLEASE REFER TO THE
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS.
8033 TA06
VIN
SHARE
RUN/SS
FIN
VIN*
11V TO 36V
VOUT
8V
3A
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
4.7µF
SYNC GND ADJ
1µF
52.3k 54.9k
f = 700kHz
47µF
* RUNNING VOLTAGE RANGE. PLEASE REFER TO THE
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS.
2.5V Step-Down Converter
5V Step-Down Converter
8V Step-Down Converter
LTM8033
21
8033f
TYPICAL APPLICATIONS
8033 TA07
VIN
FIN
RUN/SS
SHARE
VIN*
4.8V TO 36V
VOUT
2.5V
5.8A
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
4.7µF
SYNC GND ADJ
10µF
137k
2.8V to 25V
113k
300µF
VIN
FIN
RUN/SS
SHARE
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
SYNC GND ADJ
137k
4.7µF
OPTIONAL
SYNCHRONIZATION
CLOCK
* RUNNING VOLTAGE RANGE. PLEASE REFER TO THE APPLICATIONS
INFORMATION SECTION FOR START-UP DETAILS.
NOTE: SYNCHRONIZE THE TWO MODULES TO AVOID BEAT
FREQUENCIES, IF NECESSARY. OTHERWISE, TIE EACH SYNC TO GND.
10µF
Current Sharing Two LTM8033 Parts
LTM8033
22
8033f
PACKAGE DESCRIPTION
Pin Assignment Table
(Arranged by Pin Number)
PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME
A1 VOUT B1 VOUT C1 VOUT D1 VOUT E1 GND F1 GND
A2 VOUT B2 VOUT C2 VOUT D2 VOUT E2 GND F2 GND
A3 VOUT B3 VOUT C3 VOUT D3 VOUT E3 GND F3 GND
A4 GND B4 GND C4 GND D4 GND E4 GND F4 GND
A5 GND B5 GND C5 GND D5 GND E5 GND F5 GND
A6 SHARE B6 RT C6 GND D6 GND E6 GND F6 GND
A7 ADJ B7 PGOOD C7 GND D7 GND E7 GND F7 GND
A8 GND B8 SYNC C8 GND D8 GND E8 GND F8 GND
PIN NAME PIN NAME PIN NAME PIN NAME PIN NAME
G1 GND J1 VIN K1 VIN L1 VIN
G2 GND J2 VIN K2 VIN L2 VIN
G3 AUX J3 VIN K3 VIN L3 VIN
G4 BIAS
G5 GND H5 GND J5 GND K5 GND L5 GND
G6 GND H6 GND J6 GND K6 GND L6 GND
G7 GND
G8 RUN J8 FIN K8 FIN L8 FIN
PACKAGE PHOTOGRAPH
LTM8033
23
8033f
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.
PACKAGE DESCRIPTION
LGA Package
76-Lead (15mm × 11.25mm × 4.32mm)
(Reference LTC DWG # 05-08-1560 Rev Ø)
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
2. ALL DIMENSIONS ARE IN MILLIMETERS
LAND DESIGNATION PER JESD MO-222
5. PRIMARY DATUM -Z- IS SEATING PLANE
6. THE TOTAL NUMBER OF PADS: 76
4
3
DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
DETAIL B
DETAIL B
SUBSTRATE
MOLD
CAP
0.270 – 0.370
3.95 – 4.05
bbb Z
Z
PACKAGE TOP VIEW
11.25
BSC
15.00
BSC
4
PAD “A1”
CORNER
X
Y
aaa Z
aaa Z
PACKAGE BOTTOM VIEW
3
PADS
SEE NOTES
SUGGESTED PCB LAYOUT
TOP VIEW
LGA 76 0809 REV Ø
LTMXXXXXX
µModule
TRAY PIN 1
BEVEL
PACKAGE IN TRAY LOADING ORIENTATION
COMPONENT
PIN “A1”
8.89
BSC
1.27
BSC
PAD 1
0.635
0.635
1.905
1.905
3.175
3.175
4.445
4.445
6.350
5.080
3.810
3.810
5.080
6.350
2.540
2.540
1.270
1.270
0.000
SYMBOL
aaa
bbb
eee
TOLERANCE
0.15
0.10
0.05
DETAIL A
0.635 ±0.025 75SQ
SYXeee
DETAIL C
0.635 ±0.025 75SQ
SYXeee
F
G
H
L
J
K
E
A
B
C
D
2143567
4.22 – 4.42
DETAIL A
12.70
BSC
8
DETAIL C
LTM8033
24
8033f
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com
© LINEAR TECHNOLOGY CORPORATION 2010
LT 0710 • PRINTED IN USA
RELATED PARTS
TYPICAL APPLICATION
PART NUMBER DESCRIPTION COMMENTS
LTM8031 Ultralow Noise EMC 1A µModule Regulator EN55022 Class B Compliant, 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V
LTM8032 Ultralow Noise EMC 2A µModule Regulator EN55022 Class B Compliant, 3.6V ≤ VIN ≤ 36V; 0.8V ≤ VOUT ≤ 10V
3.3V Step-Down Converter
8033 TA08
VIN
SHARE
RUN/SS
FIN
VIN
5.5V TO 36VDC
VOUT
3.3V
3A
VOUT
AUX
BIAS
PGOOD
RT
LTM8033
4.7µF
SYNC GND ADJ
10µF
93.1k 154k
f = 425kHz
100µF