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PDF LTM8031 Data sheet ( Hoja de datos )
| Número de pieza | LTM8031 | |
| Descripción | Ultralow Noise EMC 36V | |
| Fabricantes | Linear Technology Corporation | |
| Logotipo |  |
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FEATURES
n Complete Step-Down Switch Mode Power Supply
n Wide Input Voltage Range: 3.6V to 36V
n 1A Output Current
n 0.8V to 10V Output Voltage
n Switching Frequency from 200kHz to 2.4MHz
n EN55022 Class B Compliant
n Current Mode Control
n (e4) RoHS Compliant Package with Gold Pad Finish
n Programmable Soft-Start
n Low Profile (9mm × 15mm × 2.82mm)
Surface Mount LGA Package
APPLICATIONS
n Automotive Battery Regulation
n Power for Portable Products
n Distributed Supply Regulation
n Industrial Supplies
n Wall Transformer Regulation
LTM8031
Ultralow Noise EMC 36V, 1A
DC/DC µModule Regulator
DESCRIPTION
The LTM®8031 is an electromagnetic compatible (EMC)
36V, 1A DC/DC μModule® 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 LTM8031 supports an output
voltage range of 0.8V to 10V, 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 low profile package (2.82mm)
enables utilization of unused space on the bottom of PC
boards for high density point of load regulation.
The LTM8031 is packaged in a thermally enhanced, compact
(9mm × 15mm) and low profile (2.82mm) overmolded land
grid array (LGA) package suitable for automated assembly
by standard surface mount equipment. The LTM8031 is
RoHS compliant.
L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
www.DataSheet4U.com
TYPICAL APPLICATION
Ultralow Noise 5V/1A DC/DC μModule Regulator
VIN*
7VDC TO 36VDC
VIN OUT
FIN LTM8031
RUN/SS
AUX
1μF BIAS
SHARE
PGOOD
RT SYNC GND ADJ
44.2k
47.5k
8031 TA01a
10μF
VOUT
5V
1A
*RUNNING VOLTAGE RANGE.
SEE APPLICATIONS FOR START-UP DETAILS
LTM8031 EMI Performance
VIN = 36V
80
70
60
50
40
EN55022
CLASS B
30 LIMIT
20
10
0
–10
0 100 200 300 400 500 600 700 800 900 1000
FREQUENCY (MHz)
8031 TA01b
8031fa
1
1 page  
LTM8031
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
Minimum VIN vs Output Current
8V VOUT
12
11
RUN/SS = VIN
10
9 RUNNING OR RUN/SS TOGGLED
8
7
6
5
4
0 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G10
Output Current vs Input Voltage
(Output Shorted)
2.75
2.70
2.65
2.60
2.55
2.50
2.45
2.40
www.Da2ta.3S5heet4U.com
0 4 8 12 16 20 24 28 32 36
VIN (V)
8031 G13
Temperature Rise vs
Load Current, VOUT = 5V
30
36VIN
24VIN
25 12VIN
20
15
10
5
0
1 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G16
Minimum Input Running Voltage
vs Output Voltage, IOUT = 1A
16
14
12
10
8
6
4
2
0
0 2 4 6 8 10
VOUT (V)
8031 G11
Input Current vs Input Voltage
(Output Shorted)
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
0 10 20 30 40
VIN (V)
8031 G14
Temperature Rise vs
Load Current, VOUT = 8V
30
36VIN
24VIN
25 12VIN
20
15
10
5
0
1 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G17
Bias Current vs Output Current
35
8VOUT
30
5VOUT
3.3VOUT
25
20
15
10
5
0
0 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G12
Temperature Rise vs
Load Current, VOUT = 3.3V
30
36VIN
25
24VIN
12VIN
5VIN
20
15
10
5
0
0 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G15
Temperature Rise vs
Load Current, VOUT = 10V
30
36VIN
25 24VIN
20
15
10
5
0
1 200 400 600 800 1000
OUTPUT CURRENT (mA)
8031 G18
8031fa
5
5 Page 
LTM8031
APPLICATIONS INFORMATION
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 LTM8031.
Load Sharing
Two or more LTM8031s may be paralleled to produce higher
currents. This may, however, alter the EMI performance of
the LTM8031s. To do this, tie the VIN, ADJ, VOUT and SHARE
pins of all the paralleled LTM8031s together. To ensure that
paralleled modules start up together, the RUN/SS pins may
be tied together, as well. Synchronize the LTM8031s to an
external clock to eliminate beat frequencies, if required.
If the RUN/SS pins are not tied together, make sure that
the same valued soft-start capacitors are used for each
module. An example of two LTM8031 modules configured
for load sharing is given in the Typical Applications sec-
tion. For 2A applications also see the LTM8032, 2A EMC
DC/DC μModule regulator
Burst Mode Operation
To enhance efficiency at light loads, the LTM8031 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 LTM8031 delivers single cycle bursts of
current to the output capacitor followed by sleep periods
wwww.DhaetarSehteheet4oUu.ctpomut power is delivered to the load by the output
capacitor. In addition, VIN and BIAS quiescent currents are
reduced to typically 20μA and 50μA respectively during
the sleep time. As the load current decreases towards a
no-load condition, the percentage of time that the LTM8031
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 LTM8031 is a step-down converter, so a minimum
amount of headroom is required to keep the output in regu-
lation. In addition, the input voltage required to turn on is
higher than that required to run, and depends upon whether
the RUN/SS is used. As shown in the Typical Performance
Characteristics section, it takes only about 3.6VIN for the
LTM8031 to run a 3.3V output at light load. If RUN/SS is
pulled up to VIN, it takes 5.7VIN to start. If the LTM8031
is enabled via the RUN/SS pin, the minimum voltage to
start at light loads is lower, about 4.4V. Similar curves for
2.5VOUT, 5VOUT and 8VOUT operation are also provided in
the Typical Performance Characteristics section.
Soft-Start
The RUN/SS pin can be used to soft-start the LTM8031,
reducing the maximum input current during start-up. The
RUN/SS pin is driven through an external RC network to
create a voltage ramp at this pin. Figure 1 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 20μA when
the RUN/SS pin reaches 2.5V.
RUN
15k
0.22μF
RUN/SS
GND
IL
0.5A/DIV
VRUN/SS
2V/DIV
VOUT
2V/DIV
2ms/DIV
8031 F01
Figure 1. To Soft-Start the LTM8031, Add a Resistor
and Capacitor to the RUN/SS Pin
Synchronization
The internal oscillator of the LTM8031 can be synchro-
nized by applying an external 250kHz to 2MHz clock to
the SYNC pin. Do not leave this pin floating. The resistor
tied from the RT pin to ground should be chosen such
that the LTM8031 oscillates 20% lower than the intended
synchronization frequency (see the Frequency Selection
section). The LTM8031 will not enter Burst Mode operation
while synchronized to an external clock, but will instead
skip pulses to maintain regulation.
8031fa
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11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet LTM8031.PDF ] | |
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