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LTM8045EY#PBF

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LTM8045
10
8045fc
For more information www.linear.com/LTM8045
block DiagraM
CURRENT
MODE
CONTROLLER
1µF
V
IN
V
OUT
–
V
OUT
+
RUN
SS
SYNC
GND
8045 BD
0.1µF
•
•
2µF
10µH 10µH
RT
FB
LTM8045
11
8045fc
For more information www.linear.com/LTM8045
operaTion
The LTM8045 is a stand-alone switching DC/DC converter
that may be configured either as a SEPIC (single-ended
primary inductance converter) or inverting power supply
simply by tying V
OUT
–
or V
OUT
+
to GND, respectively.
It accepts an input voltage up to 18VDC. The output is
adjustable between 2.5V and 15V for the SEPIC, and
between –2.5V and –15V for the inverting configuration.
The LTM8045 can provide 700mA at V
IN
= 12V when V
OUT
= 2.5V or –2.5V.
As shown in the Block Diagram, the LTM8045 contains a
current mode controller, power switching element, power
coupled inductor, power Schottky diode and a modest
amount of input and output capacitance. The LTM8045
is a fixed frequency PWM converter.
The LTM8045 switching can free run by applying a resis
-
tor to
the RT
pin or synchronize to an external source at
a frequency between 200kHz and 2MHz. To synchronize
to an external source, drive a valid signal source into the
SYNC pin. An R
T
resistor is required whether or not a
SYNC signal is applied. See the Applications Information
section for more details.
The LTM8045 also features RUN and SS pins to control
the start-up
behavior of the device. The RUN pin may also
be
used to implement an accurate undervoltage lockout
function by applying just one or two resistors.
The LTM8045 is equipped with a thermal shutdown to
protect the device during momentary overload conditions.
It is set above the 125°C absolute maximum internal tem
-
perature rating to avoid interfering with normal specified
operation, so internal device temperatures will exceed
the absolute maximum rating when the overtemperature
protection is active. Therefore, continuous or repeated
activation of the thermal shutdown may impair device
reliability.
LTM8045
12
8045fc
For more information www.linear.com/LTM8045
applicaTions inForMaTion
For most applications, the design process is straight
forward, summarized as follows:
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
2. Apply the recommended C
IN
, C
OUT
, R
FB
and R
T
values.
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
magnitudes, polarity and other factors. Please refer to the
graphs in the Typical Performance Characteristics section
for guidance.
The maximum frequency (and attendant R
T
value) at which
the LTM8045 should be allowed to switch is given in
Table 1 in the
f
MAX
column, while the recommended fre-
quency (and R
T
value) for optimal efficiency over the given
input condition is given in the f
OPTIMAL
column.
Table 1. Recommended Component Values and Configuration
(T
A
= 25°C. See the Typical Performance Characteristics for Load Conditions)
SEPIC Topology
V
IN
(V) V
OUT
(V) C
IN
C
OUT
R
FB
(k) f
OPTIMAL
R
T(OPTIMAL)
(k) f
MAX
(MHz) R
T(MIN)
(k)
2.8 to 18 2.5 4.7µF, 25V, 1206 100µF, 6.3V, 1210 15.4 600kHz 154 1.3 69.8
2.8 to 18 3.3 4.7µF, 25V, 1206 100µF, 6.3V, 1210 24.9 700kHz 130 1.5 60.4
2.8 to 18 5 4.7µF, 25V, 1206 100µF, 6.3V, 1210 45.3 800kHz 115 2 45.3
2.8 to 18 8 4.7µF, 25V, 1206 47µF, 10V, 1210 80.6 1MHz 90.9 2 45.3
2.8 to 18 12 4.7µF, 25V, 1206 22µF, 16V, 1210 130 1.2MHz 75.0 2 45.3
4.5 to 18 15 4.7µF, 25V, 1206 22µF, 25V, 1210 165 1.5MHz 60.4 2 45.3
Inverting Topology
V
IN
(V) V
OUT
(V) C
IN
C
OUT
R
FB
(k) f
OPTIMAL
R
T(OPTIMAL)
(k) f
MAX
(MHz) R
T(MIN)
(k)
2.8 to 18 –2.5 4.7µF, 25V, 0805 47µF, 6.3V, 1206 30.1 600kHz 154 1.3 69.8
2.8 to 18 –3.3 4.7µF, 25V, 0805 47µF, 6.3V, 1206 39.2 650kHz 140 1.5 60.4
2.8 to 18 –5 4.7µF, 25V, 0805 22µF, 6.3V, 1206 60.4 700kHz 130 2 45.3
2.8 to 18 –8 4.7µF, 25V, 1206 22µF, 10V, 1206 95.3 1MHz 90.9 2 45.3
2.8 to 18 –12 4.7µF, 25V, 1206 10µF, 16V, 1206 143 1.2MHz 75.0 2 45.3
4.5 to 18 –15 4.7µF, 25V, 1206 4.7µF, 25V, 1206 178 1.5MHz 60.4 2 45.3
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LTM8045EY#PBF

Mfr. #:
Buy LTM8045EY#PBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Switching Voltage Regulators Inverting or SEPIC Module DC/DC Converter with Up to 700mA Output Current
Lifecycle:
New from this manufacturer.
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