Crane Aerospace & Electronics Power Solutions
MFL sꢀꢁglꢂ aꢁꢃ dual dc/dc cꢄꢁvꢂꢅꢆꢂꢅꢇ
28 VoLt inpꢈt – 65 Wꢉtt
Features
Parallel operation with current share,
up to 3 units (up to 185 watts)
•ꢀ -55° to +125°C operation
•ꢀ 16 to 40 VDC input
•ꢀ 50 V for 50 ms transient protection
•ꢀ Fully isolated, magnetic feedback
•ꢀ Fixed high frequency switching
MODELS
VDc Ou t P u t
s i n g l e
D u a l
±5
3.3
5
12
15
28
•ꢀ Remote sense or output trim on
±12
±15
single output models
•ꢀ Inhibit function
•ꢀ Sync in and Sync Out
•ꢀ Indefinite short circuit protection
Other output voltages
available upon request,
including 2 V, 8 V and
54 V single.
•ꢀ High power density with up to 87% efficiency
description
in h i b i t
The Interpoint™ MFL Series™ 28-volt DC/DC converters are
rated up to 65 watts of output power over a -55°C to +125°C
temperature range with a 28 VDC nominal input. On dual output
models up to 70% of the rated output power can be drawn from
either the positive or negative output. Current sharing allows
the units to be paralleled for total power of up to 185 watts. The
welded, hermetically sealed package is only 3.005 x 1.505 x
0.400 inches, giving the series an overall power density of up to
43 watts per cubic inch. The converters are offered with standard
screening, “ES” screening, or fully compliant to “883” MIL-PRF-
38534 Class H screening. Standard microcircuit drawings (SMD)
are available.
The MFL Series converters have two inhibit terminals (INH1 and
INH2) that can be used to disable power conversion, resulting in
a very low quiescent input current and no generation of switching
noise. An active low (<0.8 volts) is required to inhibit the
converter between INH1 (pin 4) and Input Common (pin 2). An
active low (<0.5 volts) is required to inhibit the converter between
INH2 (pin 12) and Output Common (pin 8).
sy n c
Converters may be synced to an external clock (525 to 675 kHz)
or to one another by using the sync in or out pins. The nominal
free-run switching frequency is 600 kHz.
De s i g n Fe a t u r e s
cu r r e n t sh a r e a n D Pa r a l l e l OP e r a t i O n
The MFL Series converters are switching regulators that use a
quasi-square wave, single ended forward converter design with a
constant switching frequency of 600 kHz.
Multiple MFL converters may be used in parallel to drive a
common load (see Figure 2). Only single output models with
SENSE and SNS RTN can be used in the share mode. In this
mode of operation the load current is shared by two or three
MFL converters. In current sharing mode, one MFL converter is
designated as a master. The SLAVE pin (pin 11) of the master is
left unconnected and the MSTR/INH2 pin (pin 12) of the master
is connected to the SLAVE pin (pin 11) of the slave units. The
units designated as slaves have the MSTR/INH2 pin (pin 12)
connected to the SNS RTN pin (pin 9). Figure 2 shows the typical
setup for two or three units in parallel. Note that synchronizing
the units together (though shown in the figure) is not required for
current sharing operation. A second slave unit may be placed in
parallel with a master and slave; this requires the TRI pin (pin 3)
of the master unit to be connected to the SNS RTN pin (pin 9).
Isolation between input and output circuits is provided with a
transformer in the forward path and a wide bandwidth magnetic
coupling in the feedback control loop. The MFL uses a unique
dual loop feedback technique that controls output current with
an inner feedback loop and an output voltage with a cascaded
voltage mode feedback loop.
The additional secondary current mode feedback loop improves
transient response in a manner similar to primary current mode
control and allows for ease of paralleling, but without the cost
and complexity.
The constant frequency, pulse-width modulated converters
use a quasi-square wave single-ended forward design. Tight
load regulation is achieved through a wide-bandwidth magnetic
feedback circuit. The output on single MFL models can be
trimmed (see Figure 1 for voltage changes with different resistor
values).
When paralleled, up to 95% of the total combined power ratings
of the MFL converters is available at the load. Overload and
short circuit performance are not adversely affected during
parallel operation.
Crane Aerospace & Electronics
Crane Electronics, Inc.
Power Solutions – Interpoint
POꢀBoxꢀ97005ꢀꢀ•ꢀꢀRedmondꢀWAꢀ98073-9705
425.882.3100ꢀꢀꢀ•ꢀꢀpower@crane-eg.com
www.craneae.com/interpoint
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MFL Rev G - 2011.03.15