MFL283R3S Datasheet, PDF (1/13 Pages) Crane Aerospace & Electronics. – MFL Single and Dual DC/DC Converters

Crane Aerospace & Electronics Power Solutions
MFL Single and Dual DC/DC Converters
28 VOLT INPUT – 65 WATT
FEATURES
• –55° to +125°C operation
• 16 to 40 VDC input
• Fully Isolated
• Magnetic feedback
• Fixed frequency, 600 kHz typical
• Topology – Single Ended Forward
• 50 V for up to 120 ms transient protection
• Inhibit (input & output side)
• Sync function (in and out)
• Output trim on single output models
• Indefinite short circuit protection
• Remote sense on single output models
• Up to 87% efficiency / 43 W/in³
• Parallelable up to 148 watts
DESCRIPTION
The 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 148 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.
DESIGN FEATURES
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.
Isolation between input and output circuits is provided with a trans-
former in the forward path and a wide bandwidth magnetic coupling
in the feedback control loop. The MFL uses a unique dual loop feed-
back 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 regula-
tion 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).
MODELS
VDC OUTPUT
SINGLE
3.3
5
12
15
28
DUAL
±5
±12
±15
Other output voltages
available upon request,
including 2 V, 8 V and
54 V single.
INHIBIT
The MFL Series converters have two TTL compatible inhibit termi-
nals (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 open collector TTL compatible low (<0.8 volts)
is required to inhibit the converter between INH1 (pin 4) and Input
Common (pin 2). An open collector TTL compatible low (<0.5 volts)
is required to inhibit the converter between INH2 (pin 12) and Output
Common (pin 8). The application of intermediate voltages to these
pins (1.5 to 10.5 volts) should be avoided.
SYNC
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.
CURRENT AND PARALLEL OPERATION
Multiple MFL converters may be used in parallel to drive a common
load (see Figure 2). 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 synchro-
nizing 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).
When paralleled, 76% of the total combined power ratings of the
MFL converters are available at the load. Overload and short circuit
performance are not adversely affected during parallel operation.
Crane Aerospace & Electronics
Electronics Group (Interpoint Brand)
PO Box 97005 • Redmond WA 98073-9705
425.882.3100 • [e-mail]
www.craneae.com
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Rev D - 20060601