MODELS

B2-19

Size (max.): 3.005 x 1.505 x 0.400 inches (76.33 x 38.23 x 10.16 mm)

See Section B8, case U1, for dimensions.

Weight:

100 grams maximum

Screening:

Standard or ES. See Section C2 for screening options,

see Section A5 for ordering information.

SINGLE

5

12

15

DUAL

±5

±12

±15

DESCRIPTION

The MFLHP Series™ 28 volt DC/DC converters are rated up to 100

watts output power over a –55° to +100°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

outputs. Current sharing allows the units to be paralleled for total

power of up to 270 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 67 watts per cubic inch.

The MFLHP 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 wide bandwidth magnetic coupling in

the feedback control loop. The MFLHP Series uses a unique dual

loop feedback technique that controls output current with an inner

feedback loop and 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.

Tight load regulation is achieved through a wide-bandwidth

magnetic feedback circuit. The output voltage on single MFLHP

models can be easily trimmed by adding an external resistor. (See

Figure 1 for voltage changes with different resistor values.)

The MFLHP Series converters have two TTL compatible inhibit

terminals (INH1 and INH2) that can be used to disable power

conversion, resulting in a very low quiescent input current. An open

collector TTL compatible low (<0.8 volts) is required between INH1

(pin 4) and Input Common (pin 2) to inhibit the converter. An open

collector TTL compatible low (<0.5 volts) is required between INH2

(pin 12) and Output Common (pin 8) to inhibit the converter. The

application of intermediate voltages to these pins (1.5 to 10.5 volts)

should be avoided.

Multiple MFLHP 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 MFLHP converters. In current

sharing mode, one MFLHP 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).

When paralleled, 76% of the total combined power ratings of the

MFLHP converters are available at the load. Overload and short

circuit performance are not adversely affected during parallel

operation.

MFLHP SERIES

100 WATT

• –55° to +100°C operation

• 19 to 40 VDC input

• Fully Isolated

• Magnetic feedback

• Fixed frequency, 600 kHz typical

• Topology – Single Ended Forward

• 80 V for up to 50 ms transient protection

• Inhibit function – input and output

• Sync function – input and output

• Output trim on single output models

• Indefinite short circuit protection

• Remote sense on single output models

• Up to 87% efficiency

• Parallelable up to 228 watts