B4-3

MFW SERIES

70 WATTS

MODELS

VDC O

UTPUT

SINGLE

12
15

DUAL

±12
±15

TRIPLE

+5 & ±12
+5 & ±15

DC/DC C

ONVERTERS

28 V

OLT

NPUT

Size (max.): 3.20 x 2.46 x 0.595 inches (81.3 x 62.5 x 15.11 mm)

See Section B8, case L, for dimensions.

Weight:

140 grams typical

Screening: Standard or ES.See Section C2 for screening

options, see Section A5 for ordering information.

DESCRIPTION

The MFW SeriesTM of DC/DC converters offers up to 70 watts of
power from single, dual, or triple outputs in one package. Using
hybrid thick film technology a power density of over 20 watts per
cubic inch is achieved. These devices are packaged in hermetically
sealed cold rolled steel enclosures with a tin plate finish making
them ideal for use in military, aerospace, or other high reliability
applications. Unscreened models are guaranteed to pass a gross
leak test (maximum leak rate of 0.001 atm-cc/sec). Environmentally
screened units (designated by the /ES suffix) are hermetically solder
sealed. See Section C2 for screening specifications.

ESIGN

ETHODOLOGY

The MFW Series converters utilize a quasi-square wave forward
converter design with a nominal switching frequency of 245 kHz.
Isolation between input and output is provided with a transformer in
the forward power loop and a wideband, temperature insensitive
optical link in the feedback control loop. Output regulation is accom-
plished with constant frequency pulse width modulation. In addition,
the load regulation of the single output models is further enhanced
through the use of remote output voltage sense pins to overcome
the adverse effects of line resistance voltage drops. Short circuit
protection is provided by detecting peak primary switching current
on a cycle by cycle basis and limiting it to approximately 130% of the
full load input current. This method results in quick and positive
current limiting under short circuit conditions.

OISE

The MFW Series converters offer low noise on both the input and
output lines. A two section, four pole LC input filter is included to
provide very low reflected line ripple current. Adherence to MIL-
STD-461C (CE03) is possible with the addition of the FMB-461 filter.
Output ripple is maintained at less than 50 mV p-p for single and
dual output models and 85 mV for triple output models.

IDE

OLTAGE

ANGE

All models of the MFW Series are designed to provide full power
operation over an input voltage range of 19 to 40 VDC. Operation
below an input of 19 volts, including operation in MIL-STD-704E
emergency power conditions, is possible with derated output power.
Please refer to the derating information and the low voltage drop-out
graphs (Figures 10 and 11) on the following pages.

IDE

EMPERATURE

ANGE

Full load operation of any of the MFW Series converters is available
at case temperatures of 55°C to + 85°C. Operation up to +125°C
is possible with derated output power. The MFW Series converters
are provided in a flange mount case designed to facilitate the
removal of internally generated heat. Because of this, heat sinking
requirements are minimal. Sustained full power operation does
however require that an efficient heat sink be attached to the base-
plate. Please refer to the heat sink requirements section for more
information.

NHIBIT

YNC

EATURE

Standard on all models of the MFW Series is a dual mode
inhibit/sync pin. This pin serves as both an output inhibit and as a
synchronization input. In the inhibit mode an open collector TTL
compatible low (<0.8 V) will disable internal switching thereby
inhibiting the unit's output. Inhibiting in this manner results in an
extremely low quiescent current. Since a pull-up resistor is included
internally, this pin may be left open should the inhibit function not be
desired.

In a digital system it is often desirable to synchronize the input or
output ripple with the system clock. For this reason each model of
the MFW Series was designed to synchronize with a system clock
applied to the inhibit/sync pin. Please refer to the technical data
section for timing details for the external sync feature.

EATURES

· 55°C to + 85°C operation
· 19 to 40 VDC input
· Fully Isolated
· Optocoupler feedback
· Fixed frequency, 245 kHz typical
· Topology Push-Pull Forward
· 50 V for up to 50 ms transient protection
· Inhibit/sync function
· Indefinite short circuit protection
· Remote sense on single models
· Up to 84% efficiency

RECOMMENDED OPERATING CONDITIONS

ABSOLUTE MAXIMUM RATINGS

TYPICAL CHARACTERISTICS

B4-4

MFW SERIES
70 WATT

DC/DC C

ONVERTERS

SINGLE OUTPUTS

MFW2805S

MFW2812S

MFW2815S

PARAMETER

CONDITION

MIN

TYP

MAX

MIN

TYP MAX

MIN.

TYP

MAX

UNITS

OUTPUT

FULL LOAD

4.95

5.00

5.05

11.88 12.00 12.12

14.85 15.00 15.15

VDC

VOLTAGE

OUTPUT

= 19 TO 40

12.00

5.83

4.67

CURRENT

OUTPUT

Tc = 55°C TO +85°C

POWER

OUTPUT

FULL LOAD BW

2 MHz

mV p-p

RIPPLE

LINE

= 19 TO 40

REGULATION

LOAD

NO LOAD TO FULL

REGULATION

INPUT

VOLTAGE

VDC

INPUT

NO LOAD

CURRENT

INHIBITED

INPUT REFL.

FULL LOAD

mA p-p

RIPPLE

10 MHz

EFFICIENCY

STARTUP

WITH LOW

DELAY

IMPEDANCE SOURCE

Output Power

· 60 to 70 watts depending on model

Lead Soldering Temperature (10 sec per lead)

· 300°C

Storage Temperature Range (Case)

· 55°C to +125°C

Output Voltage Temperature Coefficient

· 150 ppm/°C, typical

Input to Output Capacitance

· 160 pF, typical

Isolation

· 100 megohm minimum at 500 V

Conversion Frequency

· Free run mode 245 kHz, typical

Inhibit Pin Voltage (unit enabled)

· 4.5 to 5.5 V

Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, free run, unless otherwise specified.

Input Voltage Range

· 19 to 40 VDC continuous (see Derating)

Case Operating Temperature (Tc)

· 55°C to +85°C full power

SYNC AND INHIBIT

DERATING OUTPUT POWER/CURRENT AND INPUT VOLTAGE

Sync In (245 to 370 kHz.)

· Duty cycle 70% min, 98% max
· Logic low 0.8 V max
· Logic high 4.5 V min
· Referenced to input common
· If sync is not used, leave unconnected

Inhibit TTL Open Collector

· Logic low (output disabled)

Inhibit pin current 1 mA max

· Referenced to input common
· Logic high (output enabled)

V =

4.5 V

Temperatures are referenced to the temperature at the converter's baseplate

· Linearly derate output power/current from 100% at 85°C to 0% at 125°C.
· Above 105°C linearly derate steady state input voltage to 33 volts at 125°C.
· Indefinite short circuit protection is not guaranteed above 85°C case.
· Operation below an input voltage of 19 volts, including operation in MIL-

STD-704E emergency power conditions, is possible with derated output
power. See Figures 10 and 11.

B4-5

MFW SERIES

70 WATT

DC/DC C

ONVERTERS

DUAL AND TRIPLE OUTPUTS

MFW2812D

MFW2815D

MFW28512T

MFW28515T

PARAMETER

CONDITION

MIN

TYP

MAX

MIN

TYP

MAX

MIN

TYP

MAX

MIN

TYP

MAX

UNITS

OUTPUT

FULL

MAIN

4.95

5.05

5.10

4.90

4.95

5.05

VOLTAGE

LOAD

DUAL

±11.88 ±12.00 ±12.12

±14.85 ±15.00 ±15.15 ±11.65

±11.80 ±12.05 ±15.05 ±15.30 ±15.55

VDC

OUTPUT

MAIN

4.0

10.0

4.0

10.0

CURRENT

1, 2

19 TO 40

DUAL

2.92

5.5

2.33

4.4

1.67

4.2

1.33

3.33

OUTPUT

MAIN

POWER

1, 2

±DUAL

66.5

TOTAL

OUTPUT

FULL LOAD

MAIN

mV p-p

RIPPLE

2 MHz

DUAL

LINE

MAIN

REGULATION 19 TO 40

DUAL

100

200

100

200

LOAD

NO LOAD

MAIN

REGULATION TO FULL

DUAL

480

600

300

450

CROSS

DUAL

REGULATION +PO = 3 W TO 35 W

PO = 35 W

1.5

3.0

1.5

3.0

+PO = 20 W TO 50 W

PO = 50 W TO 20 W

2.0

4.0

2.0

3.5

CROSS

MAIN +PO = 33 W

REGULATION DUAL

+PO = 3 W TO 27 W

2.3

6.0

2.3

5.0

PO = 27 W TO 3 W

MAIN

+PO = 3 W TO 30 W
DUAL ±PO = 15 W

5.4

9.0

5.0

7.0

INPUT
VOLTAGE

VDC

INPUT

NO LOAD

110

CURRENT

INHIBITED

INPUT REFL.

FULL LOAD

mA p-p

RIPPLE

10 MHz

EFFICIENCY

STARTUP

DELAY

Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, free run, unless otherwise specified.

Notes
1. On dual output models the maximum combined output power is 70 watts.

A maximum of 95% (66.5 W) is available from any single output.

2. On triple output models the maximum combined output power is 60 watts.

A maximum of 50 watts is available from a single output.

3. Balanced loads.
4. Regulation effect on the negative dual output during the defined conditions.
5. Regulation effect on both dual outputs during the defined conditions.

B4-6

MFW SERIES
70 WATT

DC/DC C

ONVERTERS

ALCULATING

AXIMUM

MBIENT

EMPERATURE

The MFW Series of DC/DC converters has an upper operating

temperature of + 85°C at the baseplate of the case. The degree of

heat sinking required to remain within this limit may be determined

from Figure 1 which shows the maximum allowed internal power

dissipation (P

DISS

vs. ambient temperature for various heat sink

thermal resistances. P

DISS

may be calculated as:

DISS

= P

OUT

/ efficiency P

OUT

The efficiency for all combinations of P

OUT

and V

for the various

models may be obtained from the graphs on the preceding pages.

Example:

Converter = MFW2815D, T

AMB

= 70°C,

= 28 VDC, P

OUT

= 45 watts

Efficiency = 85% (From Figure 7)

DISS

= (45 / 85) 45 = 7.95 watts

From Figure 1 we can see that this situation will require thermal

resistance of approximately 4.5°C / watt.

Conversely we may also find the maximum ambient temperature

which can be tolerated if we know the heat sink thermal resistance.

Example:

Converter = MFW2805S, V

= 28 VDC, P

OUT

= 45 W.

Thermal Resistance = 3°C / watt.

Efficiency = 83.5% (From Figure 3)

DISS

= (45 / 0.835) 45 = 8.89 watts.

From Figure 1 we can see that the maximum allowed ambient

temperature is approximately 75°C.

EAT

INK

ECOMMENDATIONS

An MFW Series converter in still air (other than convective currents)

and with no conductive cooling paths other than through electrical

connections at the pins will exhibit a thermal resistance of approxi-

mately 4°C / watt. In cases where this value proves to be too high it

is recommended that additional heat sinking be supplied. The

simplest method of accomplishing this is to firmly attach the

converter to a PCB thereby providing a conductive thermal path.

Secondly it is recommended that airflow be provided over the

converter. Although each situation requires a thorough thermal

analysis these two measures can reduce the thermal resistance to

as low as 2°C / watt. If calculations indicate further heat sinking is

required it is recommended that additional thermal mass be

provided either under the base plate or on top of the converter's

mounting flanges or both.

THERMAL MANAGEMENT

Degrees Centigrade

Watts

100

120

140

U=4

C/W

U=3

C/W

U=2

C/W

U=0

C/W

Internal Power Dissipation (max)

vs. Ambient Temperature

IGURE

PIN OUT

B4-7

MFW SERIES

70 WATT

DC/DC C

ONVERTERS

Squared corner indicates pin one.

BOTTOM VIEW

MFW

IGURE

2: P

MODEL NUMBERING KEY

MFW 28 512 T / ES

Base Model

Input Voltage

Output Voltage

Screening

Number of Outputs

(S = single, D = dual, T = triple)

(Main and Aux. Vout for triple models)

(Standard screening has no designator
in this position.)

Pin

Single Output

Dual Output

Triple Output

Positive Input

Case Ground

Input Common

Inhibit/Sync In

Negative Sense

Negative Output

Negative Aux. Output

Positive Sense

Positive Output

Positive Aux. Output

7, 8

Output Common

9, 10

Positive Output

No Connection

Main (+5) Output

See Section B8, case L, for dimensions.

B4-8

MFW SERIES
70 WATT

DC/DC C

ONVERTERS

Typical Performance Curves: 25°C Tc , 28 VDC Vin, 100% load, free run, unless otherwise specified.

IGURE

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW2812D Efficiency vs Line & Load

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW28512T Efficiency vs Line & Load

Efficiency (%)

40 V

28 V

20 V

Output Power (Watts)

MFW2805S Efficiency vs Line & Load

IGURE

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW2812S Efficiency vs Line & Load

IGURE

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW2815D Efficiency vs Line & Load

IGURE

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW2815S Efficiency vs Line & Load

40 V

28 V

19 V

Efficiency (%)

Output Power (Watts)

MFW28515T Efficiency vs Line & Load

IGURE

Input Voltage (Volts)

283R5S

2815S

2812S

2805S

Output Power (Watts)

Low Line Dropout vs. Load (50 mV drop)

MFW Single Output Models

IGURE

MFW2815D

MFW2812D

MFW28512T
MFW28515T

Input Voltage (Volts)

Output Power (Watts)

Low Line Dropout vs. Load (50 mV drop)

MFW Dual and Triple Output Models

20621-001-DTS Rev A

DQ# 1016

All technical information is believed to be accurate, but no responsibility is
assumed for errors or omissions. Interpoint reserves the right to make changes in
products or specifications without notice. MFW Series is a trademark of Interpoint.
Copyright © 1991- 1999 Interpoint. All rights reserved.

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