F
EATURES
• Internal EMI filter meets
MIL-STD-461E CE102,
and MIL-STD-461C CE03
• Wide 5:1 input range:
80 to 400 VDC
• Output voltage adjustable to
include 3.3, 5, 15, and 28
• Operating temp. (baseplate)
100% power –55°C to +100°C
Derate to 0% power at 130°C
• Sync, inhibit and
remote sense functions
• Magnetic isolated feedback
• Up to 89% efficiency
DC/DC C
ONVERTERS
120/270 V
OLT
I
NPUT
MSS-MH SERIES
125 WATT
Size (typ.): 4.60 x 2.40 x 0.55 inches
(116.8 x 61.0 x 14.0 mm)
Weight:
300 grams maximum
MODELS
MODEL
MSS-MHL
MSS-MHH
MSS-MH28
V OUT Pre-Set
6
18
28
V OUT Adjust*
2.5 to 6.4
6 to 19.3
24 to 30.0
*Please see “Output Voltage Adjust” Figures 2 and 3.
DESCRIPTION
Interpoint’s 125 watt MSS-MHL, MHH, and MH28 DC/DC converters
are the first models in a new series of high reliability DC/DC
converters. A built in EMI filter compliant to MIL-STD-461E, CE102
and MIL-STD-461C CE03, plus an output filter eliminate the need
for additional modules or components. With an 80 to 400 VDC input,
a 2.5 to 6 VDC output, and a wide operating temperature range of
–55° to +100°C, the MSS-MHL is well suited for aerospace, auto-
motive, commercial, and industrial applications. The trimmable
output can provide 5 VDC for current or older applications while the
same device can later be trimmed to 3 or 2.5 VDC to accommodate
newer voltage requirements. Typical efficiency ranges from 79% to
82%. Two screening levels are available—standard and ST—
offering varying levels of temp cycle, burn-in, and electrical test.
Please see Table 1 for screening information.
The MSS Series™ converters offer three output voltage ranges. The
high input voltage of 80 to 400 VDC encompasses 120 volt and 270
volt busses. The three output voltage choices of 2.5 to 6, 6 to 18
and 24 to 28 cover the newer low voltage requirements; the stan-
dard 5 volt requirements; plus the 12, 15, 24, and 28 volt require-
ments of distributed power.
CE102 and CE03. Each converter switches at a fixed frequency of
520 kHz typical. There is a protection circuit for input overshoot
during input power fast turn-on. This design uses a current mode
control method with a feedback transformer that provides isolation
between input and output.
S
YNC
, I
NHIBIT
, R
EMOTE
S
ENSE
,
AND
V O
UT
A
DJUST
Sync in, sync out, inhibit, and remote sense are additional controls
to enhance converter performance. Sync in, sync out, and inhibit are
referenced to control return (Ctrl Rtn, pin 7). The converters can be
synchronized to an external clock using the sync in terminal (pin 9).
Two or more converters can be synchronized by using the sync out
terminal (pin 6) which helps reduce interference and the possible
generation of beat frequencies. The sync terminals can be left
unconnected when not used.
The converter operates normally when the Inhibit terminal (pin 8) is
left open or connected to an open collector interface. Pulling the
inhibit low disables switching and results in no output and a low 5
mA input current.
The remote sense terminals (pins 3 and 4) can be connected at the
load to minimize line voltage drops, maintaining the desired output
voltage directly at the load. If not used, the sense terminals should
be connected to their respective Vout terminals (pins 1 and 2).
Vout can be adjusted down using the trim pin or adjusted up using
the sense pins. Please see Figures 2 and 3 for Vout tables.
I
NPUT AND
O
UTPUT
F
ILTERING
: L
OW
N
OISE
All converters have an integrated input EMI filter and output filter.
The MSS 125 watt series, in a package 4.6 x 2.4 x 0.55 inches
(116.8 x 61.0 x 14.0 mm), replaces an industry standard configura-
tion of three half bricks (input filter, converter, and output filter). The
EMI filter meets the conducted emission requirements of MIL-STD-
461E, CE102 and MIL-STD-461C CE03. The output filter keeps the
output ripple to a typical of 75 mV peak-to-peak from 2
MHz to 20 MHz and 12 mV peak-to-peak from 10 kHz to 2 MHz.
C
ONVERTER
C
ONSTRUCTION
/P
ACKAGING
MSS Series converters are constructed from surface mount compo-
nents soldered to a printed circuit board. The PCB is attached to a
lightweight, metal matrix composite, baseplate which provides the
high thermal conductivity of aluminum but has the advantage of a
low Coefficient of Thermal Expansion (CTE) and higher strength. A
potting compound is used to enhance the assembly’s ability to meet
harsh environmental requirements.
O
PERATION
The MSS Series DC/DC converters use a boost converter followed
by a forward converter to achieve the wide 5 to 1 input voltage range
(80 to 400 VDC) and a 3 to 1 output ranges (2.5, 6 or 28VDC). The
boost stage provides low input noise and extra filtering for the 200
to 400 volt input range. The EMI filter provides both differential and
common mode rejections in a wide frequency range to meet both
1
MSS-MH SERIES
125 WATT
ABSOLUTE MAXIMUM RATINGS
Input Voltage
• 80 to 400 VDC
Output Power
• 125 W at maximum Vout
Lead Soldering Temperature (10 sec per lead)
• 300°C
Storage Temperature Range (Base plate)
• –55°C to +130°C
DC/DC C
ONVERTERS
SYNC AND INHIBIT
Sync In (500 to 600 kHz)
• Logic low 0.8 V max, duty cycle 50%
• Logic high 3.5 V min, 10 V max
• Referenced to Control Return
Sync Out - Referenced to Control
Inhibit – TTL Open Collector
• Logic low (output disabled) <5 V
• Inhibit pin current 2 mA typ
• Referenced to Control Return
• Logic high (output enabled) open collector
TYPICAL CHARACTERISTICS
Output Voltage Temperature Coefficient
• 150 ppm/°C maximum
Temperature Rise (Still Air)
• 3°C / watt dissipated, typical
Input to Output Capacitance
• 25 nF typical, with case grounded
Undervoltage Lockout, Typical
• Turn-on >80 VDC
• Turn-off <72 VDC
Current Limit
• 120% of full load typical
Isolation
• 100 megohm minimum at 500 V
Conversion Frequency (kHz)
• 25°C, 520 typical
Inhibit Pin Voltage (unit enabled)
• 12 V, typical
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
• 80 to 400 VDC
425 V transient for 120 msec
Case Operating Temperature (Tc)
• –55°C to +100°C full power
• –55°C to +130°C absolute
Derating Output Power/Current (Tc)
• Linearly from 100% at 100°C to 0% at 130°C
Electrical Characteristics: Pre-set Vout, 25°C Tc, Vin 270 VDC, 100% load, unless otherwise specified.
PARAMETER
OUTPUT VOLTAGE
OUTPUT VOLTAGE
1
OUTPUT CURRENT
1
OUTPUT POWER
1
CONDITIONS
PRE-SET VOUT
ADJUST RANGE
V
OUT
= PRE-SET
MAXIMUM V
OUT
MINIMUM V
OUT
10 kHz - 20 MHz
2
MSS-MHL
MIN TYP MAX
5.14
6
6.06
2.5
—
—
—
—
—
—
—
80
0
—
—
80
77
—
—
—
—
60
15
—
—
270
—
—
—
83
79
6.4
20.8
125
52
150
27
30
30
400
425
25
5
—
—
MSS-MHH
MIN TYP MAX
17.82 18 18.18
6
—
—
—
—
—
—
—
80
0
—
—
86
81
—
—
—
—
75
10
—
—
270
—
—
—
88
83
19.3
7.0
125
42
150
18
80
80
400
425
25
5
—
—
MSS-MH28
MIN TYP MAX
27.72 28 28.28
24
—
—
—
—
—
—
—
80
0
—
—
85
79
—
—
—
—
75
10
—
—
270
—
—
—
87
82
30.0
4.5
125
107
150
18
120
120
400
425
25
5
—
—
UNITS
VDC
VDC
A
W
OUTPUT RIPPLE
VOLTAGE
LINE REGULATION
LOAD REGULATION
INPUT VOLTAGE
10% LOAD TO FULL
INPUT CURRENT
EFFICIENCY
3
10 kHz - 2 MHz
2
V
IN
MIN TO MAX
10% LOAD TO FULL
CONTINUOUS
TRANSIENT 120 ms
NO LOAD
INHIBITED
V
IN
= 270V
V
IN
= 120V
POWER DISSIPATION
SHORT CIRCUIT
2, 5
4
mV p-p
mV
mV
VDC
V
mA
mA
%
LOAD FAULT
—
—
—
—
—
—
—
—
—
—
—
28
5
25
29
250
250
400
400
120
0
2
35
—
27.5
—
—
—
—
—
145
—
6
—
—
—
—
—
—
—
—
—
—
—
11
5
8.3
10.4
600
350
800
400
120
0
2
25
—
9.2
—
—
—
—
—
145
—
6
—
—
—
—
—
—
—
—
—
—
—
15
20
5.6
6.8
750
250
1000
400
120
0
2
35
—
5.9
—
—
—
—
—
145
—
6
W
ms
STEP LOAD
RESPONSE
STEP LINE
RESPONSE
2
START-UP
6
0 TO NOMINAL V
IN
INHIBIT PIN
2
CURRENT
RECOVERY
OUTPUT CURRENT
1
TRIP POINT
SHORT CIRCUIT
50 %–100%– 50%
5
TRANSIENT
5
RECOVERY
V
IN
MIN TO MAX TO MIN
TRANSIENT
5
RECOVERY
5
DELAY
OVERSHOOT
2
A
mV pk
µs
mV pk
µs
ms
mV pk
mA
UNIT INHIBITED
Notes:
1. When adjusting Vout down: output current may not exceed max. current
When adjusting Vout up output power may not exceed max. power
2. Guaranteed by design.
3. Overload measured with a resistive load.
4. Short circuit measured with 0.01 ohm load.
5. Time to settle within 1% of V
OUT
6. V
IN
step or release from inhibit.
2