F
EATURES
•
•
•
•
•
•
•
•
•
•
•
–55° to +125°C operation
16 to 40 VDC input
Fully isolated
Optocoupler feedback
Fixed frequency, 550 kHz typical
Topology – Single Ended Forward
50 V for up to 50 ms transient protection
Inhibit and sync functions
Indefinite short circuit protection
Undervoltage lockout
Up to 84% efficiency, 28 W/in
3
DC/DC C
ONVERTERS
28 V
OLT
I
NPUT
MHF+ SERIES
SINGLE & DUAL
15 WATT
MODELS
VDC O
UTPUT
SINGLE
DUAL
3.3
±5
5
±12
5.2
±15
12
15
28
Size (max.): Non flanged 1.460 x 1.130 x 0.330 (37.08 x 28.70 x 8.38 mm)
Flanged 2.005 x 1.130 x 0.330 (50.93 x 28.70 x 8.38 mm)
Weight:
30 grams maximum.
Screening: Standard, ES, or 883 (Class H).
DESCRIPTION
The MHF+ Series™ of high frequency DC/DC converters offers a
wide input voltage range of 16 to 40 volts and up to 15 watts of
output power. The units are capable of withstanding short term tran-
sients up to 50 volts. The package is a hermetically sealed, welded
metal case. Flanged and non-flanged models are available.
I
NHIBIT
F
UNCTION
MHF+ converters provide an inhibit terminal that can be used to
disable internal switching, resulting in no output and very low quies-
cent input current. The converter is inhibited when a TTL compatible
low (≤0.8 – output disabled) is applied to the inhibit pin. The unit is
enabled when the pin, which is internally connected to a pull-up
resistor, is left unconnected or is connected to an open-collector
gate. The open circuit output voltage associated with the inhibit pin
is 8.5 to 12 V. In the inhibit mode, a maximum of 4 mA must be sunk
from the inhibit pin.
C
ONVERTER
D
ESIGN
The MHF+ converters are switching regulators that use a quasi-
square wave, single-ended forward converter design with a constant
switching frequency of 550 kHz. Isolation between input and output
circuits is provided with a transformer in the forward path and a
temperature compensated optical link in the feedback control loop.
For the MHF+ dual output models, good cross regulation is main-
tained by tightly coupled output magnetics. Up to 90% of the total
output power (80% on 2805D) is available from either output,
providing the opposite output is simultaneously carrying 10% of the
total output power (20% on 2805D models). Predictable current limit
is accomplished by directly monitoring the output load current and
providing a constant current output above the overload point.
S
YNCHRONIZATION
A synchronization feature is included with the MHF+ Series that
allows the user to match the switching frequency of the converter to
the frequency of the system clock. An external synchronization
feature is included that allows the user to adjust the nominally 550
kHz operating frequency to any frequency within the range of 500
kHz to 600 kHz. This is initiated by applying a TTL compatible input
of the desired frequency to pin 5.
H
IGHER
P
OWER
D
ENSITY
The MHF+ Series offers a new standard of performance for small
size and high power density. At just 0.33 inch high and a total foot-
print of 1.7 in
2,
this low profile package offers a total power density
of up to 28 watts per cubic inch.
S
HORT
C
IRCUIT
P
ROTECTION
MHF+ Series converters provide short circuit protection by
restricting the output current to approximately 115% of the full load
output current. The output current is sensed in the secondary stage
to provide highly predictable and accurate current limiting, and to
eliminate foldback characteristics.
L
OW
N
OISE
, H
IGH
A
UDIO
R
EJECTION
The MHF+ converters’ feed-forward compensation system provides
excellent dynamic response and noise rejection. Audio rejection is
typically 50 dB. Typical output voltage response for a 50% to 100%
step load transient is as low as 1.3% with a 150 msec recovery time.
Input ripple current is typically 35 mA p-p with output ripple voltage
typically 30 mV p-p .
U
NDERVOLTAGE
L
OCKOUT
Undervoltage lockout prevents the units from operating below
approximately 12 VDC input voltage to keep system current levels
smooth, especially during initialization or re-start operations.
1
MHF+ SERIES
SINGLE AND DUAL
15 WATT
DC/DC C
ONVERTERS
SYNC AND INHIBIT
Sync In (500 to 600 kHz)
• Duty cycle 40% to 60%
• Logic low 0.8 V max
• Logic high 4.5 V min, 5 V max
• Referenced to input common
• If not used, connect to input common
Inhibit TTL Open Collector
• Logic low (output disabled)
Logic low voltage
≤0.8
V
Inhibit pin current 4.0 mA max
• Referenced to input common
• Logic high (output enabled)
Open collector or unconnected
ABSOLUTE MAXIMUM RATINGS
Input Voltage
• 16 to 40 VDC
Power Dissipation (Pd)
• 6W
Output Power
• 12 to 15 watts depending on model
Lead Soldering Temperature (10 sec per lead)
• 300°C
Storage Temperature Range (Case)
• –65°C to +150°C
TYPICAL CHARACTERISTICS
Output Voltage Temperature Coefficient
• 100 ppm/°C typical
• 150 ppm/°C maximum
Input to Output Capacitance
• 60 pF typical
Undervoltage Lockout
• 12 V input typical
Current Limit
• 115% of full load typical
Isolation
• 100 megohm minimum at 500 V
Audio Rejection
• 50 dB typical
Conversion Frequency (55°C to +125°C Tc)
• Free run 550 kHz typical
480 kHz min, 620 kHz max
Inhibit Pin Voltage (unit enabled)
• 8.5 to 12 V
RECOMMENDED OPERATING CONDITIONS
Input Voltage Range
• 16 to 40 VDC continuous
• 50 V for up to 50 msec transient
Case Operating Temperature (Tc)
• –55°C to +125°C full power
• –55°C to +135°C absolute
Derating Output Power/Current (Tc)
• Linearly from 100% at 125°C to 0% at 135°C
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, free run, unless otherwise specified.
SINGLE OUTPUT MODELS
PARAMETER
OUTPUT VOLTAGE
OUTPUT CURRENT
OUTPUT POWER
OUTPUT RIPPLE
VOLTAGE
LINE REGULATION
LOAD REGULATION
INPUT VOLTAGE
NO LOAD TO FULL
INPUT CURRENT
CONDITION
V
IN
= 16 to 40 VDC
V
IN
= 16 to 40 VDC
10 kHz - 2 MHz
Tc = –55°C to +125°C
Vin = 16 to 40 VDC
NO LOAD TO FULL
CONTINUOUS
TRANSIENT 50 ms
NO LOAD
FULL LOAD
INHIBITED
10 kHz - 10 MHz
Tc = –55°C to +125°C
SHORT CIRCUIT
POWER DISSIPATION
RECOVERY
2
50% – 100% – 50%
TRANSIENT
RECOVERY
2
16 – 40 – 16 VDC
TRANSIENT
3
RECOVERY
2
DELAY
OVERSHOOT
4
MHF+283R3S
MIN
3.27
0
0
—
—
—
—
16
—
—
—
—
—
—
72
—
—
–400
—
–800
—
—
—
TYP MAX
3.30 3.33
—
2.4
—
30
50
5
20
28
—
25
—
5
45
—
75
5
7.5
150
150
550
0.8
10
200
8
80
120
100
50
40
50
65
397
12
80
120
—
8
30
500
300
800
1.2
25
300
MHF+2805S
MIN
4.95
0
0
—
—
—
—
16
—
—
—
—
—
—
75
—
—
–400
—
–800
—
—
—
TYP MAX
5.00 5.05
—
2.4
—
30
60
5
20
28
—
25
560
5
35
—
77
3.5
7.5
150
150
550
0.8
10
100
12
80
100
50
50
40
50
40
624
12
80
100
—
6
30
400
300
800
1.2
25
600
MHF+285R2S
MIN
5.16
0
0
—
—
—
—
16
—
—
—
—
—
—
75
—
—
–400
—
–800
—
—
—
TYP MAX
5.20 5.24
—
2.4
—
30
60
5
20
28
—
25
560
5
35
—
77
3.5
7.5
150
150
550
0.8
10
100
12.48
50
100
35
35
40
50
42
605
12
100
100
—
6
30
400
300
800
1.2
25
600
UNITS
VDC
A
W
mV p-p
mV
mV
VDC
V
mA
INPUT RIPPLE
CURRENT
EFFICIENCY
LOAD FAULT
1
mA pp
%
W
ms
mV pk
µs
mV pk
ms
ms
mV pk
STEP LOAD RESP.
STEP LINE RESP.
START-UP
Notes
1. Indefinite short circuit protection not guaranteed above 125°C (case)
2. Recovery time is measured from application of the transient
to the point at which Vout is within regulation.
3. Input step transition time >10 µs.
4. Input step transition time <100 µs.
2
MHF+ SERIES
SINGLE AND DUAL
15 WATT
DUAL OUTPUT MODELS
PARAMETER
OUTPUT VOLTAGE
CONDITIONS
+V
OUT
–V
OUT
OUTPUT CURRENT
1
OUTPUT POWER
1
OUTPUT RIPPLE
VOLTAGE ±V
OUT
LINE REGULATION
Vin = 16 to 40 VDC
LOAD REGULATION
V
IN
= 16 to 40 VDC
V
IN
= 16 to 40 VDC
10 kHz - 2 MHz
Tc = –55°C to +125°C
BALANCED +V
OUT
LOAD
–V
OUT
–V
OUT
BALANCED +V
OUT
LOAD
CROSS REGULATION
2
INPUT VOLTAGE
NO LOAD TO FULL
INPUT CURRENT
DC/DC C
ONVERTERS
MHF+2805D
MIN
4.95
4.92
—
—
—
—
—
—
—
—
—
16
—
—
—
—
—
—
77
—
—
–600
–600
—
–800
—
—
0
TYP
5.00
5.00
±1.2
—
30
60
5
—
20
—
6
28
—
20
540
6
20
40
79
3
7.5
200
150
150
600
0.8
12
100
MAX
5.05
5.08
1.92
12
80
120
50
80
50
100
7.5
40
50
40
600
12
50
80
—
6
30
600
600
500
800
1.2
20
250
MIN
11.88
11.82
—
—
—
—
—
—
—
—
—
16
—
—
—
—
—
—
76
—
—
–600
–600
—
–750
—
—
0
MHF+2812D
TYP
12.00
12.00
±0.625
—
30
60
5
—
20
—
3
28
—
25
645
5
35
50
83
3
7.5
300
100
200
550
0.8
12
200
MAX
12.12
1218
1.125
15
80
120
50
100
50
100
6
40
50
50
754
12
60
100
—
6
50
600
500
400
750
1.2
25
750
MIN
14.85
14.78
—
—
—
—
—
—
—
—
—
16
—
—
—
—
—
—
76
—
—
–600
–600
—
–750
—
—
0
MHF+2815D
TYP
15.00
15.00
±0.500
—
30
50
5
—
20
—
3
28
—
25
638
5
35
50
84
3
7.5
300
100
200
550
0.8
12
200
MAX
15.15
15.23
0.900
15
80
120
50
100
50
100
6
40
50
50
754
12
60
100
—
6
50
600
600
500
750
1.2
25
750
µs
mV pk
ms
ms
mV pk
%
VDC
V
mA
mV
A
W
mV p-p
mV
UNITS
VDC
Electrical Characteristics: 25°C Tc, 28 VDC Vin, 100% load, free run, unless otherwise specified.
NEGATIVE V
OUT
CONTINUOUS
TRANSIENT 50 msec
NO LOAD
FULL LOAD
INHIBITED
10 kHz - 10 MHz
Tc = –55°C to +125°C
SHORT CIRCUIT
3
POWER DISSIPATION
RECOVERY
4
50% – 100% – 50%
+V
OUT
TRANSIENT
–V
OUT
RECOVERY
4
16 – 40 – 40 VDC
TRANSIENT
6
RECOVERY
4
DELAY
OVERSHOOT
7
INPUT RIPPLE
CURRENT
EFFICIENCY
LOAD FAULT
mA p-p
%
W
ms
STEP LOAD RESP.
5
BALANCED LOADS
mV pk
STEP LINE RESP.
± V
OUT
START-UP
Notes
1. Up to 13.5 watts, 90% (9.6W, 80% for 2805D) of the total output power is
available from either output providing the opposite output is simultaneously
carrying 10% (20% for 2805D) of the total output power. Each
output must carry a minimum of 10% (20% for 2805D) of the total output
power in order to maintain regulation on the negative output.
2. Effect on –Vout for the following conditions:
+Po = 50% to 10% and –Po = 50%
+Po = 50% and –Po = 50% to 10%
3. Indefinite short circuit protection not guaranteed above 125°C (case)
4. Recovery time is measured from application of the transient to point at
which Vout is within regulation.
5. Response of either output with the opposite output held at half of the total
output power.
6. Input step transition time >10 µs.
7. Input step transition time <100 µs.
4
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