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Page 1
MQFL-28E-28S-Y-ES
28Vin 28Vout@4.0A
DC-DC CONVERTER
+VIN
IN RTN
CASE
ENA 1
SYNC OUT
SYNC IN
ENA 2
SHARE
+SNS
-SNS
OUT RTN
+VOUT
S/N 0000000 D/C 3205-301 CAGE 1WX10
HigH Reliability DC-DC ConveRteR
Full PoweR oPeRation: -55ºC to +125ºC
Features
MQFL series converters (with MQME filter) are designed to meet:
Specification Compliance
MQFL series converters are:
Design Process
MQFL series converters are qualified to:
Qualification Process
In-Line Manufacturing Process
DesigneD & ManufactureD in the usa
featuring Qorseal
™
hi-rel asseMbly
• Designed for reliability per NAVSO-P3641-A guidelines
• Designed with components derated per:
— MIL-HDBK-1547A
— NAVSO P-3641A
• MIL-STD-810F
— consistent with RTCA/D0-160E
• SynQor’s First Article Qualication
— consistent with MIL-STD-883F
• SynQor’s Long-Term Storage Survivability Qualication
• SynQor’s on-going life test
• AS9100 and ISO 9001:2008 certied facility
• Full component traceability
• Temperature cycling
• Constant acceleration
• 24, 96, 160 hour burn-in
• Three level temperature screening
• MIL-HDBK-704-8 (A through F)
• RTCA/DO-160 Section 16, 17, 18
• MIL-STD-1275 (B, D)
• DEF-STAN 61-5 (part 6)/(5, 6)
• MIL-STD-461 (C, D, E, F)
• RTCA/DO-160(E, F, G) Section 22
• Fixed switching frequency
• No opto-isolators
• Parallel operation with current share
• Remote sense
• Clock synchronization
• Primary and secondary referenced enable
• Continuous short circuit and overload protection
• Input under-voltage and over-voltage shutdown
The MilQor@ series of high-reliability DC-DC converters
brings SynQor’s eld proven high-efciency synchronous
rectier technology to the Military/Aerospace industry.
SynQor’s innovative QorSealTM packaging approach ensures
survivability in the most hostile environments. Compatible
with the industry standard format, these converters operate
at a xed frequency, have no opto-isolators, and follow
conservative component derating guidelines. They are
designed and manufactured to comply with a wide range of
military standards.
MQFL-28E-28S
Single Output
16-70V 16-80V 28V 4.0A 89% @ 2A / 87% @ 4A
Continuous Input Transient Input Output Output Efciency
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Technical Specification
MQFL-28E-28S
Output: 28V
Current: 4.0A
BLOCK DIAGRAM
TYPICAL CONNECTION DIAGRAM
− SENSE
ISOLATION STAGE
REGULATION STAGE
7
8
UVLO
SECONDARY
CONTROL
GATE DRIVERS
CONTROL
POWER
POSITIVE
INPUT
INPUT
RETURN
CASE
ENABLE 1
SYNC OUT
SYNC IN
1
1
1
9
1
2
3
4
5
6
POSITIVE
OUTPUT
OUTPUT
RETURN
SHARE
ENABLE 2
+ SENSE
MAGNETIC
FEEDBACK
ISOLATION BARRIER
CURRENT
LIMIT
CURRENT
SENSE
0
1
2
PRIMARY
CONTROL
GATE DRIVERS
MQFL
+VIN
IN RTN
CASE
ENA 1
SYNC OUT
SYNC IN
ENA 2
SHARE
+SNS
-SNS
OUT RTN
+VOUT
1
2
3
4
5
6
12
11
10
9
8
7
Load
open
means
on
+
+
28 Vdc
open
means
on
_
_
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Technical Specification
MQFL-28E-28S
Output: 28V
Current: 4.0A
MQFL-28E-28S ELECTRICAL CHARACTERISTICS
Parameter Min. Typ. Max. Units Notes & Conditions Group A
Vin=28V dc ±5%, Iout=4.0A, CL=0µF, free running (see Note 10)
unless otherwise specied Subgroup
ABSOLUTE MAXIMUM RATINGS
Input Voltage
Non-Operating 100 V
Operating 100 V See Note 1
Reverse Bias (Tcase = 125ºC) -0.8 V
Reverse Bias (Tcase = -55ºC) -1.2 V
Isolation Voltage (I/O to case, I to O)
Continuous -500 500 V
Transient (≤100µs) -800 800 V
Operating Case Temperature -55 125 °C HB Grade Products, See Notes 2 & 16
Storage Case Temperature -65 135 °C
Lead Temperature (20s) 300 °C
Voltage at ENA1, ENA2 -1.2 50 V
INPUT CHARACTERISTICS
Operating Input Voltage Range 16 28 70 V Continuous 1, 2, 3
“ 16 28 80 V Transient, 1s 4, 5, 6
Input Under-Voltage Lockout See Note 3
Turn-On Voltage Threshold 14.75 15.50 16.00 V 1, 2, 3
Turn-Off Voltage Threshold 13.80 14.40 15.00 V 1, 2, 3
Lockout Voltage Hysteresis 0.50 1.10 1.80 V 1, 2, 3
Input Over-Voltage Shutdown See Note 15
Turn-Off Voltage Threshold 90 95 100 V 1, 2, 3
Turn-On Voltage Threshold 82 86 90 V 1, 2, 3
Shutdown Voltage Hysteresis 3 9 15 V 1, 2, 3
Maximum Input Current 9.5 A Vin = 16V; Iout = 4A 1, 2, 3
No Load Input Current (operating) 110 160 mA 1, 2, 3
Disabled Input Current (ENA1) 2 5 mA Vin = 16V, 28V, 70V 1, 2, 3
Disabled Input Current (ENA2) 25 50 mA Vin = 16V, 28V, 70V 1, 2, 3
Input Terminal Current Ripple (pk-pk) 40 60 mA Bandwidth = 100kHz – 10MHz; see Figure 14 1, 2, 3
OUTPUT CHARACTERISTICS
Output Voltage Set Point (Tcase = 25ºC) 27.72 28.00 28.28 V Vout at sense leads 1
Output Voltage Set Point Over Temperature 27.60 28.00 28.40 V “ 2, 3
Output Voltage Line Regulation -20 0 20 mV “ ; Vin = 16V, 28V, 70V; Iout=4A 1, 2, 3
Output Voltage Load Regulation 120 135 150 mV “ ; Vout @ (Iout=0A) - Vout @ (Iout=4A) 1, 2, 3
Total Output Voltage Range 27.44 28.00 28.56 V “ 1, 2, 3
Output Voltage Ripple and Noise Peak to Peak 30 100 mV Bandwidth = 10MHz; CL=11µF 1, 2, 3
Operating Output Current Range 0 4 A 1, 2, 3
Operating Output Power Range 0 112 W 1, 2, 3
Output DC Current-Limit Inception 4.1 4.6 5.0 A See Note 4 1, 2, 3
Short Circuit Output Current 4.1 4.8 5.5 A Vout ≤ 1.2V 1, 2, 3
Back-Drive Current Limit while Enabled 1.2 A 1, 2, 3
Back-Drive Current Limit while Disabled 10 60 mA 1, 2, 3
Maximum Output Capacitance 3,000 µF See Note 5
DYNAMIC CHARACTERISTICS
Output Voltage Deviation Load Transient See Note 6
For a Pos. Step Change in Load Current -1200 -650 mV Total Iout step = 2A‹-›4A, 0.4A‹-›2A; CL=11µF 4, 5, 6
For a Neg. Step Change in Load Current 650 1200 mV “ 4, 5, 6
Settling Time (either case) 100 200 µs See Note 7 4, 5, 6
Output Voltage Deviation Line Transient Vin step = 16V‹-›50V; CL=11µF; see Note 8
For a Pos. Step Change in Line Voltage -800 800 mV 4, 5, 6
For a Neg. Step Change in Line Voltage -800 800 mV 4, 5, 6
Settling Time (either case) 250 500 µs See Note 7 See Note 5
Turn-On Transient
Output Voltage Rise Time 6 10 ms Vout = 2.8V-›25.2V 4, 5, 6
Output Voltage Overshoot 0 2 % See Note 5
Turn-On Delay, Rising Vin 5.5 8.0 ms ENA1, ENA2 = 5V; see Notes 9 & 12 4, 5, 6
Turn-On Delay, Rising ENA1 3.0 6.0 ms ENA2 = 5V; see Note 12 4, 5, 6
Turn-On Delay, Rising ENA2 1.5 3.0 ms ENA1 = 5V; see Note 12 4, 5, 6
EFFICIENCY
Iout = 4A (16Vin) 82 87 % 1, 2, 3
Iout = 2A (16Vin) 86 90 % 1, 2, 3
Iout = 4A (28Vin) 82 87 % 1, 2, 3
Iout = 2A (28Vin) 85 89 % 1, 2, 3
Iout = 4A (40Vin) 80 85 % 1, 2, 3
Iout = 2A (40Vin) 84 87 % 1, 2, 3
Iout = 4A (70Vin) 76 82 % 1, 2, 3
Load Fault Power Dissipation 20 32 W Iout at current limit inception point; See Note 4 1, 2, 3
Short Circuit Power Dissipation 23 34 W Vout ≤ 1.2V 1, 2, 3
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Technical Specification
MQFL-28E-28S
Output: 28V
Current: 4.0A
MQFL-28E-28S ELECTRICAL CHARACTERISTICS (Continued)
Parameter Min. Typ. Max. Units Notes & Conditions Group A
Vin=28V dc ±5%, Iout=4.0A, CL=0µF, free running (see Note 10)
unless otherwise specied Subgroup
ISOLATION CHARACTERISTICS
Isolation Voltage Dielectric strength
Input RTN to Output RTN 500 V 1
Any Input Pin to Case 500 V 1
Any Output Pin to Case 500 V 1
Isolation Resistance (in rtn to out rtn) 100 MΩ 1
Isolation Resistance (any pin to case) 100 MΩ 1
Isolation Capacitance (in rtn to out rtn) 44 nF 1
FEATURE CHARACTERISTICS
Switching Frequency (free running) 500 550 600 kHz 1, 2, 3
Synchronization Input
Frequency Range 500 700 kHz 1, 2, 3
Logic Level High 2.0 10 V 1, 2, 3
Logic Level Low -0.5 0.8 V 1, 2, 3
Duty Cycle 20 80 % See Note 5
Synchronization Output
Pull Down Current 20 mA VSYNC OUT = 0.8V See Note 5
Duty Cycle 25 75 % Output connected to SYNC IN of other MQFL unit See Note 5
Enable Control (ENA1 and ENA2)
Off-State Voltage 0.8 V 1, 2, 3
Module Off Pulldown Current 80 µA Current drain required to ensure module is off See Note 5
On-State Voltage 2 V 1, 2, 3
Module On Pin Leakage Current 20 µA Imax drawn from pin allowed, module on See Note 5
Pull-Up Voltage 3.2 4.0 4.5 V See Figure A 1, 2, 3
RELIABILITY CHARACTERISTICS
Calculated MTBF (MIL-STD-217F2)
GB @ Tcase = 70ºC 2800 103 Hrs.
AIF @ Tcase = 70ºC 440 103 Hrs.
WEIGHT CHARACTERISTICS
Device Weight 79 g
Electrical Characteristics Notes
1. Converter will undergo input over-voltage shutdown.
2. Derate output power for continuous operation per Figure 5. 135ºC is above specied operating range.
3. High or low state of input voltage must persist for about 200µs to be acted on by the lockout or shutdown circuitry.
4. Current limit inception is dened as the point where the output voltage has dropped to 90% of its nominal value.
5. Parameter not tested but guaranteed to the limit specied.
6. Load current transition time ≥ 10µs.
7. Settling time measured from start of transient to the point where the output voltage has returned to ±1% of its nal value.
8. Line voltage transition time ≥ 100µs.
9. Input voltage rise time ≤ 250µs.
10. Operating the converter at a synchronization frequency above the free running frequency will cause the converter’s efciency to be slightly reduced and it
may also cause a slight reduction in the maximum output current/power available. For more information consult the factory.
11. SHARE pin outputs a power failure warning pulse during a fault condition. See Current Share section of the Control Features description.
12. After a disable or fault event, module is inhibited from restarting for 300ms. See Shut Down section of the Control Features description.
13. Only the ES and HB grade products are tested at three temperatures. The C- grade products are tested at one temperature. Please refer to the
Construction and Environmental Stress Screening Options table for details.
14. These derating curves apply for the ES and HB grade products. The C- grade product has a maximum case temperature of 70ºC.
15. Input Over Voltage Shutdown test is run at no load, full load is beyond derating condition and could cause damage at 125ºC.
16. The specied operating case temperature for ES grade products is -45ºC to 100ºC. The specied operating case temperature for C- grade
products is 0ºC to 70ºC.
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Technical Figures
MQFL-28E-28S
Output: 28V
Current: 4.0A
60
65
70
75
80
85
90
95
100
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Efficiency (%)
Load Current (A)
16 Vin
28 Vin
40 Vin
70 Vin
60
65
70
75
80
85
90
95
100
-55ºC
25ºC
Efficiency (%)
Case Temperature (ºC)
16 Vin
28 Vin
40 Vin
70 Vin
0
4
8
12
16
20
24
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
Power Dissipation (W)
Load Current (A)
16 Vin
28 Vin
40 Vin
70 Vin
0
4
8
12
16
20
24
-55ºC
25ºC
125ºC
Power Dissipation (W)
Case Temperature (ºC)
16 Vin
28 Vin
40 Vin
70 Vin
0
28
56
84
112
140
0
1
2
3
4
5
25 35 45 55 65 75 85 95 105 115 125 135 145
Iout (A)
Case Temperature (ºC)
Tmax = 105ºC, Vin = 70
Tmax = 105ºC, Vin = 50
Tmax = 105ºC, Vin = 28
Tmax = 125ºC, Vin = 70
Tmax = 125ºC, Vin = 50
Tmax = 125ºC, Vin = 28
Tmax = 145ºC, Vin = 70
Tmax = 145ºC, Vin = 50
Tmax = 145ºC, Vin = 28
Pout (W)
0
4
8
12
16
20
24
28
32
0 1 2 3 4 5
Output Voltage (V)
Load Current (A)
Figure 1: Efciency at nominal output voltage vs. load current for
minimum, nominal, and maximum input voltage at Tcase=25°C.
Figure 2: Efciency at nominal output voltage and 60% rated power vs.
case temperature for input voltage of 16V, 28V, 40V and 70V.
Figure 3: Power dissipation at nominal output voltage vs. load current
for minimum, nominal, and maximum input voltage at Tcase=25°C.
Figure 4: Power dissipation at nominal output voltage and 60% rated
power vs. case temperature for input voltage of 16V, 28V, 40V and 70V.
Figure 5: Output Current / Output Power derating curve as a
function of Tcase and the Maximum desired power MOSFET junction
temperature (see Note 14).
Figure 6: Output voltage vs. load current showing typical current limit
curves at Vin = 28V.
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Technical Figures
MQFL-28E-28S
Output: 28V
Current: 4.0A
Figure 7: Turn-on transient at full resistive load and zero output
capacitance initiated by ENA1. Input voltage pre-applied. Ch 1: Vout
(5V/div). Ch 2: ENA1 (5V/div).
Figure 8: Turn-on transient at full resistive load and 3mF output
capacitance initiated by ENA1. Input voltage pre-applied. Ch 1: Vout
(5V/div). Ch 2: ENA1 (5V/div).
Figure 9: Turn-on transient at full resistive load and zero output
capacitance initiated by ENA2. Input voltage pre-applied. Ch 1: Vout
(5V/div). Ch 2: ENA2 (5V/div).
Figure 10: Turn-on transient at full resistive load and zero output
capacitance initiated by Vin. ENA1 and ENA2 both previously high. Ch
1: Vout (5V/div). Ch 2: Vin (10V/div).
Figure 11: Output voltage response to step-change in load current
50%-100%-50% of Iout (max). Load cap: 1µF ceramic cap and 10µF,
100mΩ ESR tantalum cap. Ch 1: Vout (500mV/div). Ch 2: Iout (2A/
div).
Figure 12: Output voltage response to step-change in load current 0%-
50%-0% of Iout (max). Load cap: 1µF ceramic cap and 10µF, 100mΩ
ESR tantalum cap. Ch 1: Vout (500mV/div). Ch 2: Iout (2A/div).
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Technical Figures
MQFL-28E-28S
Output: 28V
Current: 4.0A
Figure 13: Output voltage response to step-change in input voltage
(16V - 50V - 16V). Load cap: 10µF, 100mΩ ESR tantalum cap and 1µF
ceramic cap. Ch 1: Vout (500mV/div). Ch 2: Vin (20V/div).
Figure 14: Test set-up diagram showing measurement points for Input
Terminal Ripple Current (Figure 15) and Output Voltage Ripple (Figure
16).
Figure 17: Rise of output voltage after the removal of a short circuit
across the output terminals. Ch 1: Vout (5V/div). Ch 2: Iout (2A/div).
Figure 18: SYNC OUT vs. time, driving SYNC IN of a second SynQor
MQFL converter. Ch1: SYNC OUT: (1V/div).
Figure 15: Input terminal current ripple, ic, at full rated output current
and nominal input voltage with SynQor MQ lter module (50mA/div).
Bandwidth: 20MHz. See Figure 14.
Figure 16: Output voltage ripple, Vout, at nominal input voltage
and rated load current (20mV/div). Load capacitance: 1µF ceramic
capacitor and 10µF tantalum capacitor. Bandwidth: 10MHz. See
Figure 14.
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Technical Figures
MQFL-28E-28S
Output: 28V
Current: 4.0A
0.01
0.1
1
10 100 1,000 10,000 100,000
Output Impedance (ohms)
Hz
16Vin
28Vin
40Vin
-100
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
10 100 1,000 10,000 100,000
Forward Transmission (dB)
Hz
16Vin
28Vin
40Vin
-50
-40
-30
-20
-10
0
10
20
10 100 1,000 10,000 100,000
Reverse Transmission (dB)
Hz
16Vin
28Vin
40Vin
0.01
0.1
1
10
10 100 1,000 10,000 100,000
Input Impedance (ohms)
Hz
16Vin
28Vin
40Vin
Figure 19: Magnitude of incremental output impedance (Zout = vout/
iout) for minimum, nominal, and maximum input voltage at full rated
power.
Figure 20: Magnitude of incremental forward transmission (FT = vout/
vin) for minimum, nominal, and maximum input voltage at full rated
power.
Figure 21: Magnitude of incremental reverse transmission (RT = iin/
iout) for minimum, nominal, and maximum input voltage at full rated
power.
Figure 22: Magnitude of incremental input impedance (Zin = vin/iin)
for minimum, nominal, and maximum input voltage at full rated power.
Figure 23: High frequency conducted emissions of standalone MQFL-
28-05S, 5Vout module at 120W output, as measured with Method
CE102. Limit line shown is the ‘Basic Curve’ for all applications with a
28V source.
Figure 24: High frequency conducted emissions of MQFL-28-05S,
5Vout module at 120W output with MQFL-28-P lter, as measured
with Method CE102. Limit line shown is the ‘Basic Curve’ for all
applications with a 28V source.
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Page 9
BASIC OPERATION AND FEATURES
The MQFL DC/DC converter uses a two-stage power conversion
topology. The first, or regulation, stage is a buck-converter that
keeps the output voltage constant over variations in line, load,
and temperature. The second, or isolation, stage uses trans-
formers to provide the functions of input/output isolation and
voltage transformation to achieve the output voltage required.
Both the regulation and the isolation stages switch at a fixed
frequency for predictable EMI performance. The isolation stage
switches at one half the frequency of the regulation stage, but
due to the push-pull nature of this stage it creates a ripple at
double its switching frequency. As a result, both the input and
the output of the converter have a fundamental ripple frequency
of about 550 kHz in the free-running mode.
Rectification of the isolation stage’s output is accomplished with
synchronous rectifiers. These devices, which are MOSFETs
with a very low resistance, dissipate far less energy than would
Schottky diodes. This is the primary reason why the MQFL
converters have such high efficiency, particularly at low output
voltages.
Besides improving efficiency, the synchronous rectifiers permit
operation down to zero load current. There is no longer a need
for a minimum load, as is typical for converters that use diodes
for rectification. The synchronous rectifiers actually permit a
negative load current to flow back into the converter’s output
terminals if the load is a source of short or long term energy.
The MQFL converters employ a “back-drive current limit” to
keep this negative output terminal current small.
There is a control circuit on both the input and output sides
of the MQFL converter that determines the conduction state
of the power switches. These circuits communicate with each
other across the isolation barrier through a magnetically coupled
device. No opto-isolators are used.
A separate bias supply provides power to both the input and
output control circuits. Among other things, this bias supply
permits the converter to operate indefinitely into a short circuit
and to avoid a hiccup mode, even under a tough start-up condi-
tion.
An input under-voltage lockout feature with hysteresis is pro-
vided, as well as an input over-voltage shutdown. There is also
an output current limit that is nearly constant as the load imped-
ance decreases to a short circuit (i.e., there is not fold-back
or fold-forward characteristic to the output current under this
condition). When a load fault is removed, the output voltage
rises exponentially to its nominal value without an overshoot.
The MQFL converter’s control circuit does not implement an out-
put over-voltage limit or an over-temperature shutdown.
The following sections describe the use and operation of addi-
tional control features provided by the MQFL converter.
CONTROL FEATURES
ENABLE: The MQFL converter has two enable pins. Both must
have a logic high level for the converter to be enabled. A logic
low on either pin will inhibit the converter.
The ENA1 pin (pin 4) is referenced with respect to the convert-
er’s input return (pin 2). The ENA2 pin (pin 12) is referenced
with respect to the converter’s output return (pin 8). This per-
mits the converter to be inhibited from either the input or the
output side.
Regardless of which pin is used to inhibit the converter, the
regulation and the isolation stages are turned off. However,
when the converter is inhibited through the ENA1 pin, the bias
supply is also turned off, whereas this supply remains on when
the converter is inhibited through the ENA2 pin. A higher input
standby current therefore results in the latter case.
Both enable pins are internally pulled high so that an open con-
nection on both pins will enable the converter. Figure A shows
the equivalent circuit looking into either enable pins. It is TTL
compatible.
SHUT DOWN: The MQFL converter will shut down in response
to only four conditions: ENA1 input low, ENA2 input low, VIN
input below under-voltage lockout threshold, or VIN input above
over-voltage shutdown threshold. Following a shutdown event,
there is a startup inhibit delay which will prevent the converter
from restarting for approximately 300ms. After the 300ms delay
elapses, if the enable inputs are high and the input voltage is
within the operating range, the converter will restart. If the VIN
input is brought down to nearly 0V and back into the operating
range, there is no startup inhibit, and the output voltage will
rise according to the “Turn-On Delay, Rising Vin” specification.
2N3904
1N4148
250K
125K
82K
5.6V
TO ENABLE
CIRCUITRY
PIN 4
(OR PIN 12)
PIN 2
(OR PIN 8) IN RTN
ENABLE
Figure A: Circuit diagram shown for reference only, actual circuit
components may differ from values shown for equivalent circuit.
Application Section
MQFL-28E-28S
Output: 28V
Current: 4.0A
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REMOTE SENSE: The purpose of the remote sense pins is
to correct for the voltage drop along the conductors that con-
nect the converter’s output to the load. To achieve this goal, a
separate conductor should be used to connect the +SENSE pin
(pin 10) directly to the positive terminal of the load, as shown
in the connection diagram on Page 2. Similarly, the –SENSE
pin (pin 9) should be connected through a separate conductor
to the return terminal of the load.
NOTE: Even if remote sensing of the load voltage is not desired,
the +SENSE and the -SENSE pins must be connected to +Vout
(pin 7) and OUTPUT RETURN (pin 8), respectively, to get proper
regulation of the converter’s output. If they are left open, the
converter will have an output voltage that is approximately
200mV higher than its specified value. If only the +SENSE pin
is left open, the output voltage will be approximately 25mV too
high.
Inside the converter, +SENSE is connected to +Vout with a
resistor value from 100W to 274W, depending on output volt-
age, and –SENSE is connected to OUTPUT RETURN with a 10W
resistor.
It is also important to note that when remote sense is used, the
voltage across the converter’s output terminals (pins 7 and 8)
will be higher than the converter’s nominal output voltage due
to resistive drops along the connecting wires. This higher volt-
age at the terminals produces a greater voltage stress on the
converter’s internal components and may cause the converter
to fail to deliver the desired output voltage at the low end of
the input voltage range at the higher end of the load current
and temperature range. Please consult the factory for details.
SYNCHRONIZATION: The MQFL converter’s switching fre-
quency can be synchronized to an external frequency source
that is in the 500 kHz to 700 kHz range. A pulse train at the
desired frequency should be applied to the SYNC IN pin (pin
6) with respect to the INPUT RETURN (pin 2). This pulse train
should have a duty cycle in the 20% to 80% range. Its low
value should be below 0.8V to be guaranteed to be interpreted
as a logic low, and its high value should be above 2.0V to be
guaranteed to be interpreted as a logic high. The transition time
between the two states should be less than 300ns.
If the MQFL converter is not to be synchronized, the SYNC IN
pin should be left open circuit. The converter will then operate
in its free-running mode at a frequency of approximately 550
kHz.
If, due to a fault, the SYNC IN pin is held in either a logic low
or logic high state continuously, the MQFL converter will revert
to its free-running frequency.
The MQFL converter also has a SYNC OUT pin (pin 5). This
output can be used to drive the SYNC IN pins of as many as
ten (10) other MQFL converters. The pulse train coming out
of SYNC OUT has a duty cycle of 50% and a frequency that
matches the switching frequency of the converter with which
it is associated. This frequency is either the free-running fre-
quency if there is no synchronization signal at the SYNC IN pin,
or the synchronization frequency if there is.
The SYNC OUT signal is available only when the DC input volt-
age is above approximately 12V and when the converter is not
inhibited through the ENA1 pin. An inhibit through the ENA2 pin
will not turn the SYNC OUT signal off.
NOTE: An MQFL converter that has its SYNC IN pin driven by
the SYNC OUT pin of a second MQFL converter will have its start
of its switching cycle delayed approximately 180 degrees rela-
tive to that of the second converter.
Figure B shows the equivalent circuit looking into the SYNC IN
pin. Figure C shows the equivalent circuit looking into the
SYNC OUT pin.
Figure B: Equivalent circuit looking into the SYNC IN pin with
respect to the IN RTN (input return) pin.
PIN 2
PIN 6
5K
5V
SYNC IN
IN RTN
TO SYNC
CIRCUITRY
5K
Figure C: Equivalent circuit looking into SYNC OUT pin with
respect to the IN RTN (input return) pin.
FROM SYNC
CIRCUITRY
5K
5V
SYNC OUT
IN RTN PIN 2
PIN 5
OPEN COLLECTOR
OUTPUT
CURRENT SHARE: When several MQFL converters are placed
in parallel to achieve either a higher total load power or N+1
redundancy, their SHARE pins (pin 11) should be connected
together. The voltage on this common SHARE node represents
the average current delivered by all of the paralleled converters.
Application Section
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 11
Each converter monitors this average value and adjusts itself
so that its output current closely matches that of the average.
Since the SHARE pin is monitored with respect to the OUTPUT
RETURN (pin 8) by each converter, it is important to connect
all of the converters’ OUTPUT RETURN pins together through a
low DC and AC impedance. When this is done correctly, the
converters will deliver their appropriate fraction of the total load
current to within +/- 10% at full rated load.
Whether or not converters are paralleled, the voltage at the
SHARE pin could be used to monitor the approximate aver-
age current delivered by the converter(s). A nominal voltage
of 1.0V represents zero current and a nominal voltage of 2.2V
represents the maximum rated current, with a linear relationship
in between. The internal source resistance of a converter’s
SHARE pin signal is 2.5 kW. During an input voltage fault or
primary disable event, the SHARE pin outputs a power failure
warning pulse. The SHARE pin will go to 3V for approximately
14ms as the output voltage falls.
NOTE: Converters operating from separate input filters with
reverse polarity protection (such as the MQME-28-T filter) with
their outputs connected in parallel may exhibit hiccup operation
at light loads. Consult factory for details.
OUTPUT VOLTAGE TRIM: If desired, it is possible to increase
the MQFL converter’s output voltage above its nominal value.
To do this, use the +SENSE pin (pin 10) for this trim function
instead of for its normal remote sense function, as shown in
Figure D. In this case, a resistor connects the +SENSE pin to
the –SENSE pin (which should still be connected to the output
return, either remotely or locally). The value of the trim resistor
should be chosen according to the following equation or from
Figure E:
where:
Vnom = the converter’s nominal output voltage,
Vout = the desired output voltage (greater than Vnom), and
Rtrim is in Ohms.
As the output voltage is trimmed up, it produces a greater
voltage stress on the converter’s internal components and may
cause the converter to fail to deliver the desired output voltage
at the low end of the input voltage range at the higher end of
the load current and temperature range. Please consult the
factory for details. Factory trimmed converters are available
by request.
INPUT UNDER-VOLTAGE LOCKOUT: The MQFL converter
has an under-voltage lockout feature that ensures the converter
will be off if the input voltage is too low. The threshold of input
voltage at which the converter will turn on is higher that the
threshold at which it will turn off. In addition, the MQFL con-
verter will not respond to a state of the input voltage unless it
has remained in that state for more than about 200
µ
s. This hys-
teresis and the delay ensure proper operation when the source
impedance is high or in a noisy environment.
Figure D: Typical connection for output voltage trimming.
Load
+
+
28 Vdc
open
means
on
Rtrim
MQFL
+VIN
IN RTN
CASE
ENA 1
SYNC OUT
SYNC IN
ENA 2
SHARE
+SNS
-SNS
OUT RTN
+VOUT
1
2
3
4
5
6
12
11
10
9
8
7
_
_
100
1,000
10,000
100,000
0.0 0.4 0.8 1.2 1.6 2.0 2.4 2.8 3.2
Trim Resistance (ohms)
Increase in Vout (V)
Figure E: Output Voltage Trim Graph
Rtrim = 100 x
Vnom
Vout - Vnom - 0.025
Application Section
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 12
INPUT OVER-VOLTAGE SHUTDOWN: The MQFL converter
also has an over-voltage feature that ensures the converter will
be off if the input voltage is too high. It also has a hysteresis
and time delay to ensure proper operation.
BACK-DRIVE CURRENT LIMIT: Converters that use MOSFETs
as synchronous rectifiers are capable of drawing a negative cur-
rent from the load if the load is a source of short- or long-term
energy. This negative current is referred to as a “back-drive
current”.
Conditions where back-drive current might occur include paral-
leled converters that do not employ current sharing, or where
the current share feature does not adequately ensure sharing
during the startup or shutdown transitions. It can also occur
when converters having different output voltages are connected
together through either explicit or parasitic diodes that, while
normally off, become conductive during startup or shutdown.
Finally, some loads, such as motors, can return energy to their
power rail. Even a load capacitor is a source of back-drive
energy for some period of time during a shutdown transient.
To avoid any problems that might arise due to back-drive cur-
rent, the MQFL converters limit the negative current that the
converter can draw from its output terminals. The threshold
for this back-drive current limit is placed sufficiently below zero
so that the converter may operate properly down to zero load,
but its absolute value (see the Electrical Characteristics page) is
small compared to the converter’s rated output current.
When the converter is mounted on a metal plate, the plate will
help to make the converter’s case bottom a uniform tempera-
ture. How well it does so depends on the thickness of the plate
and on the thermal conductance of the interface layer (e.g. ther-
mal grease, thermal pad, etc.) between the case and the plate.
Unless this is done very well, it is important not to mistake the
plate’s temperature for the maximum case temperature. It is
easy for them to be as much as 5-10ºC different at full power
and at high temperatures. It is suggested that a thermocouple
be attached directly to the converter’s case through a small hole
in the plate when investigating how hot the converter is getting.
Care must also be made to ensure that there is not a large
thermal resistance between the thermocouple and the case due
to whatever adhesive might be used to hold the thermocouple
in place.
INPUT SYSTEM INSTABILITY: This condition can occur
because any DC/DC converter appears incrementally as a nega-
tive resistance load. A detailed application note titled “Input
System Instability” is available on the SynQor website which pro-
vides an understanding of why this instability arises, and shows
the preferred solution for correcting it
.
THERMAL CONSIDERATIONS: Figure 5 shows the suggested
Power Derating Curves for this converter as a function of the
case temperature, input voltage and the maximum desired
power MOSFET junction temperature. All other components
within the converter are cooler than its hottest MOSFET.
The Mil-HDBK-1547A component derating guideline calls
for a maximum component temperature of 105ºC. Figure
5 therefore has one power derating curve that ensures
this limit is maintained. It has been SynQor’s extensive
experience that reliable long-term converter operation can
be achieved with a maximum component temperature of
125ºC. In extreme cases, a maximum temperature of 145ºC
is permissible, but not recommended for long-term operation
where high reliability is required. Derating curves for these
higher temperature limits are also included in Figure 5. The
maximum case temperature at which the converter should be
operated is 135ºC.
Application Section
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 13
Stress Screening
MQFL-28E-28S
Output: 28V
Current: 4.0A
CONSTRUCTION AND ENVIRONMENTAL STRESS SCREENING OPTIONS
Screening Consistent with
MIL-STD-883F
C-Grade ES-Grade HB-Grade
(specied from ) ( specied from ) ( specied from )
0 ºC to +70 ºC -45 ºC to +100 ºC -55 ºC to +125 ºC
Element Evaluation No Yes Yes
Internal Visual * Yes Yes Yes
Temperature Cycle Method 1010 No Condition B
(-55 ºC to +125 ºC)
Condition C
(-65 ºC to +150 ºC)
Constant Acceleration Method 2001
(Y1 Direction) No 500g Condition A
(5000g)
Burn-in Method 1015 24 Hrs @ +125 ºC 96 Hrs @ +125 ºC 160 Hrs @ +125 ºC
Final Electrical Test Method 5005 (Group A) +25 ºC -45, +25, +100 ºC -55, +25, +125 ºC
Mechanical Seal,
Thermal, and
Coating Process
Full QorSeal Full QorSeal Full QorSeal
External Visual 2009 * Yes Yes
Construction Process QorSeal QorSeal QorSeal
* Per IPC-A-610 Class 3
MilQor converters and lters are offered in three variations of environmental stress screening options. All MilQor converters use SynQor’s proprietary
QorSeal™ Hi-Rel assembly process that includes a Parylene-C coating of the circuit, a high performance thermal compound ller, and a nickel barrier
gold plated aluminum case. Each successively higher grade has more stringent mechanical and electrical testing, as well as a longer burn-in cycle. The ES-
and HB-Grades are also constructed of components that have been procured through an element evaluation process that pre-qualies each new batch of
devices.
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Page 14
MADE IN USA
1
2
3
4
5
6
12
11
10
9
8
7
1.260
[32.00]
1.50 [38.1]
0.128 [3.25]
0.22 [5.6]
0.42
[10.7] 0.050 [1.27]
0.040
[1.02]
PIN
0.200 [5.08]
TYP.
NON-CUM.
0.250 [6.35]
0.390 [9.91]
2.50 [63.5]
2.760 [70.10]
3.00 [76.2]
SEE NOTE 7
S/N 0000000 D/C 3211-301 CAGE 1WX10
2.80 [71.1]
MADE IN USA
1
2
3
4
5
6
12
11
10
9
8
7
1.260
[32.00]
1.50 [38.1]
0.128 [3.25]
0.228 [5.79]
0.22 [5.6]
0.050 [1.27]
0.040 [1.02]
PIN
0.200 [5.08]
TYP. NON-CUM.
0.250 [6.35]
0.390 [9.91]
2.50 [63.50]
2.760 [70.10]
3.00 [76.2]
2.96 [75.2]
S/N 0000000 D/C 3205-301 CAGE 1WX10
SEE NOTE 7
Case X
Case U
PIN DESIGNATIONS
Pin # Function Pin # Function
1 Positive input 7 Positive output
2 Input return 8 Output return
3 Case 9 - Sense
4 Enable 1 10 + Sense
5 Sync output 11 Share
6 Sync input 12 Enable 2
NOTES
1) Pins 0.040’’ (1.02mm) diameter
2) Pin Material: Copper Alloy
Finish: Gold over Nickel plating, followed by Sn/Pb solder dip
3) All dimensions in inches (mm) Tolerances: x.xx +/-0.02 in. (x.x +/-0.5mm)
x.xxx +/-0.010 in. (x.xx +/-0.25mm)
4) Weight: 2.8 oz (78.5 g) typical
5) Workmanship: Meets or exceeds IPC-A-610 Class III
6) Print Labeling on Top Surface per Product Label Format Drawing
7) Pin 1 identication hole, not intended for mounting (case X and U)
8) Baseplate atness tolerance is 0.004” (.10mm) TIR for surface.
+VIN ENA 2
IN RTN SHARE
CASE +SNS
ENA 1 -SNS
SYNC OUT OUT RTN
SYNC IN +VOUT
+VIN ENA 2
IN RTN SHARE
CASE +SNS
ENA 1 -SNS
SYNC OUT OUT RTN
SYNC IN +VOUT
MQFL-28E-28S-X-ES
DC-DC CONVERTER
28Vin 28Vout @ 4.0A
MQFL-28E-28S-U-ES
DC-DC CONVERTER
28Vin 28Vout @ 4.0A
Mechanical Diagrams
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 15
1
2
3
4
5
6
12
11
10
9
8
7
1.750
[44.45]
1.50
[38.1]
0.228 [5.79]
0.300 [7.62]
0.140 [3.56]
0.22 [5.6]
0.050 [1.27]
0.040 [1.02]
PIN
0.200 [5.08]
TYP. NON-CUM.
0.250 [6.35]
0.250 [6.35]
TYP
0.375 [9.52]
2.50 [63.5]
2.96 [75.2]
0.390 [9.91]
2.000
[50.80]
1.150 [29.21]
1.750 [44.45]
S/N 0000000 D/C 3211-301 CAGE 1WX10
MADE IN USA
0.390
[9.91]
0.050 [1.27]
0.36 [9.14]
0.250 [6.35]
0.22 [5.6]
2.80 [71.1]
0.525 [13.33]
0.040 [1.02]
PIN
0.200 [5.08]
TYP. NON-CUM.
0.390
[9.91]
0.050 [1.27]
0.250 [6.35]
0.22 [5.6]
0.42 [10.7]
2.80 [71.1]
0.525 [13.33]
0.040 [1.02]
PIN
0.200 [5.08]
TYP. NON-CUM.
Case Y
Case Z
(variant of Y)
Case W
(variant of Y)
PIN DESIGNATIONS
Pin # Function Pin # Function
1 Positive input 7 Positive output
2 Input return 8 Output return
3 Case 9 - Sense
4 Enable 1 10 + Sense
5 Sync output 11 Share
6 Sync input 12 Enable 2
NOTES
1) Pins 0.040’’ (1.02mm) diameter
2) Pin Material: Copper Alloy
Finish: Gold over Nickel plating, followed by Sn/Pb solder dip
3) All dimensions in inches (mm) Tolerances: x.xx +/-0.02 in. (x.x +/-0.5mm)
x.xxx +/-0.010 in. (x.xx +/-0.25mm)
4) Weight: 2.8 oz (78.5 g) typical
5) Workmanship: Meets or exceeds IPC-A-610 Class III
6) Print Labeling on Top Surface per Product Label Format Drawing
7) Pin 1 identication hole, not intended for mounting (case X and U)
8) Baseplate atness tolerance is 0.004” (.10mm) TIR for surface.
+VIN ENA 2
IN RTN SHARE
CASE +SNS
ENA 1 -SNS
SYNC OUT OUT RTN
SYNC IN +VOUT
MQFL-28E-28S-Y-ES
DC-DC CONVERTER
28Vin 28Vout @ 4.0A
Mechanical Diagrams
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 16
MilQor Converter FAMILY MATRIX
The tables below show the array of MilQor converters available. When ordering SynQor converters, please ensure that
you use the complete part number according to the table in the last page. Contact the factory for other requirements.
Single Output Dual Output †
Full Size 1.5V 1.8V 2.5V 3.3V 5V 6V 7.5V 9V 12V 15V 28V 5V 12V 15V
(1R5S) (1R8S) (2R5S) (3R3S) (05S) (06S) (7R5S) (09S) (12S) (15S) (28S) (05D) (12D) (15D)
MQFL-28
40A 40A 40A 30A 24A 20A 16A 13A 10A 8A 4A 24A
Total
10A
Total
8A
Total
16-40Vin Cont.
16-50Vin 1s Trans.*
Absolute Max Vin = 60V
MQFL-28E
40A 40A 40A 30A 24A 20A 16A 13A 10A 8A 4A 24A
Total
10A
Total
8A
Total
16-70Vin Cont.
16-80Vin 1s Trans.*
Absolute Max Vin =100V
MQFL-28V
40A 40A 40A 30A 20A 17A 13A 11A 8A 6.5A 3.3A
16-40Vin Cont.
5.5-50Vin 1s Trans.*
Absolute Max Vin = 60V
MQFL-28VE
40A 40A 40A 30A 20A 17A 13A 11A 8A 6.5A 3.3A
16-70Vin Cont.
5.5-80Vin 1s Trans.*
Absolute Max Vin = 100V
MQFL-270
40A 40A 40A 30A 24A 20A 16A 13A 10A 8A 4A 24A
Total
10A
Total
8A
Total
155-400Vin Cont.
155-475Vin 1s Trans.*
Absolute Max Vin = 550V
MQFL-270L
40A 40A 30A 22A 15A 12A 10A 8A 6A 5A 2.7A 15A
Total
6A
Total
5A
Total
65-350Vin Cont.
65-475Vin 1s Trans.*
Absolute Max Vin = 550V
Single Output Dual Output †
Half Size 1.5V 1.8V 2.5V 3.3V 5V 6V 7.5V 9V 12V 15V 28V 5V 12V 15V
(1R5S) (1R8S) (2R5S) (3R3S) (05S) (06S) (7R5S) (09S) (12S) (15S) (28S) (05D) (12D) (15D)
MQHL-28
20A 20A 20A 15A 10A 8A 6.6A 5.5A 4A 3.3A 1.8A 10A
Total
4A
Total
3.3A
Total
16-40Vin Cont.
16-50Vin 1s Trans.*
Absolute Max Vin = 60V
MQHL-28E
20A 20A 20A 15A 10A 8A 6.6A 5.5A 4A 3.3A 1.8A 10A
Total
4A
Total
3.3A
Total
16-70Vin Cont.
16-80Vin 1s Trans.*
Absolute Max Vin =100V
MQHR-28
10A 10A 10A 7.5A 5A 4A 3.3A 2.75A 2A 1.65A 0.9A 5A
Total
2A
Total
1.65A
Total
16-40Vin Cont.
16-50Vin 1s Trans.*
Absolute Max Vin = 60V
MQHR-28E
10A 10A 10A 7.5A 5A 4A 3.3A 2.75A 2A 1.65A 0.9A 5A
Total
2A
Total
1.65A
Total
16-70Vin Cont.
16-80Vin 1s Trans.*
Absolute Max Vin = 100V
Check with factory for availability.
†80% of total output current available on any one output.
*Converters may be operated at the highest transient input voltage, but some component electrical and thermal stresses would be beyond MIL-
HDBK-1547A guidelines.
Ordering Information
MQFL-28E-28S
Output: 28V
Current: 4.0A
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Page 17
Model
Name
Input
Voltage
Range
Output Voltage(s) Package Outline/
Pin Conguration
Screening
Grade
Single
Output
Dual
Output
MQFL
MQHL
MQHR
28
28E
28V
28VE
270
270L
1R5S
1R8S
2R5S
3R3S
05S
06S
7R5S
09S
12S
15S
28S
05D
12D
15D
U
X
Y
W
Z
C
ES
HB
Warranty
SynQor offers a two (2) year limited warranty. Complete warranty informa-
tion is listed on our website or is available upon request from SynQor.
Information furnished by SynQor is believed to be accurate and reliable.
However, no responsibility is assumed by SynQor for its use, nor for any
infringements of patents or other rights of third parties which may result
from its use. No license is granted by implication or otherwise under any
patent or patent rights of SynQor.
Contact SynQor for further information and to order:
Phone: 978-849-0600
Toll Free: 1-888-567-9596
Fax: 978-849-0602
E-mail: mqnbofae@synqor.com
Web:
www.synqor.com
Address: 155 Swanson Road
Boxborough, MA 01719
USA
PATENTS
SynQor holds the following U.S. patents, one or more of which apply to each product listed in this document. Additional patent applications may be
pending or led in the future.
5,999,417 6,222,742 6,545,890 6,577,109 6,594,159 6,731,520
6,894,468 6,896,526 6,927,987 7,050,309 7,072,190 7,085,146
7,119,524 7,269,034 7,272,021 7,272,023 7,558,083 7,564,702
7,765,687 7,787,261 8,023,290 8,149,597
APPLICATION NOTES
A variety of application notes and technical white papers can be downloaded in pdf format from the SynQor website.
PART NUMBERING SYSTEM
The part numbering system for SynQor’s MilQor DC-DC converters follows the format shown in the table below.
Not all combinations make valid part numbers, please contact SynQor for availability. See the Product Summary web page for more options.
Example: MQFL-28E-28S-Y-ES
Ordering Information
MQFL-28E-28S
Output: 28V
Current: 4.0A
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