MQFL-28-28S-Y-C - SynQor, Inc.

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 1

MQFL-28-28S-Y-ES

28Vin 28Vout@4A

DC-DC CONVERTER

+VIN

IN RTN

CASE

ENA 1

SYNC OUT

SYNC IN

ENA 2

+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-28-28S

Single Output

16-40V 16-50V 28V 4A 91% @ 2A / 88% @ 4A

Continuous Input Transient Input Output Output Efciency

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 2

Technical Specification

MQFL-28-28S

Output: 28V

Current: 4A

BLOCK DIAGRAM

TYPICAL CONNECTION DIAGRAM

− SENSE

ISOLATION STAGE

REGULATION STAGE

UVLO

SECONDARY

CONTROL

GATE DRIVERS

CONTROL

POWER

POSITIVE

INPUT

RETURN

CASE

ENABLE 1

SYNC OUT

SYNC IN

POSITIVE

OUTPUT

RETURN

ENABLE 2

+ SENSE

MAGNETIC

FEEDBACK

ISOLATION BARRIER

CURRENT

LIMIT

CURRENT

SENSE

PRIMARY

CONTROL

GATE DRIVERS

MQFL

+VIN

IN RTN

CASE

ENA 1

SYNC OUT

SYNC IN

ENA 2

+SNS

-SNS

OUT RTN

+VOUT

Load

open

means

28 Vdc

open

means

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 3

Technical Specification

MQFL-28-28S

Output: 28V

Current: 4A

MQFL-28-28S ELECTRICAL CHARACTERISTICS

Parameter Min. Typ. Max. Units Notes & Conditions Group A

Vin=28V dc ±5%, Iout=4A, CL=0µF, free running (see Note 10) unless otherwise

specied Subgroup

ABSOLUTE MAXIMUM RATINGS

Input Voltage

Non-Operating 60 V

Operating 60 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 & 15

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 40 V Continuous 1, 2, 3

Operating Input Voltage Range 16 28 50 V Transient, 1 sec 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 3

Turn-Off Voltage Threshold 54.0 56.8 60.0 V 1, 2, 3

Turn-On Voltage Threshold 50.0 51.4 54.0 V 1, 2, 3

Shutdown Voltage Hysteresis 2.0 5.3 8.0 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, 40V 1, 2, 3

Disabled Input Current (ENA2) 25 50 mA Vin = 16V, 28V, 40V 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, 40V; 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) 50 200 µs See Note 7 4, 5, 6

Output Voltage Deviation Line Transient See Note 8

For a Pos. Step Change in Line Voltage -800 800 mV Vin step = 16V‹-›50V; CL=11µF 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 & 11 4, 5, 6

Turn-On Delay, Rising ENA1 3.0 6.0 ms ENA2 = 5V; see Note 11 4, 5, 6

Turn-On Delay, Rising ENA2 1.5 3.0 ms ENA1 = 5V; see Note 11 4, 5, 6

EFFICIENCY

Iout = 4A (16Vin) 84 88 % 1, 2, 3

Iout = 2A (16Vin) 88 91 % 1, 2, 3

Iout = 4A (28Vin) 84 88 % 1, 2, 3

Iout = 2A (28Vin) 87 91 % 1, 2, 3

Iout = 4A (40Vin) 83 87 % 1, 2, 3

Iout = 2A (40Vin) 85 89 % 1, 2, 3

Load Fault Power Dissipation 22 32 W Iout at current limit inception point; see Note 4 1, 2, 3

Short Circuit Power Dissipation 24 33 W Vout ≤ 1.2V 1, 2, 3

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 4

Technical Specification

MQFL-28-28S

Output: 28V

Current: 4A

MQFL-28-28S ELECTRICAL CHARACTERISTICS (Continued)

Parameter Min. Typ. Max. Units Notes & Conditions Group A

Vin=28V dc ±5%, Iout=4A, CL=0µF, free running (see Note

10) unless otherwise specied Subgroup

(see Note 13)

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 (input rtn to output rtn) 100 MΩ 1

Isolation Resistance (any pin to case) 100 MΩ 1

Isolation Capacitance (input rtn to output 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 to 50% of rated power at Tcase = 135°C. 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. After a disable or fault event, module is inhibited from restarting for 300ms. See Shut Down section on Page 9.

12. SHARE pin outputs a power failure warning pulse during a fault condition. See Current Share section on Page 11

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 and a maximum junction

temperature rise of 20ºC above Tcase.

15. 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.

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 5

Technical Figures

MQFL-28-28S

Output: 28V

Current: 4A

100

0 1 2 3 4

Efficiency (%)

Load Current (A)

16 Vin

28 Vin

40 Vin

100

-55ºC

25ºC

125ºC

Efficiency (%)

Case Temperature (ºC)

16 Vin

28 Vin

40 Vin

0 1 2 3 4

Power Dissipation (W)

Load Current (A)

16 Vin

28 Vin

40 Vin

-55ºC

25ºC

125ºC

Power Dissipation (W)

Case Temperature (ºC)

16 Vin

28 Vin

40 Vin

112

140

168

25 45 65 85 105 125 145

Iout (A)

Case Temperature (ºC)

= 105ºC

= 125ºC

= 145ºC

Pout (W)

0 1 2 3 4 5 6

Output Voltage (V)

Load Current (A)

28 Vin

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.

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, and 40V.

Output Current / Output Power derating curve as a function of Tcase

and the Maximum desired power MOSFET junction temperature at Vin

= 28V (see Note 14).

Figure 6: Output voltage vs. load current showing typical current limit

curves..

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 6

Technical Figures

MQFL-28-28S

Output: 28V

Current: 4A

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 3 mF 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,

100 mΩ ESR tantalum cap. Ch 1: Vout (500mV). 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, 100 mΩ

ESR tantalum cap. Ch 1: Vout (500mV/div). Ch 2: Iout (2A/div)

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 7

Technical Figures

MQFL-28-28S

Output: 28V

Current: 4A

Figure 13: Output voltage responseto step-change in input voltage

(16V-50V-16V). Load cap: 10µF, 100 mΩ 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: 20 MHz. See Figure 14.

Figuire 16: Output voltage ripple, Vout, at nominal input voltage

and rated load current (20 mV/div). Load capacitance: 1µF ceramic

capacitor and 10µF tantalum capacitor. Bandwidth: 10 MHz. See

Figure 14.

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 8

Technical Figures

MQFL-28-28S

Output: 28V

Current: 4A

0.01

0.1

10 100 1,000 10,000 100,000

Output Impedance (ohms)

16Vin

28Vin

40Vin

-100

-90

-80

-70

-60

-50

-40

-30

-20

-10

10 100 1,000 10,000 100,000

Forward Transmission (dB)

16Vin

28Vin

40Vin

-50

-40

-30

-20

-10

10 100 1,000 10,000 100,000

Reverse Transmission (dB)

16Vin

28Vin

40Vin

0.01

0.1

100

10 100 1,000 10,000 100,000

Input Impedance (ohms)

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 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.

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

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-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 10

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

SYNC IN

IN RTN

TO SYNC

CIRCUITRY

Figure C: Equivalent circuit looking into SYNC OUT pin with

respect to the IN RTN (input return) pin.

FROM SYNC

CIRCUITRY

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-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

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

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

Rtrim

MQFL

+VIN

IN RTN

CASE

ENA 1

SYNC OUT

SYNC IN

ENA 2

+SNS

-SNS

OUT RTN

+VOUT

100

1,000

10,000

100,000

0 0.5 1 1.5 2 2.5 3

Trim Resistance (ohms)

Increase in Vout (V)

Figure E: Output Voltage Trim Graph

Rtrim = 100 x

Vnom

Vout - Vnom - 0.025

Application Section

MQFL-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

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 and the maximum

desired power MOSFET junction temperature. All other

components within the converter are cooler than its hottest

MOSFET, which at full power is no more than 20ºC higher

than the case temperature directly below this 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

Application Section

MQFL-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 13

Stress Screening

MQFL-28-28S

Output: 28V

Current: 4A

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.

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 14

MADE IN USA

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]

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

1.260

[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]

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-28-28S-X-ES

DC-DC CONVERTER

28Vin 28Vout @ 4A

MQFL-28-28S-U-ES

DC-DC CONVERTER

28Vin 28Vout @ 4A

Mechanical Diagrams

MQFL-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 15

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]

0.200 [5.08]

TYP. NON-CUM.

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]

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]

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-28-28S-Y-ES

DC-DC CONVERTER

28Vin 28Vout @ 4A

Mechanical Diagrams

MQFL-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

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

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

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

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

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

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

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

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

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-28-28S

Output: 28V

Current: 4A

Doc.# 005-2MQ280S Rev. CProduct# MQFL-28-28S Phone 1-888-567-9596 www.SynQor.com 10/24/13

Page 17

Model

Name

Input

Voltage

Range

Output Voltage(s) Package Outline/

Pin Conguration

Screening

Grade

Single

Output

Dual

Output

MQFL

MQHL

MQHR

28E

28V

28VE

270

270L

1R5S

1R8S

2R5S

3R3S

05S

06S

7R5S

09S

12S

15S

28S

05D

12D

15D

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 8,493,751

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-28-28S-Y-ES

Ordering Information

MQFL-28-28S

Output: 28V

Current: 4A