Product # MQME-28-T

Phone 1-888-567-9596

www.synqor.com

Doc.# 005-2ME028T Rev. H

05/27/16

Page 7

MQME-28-T

Technical Specification

Once the input voltage exceeds the turn-on threshold value,

the Soft-Start circuitry controls the filter’s output current to be

approximately 1.6A. This mode of operation continues until the

filter’s output voltage reaches the input voltage, at which time the

filter is able to deliver its rated output current. If after the Soft-

Start duration period the filter’s output has not risen to the input

voltage, then the filter will disconnect the output from the input,

wait for a time equal to the Soft-Start recycle period, and initiate

a new Soft-Start.

Since, during Soft-Start, the filter will deliver only 1.6A to its

output, it is important to limit the load current so that the total bulk

capacitance can be fully charged before the Soft-Start duration

period is over. To facilitate this, the filter’s ENABLE OUTPUT pin

is held low during the Soft-Start mode. This signal can therefore

be used to disable the filter’s loads during this time. Once the Soft-

Start mode is completed, ENABLE OUTPUT will follow ENABLE

INPUT.

OUTPUT POWER LIMIT: The MQME-28-T filter has an output

power limit feature to protect against a short circuit at its output

pins. This limit is disabled whenever the output voltage is rising so

that it will not be encountered when charging output capacitance.

When the output power exceeds ~450W and its output voltage

is decreasing however, this feature will turn the filter off and

reinstitute a soft-start cycle in 500ms. Figure C shows the output

power limit threshold as a function of output voltage.

STANDBY: The MQME-28-T filter has standby circuitry that

minimizes the power drawn from the filter’s input power source

when the standby feature is activated.

It does this in two ways. First, the output of the filter is disconnected

from the input so that there will be no power drawn by downstream

converters or other loads. Second, the active circuitry within the

filter is placed into a reduced power consumption mode. The

net result is a current draw of only about 2mA from a 28V input

power source.

Figure D shows the equivalent circuit looking into the STANDBY

pin (pin 8).

This pin is referenced with respect to the filter’s OUTPUT RETURN

pin (pin 7). It should be pulled low to have the filter operate in

its normal mode. If the pin is instead left open-circuit and pulled

high by its internal circuitry, the standby feature will be activated.

Application Note: A typical application would place the

MQME filter close to the input of the DC/DC converter, with the

cases of the filter and the converter connected together through

a ground plane. Both cases are electrically conductive, so

connection to the cases can be made with the fasteners used to

secure the device.

Do not connect the outputs of multiple MQME-28-T filters in

parallel. Connecting filters in this manner may result in slightly

unequal currents to flow in the positive and return paths of each

filter. These unequal currents may cause the internal common-

mode chokes to saturate and thus cause degraded common-mode

rejection performance.

PIN 9

(ENABLE OUTPUT)

PIN 7

(OUTPUT RETURN)

0.01

µF

Figure B: Equivalent circuit looking into the ENABLE OUTPUT pin

with respect to the OUTPUT RETURN pin.

5V

50k

0.01 µF

To Standby Circuitry

PIN 8

(Standby)

PIN 7

(Output Return)

Figure D: Equivalent circuit looking into the STANDBY pin with

respect to the OUTPUT RETURN pin.

Figure C: Output Power Limit.

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Output Voltage (V)

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Current

Power