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SDC_DSQ_DAQ_DCQ0150V2.A04.D02 Page 15 of 25

DSQ/DAQ/DCQ Series

600W Quarter Brick

DOSA Digital PMBus Interface

forced airflow measured in Linear Feet per Minute (“LFM”). Note that these are

AVERAGE measurements. The converter will accept brief increases in current or

reduced airflow as long as the average is not exceeded.

Note that the temperatures are of the ambient airflow, not the converter itself

which is obviously running at higher temperature than the outside air. Also note

that “natural convection” is defined as very flow rates which are not using fan-

forced airflow. Depending on the application, “natural convection” is usually about

30-65 LFM but is not equal to still air (0 LFM).

Murata Power Solutions makes Characterization measurements in a closed

cycle wind tunnel with calibrated airflow. We use both thermocouples and an

infrared camera system to observe thermal performance. As a practical matter, it is

quite difficult to insert an anemometer to precisely measure airflow in most appli-

cations. Sometimes it is possible to estimate the effective airflow if you thoroughly

understand the enclosure geometry, entry/exit orifice areas and the fan flow rate

specifications.

CAUTION: If you exceed these Derating guidelines, the converter may have an

unplanned Over Temperature shut down. Also, these graphs are all collected near

Sea Level altitude. Be sure to reduce the derating for higher altitude.

Output Short Circuit Condition

The short circuit condition is an extension of the “Current Limiting” condition. When

the monitored peak current signal reaches a certain range, the PWM controller’s

outputs are shut off thereby turning the converter “off.” This is followed by an

extended time out period. This period can vary depending on other conditions such

as the input voltage level. Following this time out period, the PWM controller will

attempt to re-start the converter by initiating a “normal start cycle” which includes

soft start. If the “fault condition” persists, another “hiccup” cycle is initiated. This

“cycle” can and will continue indefinitely until such time as the “fault condition” is

removed, at which time the converter will resume “normal operation.” Operating in

the “hiccup” mode during a fault condition is advantageous in that average input

and output power levels are held low preventing excessive internal increases in

temperature.

Remote On/Off Control

The DSQ series modules are equipped with an On/Off control pin (internal pull

up, TTL open-collector and/or CMOS open-drain compatible) and is configurable

via PMBus interface. Output is enabled when the On/Off is grounded or brought

to within a low voltage (see specifications) with respect to –Vin. The device is off

(disabled) when the On/Off is left open or is pulled high to +13.5Vdc with respect

to –Vin. The On/Off function allows the module to be turned on/off by an external

device switch.

The restart delay for this module to turn On/Off by the On/Off control pin is

200ms.

On/Off can be configured by PMBus command 0xDD (MFR_PRIMARY_ON_

OFF_ CONFIG); default configuration does not ignore the control pin and therefore

requires the On/Off control pin to be asserted to start the unit.

On/Off status is dependent on On/Off control and OPERATION (PMBus com-

mand) status; both must be ON to turn DSQ on; if one of them is OFF, unit will be

turned off.

Output Capacitive Load

These converters do not require external capacitance added to achieve rated

specifications. Users should only consider adding capacitance to reduce switching

noise and/or to handle spike current load steps. Install only enough capacitance

to achieve noise objectives. Excess external capacitance may cause degraded

transient response and possible oscillation or instability.

Remote Sense Input

Use the Sense inputs with caution. Sense is normally connected at the load. Sense

inputs compensate for output voltage inaccuracy delivered at the load. This is done

by correcting IR voltage drops along the output wiring and the current carrying

capacity of PC board etches. This output drop (the difference between Sense and

Vout when measured at the converter) should not exceed 0.5V. Consider using

heavier wire if this drop is excessive. Sense inputs also improve the stability of the

converter and load system by optimizing the control loop phase margin.

Figure 16. Remote Sense Circuit Configuration

Note: The Sense input and power Vout lines are internally connected through

low value resistors to their respective polarities so that the converter can operate

without external connection to the Sense. Nevertheless, if the Sense function is not

used for remote regulation, the user should connect +Sense to +Vout and –Sense

to –Vout at the converter pins.

The remote Sense lines carry very little current. They are also capacitively cou-

pled to the output lines and therefore are in the feedback control loop to regulate

and stabilize the output. As such, they are not low impedance inputs and must be

treated with care in PC board layouts. Sense lines on the PCB should run adjacent

to DC signals, preferably Ground. In cables and discrete wiring, use twisted pair,

shielded tubing or similar techniques.

Any long, distributed wiring and/or significant inductance introduced into the

Sense control loop can adversely affect overall system stability. If in doubt, test

your applications by observing the converter’s output transient response during

step loads. There should not be any appreciable ringing or oscillation. You may also

adjust the output trim slightly to compensate for voltage loss in any external filter

elements. Do not exceed maximum power ratings.

Please observe Sense inputs tolerance to avoid improper operation:

[Vout(+) −Vout(-)] − [Sense(+) −Sense(-)] ≤ 5% of Vout