Datasheet

UWQ-12/20-T48 Series
Wide Input, Isolated DOSA Quarter Brick DC-DC Converters
MDC_UWQ-12/20-T48 Series.A02 Page 27 of 29
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Dynamic control of the On/Off function should be able to sink the specifi ed
signal current when brought low and withstand specifi ed voltage when brought
high. Be aware too that there is a fi nite time in milliseconds (see Specifi cations)
between the time of On/Off Control activation and stable, regulated output. This
time will vary slightly with output load type and current and input conditions.
There are two CAUTIONs for the On/Off Control:
CAUTION: While it is possible to control the On/Off with external logic if you
carefully observe the voltage levels, the preferred circuit is either an open
drain/open collector transistor or a relay (which can thereupon be controlled
by logic). The On/Off prefers to be set at approx. +13.5V (open pin) for the ON
state, assuming positive logic.
CAUTION: Do not apply voltages to the On/Off pin when there is no input power
voltage. Otherwise the converter may be permanently damaged.
Figure 7. Driving the On/Off Control Pin (suggested circuit)
ON/OFF
CONTROL
-VIN
+VCC
Emissions Performance
Murata Power Solutions measures its products for radio frequency emissions
against the EN 55022 and CISPR 22 standards. Passive resistance loads are
employed and the output is set to the maximum voltage. If you set up your
own emissions testing, make sure the output load is rated at continuous power
while doing the tests.
The recommended external input and output capacitors (if required) are includ-
ed. Please refer to the fundamental switching frequency. All of this information
is listed in the Product Specifi cations. An external discrete fi lter is installed and
the circuit diagram is shown below.
Reference Part Number Description Vendor
L1 PE-62913 1mH, 6A Pulse
L3 500uH,10A, MPS 500uH,10A Murata
C8 2.2µFd Murata
C7 VZ Series
Qty 2 - Electrolytic Capacitor
22µFd, 100V
Panasonic
C16, C17 .22µFd Unknown
UWQ EMI 200W Test Card
48Vdc in, 12Vout, 17Amps
V+
V-
Black
Vin -
Vout -
Vout +Vin +
Resistive
Load
UUT
Resistive
Load
inside a
metal
container
L1
L3
C7
C16
C17
C8C8
C8
C8C8
C8
Figure 8. Conducted Emissions Test Circuit
[1] Conducted Emissions Parts List
[2] Conducted Emissions Test Equipment Used
Rohde & Schwarz EMI Test Receiver (9KHz – 1000MHz) ESPC
Rohde & Schwarz Software ESPC-1 Ver. 2.20
HP11947A Transient Limiter (Agilent)
OHMITE 25W – Resistor combinations
DC Source Programmable DC Power Supply Model 62012P-100-50
[3] Layout Recommendations
Most applications can use the fi ltering which is already installed inside the
converter or with the addition of the recommended external capacitors. For
greater emissions suppression, consider additional fi lter components and/or
shielding. Emissions performance will depend on the user’s PC board layout,
the chassis shielding environment and choice of external components. Please
refer to Application Note GEAN02 for further discussion.
Since many factors affect both the amplitude and spectra of emissions, we
recommend using an engineer who is experienced at emissions suppression.
Trimming Output Voltage
UWQ converters have a trim capability (pin 6) that enables users to adjust the
output voltage from +10% to –10% (refer to the trim equations in the table
below). Adjustments to the output voltage can be accomplished with a single
fi xed resistor as shown in Figures 9 and 10. A single fi xed resistor can increase
or decrease the output voltage depending on its connection. Resistors should
be located close to the converter and have TCR’s less than 100ppm/°C to
minimize sensitivity to changes in temperature. If the trim function is not used,
leave the trim pin open.
Standard UWQs have a “positive trim” where a single resistor connected from
the Trim pin (pin 6) to the +Sense (pin 7) will increase the output voltage. A
resistor connected from the Trim Pin (pin 6) to the –Sense (pin 5) will decrease
the output voltage.
Trim adjustments greater than the specifi ed +10%/–10% can have an adverse
affect on the converter’s performance and are not recommended. Excessive
voltage differences between V
OUT and Sense, in conjunction with trim adjust-
ment of the output voltage, can cause the overvoltage protection circuitry to
activate (see Performance Specifi cations for overvoltage limits).
Temperature/power derating is based on maximum output current and voltage
at the converter’s output pins. Use of the trim and sense functions can cause
output voltages to increase, thereby increasing output power beyond the UWQ’s
specifi ed rating, or cause output voltages to climb into the output overvoltage
region. Therefore:
(V
OUT at pins) x (IOUT)  rated output power