Datasheet
UWQ-12/20-T48 Series
Wide Input, Isolated DOSA Quarter Brick DC-DC Converters
MDC_UWQ-12/20-T48 Series.A02 Page 28 of 29
www.murata-ps.com/support
The Trim pin (pin 6) is a relatively high impedance node that can be susceptible
to noise pickup when connected to long conductors in noisy environments.
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 etch. 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.
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
coupled 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 signifi cant 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 fi lter elements. Do not exceed maximum power ratings.
Figure 11. Remote Sense Circuit Confi guration
LOAD
Contact and PCB resistance
losses due to IR drops
Contact and PCB resistance
losses due to IR drops
+VOUT
+SENSE
TRIM
−
SENSE
-VOUT
+
VIN
ON/OFF
CONTROL
–VIN
Sense Current
I OUT
Sense Return
I OUT Return
LOAD
R
TRIM UP
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
Figure 9. Trim Connections To Increase Output Voltages Using Fixed Resistors
LOAD
R
TRIM DOWN
+VOUT
+VIN
–VIN
ON/OFF
CONTROL
TRIM
+SENSE
–VOUT
–SENSE
Figure 10. Trim Connections To Decrease Output Voltages Using Fixed Resistors
UP
VO – 12
R
T (kΩ) =
–10.2
49.6(VO – 1.226)
12 – V
O
RT (kΩ) =
–10.2
60.45
DOWN
Trim Up* Trim Down*
*Vo = Desirable output voltage in Volts