Datasheet
HPQ-12/25-D48 Series
Isolated 300-Watt Quarter Brick DC-DC Converters
MDC_HPQ-12/25-D48 Series.B07 Page 15 of 16
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Remote Sense Input (See Specifi cation Note 7)
Sense inputs compensate for output voltage inaccuracy delivered at the load.
This is done by correcting voltage drops along the output wiring such as mod-
erate IR drops and the current carrying capacity of PC board etch. 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
Please observe Sense inputs tolerance to avoid improper operation:
[Vout(+) –Vout(-)] – [ Sense(+) – Sense(-)] ≤ 10% of Vout
Output overvoltage protection is monitored at the output voltage pin, not the
Sense pin. Therefore excessive voltage differences between Vout and Sense
together with trim adjustment of the output can cause the overvoltage protec-
tion circuit to activate and shut down the output.
Power derating of the converter is based on the combination of maximum
output current and the highest output voltage. Therefore the designer must
ensure:
(Vout at pins) x (Iout) ≤ (Max. rated output power)
Figure 8. 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