HPQ-12-25-D48 Datasheet, PDF (12/12 Pages) Murata Manufacturing Co., Ltd. – Isolated 300-Watt Quarter Brick DC/DC Converters

HPQ-12/25-D48 Series
Isolated 300-Watt Quarter Brick DC/DC Converters
Remote Sense Input (See Specification 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
On/Off Enable Control Ground Bounce Protection
To improve reliability, if you use a small signal transistor or other external
circuit to select the Remote On/Off control, make sure to return the LO side
directly to the –Vin power input on the DC/DC converter. To avoid ground
bounce errors, do not connect the On/Off return to a distant ground plane or
current-carrying bus. If necessary, run a separate small return wire directly to
the –Vin terminal. There is very little current (typically 1-5 mA) on the On/Off
control however, large current changes on a return ground plane or ground bus
can accidentally trigger the converter on or off. If possible, mount the On/Off
transistor or other control circuit adjacent to the converter.
ON/OFF
CONTROL
+VCC
-INPUT
+OUTPUT
+SENSE
Contact and PCB resistance
losses due to IR drops
I OUT
Sense Current
ON/OFF
CONTROL
TRIM
Sense Return
LOAD
-SENSE
+INPUT
-OUTPUT
I OUT Return
Contact and PCB resistance
losses due to IR drops
Figure 6. Remote Sense Circuit Configuration
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 out-
put current and the highest output voltage. Therefore the designer must insure:
(Vout at pins) x (Iout) ≤ (Max. rated output power)
-INPUT
Figure 7. Driving the On/Off Control Pin (suggested circuit)
On/Off
Control
Transistor
Preferred location
of On/Off control
adjacent to -Vin
terminal
DC/DC Converter
+ Vin
On/Off Enable
-Vin return
Do not connect
control transistor
through remote
power bus
Ground plane or power return bus
Install separate
return wire for
On/Off control
with remote
transistor
Figure 8. On/Off Enable Control Ground Bounce Protection
Murata Power Solutions, Inc.
11 Cabot Boulevard, Mansfield, MA 02048-1151 U.S.A.
ISO 9001 and 14001 REGISTERED
Murata Power Solutions, Inc. makes no representation that the use of its products in the circuits described herein, or the use of other
technical information contained herein, will not infringe upon existing or future patent rights. The descriptions contained herein do not imply
the granting of licenses to make, use, or sell equipment constructed in accordance therewith. Specifications are subject to change without
notice.
© 2010 Murata Power Solutions, Inc.
www.murata-ps.com/locations
email: [e-mail]
09 Nov 2010 MDC_HPQ-12/25-D48 Series.A03 Page 12 of 12