HPQ-12-D48_11 Datasheet, PDF (11/14 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
CAUTION: Be careful of external electrical noise. The Trim input is a senstive
input to the converter’s feedback control loop. Excessive electrical noise may
cause instability or oscillation. Keep external connections short to the Trim
input. Use shielding if needed.
Trim Equations
Radj_up ⁽ⁱⁿ kΩ) = ^{Vnominal x (1+Δ)} - ¹ - 2
1.225 x Δ Δ
where Δ =
Vout -Vnominal
Vnominal
Radj_down
(in
kΩ)
=
1
Δ
-2
where Δ =
Vnominal -Vout
Vnominal
Where Vo = Desired output voltage. Adjustment accuracy is subject to resistor
tolerances and factory-adjusted output accuracy. Mount trim resistor close
to converter. Use short leads. Note that “Δ” is given as a small fraction, not a
percentage.
-INPUT
+OUTPUT
+SENSE
ON/OFF
CONTROL
TRIM
-SENSE
R TRIM UP
LOAD
+INPUT
-OUTPUT
Figure 4. Trim adjustments to Increase Output Voltage using a Fixed Resistor
-INPUT
+OUTPUT
+SENSE
Remote On/Off Control
On the input side, a remote On/Off Control can be specified with either positive
or negative logic as follows:
Positive: Models equipped with Positive Logic are enabled when the On/Off
pin is left open or is pulled high to +13.5VDC with respect to –VIN. An internal
bias current causes the open pin to rise to +VIN. Positive-polarity devices are
disabled when the On/Off is grounded or brought to within a low voltage (see
Specifications) with respect to –VIN.
On positive-polarity models, to reduce noise coupling on the external on/off
control, use the circuit shown in figure 6.
316 KΩ
47 KΩ
+INPUT
ON/OFF
0.1 μF
2.5V CIRCUIT
-INPUT
Figure 6. On/Off Control Filter
Negative: Models with negative polarity are on (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 Max. with respect to –VIN.
Dynamic control of the On/Off function should be able to sink the specified
signal current when brought low and withstand specified voltage when brought
high. Be aware too that there is a finite time in milliseconds (see Specifications)
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.
ON/OFF
CONTROL
TRIM
R TRIM DOWN
LOAD
+VCC
-SENSE
+INPUT
-OUTPUT
ON/OFF
CONTROL
Figure 5. Trim adjustments to Decrease Output Voltage using a Fixed Resistor
-INPUT
Figure 7. Driving the On/Off Control Pin (suggested circuit)
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21 Feb 2011 MDC_HPQ-12/25-D48 Series.A07 Page 11 of 14