UEI25-120-D48P-C(2010) Просмотр технического описания (PDF) - Murata Manufacturing
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UEI25-120-D48P-C Datasheet PDF : 11 Pages
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UEI25-120 Series
Single Output Isolated 25-Watt DC/DC Converters
close to the converter. Keep leads short. If the trim function is not used, leave
the trim unconnected. With no trim, the converter will exhibit its specified output
voltage accuracy.
There are two CAUTIONs to observe for the Trim input:
CAUTION: To avoid unplanned power down cycles, do not exceed EITHER the
maximum output voltage OR the maximum output power when setting the trim.
If the output voltage is excessive, the OVP circuit may inadvertantly shut down
the converter. If the maximum power is exceeded, the converter may enter
current limiting. If the power is exceeded for an extended period, the converter
may overheat and encounter overtemperature shut down.
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
Trim Up
<Connect trim resistor
between Trim and –Vout>
Trim Down
<Connect trim resistor
between Trim and +Vout>
RTUP (Ω) =
UEI25-120-D48
25000
– 5110
VO – 12
10000 (Vo-2.5)
RTDOWN (Ω) =
– 5110
12 – VO
Where Vo = Desired output voltage. Adjustment accuracy is subject to resis-
tor tolerances and factory-adjusted output accuracy. Mount trim resistor close
to converter. Use short leads.
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 +15VDC 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.
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 +15VDC 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. +15V (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.
−INPUT
+OUTPUT
−INPUT
+OUTPUT
ON/OFF
CONTROL
TRIM
RTRIM DOWN
LOAD
ON/OFF
CONTROL
TRIM
R TRIM UP
LOAD
+INPUT
−OUTPUT
Figure 4. Trim adjustments to decrease Output Voltage using a Fixed Resistor
+INPUT
−OUTPUT
Figure 5. Trim adjustments to increase Output Voltage using a Fixed Resistor
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email: sales@murata-ps.com
17 Aug 2010 MDC_UEI25-120.A02 Page 10 of 11
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