UEI Series
50-60W Isolated Wide-Range DC/DC Converters
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 overtem-
perature 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.
Positive: Standard models are enabled when the On/Off pin is left open or
is pulled high to +15V with respect to –V
IN
. An internal bias current causes the
open pin to rise to +15V. Some models will also turn on at lower intermediate
voltages (see Specifications). Positive-polarity devices are disabled when the
On/Off is grounded or brought to within a low voltage (see Specifications) with
respect to –V
IN
.
Negative: Optional negative-polarity devices are on (enabled) when the On/
Off is grounded or brought to within a low voltage (see Specifications) with
respect to –V
IN
. The device is off (disabled) when the On/Off is left open or is
pulled high to +15V
DC
Max. with respect to –V
IN
.
Dynamic control of the On/Off function should be able to sink appropriate
signal current when brought low and withstand appropriate 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.
LOAD
R
TRIM UP
−
SENSE
2
−
INPUT
6
+OUTPUT
+SENSE
5
4
ON/OFF
CONTROL
TRIM
9
8
+ Vcc
3
1
+INPUT
−
OUTPUT
7
Figure 7 – Trim adjustments to increase Output Voltage using a Fixed Resistor
ON/OFF
CONTROL
Trim Equations
Trim Up
<Connect trim resistor
between Trim and –Sense>
Trim Down
<Connect trim resistor
between Trim and +Sense>
Figure 8 – Driving the On/Off Control Pin (suggested circuit)
5110 (Vo - 2.5)
3.3
–
V
O
–
2050
1
-INPUT
UEI-3.3/15-Q12, -3.3/18-Q48
R
T
UP
(:) =
12775
V
O
–
3.3
–
2050
R
T
DOWN
(:) =
UEI-5/10-Q12, -5/12-Q48
R
T
UP
(:) =
12775
V
O
–
5
–
2050
5110 (Vo - 2.5)
–
2050
R
T
DOWN
(:) =
5
–
V
O
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).
CAUTION: Do not apply voltages to the On/Off pin when there is no input
power voltage. Otherwise the converter may be permanently damaged.
UEI-12/4.2-Q12, -12/5-Q48
R
T
UP
(:) =
25000
V
O
–
12
–
5110
R
T
DOWN
(:) =
10000 (Vo-2.5)
–5110
12
–
V
O
UEI-15/3.3-Q12, UEI-15/4-Q48
R
T
UP
(:) =
25000
V
O
–
15
–
5110
R
T
DOWN
(:) =
10000 (Vo-2.5)
–5110
15
–
V
O
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 ordered with either polarity.
www.murata-ps.com
27 May 2010
email: sales@murata-ps.com
MDC_UEI Series 50-60W.B31
Page 9 of 13
MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
