UEI30 Series
30W Isolated Wide-Range DC/DC Converters
may also be used for trimming). Trimming resistors should have a low tempera-
ture coefficient (±100 ppm/deg.C or less) and be mounted 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.
Be particularly careful with a trimpot. 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 overtempera-
ture 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
R
T
UP
(:) =
25000
V
O
–
12
Trim Up
<Connect trim resistor
between Trim and –Sense>
Trim Down
<Connect trim resistor
between Trim and +Sense>
UEI30-033-Q12/-Q48
R
T
UP
(:) =
12775
V
O
–
3.3
–
2050
R
T
DOWN
(:) =
5110 (Vo - 2.5)
3.3
–
V
O
–
2050
UEI30-050-Q12/-Q48
R
T
UP
(:) =
12775
V
O
–
5
–
2050
R
T
DOWN
(:) =
5110 (Vo - 2.5)
–
2050
5
–
V
O
UEI30-120-Q12/-Q48
–
5110
R
T
DOWN
(:) =
10000 (Vo-2.5)
–5110
12
–
V
O
−INPUT
+OUTPUT
25000
V
O
–
15
UEI30-150-Q12/-Q48
R
T
UP
(:) =
–
5110
R
T
DOWN
(:) =
10000 (Vo-2.5)
–5110
15
–
V
O
ON/OFF
CONTROL
TRIM
7 5-22
TURNS
LOAD
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.
−OUTPUT
+INPUT
Figure 4 – Trim adjustments using a trimpot
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 +V
IN
with respect to –V
IN
. An internal bias
current causes the open pin to rise to +V
IN
. 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
.
cause instability or oscillation. Keep external connections short to the Trim
input. Use shielding if needed.
Trim Equations
−INPUT
+OUTPUT
−INPUT
+OUTPUT
ON/OFF
CONTROL
TRIM
R
TRIM DOWN
LOAD
ON/OFF
CONTROL
TRIM
R
TRIM UP
LOAD
+INPUT
−OUTPUT
+INPUT
−OUTPUT
Figure 5 – Trim adjustments to decrease Output Voltage using a Fixed Resistor
Figure 6 – Trim adjustments to increase Output Voltage using a Fixed Resistor
www.murata-ps.com
14 Dec 2009
email: sales@murata-ps.com
MDC_UEI Series 30W.A13_long
Page 8 of 16
MURATA-PS [ MURATA POWER SOLUTIONS INC. ]
