MDC_UEI-30W MURATA [Murata Manufacturing Co., Ltd.], MDC_UEI-30W Datasheet - Page 8

• Manufacturer Part Number: MDC_UEI-30W
• Description: 30W Isolated Wide-Range DC/DC Converters
• Manufacturer: MURATA [Murata Manufacturing Co., Ltd.]

current, thereby maintaining a somewhat constant power output. This is com-
monly referred to as power limiting.
below the rated tolerance. See the Performance/Functional Specifi cations. Note
particularly that the output current may briefl y rise above its rated value. This
enhances reliability and continued operation of your application. If the output
current is too high, the converter will enter the short circuit condition.
Output Short Circuit Condition
When a converter is in current-limit mode, the output voltage will drop as the
output current demand increases. If the output voltage drops too low, the mag-
netically coupled voltage used to develop primary side voltages will also drop,
thereby shutting down the PWM controller. Following a time-out period, the
PWM will restart, causing the output voltage to begin ramping up to its appro-
priate value. If the short-circuit condition persists, another shutdown cycle will
initiate. This on/off cycling is called “hiccup mode”. The hiccup cycling reduces
the average output current, thereby preventing excessive internal tempera-
tures. A short circuit can be tolerated indefi nitely.
Trimming the Output Voltage
The Trim input to the converter allows the user to adjust the output voltage over
the rated trim range (please refer to the Specifi cations). In the trim equations and
circuit diagrams that follow, trim adjustments use either a trimpot or a single
fi xed resistor connected between the Trim input and either the +Sense or –Sense
terminals. (On some converters, an external user-supplied precision DC voltage
may also be used for trimming). Trimming resistors should have a low tempera-
ture coeffi cient (±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 specifi ed output voltage accuracy.
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.
Current limiting inception is defi ned as the point at which full power falls
There are two CAUTIONs to be aware for the Trim input:
CAUTION: To avoid unplanned power down cycles, do not exceed EITHER the
−INPUT
CONTROL
+INPUT
ON/OFF
Figure 4 – Trim adjustments using a trimpot
+OUTPUT
−OUTPUT
TRIM
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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.
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.
is pulled high to +V
open pin to rise to +V
voltages (see Specifi cations). Positive-polarity devices are disabled when the
Trim Equations
Figure 5 – Trim adjustments to decrease Output Voltage using a Fixed Resistor
CAUTION: Be careful of external electrical noise. The Trim input is a senstive
Where Vo = Desired output voltage. Adjustment accuracy is subject to resis-
Positive: Standard models are enabled when the On/Off pin is left open or
R
R
R
R
T
T
T
T
UP
UP
UP
UP
between Trim and –Sense>
(:) =
(:) =
(:) =
(:) =
<Connect trim resistor
−INPUT
30W Isolated Wide-Range DC/DC Converters
CONTROL
+INPUT
Trim Up
ON/OFF
V
V
V
12775
25000
25000
O
V
12775
IN
O
O
Technical enquiries email: [e-mail], tel:
O
with respect to –V
IN
3.3
. Some models will also turn on at lower intermediate
12
15
5
UEI30-033-Q12/-Q48
UEI30-050-Q12/-Q48
UEI30-120-Q12/-Q48
UEI30-150-Q12/-Q48
2050
5110
5110
2050
+OUTPUT
−OUTPUT
TRIM
IN
MDC_UEI Series 30W.A01 Page 8 of 11
. An internal bias current causes the
R
R
R
R
T
T
T
T
DOWN
DOWN
DOWN
DOWN
between Trim and +Sense>
UEI30 Series
<Connect trim resistor
R
(:) =
(:) =
(:) =
(:) =
TRIM DOWN
Trim Down
5110 (Vo - 2.5)
5110 (Vo - 2.5)
10000 (Vo-2.5)
10000 (Vo-2.5)
3.3 V
12 V
15 V
5 V
[phone]
O
O
O
O
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5110
5110
2050
2050