UWR-12/1250-D12A 查看數據表（PDF） - C and D TECHNOLOGIES
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UWR-12/1250-D12A Datasheet PDF : 12 Pages
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A Series
7-15W, SINGLE OUTPUT DC/DC CONVERTERS
TECHNICAL NOTES
Floating Outputs
Since these are isolated DC/DC converters, their outputs are "floating."
Designers will usually use the output Common (pin 6) as the ground/return of
the load circuit. You can, however, use the +Output (pin 4) as ground/return to
effectively reverse the output polarity.
Minimum Output Loading Requirements
1.2 to 5V models employ a synchronous-rectifier design topology. All models
regulate within spec and are stable under no-load conditions. 12/15V models
employ a traditional forward architecture and require 10% loading (125mA for
12V models, 100mA for 15V models) to achieve their listed regulation specs.
12/15V models also have a minimum-load-for-stability requirement (20mA).
For 12/15V models, operation below 20mA or 10% loading will be stable but
regulation may degrade. A 100µF output capacitor is recommended below
10% loading. Users should verify whether this relaxed regulation will have
any effect on output circuits. If so, add a small load of 10% or greater.
Operation under no-load conditions will not damage 12/15V converters.
However they may not meet all listed specifications.
Filtering and Noise Reduction
All A-Series UWR DC/DC Converters achieve their rated ripple and noise
specifications using the external input and output capacitors specified in the
Performance/Functional Specifications table. In critical applications, input/
output noise may be further reduced by installing additional external I/O caps.
Input capacitors should be selected for bulk capacitance, low ESR and high
rms-ripple-current ratings. Output capacitors should be selected for low ESR
and appropriate frequency response. All caps should have appropriate volt-
age ratings and be mounted 2-3 inches from the converter to achieve
published ratings.
The most effective combination of external I/O capacitors will be a function
of your particular load and layout conditions. Our Applications Engineers will
be happy to recommend potential solutions and can discuss the possibility of
our modifying a given device’s internal filtering to meet your specific require-
ments. Contact our Applications Engineering Group for additional details.
Input Fusing
Certain applications and/or safety agencies may require the installation of
fuses at the inputs of power conversion components. Fuses should also be
used if the possibility of sustained, non-current-limited, input-voltage polarity
reversals exists. For DATEL A-Series UWR 7-15 Watt DC/DC Converters, you
should use slow-blow type fuses with values no greater than the following.
VIN Range
"D12A" Models
"D24A" Models
"D48A" Models
Fuse Value
3 Amps
2 Amps
1 Amp
Trimming Output Voltages
These converters have a trim capability (pin 5) that allows users to adjust the
output voltage ±5%. Adjustments to the output voltage can be accomplished
via a trim pot, Figure 2, or a single fixed resistor as shown in Figures 3 and 4.
A single fixed resistor can increase or decrease the output voltage depending
on its connection. Fixed resistors should have an absolute TCR less than
100ppm/°C to minimize sensitivity to changes in temperature.
A single resistor connected from the Trim (pin 5) to the +Output (pin 4), see
Figure 3, will decrease the output voltage. A resistor connected from the Trim
(pin 5) to Output Common (pin 6) will increase the output voltage.
Trim adjustment greater than 5% can have an adverse effect on the convert-
er's performance and is not recommended.
1
+INPUT
2
–INPUT
3 ON/OFF
CONTROL
4
+OUTPUT
5
TRIM
6
COMMON
20kΩ
5-22
Turns
LOAD
Figure 2. Trim Connections Using A Trim Pot
1
+INPUT
2
–INPUT
3 ON/OFF
CONTROL
4
+OUTPUT
5
TRIM
RTRIM DOWN
LOAD
6
COMMON
Figure 3. Trim Connections To Decrease Output Voltage Using Fixed Resistors
1
+INPUT
2
–INPUT
3 ON/OFF
CONTROL
4
+OUTPUT
5
TRIM
6
COMMON
LOAD
RTRIM UP
Figure 4. Trim Connections To Increase Output Voltage Using Fixed Resistors
4
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