DFA20 SERIES – SINGLE OUTPUT
DFA20 SERIES APPLICATION NOTES:
External Capacitance Requirements
No external capacitance is required for operation of the DFA20
Series. The use of input capacitors with less than 0.5 ESR may
cause peaking in the input filter and degrade filter performance.
External output capacitance is not required for operation, however
it is recommended that 1 F to 10 F of tantalum and 0.001 to
0.1 F ceramic capacitance be selected for reduced system noise.
Additional output capacitance may be added for increased
filtering, but should not exceed 400 F.
Negative Outputs
A negative output voltage may be obtained by connecting the
+OUT to circuit ground and connecting -OUT as the negative
output.
Remote ON/OFF Operation
The remote ON/OFF pin may be left floating if this function is not
used. It is recommended to drive this pin with an open collector
arrangement or a relay contact. When the ON/OFF pin is pulled
low with respect to the -INPUT, the converter is placed in a low
power drain state.
Output TRIM
The TRIM pin may be used to adjust the output ±5% from the
nominal setting. This function allows adjustment for voltage drops
in the system wiring, as well 5.2 volt outputs for ECL applications.
Figure 1 shows the proper connections to use this function. A
trimpot value of 10K should be used for 3.3 and 5 volt outputs.
A trimpot value of 20K should be used for 12 and 15 volt
outputs. If the TRIM function is not required the pin may be
left floating.
+OUT
5
TRIM
7
-OUT
6
USING TRIMPOT
10K
LOAD
+OUT
5
TRIM
DOWN
TRIM
7
-OUT
6
USING FIXED RESISTORS
LOAD
TRIM
UP
Figure 1.
DFA20 SERIES BLOCK DIAGRAM
OUTPUT POWER DERATING
20
ISOLATION TRANSFORMER
THERMAL SHUTDOWN
5
+
+ OUTPUT
15
POWER OUTPUT
+ INPUT
1
– INPUT
2
LC
INPUT
FILTER
CURRENT
MODE
PWM
6
- OUT
10
+
ON/OFF
7
TRIM
3
ISOLATED
FEEDBACK
–
5
FIVE SIDED SHIELDED COPPER CASE
LOW TC
BANDGAP
REFERENCE
0
50
60
70
80
90
AMBIENT TEMPERATURE
100
NUCLEAR AND MEDICAL APPLICATIONS Power-One products are not authorized for use as critical components in life support systems, equipment used in hazardous environments,
or nuclear control systems without the express written consent of the President of Power-One, Inc.
TECHNICAL REVISIONS The appearance of products, including safety agency certifications pictured on labels, may change depending on the date manufactured. Specifications are
subject to change without notice.
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