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DFA20

DFA20 SERIES SINGLE OUTPUT

Power-One Inc. 

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

10K LOAD

+OUT 5

TRIM 7

-OUT 6

TRIM

DOWN

TRIM

UP

LOAD

USING TRIMPOT

Figure 1. USING FIXED RESISTORS

+ INPUT 1

– INPUT 2

ON/OFF 3

DFA20 SERIES BLOCK DIAGRAM

ISOLATION TRANSFORMER

THERMAL SHUTDOWN

+

LC

INPUT

FILTER

CURRENT

MODE

PWM

+

ISOLATED

–

FEEDBACK

FIVE SIDED SHIELDED COPPER CASE

LOW TC

BANDGAP

REFERENCE

5 + OUTPUT

6 - OUT

7 TRIM

OUTPUT POWER DERATING

20

15

10

5

0

50

60

70

80

90 100

AMBIENT TEMPERATURE

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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