3

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. Figure 1 shows the proper connections

to use this function. If the TRIM function is not required the pin

may be left floating.

DFA20 SERIES – DUAL OUTPUT

NOTES

(1)

All parameters measured at Tc=25°C, nominal input voltage and full rated load unless otherwise noted.

Refer to the Technical Reference Section for the definition of terms, measurement circuits and other

information.

(2)

Noise is measured per Technical Reference Section. Measurement bandwidth is 0-20 MHz for peak-peak

measurements, 10 kHz to 1 MHz for RMS measurements. Output noise is measured with a

1µF tantalum located 1" away from the converter to simulate PCB standard decoupling. Input reflected

ripple is measured into a 1 µH source impedance.

(3)

Load regulation for the outputs is specified as the voltage change when both outputs are changed from

maximum to minimum at the same time.

(4)

Cross regulation is defined as the change in one output when the other output is changed from full load

to 25% of full load. The converter can be run at no load on either or both outputs with no damage.

(5)

Short term stability is specified after a 30 minute warmup at full load, constant line and recording the

drift over a 24 hour period.

(6)

The input ripple rejection is specified for DC to 120 Hz ripple with a modulation amplitude of 1% of Vin.

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.

DFA20 SERIES BLOCK DIAGRAM

4

+ OUTPUT

SHIELDED ISOLATION TRANSFORMER

+

6

– OUTPUT

5

CMN

7

TRIM

SHIELDED COPPER CASE

+

+

–

2

– INPUT

ON/OFF

1

3

+ INPUT

CURRENT

MODE

PWM

THERMAL LIMIT

LOW

NOISE

FILTER

50

0

5

10

15

20

60

70

80

90

100

OUTPUT POWER DERATING

AMBIENT TEMPERATURE

4

+OUT

7

TRIM

10K

LOAD

USING TRIMPOT

6

-OUT

4

+OUT

7

TRIM

TRIM

DOWN

TRIM

UP

LOAD

USING FIXED RESISTORS

6

-OUT

Figure 1.

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.