Product Specifications

RND Series: 8-10W DC/DC Converters

Nov 2001

38-75V Input

3.3V & 5.0V, ±12V Dual Outputs (±15V, available with trimming)

5-Nov-01

Rev 1.1

Page 9 of 14

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Output Voltage Trim

Note: For setting nominal output voltage pin 8

must be connected to pin 9.

The trim feature allows the user to adjust the

output voltage from the nominal.

This can be

used to accommodate a different requirement or

to do production margin testing.

Output voltage can be adjusted by an external

resistor. If pin 8 and pin 9 are not connected

together the output will decrease to a low value.

To increase Vo a resistor should be connected

between pin 8 / 9 and pin 17 ( -Vin). To decrease

Vo, a resistor should be connected between pin 8

and 9 (NOR).

To increase Vo:

Radj = A x (B - Vd) / (Vd - Vo) k

Ω

Where: Vd = Desired output voltage

Vo = Nominal output voltage.

To reduce Vo:

Radj = C x (Vo - Vd) / (Vd - D) k

Ω

Where: Vd = Desired output voltage

Vo = Nominal output voltage.

Model

A

B

C

D

RND02ZGE

0.5

3.92

2.0

2.56

RND0.8ZHH

0.572

16.126

2.243

8.295

Notes:

1. When the output voltage is trimmed up, the

output power from the converter must not

exceed its maximum

rating.

This is

determined by measuring the output voltage

on the output pins, and multiplying it by the

output current.

2.

The trim feature allows the generation of

additional standard voltages such as ±15V

from the ±12V model.

Parallel Operation

Paralleling of two converters is possible by direct

connection of the output voltage terminal pins.

The load regulation characteristic is designed to

facilitate current sharing (typically ± 20%).

Output Current Limiting

When the output is overloaded above the

maximum output current rating, the voltage will

start to reduce to maintain the output power to a

safe level.

In a condition of high overload or

short-circuit where the output voltage is pulled

below approximately 30% of Vo.Nom, the unit will

enter a ‘Hiccup’ mode of operation. Under this

condition

the

unit

will

attempt

to

restart,

approximately every 100ms until the overload has

cleared.

Thermal Considerations

The converter is designed for natural or forced

convection cooling.

The output power of the

converter is limited by the maximum case

temperature (Tc). To ensure reliable long term

operation of the converters, and to comply with

safety agency requirements, Power-One limits

maximum allowable case temperature (Tc) to

110°C (see Mechanical Drawings).

Remote Control Feature

The remote control pin functions as a normal soft

shutdown. It is referenced to the –Vin pin. With

positive logic, when the remote control pin is

pulled low, the output is turned off and the unit

goes into a very low input power mode.

An open collector switch is recommended to

control the voltage between the remote control pin

and the -Vin pin of the converter. The remote

control pin is pulled up internally, so no external

voltage source is required. The user should avoid

connecting a resistor between the remote control

pin and the +Vin pin.

The user must take care to ensure that the pin

reference for the control is connected close to the

-Vin pin.

The control signal must not be

referenced ahead of EMI filtering, or remotely

from the unit. If the remote control pin is not used,

it can be left floating.