Output current may be adjusted

by using a pulse width modu-

lated (PWM) signal. By varying

the signal duty cycle (as shown

at right) the output current is

adjusted up or down.

Output current may be calcu-

lated by using the formula:

(DT - 0.6)

T

= Required output current

D

= Pulse width of the he control signal

T

= Cycle of the control signal

during the digital dimming process of the driver, since the control circuit frequency is within the

is within the range of human hearing (20 Hz - 20 kHz).

Specification Notes:

1. Exceeding 55V on the unit input could damage the unit.

2. No connection should be made between input ground and

the output.

3. These are step-down devices, the maximum output open

voltage is equal to the input voltage.

4. When not used, the PWM/Cont input (Pin 3) or should be left

open if not used.

5. Exceeding the specified maximum output power could cause

damage to the unit.

PWM Output Current Control

Analog dimming is accomplished

by using a simple resistor divider

network, as illustrated above.

The output current is varied by

changing the voltage level pres-

ent at Pin 10. The amount varia-

tion is shown in chart at right.

The maximum voltage level that

can be applied to Pin 10 is 15V.

Exceeding this may damage

the driver.

Analog and PWM control of the

driver should not be attempted

at the same time. The control

pin not being used should be

left open.

Mechanical Dimensions

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Notes:

the top of the unit

Pin Connections

Pin

Function

Pin

Function

1

Gnd

9

7

PWM, On/Off

10

Analog Dimming

16

Model

Number

Input

Output

Dimming

Control

Efficiency

(%, Max)

Voltage

(VDC)

Current

(mA)

Nominal

Range

LDF24E-10-300

24

5.5 - 48.0

3.3 - 36.0

0.0 - 300

PWM/Analog

96

LDF24E-12-350

24

5.5 - 48.0

3.3 - 36.0

0.0 - 350

PWM/Analog

96

LDF24E-18-500

24

5.5 - 48.0

3.3 - 36.0

0.0 - 500

PWM/Analog

96

LDF24E-21-600

24

5.5 - 48.0

3.3 - 36.0

0.0 - 600

PWM/Analog

96

LDF24E-25-700

24

5.5 - 48.0

3.3 - 36.0

0.0 - 700

PWM/Analog

96

Model Selection Guide

Connection Notes:

1. A positive temperature coefficient PTC is connected to each parallel channel for protection.

Analog Output Current Control

Solder Layout

Analog Control vs Output