PRODUCT SPECIFICATION

FAN5609

REV. 1.0.2 5/30/03

5

Shutdown and Short Circuit Current Limit

Set both DAC inputs low to shut down the device. Built-in

short circuit protection limits the supply current to a maxi-

mum of 50mA.

Digital Control

A digital-to-analog converter (DAC) allows selection of the

following modes: OFF, 7mA, 14mA, 20mA, per diode.

By turning the IN B pin ON and OFF, the current can be

(PWM). In PWM mode, the modulating frequency has to be

set sufficiently high in order to avoid a flickering effect

(100Hz to 1kHz).

Digital Control with PWM

Any input can be modulated by a pulse train of variable duty

cycle (

δ). By turning ON and OFF DAC inputs A or B, the

current can be continuously modulated to any average value

between 1 to 19mA. For a maximum range of LED current,

both A&B can be modulated at the same time.

A

0101

B

0011

OFF

7mA

14mA

20mA

Switch Configuration

Figure 1

Step-up, 2:1 configuration.

Switch positions shown in charge phase.

Reverse all switches for pump phase.

CAP1

GND

GND

CAP2

Figure 2

Step-up

3:2 configuration

Switch positions shown in charge phase.

Reverse all switches for pump phase.

+

+

-

-