FAN5606

PRODUCT SPECIFICATION

4

REV. 1.0.3 1/7/05

COIL DRIVER

DBB

START-UP

POWER GOOD

LINEAR REGULA TOR

OSC

REF

DAC

BG

V

IN

V

OUT

GND

B

A

CAT

IND

AMPLIFIER

Block Diagram

Circuit Description

turned on, the bandgap reference acquires its nominal volt-

age and the soft-start cycle begins. Once "power good" is

achieved (0.5mA in the diodes), the soft-start cycle stops and

the boost voltage increases to generate the desired current

selected by the input control pins.

The FAN5606 DC/DC converter automatically adjusts its

internal duty cycle to achieve high efficiency. If the output

external capacitor is shorted, the Schottky diode can be dam-

aged, therefore such a condition should be avoided.

LED Brightness Control

The inputs A and B can be digitally controlled LOW (GND)

nected to an external stable voltage source via an external

resistor and B input is connected to ground. The current

flowing through the resistor is scaled by a factor of approxi-

mately 1000.

Digital Control

The FAN5606’s digital decoder allows selection of the fol-

lowing modes of operation: OFF, 5mA, 10mA, 20mA per

branch.

Analog Control with PWM

In analog control mode, the LED current can go up to 25mA.

Input A is used to control the LED currents. Input B should

be connected to GND (logic level "0"). An external resistor

the formula or the graph below:

A

0101

B

0011

OFF

5mA

10mA

20mA

I

LED

V

External

V

Ref

–

R

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 Multiplication Ratio

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