© 2006 Fairchild Semiconductor Corporation

www.fairchildsemi.com

FAN5608 Rev. 1.0.5 • 8/8/06

6

Digital Static Control

The FAN5608’s digital decoder allows selection of the

following modes of operation: OFF, 5mA, 10mA, and

20mA per channel.

A

0

1

0

1

B

0

0

1

1

OFF

5mA

10mA

20mA

Analog Static Control

In Analog Mode, B1 and B2 inputs should be connected

to GND or “0” logic. A1 and A2 control the LED current

through an external resistor (R), as shown in Figure 4, or

the graph below:

EQ 2

current multiplication ratio is according to the Electrical

Specifications table. The R value should be in the (10kΩ

to 50kΩ) range.

1.0

1.25

1.5

1.75

2

2.25

R=50k

R=10k

0

5

10

15

20

25

Figure 7. Analog Control

PWM Control in Digital Dynamic Mode

In Digital Dynamic Mode, if inputs A1 and/or A2 are

externally driven by an open-drain output, the pull-up

resistance should be less than 10kΩ to ensure less than

level.

The logic level HIGH (VH) and logic level LOW (VL) of

the PWM signal should be:

EQ 3

and

0 < VL < 0.6V.

EQ 4

The frequency of the PWM signal should be within the

50Hz to 1kHz range, by default, or 30kHz at any input if

the other input is kept HIGH.

PWM Control in Analog Dynamic Mode

In Analog Dynamic Mode, the logic level HIGH (VH) and

logic level LOW (VL) of the PWM signal should be:

EQ 5

The frequency of the PWM signal should be in the range

maximum LED current, while the duty cycle of the PWM

maximum.

Open-Circuit Protection

The FAN5608 has an internal over-voltage protection

mechanism that prevents damage to the IC in a no-load

condition. If CH1 and/or CH2 LEDs are enabled in an

open-circuit condition, FAN5608 automatically sets the

duty cycle to 25%. The output voltage can reach as high

capacitor’s rating, the output capacitor may be at risk in

this condition.

Shutdown Mode

Each channel can be independently disabled by

applying LOW logic level voltage to the appropriate A

and B inputs. When both channels are disabled, the

FAN5608 enters shutdown mode and the supply current

is reduced to less than 1μA.