AAT4296 Datasheet, PDF (14/17 Pages) Advanced Analogic Technologies – Five/Six Channel Push/Pull I/O Expander

AAT4296/98
Five/Six Channel Push/Pull I/O Expander
Driving LED Loads
The AAT4296 and AAT4298 can be used to drive
LEDs or other applications with light load current
requirements. LED applications may include main
and sub-LCD display backlighting, camera photo-
flash applications, color (RGB) LEDs, and infrared
(IR) diodes for remotes. In series with LEDs, bal-
last resistors must be used to limit the LED current.
The LED current will vary with supply voltage and
LED forward voltage. Most types of LEDs have for-
ward voltage specifications ranging from 2.0V to
5.0V. Calculate the necessary ballast resistor value
from the following formula:
R_LED =
(V_IN - V_F)
I_LED
- R_DS(ON)
Where:
R_LED is the resistance of resistor to be placed in
series with the LED (Ω).
V_IN is the input supply voltage to the device (V).
V_F is the forward voltage of the LED (V).
R_DS(ON) is the resistance of the switch when it is
turned on (Ω).
I_LED is the desired operating current of the LED (A).
5V
A series of
pulses
AAT4298
OUT1
IN
OUT2
OUT3
OUT4
OUT5
EN/SET
OUT6
GND
RG B
EN _Bluetooth
Device
EN _Infrared
Device
Backlighting
Figure 5: Infrared, Bluetooth, RGB, and Backlighting Control.
14
4296.2006.02.1.1