APPLICATION INFORMATION

100 nF

Q

SI

RO

I

GND

RADJ

D

10 µF

10 k

Ω

ST

PWM

GND

D

47 nF

Q

REF

LED

Dragon

I

Microcontroller

0.47

Ω

0.25 W

TL4242

TL4242

Figure 5 shows a typical application with the TL4242 LED driver. The three LEDs are driven by a supply current

The luminosity spread arising from the LED production process can be compensated via software by an

appropriate duty cycle applied to the PWM pin. Therefore, it is not necessary to select LEDs for forward voltage

or luminosity classes. The minimum supply voltage calculates as the sum of the LED forward voltages, the

TL4242 drop voltage (maximum 0.7 V at a LED current of 300 mA) and the maximum voltage drop at the shunt

Figure 5. Application Circuit

The status output of the LED driver (ST) detects an open-load condition, enabling supervision of correct LED

case, the status output pin (ST) is set low after a delay time adjustable by an optional capacitor connected to

pin D.

The functionality and timing of ST and PWM are shown in Figure 6. The status delay can be adjusted via the

6

Submit Documentation Feedback

Copyright © 2008–2009, Texas Instruments Incorporated