t

C

D

47 nF

10 ms

t

C

D

47 nF

10 ms

100 nF

Q

SI

RO

I

GND

RADJ

D

10 µF

10 kW

ST

PWM

GND

D

47 nF

Q

REF

LED

Dragon

I

Microcontroller

0.47 W

0.25 W

TL4242-Q1

TL4242-Q1

SLVS732E – JULY 2010 – REVISED JULY 2013

www.ti.com

APPLICATION INFORMATION

resistor drives the three LEDs, preventing brightness variations due to forward voltage spread of the LEDs. An

appropriate duty cycle applied to the PWM pin can compensate through software for the luminosity spread

arising from the LED production process. 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-

Q1 drop voltage (maximum 0.7 V at an LED current of 300 mA), and the maximum voltage drop at the shunt

Figure 7. Application Circuit

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

the status output pin (ST) goes low after a delay time adjustable by an optional capacitor connected to pin D.

Figure 8 shows the functionality and timing of ST and PWM. One can adjust the status delay through the

8

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