100 nF

Q

SI

RO

I

GND

RADJ

D

10 µF

10 k

ST

PWM

GND

D

47 nF

Q

REF

VBAT

RREF

LED

Dragon

I

Microcontroller

0.47

0.25 W

TL4242-Q1

10

TL4242-Q1

SLVS732G – JULY 2010 – REVISED APRIL 2017

www.ti.com

Product Folder Links: TL4242-Q1

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Copyright © 2010–2017, Texas Instruments Incorporated

8 Application and Implementation

NOTE

Information in the following applications sections is not part of the TI component

specification, and TI does not warrant its accuracy or completeness. TI’s customers are

responsible for determining suitability of components for their purposes. Customers should

validate and test their design implementation to confirm system functionality.

8.1 Application Information

The TL4242-Q1 device is usually used in the automotive lighting applications. A microcontroller is usually used to

generate PWM waveform to dimming the LED.

8.2 Typical Applications

8.2.1 Application Circuit

Figure 6 shows a typical application with the TL4242-Q1 LED driver. A supply current adjusted by the RREF

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 should be equal to or greater than 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 resistor RREF of 185 mV.

Figure 6. Application Circuit

8.2.1.1 Design Requirements

DESIGN PARAMETER

EXAMPLE VALUE

RREF

0.47 Ω