TL4242_10 Datasheet, PDF (1/14 Pages) Texas Instruments – ADJUSTABLE LED DRIVER

TL4242
www.ti.com .............................................................................................................................................................. SLVS641A – APRIL 2008 – REVISED MAY 2009
ADJUSTABLE LED DRIVER
FEATURES
1
• Adjustable Constant Current
up to 500 mA (±5%)
• Wide Input Voltage Range up to 42 V
• Low Drop Voltage
• Open-Load Detection
• Overtemperature Protection
• Short-Circuit Proof
• Reverse-Polarity Proof
• Wide Temperature Range: –40°C to 150°C
DRJ (QFN) PACKAGE
(TOP VIEW)
PWM 1
8I
ST 2 ^Exposed 7 NC
Thermal
GND 3 Pad 6 Q
REF 4
5D
NC – No internal connection
DESCRIPTION/ORDERING INFORMATION
The TL4242 is an integrated adjustable constant-current source, driving loads up to 500 mA. The output current
level can be adjusted via an external resistor. The device is designed to supply high-power LEDs (for example,
OSRAM Dragon LA W57B) under the severe conditions of automotive applications, resulting in constant
brightness and extended LED lifetime. It is provided in the DRJ (QFN) package. Protection circuits prevent
damage to the device in case of overload, short circuit, reverse polarity, and overheat. The connected LEDs are
protected against reverse polarity as well as excess voltages up to 45 V.
The integrated PWM input of the TL4242 permits LED brightness regulation by pulse-width modulation (PWM).
Due to the high input impedance of the PWM input, the LED driver can be operated as a protected high-side
switch.
The TL4242 is characterized for operation from –40°C to 150°C.
An external shunt resistor in the ground path of the connected LEDs is used to sense the LED current. A
regulation loop holds the voltage drop at the shunt resistor at a constant level of 177 mV (typical). The
constant-current level can be adjusted by selecting the shunt resistance, R_REF. Calculate the typical output
current using the equation:
I_Q,typ = V_REF/R_REF
where V_REF is the reference voltage (typically 177 mV) (see Reference Electrical Characteristics). The equation
applies for R_REF = 0.39 Ω to 10 Ω.
The output current is shown as a function of the reference resistance in Figure 1. With the PWM input, the LED
brightness can be regulated via duty cycle. Also, PWM = L sets the TL4242 in sleep mode, resulting in a very
low current consumption of <1 µA (typical). Due to the high impedance of the PWM input (see Figure 4), the
PWM pin also can be used as an enable input.
T_J
–40°C to 150°C
QFN – DRJ
ORDERING INFORMATION⁽¹⁾
PACKAGE ⁽²⁾
ORDERABLE PART NUMBER
Reel of 1000
TL4242DRJR
TOP-SIDE MARKING
T4242
(1) For the most current package and ordering information, see the Package Option Addendum at the end of this document, or see the TI
web site at www.ti.com.
(2) Package drawings, thermal data, and symbolization are available at www.ti.com/packaging.
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2008–2009, Texas Instruments Incorporated