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TLE4242G
Voltage Regulator
Adjustable LED Driver
Target Data
TLE4242G
FeaturesAdjustable constant current up to 500mA (±5%)Wide input voltage range up to 42VLow drop voltageOpen load detectionOvertemperature protectionShort circuit proofReverse polarity proofWide temperature range : –40°Cto150°C
Functional DescriptionThe TLE4242G is an integrated adjustable constant current source driving loads up to
500mA. The output current level can be adjusted via an external resistor. The IC is
designed to supply high power LEDs (eg. Osram Dragon LA W57B) under the severe
conditions of automotive applications resulting in constant brightness and extended LED
lifetime. It is provided in the surface mounted P-TO-263-7-1 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 TLE4242G permits LED brightness regulation by
pulse width modulation. Due to the high input impedance of the PWM input the LED
driver can be operated as a protected high side switch.
Circuit Description
Figure1Block DiagramAn external shunt resistor in the ground path of the connected LEDs is used to sense the
LED current. A regultaion loop helds the voltage drop at the shunt resistor on a constant
level of typ. 180mV. Selecting the shunt resistance permits to adjust the appropriate
constant current level. The typ. output current calculates
where VREF is the reference voltage with a typical level of 180mV (see
Fig. page 10) . The equation applies in a range of 0.39Ω≤RREF≤1.8Ω.
The output current is shown as a function of the reference resistance on page 10. With
the PWM input the LED brightness can be regulated via duty cycle. Also PWM=L sets
the TLE 4242 in sleep mode resulting in a very low current consumption of << 1µA typ.
Due to the high impedance of the PWM input (see Fig. IPWM versus VPWM on page 12)
the PWM pin can thus also be used as an enable input.Qtyp,VREFREF
------------=
Figure2Pin Configuration (top view)
Pin Definitions and Functions
Application Information
Figure3Application CircuitFig. 3 shows a typical application with the TLE4242G LED driver. The 3 LEDs are
driven with an adequate supply current adjusted by the resistor RREF. Thus brightness
variations due to forward voltage spread of the LEDs are prevented. The luminosity
spread arising from the LED production process can be compensated via software by an
appropriate duty cycle applied to the PWM pin. Hence selection of the LEDs to forward
voltage as well as to luminosity classes can be spared. The minimum supply voltage
calculates as the sum of the LED forward voltages, the TLE4242G drop voltage (max.
0.7V at a LED current of 300mA) and the max. voltage drop at the shunt resistor RREF
of max 187mV.
The status output of the LED driver (ST) detects an open load condition enabling to
supervise correct LED function. A LED failure is detected if the voltage drop at the shunt
resistor RREF falls below typ. 25mV. In this case the status output pin ST is set low after
a delay time adjustable via an optional capacitor connected to the pin D.
The functionality of the ST and PWM as well as their timings are shown in Fig. 4. The
Status delay can be adjusted via the capacitor connected to the timing Pin D. The delay
time scales in linear way with the capacitance CD :
Figure4Function and Timing DiagramSTHL,typD
47nF-------------10ms×=STLH,typD
47nF-------------10µs×=
Absolute Maximum Ratings
– 40 °C < Tj < 150 °C
Input
Output
Status Output
Status Delay
Reference Input
Pulse Width Modulation Input
Temperatures
Note:Maximum ratings are absolute ratings; exceeding any one of these values may
cause irreversible damage to the integrated circuit
Thermal ResistancesWorst case regarding peak temperature; mounted on PCB FR4, 80×80×1.5mm3, 35µm Cu
Operating Range
