Data Sheet 4 Rev. 1.1, 2007-03-20
TLE 4242 G
Application Information
Figure 3 Application Circuit
Figure 3 shows a typical application with the TLE 4242 G LITIX
TM
Linear. The 3 LEDs
are driven with an adequate supply current adjusted by the resistor R
REF
. 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 TLE 4242 G drop
voltage (max. 0.7 V at a LED current of 300 mA) and the max. voltage drop at the shunt
resistor
R
REF
of max. 185 mV.
The status output of the LITIX
TM
Linear (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 R
REF
falls below typ. 25 mV. 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.
AEA03499.VSD
TLE 4269 G
100
nF
GND DRADJ
SI
Q
RO
10
µF
10 kΩ
µC
TLE 4242 G
V
BAT
I
I
47 nF
GND D
ST PWM
Q
0.47 Ω
0.25 W
R
REF
LED
Dragon
REF
