TLE4241GM_07 Datasheet, PDF (4/15 Pages) Infineon Technologies AG – LED Driver with Adjustable Current

TLE 4241 GM
Application Information
WD R
V_Q
µC
10 kΩ
W
RO _{TLE 4271}
22 µF
ST
I
PWM
SET ^{TLE 4241G Q}
R_REF
V_Batt
100 nF
LA E67B
OSRAM
AED03098
Figure 3 Application Circuit
Figure 3 shows a typical application with the TLE 4241 GM LED driver. 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 slightly negative temperature
coefficient of the TLE 4241 GM output current protects the LEDs against over-
temperature stress if the IC is placed nearby the LEDs.
The voltage drop (V_I - V_Q) across the TLE 4241 GM is monitored in order to detect an
open load condition indicated at the status output pin ST. In case of open load, the
voltage drop will decrease below the lower status switching threshold V_dr,L. Hence, the
status output ST will be driven low. In normal operation, the voltage drop is above the
upper status threshold V_dr,H, thus the open collector output ST is in high-ohmic state (see
also section Status Output at the Electrical Characteristics).
The function of ST, SET and PWM as well as their timings are shown in Figure 4.
Data Sheet
4
Rev. 1.3, 2007-03-19