TLD5098EL Datasheet, PDF (29/39 Pages) Infineon Technologies AG – DC/DC Boost, Buck-Boost, SEPIC controller

TLD5098EL
Analog Dimming
Multi-purpose usage of the Analog dimming feature
1) A µC integrated digital analog converter (DAC) output or a stand alone DAC can be used to supply the SET pin
of the TLD5098EL. The integrated voltage Regulator (V_IVCC) can be used to supply the µC or external components
if the current consumption does not exceed 25mA.
2) The analog dimming feature is directly connected to the input voltage of the system. In this configuration the
LED current is reduced if the input voltage V_IN is decreasing. The DC/DC boost converter is changing (increasing)
the switching duty cycle if V_IN drops to a lower potential. This is causing an increase of the input current
consumption. If applications require a decrease of the LED current in respect to VIN variations this setup can be
choosen.
3) The usage of an external resistor divider connected between IVCC (integrated 5V regulator output and gate
buffer pin) SET and GND can be choosen for systems without µC on board. The concept allows to control the LED
current via placing cheap low power resistors. Furthermore a temperature sensitive resistor (Thermistor) to protect
the LED loads from thermal destruction can be connected additionally.
4) If the analog dimming feature is not needed the SET pin must be connected directly to >1.6V potential (e.g.
IVCC potential)
5) Instead of an DAC the µC can provide a PWM signal and an external R-C filter is producing a constant voltage
for the analog dimming. The voltage level is depending on the PWM frequency (f_PWM) and duty cycle (DC) which
can be controlled by the µc software after reading the coding resistor placed at the LED module.
Datasheet
29
Rev. 1.0, 2010-10-13