ILD4035 Datasheet, PDF (16/29 Pages) Infineon Technologies AG – 350 mA LED Driver

ILD4035
350 mA LED Driver
Basic Application Information
PWM Dimming
The EM/PWM terminal on the PCB is an input for the pulse width modulated (PWM) signal to control the dimming
of the LED string. The PWM signal's logic high level should be at least 2.6 V or higher. The period of this PWM
signal should be higher than 200 us. For the default demo board circuit, a dimming frequency less than 300 Hz is
recommended to maintain a maximum contrast ratio of at least 100:1. The maximum contrast ratio is shown on
Figure 7, and the minimum is based on the measured average LED current at 3dB below the linear reference. The
maximum contrast ratio depends largely on the rise time of the inductor current, and hence is dependent on input
voltage, inductor size, and LED string forward voltage.
Figure 7 ILD4035; PWM Dimming
Data Sheet
16
Revision 1.0, 2010-11-11