Why Drive White LEDs with Constant Current?

Abstract: When applying white LEDs for display backlighting or other illumination applications, there are two reasons to drive them with constant current:
  1. To avoid violating the Absolute Maximum Current Rating and compromising the reliability.
  2. To obtain predictable and matched luminous intensity and chromaticity from each LED.
This application note describes the characteristics of a range of typical LEDs and circuits which achieve the necessary constant-current drive.