Power Electronics

White-LED Backlight Controller

STMicroelectronics has revealed its latest innovation for cellular handsets and other portable electronics: a display backlight controller IC that simplifies circuitry for consistent, high-quality backlighting, frees-up pc-board space for other product features, and helps extend battery life.

White LED backlights are preferred in many of today’s handset designs, for their high efficiency, small size and long-term reliability. The LEDs are driven at constant current, usually using a controller IC and several additional components. ST’s new controller, the STLED25, simplifies design and occupies less pc-board space by integrating control circuitry for up to 10 LEDs on a single chip.

Leveraging ST’s advanced design and manufacturing capabilities, the STLED25 provides five current sources that can be connected directly to the LED high-side terminals, allowing the low side to be connected directly to ground. This eliminates the need to connect each LED channel back to the control IC, enabling a compact, robust and reliable design. The LED drive current is set using a single external resistor.

The STLED25 operates from 2.3V to 5.5V, for use in battery-powered electronics and enables driving and control of 5 branch channels via two independent control pins. The voltage conversion and current control circuitry operates efficiently whether driving the LEDs at maximum brightness or dimmed, thereby helping to maximize battery life. In addition, close matching of the current in each channel ensures consistent backlight brightness, contributing to a better user experience.

  • Features 1.4 x 1.8mm chip-scale package
  • 15.6mm2 total solution footprint
  • 5 x 25mA output current
  • 85- 87% efficiency
  • PWM dimming
  • Channels can be individually enabled/disabled
  • Current limiting and protection circuitry

The STLED25 is currently sampling to lead customers now in the 12-bump, 0.4mm-pitch CSP, with full production availability expected in December 2011. The device is priced at $1.50 for orders over 1000 pieces Alternative pricing options may be available for higher quantities.

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