Backlight for Display and Keyboard

Display Backlight is made by 4 LEDs connected in parallel (in bottom of the Display).

Keyboard Backlight is made by 4 LEDs connected in parallel. Color of all LEDs is yellow-green, l = 570nm

Switching circuits for Display and keyboard backlight is controlled by the same signal: KBLIGHTS.

KBLIGHT-signal = HIGH -> the lights are on KBLIGHT-signal = LOW -> the lights are off. UISWITCH is used for controlling backlight. Ul-Switch

Detailed description ofthe UISWITCH isgiven in document/16/.

The UISWITCH is an integrated switch IC for UI (user interface) purposes. It includes control switch for buzzer and vibra, LED-control (display ft keyboard) and two current sinks for LED's.


- 2 adjustable constant current sink (60mA each) for keyboard and LCD-LEDs

- LED ON/OFF control (separated for keyboard and LCD)

- BuzzerON/OFF control

- FET switch (low Rds-on) for buzzer current

- Vibra ON/OFF control

- FET switch for vibra current

- Thermal shutdown

- Power down function for optimum current consumption

- Package TSSOP20 because of 1.5mm height requirement

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