LS7540 Datasheet | LSI

FEATURES : - Touch or pushbutton control of incandescent lamps. - Touch Sensitivity guaranteed to 600p F Touch Plate Capacitance. - Touch Operation independent of line plug polarity. - Minimal external ponents. - AGC Loop stabilizes immediately after Power-Up. - Brightness state is Off after AC power applied. - No change of Brightness state if AC power interrupted < 0.5 sec - Advanced CMOS design for reliable operating characteristics and low power. - 50/60 Hz Line Frequency. - 5V Operation (VDD - VSS). - LS7540 (DIP); LS7540-S (SOIC) - See Figure 1 APPLICATIONS: - Screw-in and built-in adapter modules for converting table and floor lamps to touch control for continuous dimming. DESCRIPTION : The LS7540 is a CMOS integrated circuit for controlling the brightness of incandescent lamps with momentary touch. When its TOUCH input is connected to a lamp body, the entire lamp turns into a touch plate. A built-in AGC circuit allows for a wide range of lamp sizes to be used, ranging from very small table lamps to very large floor lamps. The brightness is controlled by controlling the conduction angle of a triac in series with the lamp and triggered by the TRIG/ output. Between off and maximum, there are 124 steps of brightness levels, level zero being off and level 124 being maximum. The phase reference of the Trig/ signal with respect to the AC line is maintained through the SYNC input. Touch Operation The on/off and brightness control of the lamp is made with brief touches of the lamp body as described below: - In the off state a single touch will turn the lamp to full_on. - At full-on a single touch will start a dim-cycle causing the brightness to diminish gradually until the lamp turns off. - During a dim-cycle a single touch will stop the dim-cycle and lock in the brightness present at that time. Another touch will restart the dim-cycle from the present brightness causing the brightness to ramp down towards off again. The start and stop of dim-cycle can be repeated over...