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.

FEATURES:

• Touch or pushbutton control of incandescent lamps.

• Touch Sensitivity guaranteed to 600pF Touch Plate Capacitance.

• Touch Operation independent of line plug polarity.

• Minimal external components.

• 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.