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 Sensitivity is independent of Touch Plate Size and Line-Plug Polarity
• If Off, a ‘Touch’ produces Max Intensity (On) instantaneously
• If On, a ‘Touch’ initiates intensity ramp-down (Soft-Off). Max intensity to Off ramp-down time is programmable by an external RC. The Soft-Off feature provides light for the User to exit the room. Ramp-down time = 0 if no RC is connected.
• Application of a ‘Touch’ during ramp-down causes the ramp-down to stop. Once stopped, a ‘Touch’ causes the ramp-down to Off to resume. Stopping and starting the ramp-down can be repeated as often as desired thus giving the User full control in setting the light intensity.
• Push button control can be used instead of ‘Touch’.
• Applications include Wall Switches and Touch Control modules for small table lamps to large floor lamps