LS7637 Datasheet | LSI

FEATURES : - Pushbutton or touch control of high-voltage lamps and all electronic transformer-coupled low-voltage halogen lamps. - Controls Fluorescents and CFLs via dimming ballasts. - Reverse-phase technology eliminates RFI generation. - “FO" versions power up Full On after application of AC. - Soft turn-on and soft turn-off - Three operating modes. - Inputs for direct or remote activation. - 50Hz/60Hz AC line frequency. - +12V Power Supply (VDD - VSS). - LS7636, LS7637 (DIP); LS7636-S, LS7637-S (SOIC); LS7636FO, LS7637FO (DIP); LS7636FO-S, LS7637FO-S (SOIC) - See Figure 1 - REVERSE PHASE (TRAILING-EDGE) HALOGEN LAMP DIMMER PIN ASSIGNMENT - TOP VIEW V DD (+V ) MODE TEST SYNC 1 2 3 4 8 7 6 5 LSI FIGURE 1 LS7636 LS7637 GATE VSS (-V ) OVC SENS SENS (Pin 5) - See Table 1 A Logic 0 applied to this input alters the Gate Drive output APPLICATIONS: Electronic dimmers for wall-switch control of ceiling mounted either by turning it on, turning it off or by changing its lighting, foot-switch control of large floor lamps and hand- conduction angle. Specifically which action takes place is dependent on the type of activation of the SENS input, switch control of table lamps. namely SHORT or LONG duration and the prior state of the Gate Drive output. BACKGROUND AND GENERAL DESCRIPTION : Since the operating currents of some electronic transformers are below the holding current of most triacs, a typical triac- OVC - Overcurrent Sense Input (Pin 6) based (leading-edge) dimmer may not operate properly when The voltage at this input is sampled every half-cycle in a driving an electronic transformer-coupled low-voltage halogen four-cycle period. If the voltage reaches the OVC threshold lamp. The filtering ponents in the electronic transformer four times, then the Gate Output is turned Off shutting down which prevent its operating frequency from generating line in- the current through the load. Six cycles after shutdown terference can also inhibit triac triggering. The occurs, the...