LS7232NT
Key Features
- Control of incandescent and transformer coupled halogen lamps.
- No-Touch lamp control through optical sensing
- PLL synchronization of AC for wall switch application.
- Extension input for remote control
- Safety-shutdown for transformer malfunction.
- Pin-selectable operating modes
- Single 5V power supply
- 50Hz/60Hz AC line frequency
- LS7232NT (DIP), LS7232NT-S (SOIC) - See Figure 1 DESCRIPTION: LS7232NT is a CMOS integrated circuit designed for brightness control of incandescent lamps or tranformer coupled low voltage halogen lamps. The brightness is controlled by controlling the firing angle of a triac in series with the lamp and triggered by the LS7232NT. A Phase-Locked-Loop keeps the LS7232NT phase pointer locked in phase with the line voltage. A unique optical user interface provides for a smooth control of the lamp intensity without the need for touching any sensor plate. A mechanical switch interface for dimming control is also provided which can be used for a remote touch plate. The IC includes features to address problems associated with inductive loads such as transformers in low voltage halogen lamp application. The voltage to current phase lag resulting from the inductance may prevent the triac from shutting off at AC zero crossover and/or prevent the triac from maintaining conduction following the removal of the gate trigger. These problems are addressed by the LS7232NT in the following manner:
- Compensation for delayed triac cut-off. When trigger pulse is due to occur at a conduction angle which coincides with the on-state of the triac, the trigger pulse is delayed until the triac has turned off. This eliminates the underlying cause of half-waving.
