SL441

**The SL441C is a symmetrical burst control integrated circuit in an 8

pin DIL package. When used with a triac, AC power may be regulated by varying the number of mains cycles applied to the load in a fixed timing period. The device is especially suited to room temperature control applications including panel heaters, fan heaters etc. Zero**

Voltage Switching has the advantage of minimising radio frequency interference.

FEATURES

■ Balanced zero voltage point crossing detector, spike filter and pulse generator for reliable triggering of the triac.
■ A period pulse generator and bistable which are arranged to provide symmetrical burst control and eliminate 1/2 wave firing. (EN50.006 BS5406,1976)
■ A ramp generator whose output is used to modify an internal reference voltage which is then compared with the voltage appearing on the thermistor to form a proportional control system. The period of the ramp generator is defined externally and may be chosen to limit 'lamp flicker' in accordance with EN50.006/BS5406, 1976.
■ The comparison amplifier has inbuilt hysteresis to eliminate switching jitter and a spike filter/sampling circuit to provide high immunity to both spikes and coherent 50Hz/60Hz.
■ Thermistor malfunction may be sensed and power automatically removed.
■ A supply voltage sensing circuit which inhibits firing pulses when the supply is inadequate to guarantee proper circuit operation. This eliminates stressing of the triac at switch-on.