SL441C

SL441C ADVANCE INFORMATION DS3848 -1.0 SL441C ZERO VOLTAGE SWITCH 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 s Balanced zero voltage point crossing detector, spike filter and pulse generator for reliable triggering of the triac. s A period pulse generator and bistable which are arranged to provide symmetrical burst control and eliminate 1 / 2 w ave firing. (EN50.006 BS5406,1976) s 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. DP8 Fig.1 Pin Connections (top view) s 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. s Thermistor malfunction may be sensed and power automatically removed. s 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. Fig. 2 Block Schematic of SL441C 1 SL441C ELECTRICAL CHARACTERISTICS These Characteristics are guaranteed at the following temperatures (unless otherwise stated). Tamb = +25°C All voltages measured with respect to common (pin 1) Characteristics Shunt regulating voltage pin 3 @ 16mA Shunt regulating voltage pin 3 @ 16mA @ 75°C Supply voltage trip level pin 3 Supply current (less I4AV, I5) (see Note 1) Regulated voltage pin 5 Regulated voltage temperature coefficient pin 5 Triac gate drive pin 4 (see Note 2) Open circuit ON voltage Open circuit OFF voltage Output current into 2V drain Output current into 4V drain Output current into short circuit Internal drain resistance Control input pin 8 Bias current Hysteresis Sensor malfunction circuit operates at Input working voltage range Internal reference voltage (Ramp start) (see Note 3) Internal reference voltage (Ramp finish) (see Note 3) Peak-to-peak amplitude of ramp Pin 6 output impedance (R6) (see Note 2) Maximum ripple voltage pin 3 70 21.5 150 0 4.0 4.25 4.35 100 27 130 32.5 1 20 200 250 12 4.5 1 µA mV mV V V V mV kΩ VP-P 800 100 65 130 80 200 8.5 0.1 V V mA mA mA Ω 8.0 -1 8.5 12.2 7.5 9.0 +1 Min Typ 14.7 16 Max Units V V V mA V mV/ °C NOTES 1. The supply current is 0.45 x (RMS current fed into pin 2). I5 is the current drained from pin 5 externally. I4AV is the average triac gate current supplied each mains cycle. 2. Triac firing pulse. tp Pulse width = 0.69 R6CD microseconds typical tf Pulse finish = 1.09 R6CD microseconds minimum after zero voltage point R6 in kohms. CD in nF. See Application circuit tp Nominal (CD = 2.7nF) = 50 microseconds tp Minimum (CD = 2.7nF) = 63 microseconds 3. Ramp period = 0.85 ± 0.15 x RTCT sec. See Application circuit. The actual value of Rt must lie between 500kohms and 3Mohms. ABSOLUTE MAXIMUM RATINGS VOLTAGES Voltage on pin V8 - I Max. 12V Voltage on pin V4 - I Max. 10V TEMPERATURE Operating ambient temperature TAMB -10°C to +75°C Storage temperature TSTG -55°C to +150°C CURRENTS Supply current (pin 2) Peak value ± I2M 50mA. Non-repetitive peak current (tp