357 PT8A2544/PT8A2545 Universal Timer Application Note Introduction PT8A2544/PT8A2545 is a mixed signal CMOS IC designed for a fixed timer to drive RELAY to implement safety power control. It supports 120/240V and 50/60Hz AC power supply. The device automatically shuts off load in order to prevent undesired condition of the system. Internal timer is capable of several timer settings, such as 15 minutes, 30 minutes, 45 minutes, 1 hour, 1.5 hours, 2 hours, etc. Figure 1 shows a typical application diagram for 120V/60Hz power supply application, where U1 is the control IC PT8A2544/PT8A2545. Adjusting the TS0/1/2 input voltage level will result with different timer-out values. H2 D1 R3 IN4007 100 H1 C3 10uF/100V R4 10K ACL C1 0.33uF/275VAC R1 D2 R2 IN4007 10K D4 IN4148 VCC RY1 U1 1 1M C2 22uF/16V D3 IN4007 C4 104 2 3 4 TS2 VCC TS1 ACSEL TS0 RELAY GND DISC 8 7 Q2 2N5551 6 Q1 2N5551 5 K1 PT8A2544/5 ACN Figure 1: PT8A2544/PT8A2545 application diagram for 120V/60Hz Figure 2 shows a typical application diagram for 240V/50Hz power supply application, where U1 is the control IC PT8A2544/PT8A2545. Adjusting the TS0/1/2 input voltage level will result with different timer-out values. H2 D1 R3 IN4007 100 H1 C3 10uF/100V R4 10K ACL C1 0.15uF/275VAC R1 D2 R2 IN4007 10K RY1 U1 1 2.2M D3 IN4007 D4 IN4148 VCC C2 22uF/16V C4 104 2 3 4 TS2 VCC TS1 ACSEL TS0 RELAY GND DISC 8 7 Q2 2N5551 6 5 Q1 2N5551 PT8A2544/5 K1 ACN Figure 2: PT8A2544/PT8A2545 application diagram for 240V/50Hz Page 1 of 3 AN357 Pericom Semiconductor Corp. www.pericom.com 10/1/2013 357 TS0/TS1/TS2 for Timer Table 1: timer time out Timer time out 15min 30min 45min 1hour 90min 2hour 4hour 8hour TS2 GND GND GND GND VCC VCC VCC VCC TS1 GND GND VCC VCC GND GND VCC VCC TS0 GND VCC GND VCC GND VCC GND VCC Note1: ACSEL pin is for 50/60Hz selection, default 60Hz by internal pull down, connecting to VCC will select 50Hz. Note2: TS2 internal pull down, TS1 & TS0 internal pull up. The default timer is 60 minutes. K1 function for Timer Table 2: K1 function list IC Part Number Press K1 less than 1sec in Press K1 over 3sec once normal mode power on PT8A2544 Reset QTM (quick test mode) PT8A2545 On/Off Note3: IC will sample the button’s operation during first 100ms after power on. If the button K1 is pressed over 3sec just after power on, chip will enter quick test mode as soon as the button K1 is released. QTM mode for Timer Table 3: QTM mode timer out Real timer out Timer in QTM mode 15min 2sec 30min 4sec 45min 6sec 1hour 8sec 90min 10sec 2hour 12sec 4hour 14sec 8hour 16sec Quiescent Dissipation Table4: Quiescent dissipation Power Supply 240V/50Hz 120V/60Hz Quiescent dissipation 0.25W 0.25W Page 2 of 3 AN357 Pericom Semiconductor Corp. www.pericom.com 10/1/2013