PT8A2515 Simple Timer Features Description The PT8A2515 is a CMOS LSI chip designed for Operating voltage: 3.5V~5.5V timer applications, the time can be adjusted by external Have Reset function R/C. It has reset function. Relay output disable without external oscillator The chip includes: Power on reset circuit, Logic Adjustable Timer: 30s~20mins control circuit, Output driver circuit, Key scan circuit, Few external components timer circuit, Built-in internal oscillator and external R/C Low cost TO-94 and SOT23-5 package oscillator circuit etc. It is enclosed in lead free TO-94 and Applications SOT23-5 package. Toaster Controller Timer Block Diagram OSC Power On OSC/RESET VCC Timer OOsscciillllaattoorr Reset Logic control Key scan Circuit Output RELAY System GND Driver Oscillator 2013-07-0010 PT0272-3 08/01/13 1 PT8A2515 Simple Timer Pin Configuration OSC 1 5 NC PT8A2515 GND 2 SOT23-5 VCC 3 4 Relay Pin Description Pin No. Pin Name I/O Description TO-94 SOT23-5 1 4 Relay O Relay output, high active 2 3 VCC I Power supply Oscillator s Frequency of 8.192KHz with an external R1, C1. 3 1 OSC I/O As input, requires a negative pulse to active Reset function. 4 2 GND I Ground - 5 NC - Not connected Function Description (Refer to Block Diagram) The chip mainly includes: Power on reset circuit, Logic control circuit, Output driver circuit, Key scan circuit, timer circuit, external R/C oscillator circuit and internal oscillator circuit etc. Key scan circuit This circuit will detect Reset/Restart key at OSC have a low Power on reset circuit negative pulse, it will active the corresponding work status. Internal power on reset circuit will reset all the logic circuit and When IC worked at timer, it will reset the timer when timer is the timer it will clear all output pins when power on. out, it will reset the timer and restart the output. Logic control circuit Timer circuit The logic circuit will carries out all the logic control function. This circuit will provide a timer to logic control circuit. When It will check OSC pin status, then control the output drive Fosc = 8.192 KHz, timer output is 245720/8192=30s. circuit, when timer is out, it will pull down Relay pin to release relay. External R/C Oscillator circuit This will produce a system frequency depend on external Output driver circuit resistor and cap, the frequency is about 8.192 KHz when The pin Relay will drive a relay. R1=47 K and C1=332. (Refer to Fig 1). Note: The system frequency with external resistor and cap must be between 180Hz to 20 KHz. Internal oscillator An on-chip RC oscillator with frequency about 256 KHz is used to check the input signal and the wrong statue of external RC oscillator. 2013-07-0010 PT0272-3 08/01/13 2