PT8A2524 Datasheet, PDF (3/10 Pages) Pericom Semiconductor Corporation – Universal Timer Controller

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PT8A2524-26/34-36/44-46
Universal Timer Controller
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Functional Description (Note: In below description, “RELAY” presents a pin, while “relay” means a device.)
● Clock extracting circuit
VCC is not only the power supply pin but also clock
source for internal precise timer. With the help of the
external circuit, the AC 50/60Hz clock signal can be
extracted to be used as timer clock source.
● Internal RC oscillator circuit
It is employed to create pulse driving signal for RELAY,
it is a completely internal RC oscillator with frequency
of about 128KHZ.
● Timer chain
Timer chain can be used to generate various timer
including 15/30/45/60/90/120/240/480min.
● Button sampling circuit
With external buttons, ON/OFF/RESET function can be
realized. User can select one button with once ON, once
OFF or two buttons to turn ON or OFF separately, also
use one button to restart timer.
Button sampling circuit senses button’s operation 3 times
per 8ms. System will sample the button’s operation
during first 100ms after power on, if buttons are pressed
during this period, then system will start 3s timer to
check if the chip will enter into quick test mode (see test
mode section). If the related button is pressed over 3s
just after power on, chip will enter quick test mode as
soon as the button is released. If buttons are not pressed
during first 100ms, system will operate normally.
● RELAY driving circuit
RELAY driving signal is special, anytime, first 8ms is
always high following output pulse signal with about
32KHZ and 25% duty cycle.
DISC is used to limit the voltage of external high voltage
capacitor by discharging it with a NPN transistor.
After power on, DISC should be active during first 1s
before RELAY in order to charge the external high
voltage capacitor.
RELAY is active to output first 8ms high following
32KHz with 25% duty cycle. When relay is OFF,
RELAY will output a narrow pulse each 8ms, while,
DISC is active to output 32KHz with 25% duty cycle.
For PT8A2524/2534 one button (RESET)
„ Button is tied to RELAY pin.
„ Pressing button RESET to turn on relay and restart
internal timer.
„ RELAY is active once the button is released.
„ DISC will output low when relay is ON.
DISC is active
32KHz with 25%duty
DISC
8ms 8ms 8ms 8ms 8ms
RELAY
RELAY is active
Driving signals of RELAY and DISC
For PT8A2525/2535 one button (ON/OFF)
„ Button is tied to RELAY pin, once ON, once OFF.
„ Pressing button ON/OFF to turn on/off relay and
start/reset internal timer.
„ RELAY is active when the button is pressed at first time.
„ DISC is active when the button is pressed at second time.
„ DISC outputs Low when relay is ON.
For PT8A2526/2536 two buttons (ON, OFF)
„ Button tied to DISC pin is for ON, Button tied to
RELAY pin is for OFF.
„ Pressing button ON to turn on relay and start internal
timer.
„ Pressing button OFF to turn off relay and reset internal
timer.
„ RELAY is active when button ON is pressed.
„ DISC is active when button OFF is pressed.
„ DISC will output a narrow pulse each 8ms when relay is
ON.
● Buzzer
For PT8A2524/25/34/35/44/45, a buzzer will make 0.5s
sound with a frequency of 4KHz every 1s for 6 times
after internal timer times out. Pin DISC will output 4KHz
with 25% duty for 0.5s to let the buzzer work, then
output 32KHz with 25% duty for 0.5s, after the output 6
times 4KHz, DISC will keep output 32KHz.
● Quick Test Mode(QTM)
In order to make the manufacturer’s test convenient,
quick test mode is designed to speed up the test.
QTM can be accessed by pressing button (ON or
RESET) over 3s (option 2s) once power on. It can exit
automatically after quick test timer is expired, system
needs to power on again to come back normal operation
after quick test mode. Any button operations will be
ignored in QTM.
Note: For PT8A2526/2536, the button to be pressed over
3s to enter into QTM is OFF.
2013-12-0013
PT0266-5
01/03/14
3