PT8A2521 Datasheet, PDF (3/9 Pages) Pericom Semiconductor Corporation – Universal Timer Controller

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PT8A2521-23/31-33/41-43
Universal Timer Controller
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Block Diagram
Figure 2 Function block diagram
Ref erence
circuit
Clock extracting
circuit
AC SEL
GND
VC C
Shunt
Regulator
SCR driving
circuit
SCR
Internal RC
Os cil la to r
PB O
Timer Chain
1 5 /3 0 / 4 5 /6 0 m/ 9 0 m/ 2 h/ 4 h/8 h
Button sampling
circuit
Functional Description (Note: In below description, “RELAY” presents a pin, while “relay” means a device.)
● Reference and Shunt Regulator
Reference circuit generates 1.2V VCC-independent and
temperature-independent voltage to provide reference
voltage for the build-in shunt regulator. The regulator
supplies all internal function blocks.
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
● Clock extracting circuit
mode section). If the related button is pressed over 3s
VCC is not only the power supply pin but also clock
just after power on, chip will enter quick test mode as
source for internal precise timer. With the help of the
soon as the button is released. If buttons are not pressed
external circuit, the AC 50/60Hz clock signal can be
during first 100ms, system will operate normally.
extracted to be used as timer clock source.
● SCR driving circuit
● Internal RC oscillator circuit
System outputs high to drive high sensitive SCR.
It is employed to create pulse driving signal for RELAY,
it is a completely internal RC oscillator with frequency
of about 128KHZ.
● Quick Test Mode(QTM)
In order to make the manufacturer’s test convenient,
quick test mode is designed to speed up the test.
● Timer chain
QTM can be accessed by pressing button (ON/RESET)
Timer chain can be used to generate various timer
over 3s (option 2s) once power on. It can exit
including 15/30/45/60/90/120/240/480min.
automatically after quick test timer is expired, system
● Button sampling circuit
With external buttons, ON/OFF/RESET function can be
realized. User can select one button with once ON, once
needs to power on again to come back normal operation
after quick test mode. Any button operations will be
ignored in QTM.
OFF or two buttons to turn ON or OFF separately, also
use one button to rest_Fa_ir_gt t₄im_oe_pr_e. _{ration illustration of entering into and exitting Quick test mode}
<100ms
Power on
>3s
First PB ON
sampling time
Second PB ON
*12s f or 2hrs
Quick test mode
will be ignored
3s warm up
Normal mode
Operation illustration of entering into and exiting Quick test mode
Below table shows the timer in QTM corresponding to real timer.
Real timer
Timer in QTM
Table Real timer compared to the timer in QTM
15m
30m
45m
60m
90m
120m
2s
4s
6s
8s
10s
12s
240m
14s
480m
16s
2013-12-0013
PT0246-4 01/03/14
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