PT8A2621 Datasheet, PDF (5/13 Pages) Pericom Semiconductor Corporation – PIR Sensor Light Switch Controller

Data Sheet
PT8A2611/2621
PIR Sensor Light Switch Controller
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Functional Descriptions
OSCS and OSCD Pins
The PT8A2611 and PT8A2621 are CMOS LSI chips designed
for automatic PIR lamp control. They can operate in 2-wire
configuration for triac applications or in 3-wire configuration
for relay applications.
The PIR sensor detects infrared power variations caused by
motion of a human body and transfer to a voltage variation. If
the PIR output voltage variation conforms to criteria, the lamp
is turned on for an adjustable duration. The PT8A2611 (or
2621) offers three operating modes (ON, AUTO, OFF) which
can be set through a MODE pin. When the device is working
in AUTO mode, the user can override the mode to switch it to
TEST mode or manual ON mode, or return to the AUTO mode
by switching power switch.
OSCS is a system oscillator I/O pin connected to an external
RC to generate system frequency of 16kHz. OSCD is an output
timing oscillator I/O pin. It’s connected to an external RC to
obtain the desired turn-on duration by selecting various val-
ues of RC or using a variable resistor.F_OSCDis the frequency of
OSCD pin, output timing can be caculated as the formula:
TD = 21504/FOSCD
CDS Input Circuit
CDS is a CMOS schmitt trigger input pin. It is used to distin-
guish between day time and night time. When the input volt-
age of CDS is high the PIR input is enabled, when CDS low the
PIR input disabled. The input disable-to-enable debounce
time is 5 seconds. Connect this pin to V_CC when not using it.
The CDS input is ignored by PT8A2611when the TRIAC out-
put is active, however, PT8A2621’s CDS can not be ignored
anytime.
Figure 1. System Oscillator
RS _560K
OSCS PT8A2611
/2621
CS
200P
Figure 2. Output Timing Oscillator
T_D = 21504 / F _OSCD
RD
OSCD _PT8A2611
/2621
CD
Figure 3. CDS Input Circuit
V
CC
Rp
CDS
Schmitt
Driver
Control
CDS Circuit
CDS
PT8A2611/2621
Figure 4. CDS Enable Debounce
CDS
PIR Enable
< 5s
Disable
> 5s
Enable
Table 1. CDS Pin Function
CDS
Status
LOW
Day Time
HIGH
Night
PT0091(04/03)
PIR
Disabled
Enabled
5
Ver:3