
Data Sheet
PT8A2611/2621
PIR Sensor Light Switch Controller
PT0091(11/03)
Ver:3
5
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Functional Descriptions
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 and OSCD Pins
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
connected to an external RC to
抯
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
CDS can not be ignored
抯
anytime.
Figure 2. Output Timing Oscillator
Figure 3. CDS Input Circuit
CDS
Rp
V
CC
CDS
Schmitt
Driver
PT8A2611/2621
Control
Circuit
CDS
Figure 1. System Oscillator
OSCD
CD
RD
560K
200P
CS
RS
PT8A2611
/2621
OSCS
PT8A2611
/2621
T
D= 21504 / FOSCD
CDS
PIR
Disable
Enable
< 5s
> 5s
Enable
Figure 4. CDS Enable Debounce
Table 1. CDS Pin Function
CDS
Status
PIR
LOW
Day Time
Disabled
HIGH
Night
Enabled