PT8A2612 Datasheet, PDF (5/13 Pages) Pericom Semiconductor Corporation – PIR Sensor Light Switch Controller

Data Sheet
PT8A261/262
PIR Sensor Light Switch Controller
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Functional Descriptions
OSCS and OSCD Pins
The PT8A261 and PT8A262 are CMOS LSI chips designed for
automatic PIR lamp control. They can operate in 2-wire con-
figuration for triac applications or in 3-wire configuration for
relay applications.
The device consists of operational amplifiers, a comparator,
timer, a zero crossing detector, control circuit, a voltage regu-
lator, a system oscillator, and an output timing oscillator.
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 se-
lecting various values of RC or using a variable resistor.FOSCD
is the frequency of OSCD pin, output timing can be caculated
as the formula: TD = 21504/FOSCD
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 PT8A261 (or 262)
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.
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 when the TRIAC or RELAY output
is active.
Figure 3. System Oscillator
RS _560K
OSCS _PT8A261/
262
CS
200P
Figure 4. Output Timing Oscillator
TD = 21504/F OSCD
RD
OSCD _PT8A261/
262
CD
Figure 5. CDS Input Circuit
V_CC
Rp
CDS
Schmitt
Driver
Control
CDS Circuit
CDS
PT8A261/262
Figure 6. CDS Enable Debounce
PT0075(04/03)
CDS
PIR Enable
Table 2. CDS Pin Function
CDS
Status
LOW
Day Time
HIGH
Night
PIR
Disabled
Enabled
< 5s
Disable
5
> 5s
Enable
Ver:5