Data Sheet

PT8A2611/2621

PIR Sensor Light Switch Controller

PT0091(04/03)

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’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

OSCD pin, output timing can be caculated as the formula:

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

The CDS input is ignored by PT8A2611when the TRIAC out-

put is active, however, PT8A2621’s CDS can not be ignored

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

560K

200P

PT8A2611

/2621

OSCS

PT8A2611

/2621

T

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