Data Sheet

PT8A261/262

PIR Sensor Light Switch Controller

PT0075(04/03)

Ver:5

5

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Functional Descriptions

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.

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.

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 se-

is the frequency of 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 when the TRIAC or RELAY output

is active.

Figure 4. Output Timing Oscillator

Figure 5. CDS Input Circuit

CDS

Rp

V

CC

CDS

Schmitt

Driver

PT8A261/262

Control

Circuit

CDS

Figure 3. System Oscillator

OSCD

560K

200P

PT8A261/

262

OSCS

PT8A261/

262

CDS

PIR

Disable

Enable

< 5s

> 5s

Enable

Figure 6. CDS Enable Debounce

CDS

Status

PIR

LOW

Day Time

Disabled

HIGH

Night

Enabled

Table 2. CDS Pin Function