Datasheet

PT8A2651
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PIR Sensor Light Switch Controller
Features
Description

Operating voltage: 5V (Typical)

Average supply current: 120µA (Typical)
automatic PIR lamp control. The chip is equipped with

On-chip regulator
operational amplifiers, a comparator, timer, a zero

Build-in noise rejection circuit
crossing detector, control circuit, a voltage regulator, a

16KHz system oscillator
system oscillator, and an output timing oscillator.

Adjustable output duration

Override function
induced by the motion of a human body and transforms

ON/AUTO/OFF selectable by MODE pin
it to a voltage variation. If the PIR output voltage

Auto-reset with ZC signal disappearing over 3
variation conforms to the criteria (refer to the functional
seconds
description), the lamp is turned on with an adjustable

Output positive pulses to drive triac
duration. The PT8A2651 offers three operating modes

CDS to enable/disable output
(ON, AUTO, OFF) which can be set through the MODE

40 second warm-up
pin. While the chip is working in the AUTO mode the

Quick check mode for installation
user can override it and switch to the quickly install

Low cost SOIC-16 package
mode or manual ON mode or return to the AUTO mode
The PT8A2651 is a CMOS LSI chip designed for
Its PIR sensor detects infrared power variations
by switching the power switch. The chip is enclosed in a
16 pin SOIC.
Pin Configuration
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PT8A2651
PIR Sensor Light Switch Controller
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Pin Description
Pin No.
Pin Name
I/O
Pin Description
1
VSS
I
Ground
2
TRIAC
O
TRIAC drive to output two pulses, active positive pulse.
3
OSCD
I/O
4
OSCS
I/O
5
ZC
I
6
CDS
I
7
MODE
I/O
8
VDD
I
Output timing oscillator. with an external RC to adjust output duration.
System oscillator. with an external RC to set the system frequency. The system frequency
=16KHz for normal application.
Schmitt input for AC zero crossing detection
CDS is connected to a CDS voltage divider for daytime/night auto-detection. Low input to
this pin can disable the PIR input. CDS is a schmitt trigger input with 5-second input
debounce time.
Operating mode selection input:
VDD: TRIAC is always ON
VSS: TRIAC is always OFF
Open: Auto detection, outputs 31.25Hz square wave
Positive power supply
9
VEE
O
Regulated voltage output The output voltage is about 3.6V with respect to VSS.
10
RSTB
I
Chip reset input, active low
11
OP1P
I
Non-inverting input of OP1
12
OP1N
I
Inverting input of OP1
13
OP1O
O
Output of OP1
14
OP2P
I
Non-inverting input of OP2, internal 1.8V default.
15
OP2N
I
Inverting input of OP2
16
OP2O
O
Output of OP2
Block Diagram
Figure 1 Block Diagram
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PIR Sensor Light Switch Controller
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Maximum Ratings
Storage Temperature ................................................................................... -40oC to +125oC
Ambient Temperature with Power applied...............................................-20oC to +70oC
Supply Voltage to Ground Potential (Input & VCC Only).....VSS-0.5V toVDD+0.5V
Supply Voltage to Ground Potential (Onput & D/O Only)..VSS-0.5V toVDD+0.5V
DC Input Voltage .............................................................................................-0.5V to +6.0V
DC Output Current ...................................................................... 20mA
Power Dissipation ......................................................................................................... 500mW
Note:
Stresses greater than those listed under MAXIMUM
RATINGS may cause permanent damage to the
device. This is a stress rating only and functional
operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. Exposure
to absolute maximum rating conditions for extended
periods may affect reliability.
Recommended operation conditions
Sym
Parameter
VDD
VIH
VIL
Operating Voltage
“H” Input Voltage
“L” Input Voltage
VDD
-
FSYS
System Oscillator Frequency
5V
TA
Operating temperature
-
Test Conditions
Conditions
ROSCS=430K
COSCS=180P
-
Min
Typ
Max
Unit
4.75
0.8
-
5.0
-
6.0
0.2
V
VDD
VDD
12.8
16
19.2
KHz
-20
25
70
°C
Min
Typ
Max
Unit
3.0
0.9
2.6
1.1
2.7
0.8
2.7
0.8
3.3
1.2
2.9
1.4
3
1
3
1
3.6
1.5
3.2
1.7
3.3
1.2
3.3
1.2
V
V
V
V
V
V
V
V
Electrical Characteristics
Test Conditions
Conditions
Sym
Parameter
VTH1
VTL1
VTH2
VTL2
VTH3
VTL3
VTH4
VTL4
CDS “H” Transfer Voltage
CDS “L” Transfer Voltage
ZC “H” Transfer Voltage
ZC “L” Transfer Voltage
OSCS “H” Transfer Voltage
OSCS “L” Transfer Voltage
OSCD “H” Transfer Voltage
OSCD “L” Transfer Voltage
VDD
5V
5V
5V
5V
5V
5V
5V
5V
I IH
High level leakage current (ZC,CDS)
5V
VIH=4.5V
-1
-
1
A
I IL
Low level leakage current (ZC,CDS)
5V
VIL=0.5V
-1
-
1
A
I IHRSTB
IOH
IOL
RSTB Input high level current
Output source current( TRIAC)
Output sink current(TRIAC)
5V
5V
5V
VIH=4.5V
VOH=4.0V
VOL=0.5V
-1
-18
3
-
-5
-
A
mA
mA
Min
Typ
Max
Unit
3.24
1.62
3.6
1.8
3.96
1.98
V
V
-
30
50
mV
-
60
100
mV
-
Voltage regulation circuit
Sym
Parameter
VEE
OP2P
Regulator Output Voltage
Non-inverting input of OP2
VDD
5V
5V
VO
Line regulation
-
VLDR
Load regulation
5V
Test Conditions
Conditions
No load
No load
4.5VDD5.5V, IL
=1mA
0.5mA  IL2mA
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PIR Sensor Light Switch Controller
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Operational amplifier and windows comparator
Parameter
BW
VH
VL
Description
3dB band width
Threshold of windows
comparator
Test conditions
VDD=5V
VDD=5V
Min
10
2.2
0.8
Typ
2.52
1.08
Max
2.8
1.3
Unit
KHz
V
V
Typ
31.25
1.45
62.5
Max
37.5
1.74
75
Unit
Hz
ms
s
Min
Typ
Max
Unit
-
120
200
A
Frequency of oscillator and timing of ZC and trigger output
Parameter
FMODE
TDZT
TTPW
Description
Oscillator frequency/512
Delay time from ZC to TRIAC
TRIAC Pulse Width
Test conditions
VDD=5V,
RS=430K ,CS=180P
Min
25
1.16
50
Power Dissipation
Sym
Description
ICC
Power supply current
Test Conditions
VDD=5V, RS=430K ,CS=180P,
RD =2M, CD=104, other Input Pins=VSS,
all outputs float.
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PIR Sensor Light Switch Controller
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Functional Description
VEE
VEE supplies power to the analog front end circuit, it is about a stable 3.6V with respect to VSS normally.
OSCS
OSCS is a system oscillator input pin. System frequency of 16KHz can be generated when connecting to an external RC, see
figure 2 (R=430K, C=180pf).
TD=23552/FOSCD
RS
VTH3
+
VTL3 +
430k
OSCS
CS
+
VTH4
RD
OSCD
+
180P
CD
PT8A2641/2/5/6/7/8
+
VTL4 +
+
+
PT8A2641/2/5/6/7/8
Figure 2 System oscillator
Figure 3 Output timing oscillator
OSCD
OSCD is input pin of timing oscillator. It’s connected to an external RC to obtain the desired output timer. Variable output
turn-on duration can be achieved by selecting various values of RC or using a variable resistor, see figure 3.
Note: The minimum resistor should be low enough to 2K in order to provide adjustable range about 1000 times between min
and max timer.
Formula for timer calculation as below (VH=3/5VCC,VL=1/5VCC)
Charging time of Capacitor: Tc =R*C*ln[(VCC-VL)/(VCC-VH)]=0.6931*R*C
Ideal calculation formula: TD =23552*Tc.
5s
12minutes(720s)
R (C=223)
15K
2000K
Error compared to ideal formula
±15%
±5%
3s
5s
25s
R (C=104)
2K
3K
15K
Error compared to ideal formula
±100%
±80%
±15%
Note: It is recommended that C is more than 103 in order to guarantee not too bad linearity.
5000s
3000K
±5%
TRIAC
TRIAC to drive (active positive pulse) TRIAC. The output active duration is controlled by the OSCD oscillating period.
CDS
With a schmitt trigger input structure, CDS is used to distinguish lighteness. Putting a cds component in a resistor divider, if
light is weak enough, CDS is high the PIR input is active. Oppositely, the CDSO will be inactive when CDS is low. The input
debounce time from inactive to active is 5 seconds. CDS should be pulled high without using this function. The input of CDS will
be ignored once the output is active.
CDS
Status
CDSO
LOW
Day Time
inactive
HIGH
Night
active
RW
CDS
CDS
CDS CDSO enable
<5s
>5s
disable
enable
Figure
CDS
input
interface
and
enable debounce
Figure 44CDS
input
interface
and enable
debounce
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PIR Sensor Light Switch Controller
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RSTB
RSTB is used to reset the chip. It is internal pull-high and active low. The use
of CRST can extend the power-on initial time. If the RSTB pin is an open circuit
(without CRST), the initial time is the default (40 secs).
VCC
REST
Power on initial
RSTB
Because the band-pass filter and amplifier require a warm up period to reach a
stable state after power-on so any inputs should be ignored during this period.
CRST
VSS
In the AUTO mode within the first 10 seconds of power-on initialization, the
system allows override control to access the quickly install mode. However, after
FigureFig.5
5 RSTB
example
RSTBapplication
application example
40 seconds of the initial time the system allows override control between ON and
AUTO. It will remain in the warm up period if the total initial time has not elapsed
after returning to AUTO.
In case that the ZC signal disappears more than 3 seconds, the chip will restart the initialization operation. However, the restart
initial time is always 40 seconds and cannot be extended by adding CRST to the RSTB pin as shown in Fig.5.
MODE
MODE is a tri-state input pin used to select the operating mode.
MODE
Operating Mode
Description
VDD
Output always ON
TRIAC outputs positive pulse train with synchronizing to ZC
VSS
Output always OFF
TRIAC outputs low
Outputs remain off state until activated by a valid PIR trigger signal. When working in
Open
AUTO
the AUTO mode, the chip allows override control by switching the ZC signal. MODE
outputs square wave with frequency of 31.25Hz.
ZC
ZC samples AC signal and generates zero crossing pulses to synchronize the TRIAC driver. With an effective ZC signal
switching (switch OFF/ON 2 times within 3 seconds), the system provides the following additional functions:
Quickly install mode: Within 10 seconds after power-on, effective ZC switching will force the chip to enter the quickly install
mode. During the mode, the outputs will be active for a duration of 1.3 seconds each time a valid PIR trigger signal is received. If
a time interval exceeds 32 seconds without a valid trigger input, the chip will enter the AUTO mode automatically.
Figure 6 Test mode
Override control
When the chip is working in the AUTO mode (MODE= open), the output is activated by a valid PIR trigger signal and the
active output duration is controlled by the OSCD oscillating period. The lamp can be switched always to “ON” from the AUTO
mode by either switching the MODE pin to VDD or switching the ZC signal by an OFF/ON operation of the power switch
(OFF/ON twice within 3 seconds). The term "override" refers to the change of operating mode by switching the power switch. The
chip can be toggled from ON to AUTO by an override operation. Shows as Fig.7.
If the chip is overridden to ON and there is no further override operation, it will return to AUTO automatically after an internal
preset ON time duration has elapsed. This override ON time duration is set to 5 hours.
During any operation (including override and the end of warm up as well as quick install mode), output will not flash.
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PIR Sensor Light Switch Controller
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Figure 7 ZC override timing
PIR amplifier
Refer to the following diagram for details on the front end
amplifier of PIR.
In Fig.8 there are 2 op-amps with different applications.
OP1 can be used independently as a first stage inverting or noninverting amplifier for the PIR.
As the output of OP2 is directly connected to a comparator.
The non-inverting input of OP2 is connected to the
comparator’s window center point and can be used to check this
voltage and provide a bias voltage that is equal to the center
point voltage of the comparator. In Fig.8 the comparator can
have window width VCP=VCN= (1/5) VEE.
VEE
Regulator
OP1O
OP1P
OP1N
+
_
OP1
Comparator
_
OP2O
OP2P
OP2N
+
OP2
VCP
+
+
_
VCN
COMPO
+
Second stage amplifier
Usually the second stage PIR amplifier OP2 is a simple
capacitively coupled inverting amplifier with a band pass
configuration. The non-inverting input terminal is biased to the
VSS
center point of the comparator window and the output of OP2 is
Figure
8 PIR
amplifier
directly coupled to the comparator center point.
Fig.8 PIR
amplifier
In Fig.9, OP2P is directly connected to the comparator
window center, and with the C3 filter it can act as the bias for OP2. For this configuration AV = R2/R1, low cutoff
frequency fL = 1/2R1C1, high cutoff frequency fH = 1/2R2C2. By changing the value of R2 the sensitivity can be varied.
C1 and C3 should be of low leakage types to prevent the DC operating point from change due to current leakage.
Each op-amp current consumption is approximately 15A with the op-amps and comparator’s working voltage all
provided by the regulator. Refer to the following diagrams for typical PIR front end circuit.
VEE
RW
R2 1M
R1
22K
+
_
first stage
output
OP2O
Comparator
C2
0.022
_
OP2N OP2
OP2P
+
C1
22U
RW
_
+
COMPO
+
RW
10U
C3
+
RW
Typical
second
amplifier
Figure 9Fig.9
Typical
second
stagestage
amplifier
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PIR Sensor Light Switch Controller
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First stage of PIR amplifier
Fig.10 shows a typical first stage amplifier. C2 and R2 form a simple low pass filter with cut off frequency at 7Hz. The
low frequency response is governed by R1 and C1 with cut-off frequency at 0.33Hz. The formula to calculate the gain
shows as below.
AV= (R1+R2)/R1
Fig.10 and Fig.11 are similar but in Fig.10 the input signal of amplifier is taken from the drain of the PIR. This has
higher gain than that in Fig.10. Since OP1 is a PMOS input, VD has to be greater than 1.2V for adequate operation.
VSS
VSS
VEE
C1
22U
VEE
R1
22K
C1
22U
R2
1M
R13
100k~180k
VD
R1
22K
R2
1M
PIR
C2
D
G S
+
C2
PIR
0.022
0.022
D
G S
OP1
OP1 OUT
+
R4
56K
56K
VSS
Typicalfirst
firststage
stageamplifier
amplifier
FigureFig.10
10 Typical
OP1
C15
100U
OP1 OUT
VSS
Fig.11
Figure
11 High gain
gainfirst
firststage
stage
COMPO
COMPO is output from comparator, it can be output at pin 10 if needed.
Signal from two-stage opamp outputs to a window comparator as pre-operation, COMPO outputs active positive pulses with
various width once signal beyond window level. Whether an active PIR signal is detected, see figure 12 for detail.
Trigger timing
>Tmt
<Tmt
Figure 12 Trigger timing
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PIR Sensor Light Switch Controller
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Referring to Figure 12
Note: 1. One measurable trigger width (Tmt) from comparator output is 24ms~ 32ms which varies with frequency of system
oscillator (typical system frequency=16KHz ).
2. The output is activated if the trigger signal conforms to the following criteria:

A trigger signal sustains duration: 0.34 seconds.

2 trigger signals within 2 seconds with one of the trigger signal sustain:0.16 seconds.

More than 3 measurable triggers within 2 seconds.
3. The output duration is set by an external RC that is connected to the OSCD pin.
Retrigger
If another signal is attained in trigger hold time, the circuit will be retriggered, and the trigger hold time will be started from
this time.
Timing Diagram
Figure 13 Timming diagram
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PIR Sensor Light Switch Controller
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Mechanical Information
WE (SOIC-16)
PKG. DIMENSIONS(MM)
SYMBOL
MIN
MAX
A
1.35
1.75
A1
0.10
0.25
A2
1.35
1.55
b
0.33
0.51
c
0.17
0.25
D
9.80
10.20
E
3.80
4.00
E1
5.80
6.20
e
1.27 BSC
L
0.40
1.27
θ
0°
8°
Note:
1) Controlling dimensions in millimeters.
2) Ref : JEDEC MS-012E/AC
Ordering Information
Ordering No.
Package Code
Package
PT8A2651WE
W
Lead free SOIC-16
Note:

E = Pb-free

Adding X Suffix= Tape/Reel
Pericom Semiconductor Corporation  1-800-435-2336  www.pericom.com
Pericom reserves the right to make changes to its products or specifications at any time, without notice, in order to improve design or performance and to
supply the best possible product. Pericom does not assume any responsibility for use of any circuitry described other than the circuitry embodied in Pericom
product. The company makes no representations that circuitry described herein is free from patent infringement or other rights, of Pericom.
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