PT8A2641 Datasheet, PDF (6/13 Pages) Pericom Semiconductor Corporation – PIR Sensor Light Switch

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Functional Description
PT8A2641-2642/2645-2648
PIR Sensor Light Switch
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VEE: supplies power to the analog front end circuit, it is about a stable 3.6V with respect to GND normally.
OSCS: a system oscillator input pin. System frequency of 16KHz can be generated when connecting to an external RC shows
as figure 2 (R=430K, C=180pf).
Figure 2 System oscillator
Figure 3 Output timing oscillator
VTH3
RS
430k
-
OSCS
+
+
-
+
CS
VTL3 ₊
180P
TD= 23552 /FOSCD
VTH4
RD
-
OSCD
+
+
-
+
CD
VTL4 ₊
PT8A264X
PT8A264X
OSCD: 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 (The maximum resistor is 3M). It is recommended that CD is more than 103 in order to guarantee not too bad
linearity.
RELAY (TRIAC): an output pin set as a RELAY driving (active high) output for the PT8A2642/6/8, or as a TRIAC driving
(active low) output for the PT8A2641/5/7. The output active duration is controlled by the OSCD oscillating period.
CDS and CDSO: CDS has a schmitt trigger input structure. It is used to distinguish lighteness. With a resistor divider
including a CDS component, 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
LOW
HIGH
Status
Day Time
Night
CDSO
inactive
active
Figure 4 CDS input interface and enable debounce
Photo
Resistor
RW
CDS ^CDS
CDS ^{CDSO enable}
<5s
disable
>5s
enable
RSTB: 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).
Figure 5 RSTB application example
VC
C
RES
T
RST
B
CRST
VSS
12-07-0006
PT0192-3 07/06/12
6