BL59A12/BL59S12
5.Pin description
Pin
Symbol
No.
1,2
C1, C2
Input/output
External
capacitor
connection
I
Detecting
input
Strobe
Power supply
O
Output signal
Functions
By connecting external capacitor, a
voltage feedback amplifier is formed.
The gain of it is determined by
capacitor’s value.
Connect a photodiode to supply a
signal to the internal comparator.
A strobe voltage output, referenced to
VDD.
When output = VDD -5V, it enables
other internal circuits.
To supply the power
To output pulse drive signal for
external NPN transistor which drives
a IR photodiode.
It can be used to connect up to 40
detectors to make auxiliary alarm,
remote alarm, auto-dialer…
Push-pull driver outputs signal to
drive external buzzer to alarm, and to
show various operation states.
To feed ‘silver’ signal back to the
push-pull output driver circuit’s input
It is an open drain output, can drive
LED directly. The LED can tell the
detector’s various operation states.
Connected to external R and C, which
determine the internal oscillator’s
frequency.
Connected to external R and C, which
determine the output pulse period of
IRED.
It connected to external resistor
divider between VDD and LED to get
a low supply alarm threshold voltage
This pin is normally low by an internal
pull-down device. When it is set high,
the IC enters into a simulated-smoke
condition. When floating, this pin
comes back to VSS (low) by
pull-down device.
3
DETECT
4
5,14
6
STROBE
VDD, GND
IRED
O
7
I/O
BRASS,
SILVER
FEEDBACK
LED
Input/output
Push-pull
driver’s output
Feedback
terminal
Output signal
Oscillator’s
input
External R and
C connecting
terminal
I
Low
voltage
detecting input
8,9
10
11
O
I
O
12
OSC
I
13
R1
15
LOW-SUPPLY
16
TEST
I
Test terminal
6. Function of this IC:
6.1.
The variable gain photoelectric amplifier is directly connected to IR detector (photodiode).
The amplifier’s gain is determined by external capacitors C1 and C2. During standby, the
amplifier’s gain is at minimum. Under smoke condition, the amplifier’s gain is at medium.
Entering into test condition, the amplifier’s gain is at maximum. Additionally, under standby
state, if the special supervisory circuit is activated to check the chamber’s sensitivity, the
amplifier’s gain is also at its maximum.
6.2.
Using VSS as its reference, the I/O pin can be used to connect up to 40 units together.
When I/O pin is used as an input, its on-chip pull-down resistor can prevent noise from entering
into the unit. Under smoke status, the unit activates I/O driver to send a signal to its
interconnected units to activate remote alarm.
http://www.belling.com.cn
-2-
8/28/2006
Wrote by 2006
Total
8 Pages
BELLING [ SHANGHAI BELLING CO., LTD. ]
