A5350CA Allegro Microsystems Inc, A5350CA Datasheet - Page 6

• Manufacturer Part Number: A5350CA
• Description: IC SMOKE DETECTOR ION 16-DIP
• Manufacturer: Allegro Microsystems Inc
• Type: Smoke Detectorr

Specifications of A5350CA

• Input Type: Voltage
• Output Type: Voltage
• Interface: CMOS
• Current - Supply: 12µA
• Mounting Type: Through Hole
• Package / Case: 16-DIP (0.300", 7.62mm)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

A5350
ELECTRICAL CHARACTERISTICS
R
The A5350 is a low-current, BiCMOS circuit providing all of
the required features for an ionization-type smoke detector. The
alarm polarity on DETECT IN is inverted as compared with typi-
cal ion-type devices. The DETECT IN voltage must rise above
the SENSITIVITY SET voltage in order to cause an alarm.
Oscillator
An internal oscillator operates with a period of 1.67 seconds
during no-smoke conditions. Every 1.67 seconds, internal power
is applied to the entire circuit for 10 ms and a check is made for
smoke. Every 24 clock cycles (approximately 40 seconds), the
LED pin is pulsed and a check is made for low battery by com-
paring V
are used in the device, the oscillator capacitor at the OSC CAP
pin should be a low-leakage type (PTFE, polystyrene, or polypro-
pylene).
Detector Circuitry
When the voltage on the DETECT IN pin is greater than the volt-
age on the SENSITIVITY SET pin, the A5350 evaluates this as a
smoke condition.
I/O Current
I/O Alarm Voltage
I/O Delay
1
2
Negative current is defi ned as coming out of the specifi ed device pin (sourcing).
Alarm (smoke) condition is defi ned as V
TIMINGRES
Characteristic
DD
to an internal reference. Because very-low currents
= 8.2 MΩ (unless otherwise noted)
Symbol
V
I
t
I
IH(IO)
IOH
r(io)
IOL
DETECTIN
No alarm, V
Local alarm, V
External “alarm” in
Local or test alarm to I/O active
1,2
Ionization Smoke Detector with Interconnect
(continued) at T
> V
Test Conditions
SENSITIVITYSET
I/O
I/O
= V
Circuit Description
= V
DD
DD
– 2.0 V
; no alarm (no smoke) condition is defi ned as V
A
– 2.0 V
= 25°C, V
An active guard is provided on GUARD1 and GUARD2, the two
pins adjacent to the detector input, the DETECT IN pin. V
and V
keep surface leakage currents to a minimum and provide a
method of measuring the input voltage without loading the ion-
ization chamber. The active guard amplifier is not power strobed
and thus provides constant protection from surface leakage
currents. The detector input has internal diode protection against
electrostatic damage.
Alarm Circuitry
If smoke is detected, the oscillator period changes to 40 ms and
the horn is enabled. The horn output is typically 160 ms on,
80 ms off. During the off-time, smoke is checked and further
alarm output will be inhibited if smoke is not sensed. During a
smoke condition, the low-battery alarm is inhibited and the LED
is pulsed approximately once every second.
Sensitivity Adjust
The detector sensitivity must be externally set to the individual
characteristics of the ionization chamber by connecting the
Test Pin
DD
GUARD2
2
2
2
2
= 9.0 V, V
will be within 100 mV of V
Min.
–7.5
SS
3.0
25
—
= 0 V, C
115 Northeast Cutoff
1.508.853.5000; www.allegromicro.com
Allegro MicroSystems, Inc.
Worcester, Massachusetts 01615-0036 U.S.A.
OSCCAP
Typ.
DETECTIN
3.0
—
—
—
= 0.1 μF,
< V
DETECTIN
SENSITIVITYSET
Max.
60
—
—
—
. This will
.
Units
mA
GUARD1
μA
V
s
5