A5349CA ALLEGRO [Allegro MicroSystems], A5349CA Datasheet - Page 4

• Manufacturer Part Number: A5349CA
• Description: AC SMOKE DETECTOR WITH INTERCONNECT AND TIMER
• Manufacturer: ALLEGRO [Allegro MicroSystems]

ELECTRICAL CHARACTERISTICS continued
NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin.
NOTE 2: Alarm (Smoke) Condition is defined as V
5349
AC SMOKE DETECTOR
with INTERCONNECT
and TIMER
Characteristic
LED Output ON Current
LED Output ON Time
LED Output OFF Time
I/O Current
I/O Alarm Voltage
I/O Delay
Supply Current
Test
Pin
15
5
5
5
2
2
2
6
< V
13
; No Alarm (No Smoke) Condition as V
required features for an ionization-type smoke detector.
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 and a check is made for smoke.
Every 24 clock cycles (40 seconds), a check is made for low supply by
comparing V
used in the device, the oscillator capacitor at pin 12 should be a low-
leakage type (PTFE, polystyrene, or polypropylene).
Detector Circuitry. When smoke is detected, the resistor divider
network that sets the sensitivity (smoke trip point) is altered to in-
crease the sensitivity set voltage (pin 13) by typically 130 mV with no
external connections to pins 3 or 13. This provides hysteresis and
reduces false triggering. An active guard is provided on both pins
adjacent to the detector input (pin 15). The voltage at pins 14 and 16
will be within 100 mV of the input. This will keep surface leakage
currents to a minimum and provide a method of measuring the input
voltage without loading the ionization 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 static damage.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]
V
Local Alarm
Timer Mode, No Alarm
No Alarm, In Standby
No Alarm, Timer Mode After Pin 1
High-to-Low
No Alarm, V
Alarm, V
External “Alarm” In
“Alarm” Out
V
V
The A5349CA is a low-current CMOS circuit providing all of the
DD
DD
DD
= 7.2 V, V
= 9.0 V, No Alarm, No Loads
= 12 V, No Alarm, No Loads
I/O
Test Conditions
DD
= V
I/O
to an internal reference. Since very-low currents are
OUT
DD
= V
– 2.0 V
= 1.0 V
DD
CIRCUIT DESCRIPTION
– 2.0 V
15
> V
13
.
Min.
-7.5
3.0
10
—
—
25
—
—
—
constant OFF
constant ON
Typ.
8.35
1.67
3.0
5.0
—
—
—
—
—
Limits
Max.
9.0
60
12
—
—
—
—
—
—
Units
mA
mA
—
—
V
s
s
s
A
A
A