A5368 查看數據表（PDF） - Allegro MicroSystems
零件编号
产品描述 (功能)
生产厂家
A5368 Datasheet PDF : 8 Pages
| |||
5368
SMOKE DETECTOR
WITH INTERCONNECT
AND TIMER
ELECTRICAL CHARACTERISTICS continued
Characteristic
Test
Pin
Test Conditions
Min.
Limits
Typ. Max.
Timer Start Input Current
Timer Out Output Current
LED Output ON Current
LED Output ON Time
1
VIN = 9.0 V
20
—
80
4
VOUT = 0.5 V
500
—
—
5
VDD = 7.2 V, VOUT = 1.0 V
10
—
—
5
No Local Alarm; Not Latched
8.0
10
12
LED Output OFF Time
5
No Alarm, In Standby
32
40
48
No Alarm, Timer Mode
8.0
10
12
I/O Current
I/O Charge Dump Duration
2
No Alarm, VI/O = VDD - 2.0 V
25
—
60
Alarm, VI/O = VDD - 2.0 V
-7.5
—
—
Charge Dump, VI/O = 1.0 V
5.0
—
—
2
After Local Alarm or Test
1.33
1.66
1.99
I/O Alarm Voltage
2
External “Alarm” In
3.0
—
—
I/O Delay
2
“Alarm” Out
—
3.0
—
Supply Current
6
VDD = 9.0 V, No Alarm, No Loads
—
5.0
9.0
VDD = 12 V, No Alarm, No Loads
—
—
12
NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin.
NOTE 2: Alarm (Smoke) Condition is defined as V15 < V13; No Alarm (No Smoke) Condition as V15 > V13.
Units
µA
µA
mA
ms
s
s
µA
mA
mA
s
V
s
µA
µA
CIRCUIT DESCRIPTION
The A5368CA is a low-current CMOS circuit
providing all of the 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), the LED is pulsed
and a check is made for low battery by
comparing VDD to an internal reference.
Since very-low currents are used in the
device, the oscillator capacitor at pin 12
should be a low-leakage type (PTFE, polysty-
rene, or polypropylene).
Detector Circuitry. When smoke is detected, the resistor divider
network that sets the sensitivity (smoke trip point) is altered to increase
the sensitivity set voltage (pin 13) by typically 130 mV with no exter-
nal 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.
Alarm Circuitry. If smoke is detected, the oscillator period changes
to 40 ms and the horn is enabled. The horn output is typically 0.5 s
ON, 0.5 s OFF, 0.5 s ON, 0.5 s OFF, 0.5 s ON, 1.5 s OFF (temporal
horn pattern). During the OFF time, smoke is checked and will inhibit
further alarm output if smoke is not sensed. During smoke conditions
the low battery alarm is inhibited and the LED is driven at a 1 Hz rate.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000
Share Link: 