SMOKE DETECTOR

WITH INTERCONNECT

The A5355CA is a low-current, CMOS circuit providing all of the

required features for an ionization-type smoke detector. A networking
capability allows as many as 125 units to be interconnected so that if
any unit senses smoke, all units will sound an alarm. In addition,
special features are incorporated to facilitate alignment and test of the
finished smoke detector. This device is designed to comply with
Underwriters Laboratories Specification UL217.

The internal oscillator and timing circuitry keeps standby power to

a minimum by powering down the device for 1.66 seconds and sensing
smoke for only 10 ms. Every 24 on/off cycles, a check is made for low
battery condition. By substituting other types of sensors, or a switch
for the ionization detector, this very-low power device can be used in
numerous other battery-operated safety/security applications.

The A5355CA is supplied in a low-cost, 16-pin dual in-line plastic

package. It is rated for continuous operation over the temperature
range of 0

C to +50

FEATURES

Interconnect Up to 125 Detectors

Piezoelectric Horn Driver

Guard Outputs for Detector Input

Pulse Testing for Low Battery

Power-ON Reset

Internal Reverse Battery Protection

5355

Always order by complete part number: A5355CA .

ABSOLUTE MAXIMUM RATINGS

(Voltages are referenced to V

)

Supply Voltage Range,

................................ -0.5 V to +15 V

Reverse Battery (10.5 V) ....................... 20 s

Input Voltage Range,

........................ -0.3 V to V

+ 0.3 V

Input Current, I

............................... 10 mA

Operating Temperature Range,

..................................... 0

C to +50

Storage Temperature Range,

............................... -55

C to +125

CAUTION: CMOS devices have input static
protection but are susceptible to damage when
exposed to extremely high static electrical
charges.

Data Sheet

26110.5A

LOGIC

OSC. &
TIMING

HORN

DRIVER

GUARD

DETECT. IN

GUARD

SENSITIVITY
SET

OSC. CAP.

HORN

SUPPLY

NO CONNECT.

I / O

LOW-V SET

NO CONNECT.

LED

+ SUPPLY

TIMING RES.

FEEDBACK

Dwg. PC-004-1

ELECTRICAL CHARACTERISTICS at T

= +25

C, V

= 9.0 V, V

= 0 V, C

= 0.1

= 8.2 M

(unless otherwise noted).

NOTE 1: Negative current is defined as coming out of (sourcing) the specified device pin.

NOTE 2: Alarm (Smoke) Condition is defined as V

> V

; No Alarm (No Smoke) Condition as V

< V

Test

Limits

Characteristic

Pin

Test Conditions

Min.

Typ.

Max.

Units

Supply Voltage Range

Operating

6.0

9.0

Detector Input Current

0 to 40% RH, V

= 0 to 9.0 V

1.0

Input Offset Voltage

14-15

Active Guard

100

16-15

Active Guard

100

15-13

Detect Comparator

Common Mode Range

14-15

Guard Amplifier

2.0

- 0.5

13-15

Smoke Comparator

0.5

- 2.0

Active Guard Impedance

to V

500

Oscillator Period

No Alarm

1.34

1.67

2.00

Alarm

Oscillator Pulse Width

8.0

Low Voltage Threshold

= 0 to 50

7.2

7.8

Horn Output Voltage

10-11

OUT

= 16 mA, V

= 9.0 V

0.1

0.5

OUT

= 16 mA, V

= 7.2 V

0.9

OUT

= -16 mA, V

= 9.0 V

8.5

8.8

OUT

= -16 mA, V

= 7.2 V

6.3

Horn Output ON Time

10-11

Alarm

120

160

208

Low Battery

8.0

Horn Output OFF Time

10-11

Alarm

104

Low Battery

LED Output ON Current

= 7.2 V, V

OUT

= 1.0 V

LED Output ON Time

8.0

LED Output OFF Time

No Alarm, In Standby

I/O Current

No Alarm, V

I/O

= V

- 2.0 V

Alarm, V

I/O

= V

- 2.0 V

-7.5

I/O Alarm Voltage

External "Alarm" In

3.0

I/O Delay

"Alarm" Out

3.0

Supply Current

= 9.0 V, No Alarm, No Loads

5.0

9.0

= 12 V, No Alarm, No Loads

5355
SMOKE DETECTOR
WITH INTERCONNECT

5355
SMOKE DETECTOR
with INTERCONNECT

115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 (508) 853-5000

The A5355CA 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 V

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, polystyrene, or polypropylene).

Detector Circuitry. 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 ampli-
fier 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 160 ms ON, 80 ms OFF. During
the OFF time, smoke is again 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.

Sensitivity Adjust. The detector sensitivity must be
externally adjusted to the individual characteristics of the
ionization chamber by connecting resistors between pin
13 and V

, and between pin 13

and V

Low Battery. The low battery threshold is set internally
by a voltage divider connected between V

and V

The threshold can be increased by connecting a resistor
between pin 3 and V

. The threshold can be decreased

by connecting a resistor between pin 3 and V

. The

battery voltage level is checked every 40 seconds during
the 10 mA, 10 ms LED pulse. If an LED is not used, it
should be replaced with an equivalent resistor (typically
500

to 1000

) such that the battery loading remains at

10 mA.

I/O. A connection is provided at pin 2 to allow multiple
smoke detectors to be commoned. If any single unit
detects smoke (I/O is driven high), all connected units will
sound their associated horns after a nominal 3 second
delay. The LED is suppressed when an alarm is signaled
from an interconnected unit.

Testing. On power up, all internal counters are reset.
Internal test circuitry allows for low battery check by
holding pins 8 and 12 low during power up, then reducing
V

and monitoring HORN

(pin 10). All functional tests

can be accelerated by driving pin 12 with a 2 kHz square
wave. The 10 ms strobe period must be maintained for
proper operation of the comparator circuitry.

CIRCUIT DESCRIPTION

Dwg. WC-003-1

TYPICAL APPLICATION

TIMING DIAGRAMS IN TYPICAL APPLICATION

NOTE 1: An external resistor divider is used to adjust sensitivity for the particular

smoke chamber.

NOTE 2: A resistor to ground or V

may be added to this pin to modify low

battery voltage threshold.

1.67 s

10 ms

40 ms

24 CLOCK CYCLES

V15 < V13 (NO SMOKE)

V15 > V13 (SMOKE)

V12

OSC. CAP

INTERNAL

CLOCK

LED

SMOKE

COMPARATOR

SMOKE

CHAMBER

HORN

SAMPLE

ALARM

NO LOW BATTERY

30 CLOCK CYCLES

LOW BATTERY
WARNING

HORN

OFF

ALARM AND

LOW BATTERY

NO ALARM

LOW BATTERY

24 CLOCK CYCLES

LED OFF

LED
ON

12 CLOCK CYCLES

6 CLOCK CYCLES

NO ALARM

NO LOW BATTERY

STANDBY MODE

OTHER

UNITS

NOTE 1

NOTE

LOGIC

OSC. &
TIMING

HORN

DRIVER

Dwg. EC-005-5

9 V

200 k

200

8.2 M

0.1

1 M

330 k

PUSH

TEST

0.001

330

4.7 M

200 k

5355
SMOKE DETECTOR
WITH INTERCONNECT

Part Number 5355