SMOKE DETECTOR

WITH INTERCONNECT AND TIMER

The A5348CA 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 A5348CA 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

Internal Timer & Control for Reduced Sensitivity

Built-In Hysteresis Reduces False Triggering

Always order by complete part number:

A5348CA .

Data Sheet

26110.3

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.

LOGIC

OSC. &
TIMING

HORN

DRIVER

GUARD

DETECT. IN

GUARD

SENSITIVITY
SET

OSC. CAP.

HORN

SUPPLY

TIMER START

I / O

LOW-V SET

TIMER OUT

LED

+ SUPPLY

TIMING RES.

FEEDBACK

Dwg. PC-004

5348

Test

Continued next page . . .

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

Hysteresis

No Alarm to Alarm

130

170

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

Timer Period

After Pin 1 High-to-Low, No Smoke

8.0

min

Low Voltage Threshold

= 0 to 50

7.2

7.8

Sensitivity Adj. Voltage

, pin 13 open circuit

48.5

51.5

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

Timer Start Logic Levels

3.5

1.5

Timer Start Input Current

= 9.0 V

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

5348
SMOKE DETECTOR
with INTERCONNECT
and TIMER

5348
SMOKE DETECTOR
with INTERCONNECT
and TIMER

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

Limits

Characteristic

Pin

Test Conditions

Min.

Typ.

Max.

Units

ELECTRICAL CHARACTERISTICS continued

Timer Out Output Current

OUT

= 0.5 V

500

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

No Alarm, Timer Mode After Pin 1

High-to-Low

8.0

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

Test

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

CIRCUIT DESCRIPTION

The A5348CA 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, 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 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.

TYPICAL APPLICATION

Sensitivity Adjust. The detector sensitiv-
ity to smoke is set internally by a voltage
divider connected between V

and V

. The

sensitivity can be externally adjusted to the
individual characteristics of the ionization
chamber by connecting a resistor between pin
13 and V

, or 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 de-

creased 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.

Timer. An internal timer is provided that
can be used in various configurations to allow
for a period of reduced smoke detector
sensitivity ("hush"). When a high-to-low
transition occurs at pin 1, the internal timer is
reset, the timer mode enabled, and the circuit
reset to a no alarm condition. The LED will
flash at a 10 second rate. If the level of
smoke is increased such that the reduced
sensitivity level is reached, the device will go
into the alarm condition. The timer, how-
ever, will continue to completion of the
nominal 10-1/4 minute period (368 clock
cycles). If the timer mode is not used, pin 1
should be tied low.

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.

NOTE 1:Use an external resistor to adjust sensitivity for a particular

smoke chamber.

NOTE 2:Select resistor to reduce sensitivity during timer mode.

NOTE 3:A resistor to ground or V

may be added to this pin to modify

low battery voltage threshold.

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.

TIMER
MODE

OTHER

UNITS

NOTE

LOGIC

OSC. &
TIMING

HORN

DRIVER

Dwg. EC-005A

9 V

NOTE 2

200 k

50 k

200 k

200

8.2 M

0.1

1 M

200 k

PUSH

TEST

0.001

330

5348
SMOKE DETECTOR
with INTERCONNECT
and TIMER

5348
SMOKE DETECTOR
with INTERCONNECT
and TIMER

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

TIMING DIAGRAMS IN TYPICAL APPLICATION

NON-TIMER MODE

TIMER MODE

1.67 s

10 ms

V12

OSC. CAP

INTERNAL

CLOCK

LED

HORN

Dwg. WC-005

LED
ON

TIMER

START

TIMER

OUT

6 CLOCK CYCLES

368 CLOCK CYCLES

END OF TIMER
NOTIFICATION

OUTPUTS OFF (HIGH Z)

NO ALARM

NO LOW BATTERY

STANDBY MODE

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

Dwg. WC-003

24 CLOCK CYCLES

LED OFF

LED
ON

12 CLOCK CYCLES

6 CLOCK CYCLES

5348
SMOKE DETECTOR
with INTERCONNECT
and TIMER

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

NOTES:

1. Lead thickness is measured at seating plane or

below.

2. Lead spacing tolerance is non-cumulative.
3. Exact body and lead configuration at vendor's

option within limits shown.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, such departures from the detail

specifications as may be required to permit improvements in the design of its products.

The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems,

Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties
which may result from its use.

Dimensions in Inches

(controlling dimensions)

Dimensions in Millimeters

(for reference only)

0.014
0.008

0.300

BSC

Dwg. MA-001-16A in

0.430

MAX

0.280
0.240

0.210

MAX

0.070
0.045

0.015

MIN

0.022
0.014

0.100

BSC

0.005

MIN

0.150
0.115

0.775
0.735

0.355
0.204

7.62

BSC

Dwg. MA-001-16A mm

10.92

MAX

7.11
6.10

5.33

MAX

1.77
1.15

0.39

MIN

0.558
0.356

2.54

BSC

0.13

MIN

3.81
2.93

19.68
18.67

Part Number A5348CA