A5350CA - Allegro MicroSystems, LLC

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information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-

sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.

Recommended Substitutions:

Ionization Smoke Detector with Interconnect

A5350

Date of status change: November 2, 2009

These parts are no longer in production The device should not be

purchased for new design applications. Samples are no longer available.

Discontinued Product

Description

The A5350 is a low-current, BiCMOS 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 their alarm. In addition, special features are

incorporated to facilitate alignment and test of the finished

smoke detector.

The internal oscillator and timing circuitry keep standby power

to a minimum by powering down the device for 1.66 seconds

and sensing for smoke for only 10 ms. Every 24 on-off cycles,

a check is made for a 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 A5350 is supplied in a low-cost 16-pin dual in-line plastic

package (DIP). It is rated for continuous operation over the

temperature range of –10°C to 60°C. The Pb (lead) free version

(suffix –T) has 100% matte tin leadframe plating.

26110.5 Rev. 5

Features and Benefits

▪ Low average standby current for long battery life

▪ Interconnect up to 125 detectors

▪ Piezoelectric horn driver

▪ Guard outputs for detector input

▪ Pulse testing for low battery

▪ Power-on reset (POR)

▪ Internal reverse battery protection

▪ Inverted alarm polarity on DETECT IN

Ionization Smoke Detector with Interconnect

Typical Application

A5350

I/O

LOW-V SET

LED

VDD

TIMING RES

FEEDBACK

GUARD2

DETECT IN

GUARD1

SENSITIVITY SET

OSC CAP

HORN2

HORN1

VSS

To / from

other units

200 kΩ

200 Ω

8.2 MΩ

1μF

0.1 μF

1.5 MΩ

4.7 MΩ

200 k Ω

220 kΩ

Push

to Test

0.001 μF

330 Ω

9 V

Use an external resistor divider to set

sensitivity for a particular smoke chamber.

A resistor to VSS or VDD may

be added to this pin to modify

low battery voltage threshold.

Value of component will vary, based on

the piezoelectric horn used.

4.7 MΩ

Package: 16-pin DIP (suffix A):

Not to scale

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Characteristic Symbol Test Conditions* Value Units

Package Thermal Resistance RθJA 4-layer PCB based on JEDEC standard 38 ºC/W

*Additional thermal information available on Allegro website.

Number Name Function

1NC No connection

2 I/O Input/output to interconnected detectors

3LOW-V SET Optionally used with a resistor to adjust low-battery

threshold

4NC No connection

5LED Output to drive visible LED

6VDD Positive supply voltage

7TIMING RES Terminal for timing resistor, sets internal bias

(affects timing)

8FEEDBACK Input for driving piezoelectric horn

9VSS Negative supply voltage

10 HORN1 Output for driving piezoelectric horn

11 HORN2 Complementary output for driving piezoelectric horn

12 OSC CAP Terminal for charging/discharging an external

capacitor to run the oscillator

13 SENSITIVITY SET Used with a resistor divider to externally set

sensitivity for a specific chamber

14 GUARD1 Active guard 1 for detector input

15 DETECT IN Input from detector chamber

16 GUARD2 Active guard 2 for detector input

I/O

LOW-V SET

LED

VDD

TIMING RES

FEEDBACK

GUARD2

DETECT IN

GUARD1

SENSITIVITY SET

OSC CAP

HORN2

HORN1

VSS

Selection Guide

Part Number Pb-Free Packing

A5350CA-T* Yes 25 pieces per tube

A5350CA –

*Variant is in production but has been determined to be NOT FOR NEW DESIGN. This classifi-

cation indicates that sale of the variant is currently restricted to existing customer applications.

The variant should not be purchased for new design applications because obsolescence in the

near future is probable. Samples are no longer available. Status change: May 4, 2009.

Absolute Maximum Ratings*

Characteristic Symbol Notes Rating Units

Supply Voltage Range VDD Referenced to VSS –0.5 to 15 V

Input Voltage Range VIN Referenced to VSS –0.3 to VDD+ 0.3 V

Reverse Battery Condition Duration tRBAT 10.5 V 20 s

Input Current IIN 10 mA

Operating Ambient Temperature TA–10 to 60 ºC

Junction Temperature TJ(max) 150 ºC

Storage Temperature Range Tstg –55 to 125 ºC

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

Terminal List Table

Pin-out Diagram

Thermal Characteristics

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Functional Block Diagram

Low Battery

Logic

Oscillator

and Timing

Power-on

Reset

+ VDD

VDD

I/O

FEEDBACK

HORN1

HORN2

LED

TIMING RES

OSC CAP

GUARD2GUARD1

SENSITIVITY SET

LOW-V SET

+Supply

VSS

-Supply

+ VDD

600 kΩ

500 kΩ

1.1

MΩ

Smoke

Comparator

ION CHAMBER

Band

Gap

Low Battery

Sample

Smoke

Sample

LBSamp

SSamp

DETECT IN

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

ELECTRICAL CHARACTERISTICS1,2 at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSCCAP = 0.1 μF,

RTIMINGRES = 8.2 MΩ (unless otherwise noted)

Continued on the next page…

Characteristic Symbol Test Conditions Test Pin Min. Typ. Max. Units

Supply Voltage Range VDD Operating 6 6.0 9.0 12 V

Supply Current IDD

VDD = 9.0 V, no alarm, no loads 6 — 5.0 9.0 μA

VDD = 12 V, no alarm, no loads 6 — — 12 μA

Detector Input Current IDETECTIN 0% to 40% RH, VIN = 0 to 9.0 V 15 — — ±1.0 pA

Input Offset Voltage

VOS(GUARD1) Active GUARD1 14, 15 — — ±100 mV

VOS(GUARD2) Active GUARD2 16, 15 — — ±100 mV

VOS Detect comparator 15, 13 — — ±50 mV

Common Mode Range VCM(guard) Guard ampliﬁ er 14, 15 2.0 — VDD – 0.5 V

VCM Smoke comparator 13, 15 0.5 — VDD – 2.0 V

Active Guard Impedance ZAG1 GUARD1 to VSS 14 — 10 — kΩ

ZAG2 GUARD2 to VSS 16 — 500 — kΩ

Oscillator Period tosc No alarm 12 1.34 1.67 2.00 s

tosc(alarm) Local or remote alarm 12 37.50 41.67 45.84 ms

Oscillator Pulse Width tw(osc) 12 8.0 10 12 ms

Low-Battery Threshold VDD(th)

TA = 0°C to 50°C,

LOW-V SET open circuit 6 7.2 — 7.8 V

Horn Output Voltage

VOL

IOUT = 16 mA, VDD = 9.0 V 10, 11 — 0.1 0.5 V

IOUT = 16 mA, VDD = 7.2 V 10, 11 — — 0.9 V

VOH

IOUT = –16 mA, VDD = 9.0 V 10, 11 8.5 8.8 — V

IOUT = –16 mA, VDD = 7.2 V 10, 11 6.3 — — V

Horn Output On-Time ton(horn) Local or remote alarm 10,11 120 160 208 ms

tw(horn) Low battery 10, 11 8.0 10 12 ms

Horn Output Off-Time toff(horn) Local or remote alarm 10, 11 60 80 104 ms

thorn Low battery 10, 11 32 40 48 s

LED Output-On Current ILED VDD = 7.2 V, VLED = 1.0 V 5 10 — — mA

LED Output On-Time tw(LED) 5 8.0 10 12 ms

LED Output Off-Time

tLED1 No alarm, in standby 5 32 40 48 s

tLED3 Local alarm or test alarm 5 0.76 0.97 1.14 s

tLED4 Remote alarm, no local smoke 5 — No LED

pulses —s

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

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 VDD to an internal reference. Because very-low currents

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.

An active guard is provided on GUARD1 and GUARD2, the two

pins adjacent to the detector input, the DETECT IN pin. VGUARD1

and VGUARD2 will be within 100 mV of VDETECTIN. This will

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

Circuit Description

Characteristic Symbol Test Conditions Test Pin Min. Typ. Max. Units

I/O Current IIOL No alarm, VI/O = VDD – 2.0 V 2 25 — 60 μA

IIOH Local alarm, VI/O = VDD – 2.0 V 2 –7.5 — — mA

I/O Alarm Voltage VIH(IO) External “alarm” in 2 3.0 — — V

I/O Delay tr(io) Local or test alarm to I/O active 2 — 3.0 — s

1Negative current is deﬁ ned as coming out of the speciﬁ ed device pin (sourcing).

2Alarm (smoke) condition is deﬁ ned as VDETECTIN > VSENSITIVITYSET; no alarm (no smoke) condition is deﬁ ned as VDETECTIN < VSENSITIVITYSET.

ELECTRICAL CHARACTERISTICS1,2 (continued) at TA = 25°C, VDD = 9.0 V, VSS = 0 V, COSCCAP = 0.1 μF,

RTIMINGRES = 8.2 MΩ (unless otherwise noted)

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

SENSITIVITY SET pin to a resistor divider connected between

the VDD and VSS pins.

Low Battery

The low battery condition threshold is set internally by a voltage

divider connected between VDD and VSS. The threshold can

be externally adjusted by connecting a resistor between the

LOW-V SET pin and either the VDD or VSS pins.

To increase the threshold, a resistor can be connected between

LOW-V SET and VSS. Given an initial threshold, V(th)init (nomi-

nally 7.5 V), and a target threshold, V(th)set

, the resistor should

have the value:

RLOWVSET = 600E3 × K / (1 – 0.375 × K) ,

where

K = 1 / (V(th)set / [0.727 × V(th)init] – 1) .

To decrease the threshold, a resistor can be connected between

LOW-V SET and VDD. Given an initial threshold, V(th)init (nomi-

nally 7.5 V), and a target threshold, V(th)set

, the resistor should

have the value:

RLOWVSET = 960E3 × K / (0.6 – 1.6 × K) ,

where

K = V(th)set / (0.727 × V(th)init) – 1 .

The battery voltage level is checked approximately every 40 sec-

onds during the (approximately) 10 mA, 10 ms LED pulse. If an

LED is not used, it should be replaced with an equivalent resistor

(typically 500 to 1000 Ω) such that the battery loading remains

about 10 mA.

I/O

A connection to the I/O pin allows multiple smoke detectors to

be interconnected. If any single unit detects smoke, its I/O pin is

driven high (after a nominal 3 s delay), and all connected units

will sound their associated horns. When the I/O pin is driven

high by another device, the oscillator immediately speeds up to

its 41.7 ms period. The remainder of the sped-up clock cycle,

and two additional consecutive clock cycles with I/O high are

required to cause an alarm. If the I/O pin falls below its threshold

at any time during those (approximately) 83.4 ms, an internal

latch is reset and there will not be an alarm. Thus, the I/O must

remain high for (approximately) 93.9 ms in order to cause an

alarm. This filtering provides significant immunity to I/O noise.

The LED is suppressed when an alarm is signaled from an

interconnected unit, and any local alarm condition causes the I/O

pin to be ignored as an input. This pin has an on-chip pulldown

device and must be left unconnected if not used.

Testing

On power-up, all internal counters are reset. Internal test cir-

cuitry allows low battery check by holding the FEEDBACK and

OSC CAP pins low during power-up, then reducing VDD and

monitoring the HORN1 pin. HORN1 will be driven high when

VDD falls below the low-battery threshold. All functional tests

can be accelerated by driving the OSC CAP pin with a 2 kHz

square wave. The 10 ms strobe period must be maintained for

proper operation of the comparator circuitry.

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Timing Diagrams

(Not to scale)

OSC CAP Pin

Internal Clock

LED Pin

Smoke Sample

St andby Mode

Low Battery Test

tosc tw( osc)

tled1

LED on

tw(led)

Test event

VDD Pin

LED Pin

Horn Enable

Low Bat ter y Condi ti on

(Low battery)

tled1 tw(led)

LED off (high-Z) tw(horn)

thorn

LED on

LED off (high-Z)

Low Battery Test

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

OSC CAP Pin

Internal Clock

LED Pin

Smoke Sample

Horn Enable

tosc(alarm)

6 clock cycles

Local Smoke Detect i on/ Test Alar m Condi t i on

I/O Pin

tr(io)

(Output)

tw(osc)

ton(horn) toff(horn)

tled3 tw(led)

LED Pin

LED off (high-Z)

LED on

VDETECTIN > V SEN SIT IVITYSET (smoke) (no smoke )

Smoke Chamber

Smoke Sample

Horn Enable

I/O Pin

Remote Ala r m Cond it ion

(Input)

LED Pin ton(horn) toff(horn)

OSC CAP Pin

Internal Clock

tosc(alarm)

tw(osc)

I/O Pin

Test event

LED off (high-Z)

Ionization Smoke Detector with Interconnect

A5350

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

The products described here are manufactured under one or more U.S. patents or U.S. patents pending.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per-

mit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the

information being relied upon is current.

Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the

failure of that life support device or system, or to affect the safety or effectiveness of that device or system.

The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use;

nor for any in fringe ment of patents or other rights of third parties which may result from its use.

For the latest version of this document, visit our website:

www.allegromicro.com

Allegro MicroSystems, Inc.

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Allegro MicroSystems offers an industry-leading range of ionization

and photoelectric smoke detector ICs. For a current listing, please visit

our website at:

www.allegromicro.com

Package A, 16-Pin DIP

Branded Face

10.92 MAX

0.38 MIN

5.33 MAX

+0.51

–0.38

0.13 MIN

SEATING

PLANE

16X 0.25 M C

2.54 BSC

7.62 BSC

Terminal #1 mark area

+0.25

–0.38

1.52

3.30

+1.65

–0.38

3.30

+0.76

–0.25

6.35

0.46±0.10

+0.64

–0.38

19.05 +0.10

–0.05

0.25

For Reference Only; not for tooling use (reference MS-001BB)

Dimensions in millimeters

Dimensions exclusive of mold flash, gate burrs, and dambar protrusions

Exact case and lead configuration at supplier discretion within limits shown