MC14468P - Freescale Semiconductor / Motorola

Document Number: MC14468

Rev 5.0, 11/2006

Freescale Semiconductor

Technical Data

Low-Power CMOS Ionization Smoke

Detector IC with Interconnect

The MC14468, when used with an ionization chamber and a small number of

external components, will detect smoke. When smoke is sensed, an alarm is

sounded via an external piezoelectric transducer and internal drivers. This circuit

is designed to operate in smoke detector systems that comply with UL217 and

UL268 specifications.

Features

• Ionization Type with On-Chip FET Input Comparator

• Piezoelectric Horn Driver

• Guard Outputs on Both Sides of Detect Input

• Input-Production Diodes on the Detect Input

• Low-Battery Trip Point, Internally Set, can be Altered Via External Resistor

• Detect Threshold, Internally Set, can be Altered Via External Resistor

• Pulse Testing for Low Battery Uses LED for Battery Loading

• Comparator Output for Detect

• Internal Reverse Battery Protection

• Strobe Output for External Trim Resistors

• I/O Pin Allows Up to 40 Units to be Connected for Common Signaling

• Power-On Reset Prevents False Alarms on Battery Change

• Pb-Free Packaging Designated by Suffix Code ED

ORDERING INFORMATION

Device Temperature

Range Case No. Package

MC14468P –10° to 60°C648-08 Plastic Dip

MC14468ED

MC14468

LOW-POWER CMOS

IONIZATION SMOKE

DETECTOR IC

WITH INTERCONNECT

P SUFFIX

ED SUFFIX (PB-FREE)

16-LEAD PLASTIC DIP

CASE 648-08

DETECT

COMP. OUT

I/O

LOW V SET

STROBE

OUT

LED

TIMING

RESISTOR

FEEDBACK

GUARD HI-Z

DETECT INPUT

GUARD LO-Z

SENSITIVITY

SET

OSC

CAPACITOR

SILVER

BRASS

VSS

VDD

Figure 1. Pin Connections

Sensors

2Freescale Semiconductor

MC14468

Figure 2. Block Diagram

Table 1. Maximum Ratings(1)

(Voltages referenced to VSS)

1. Maximum Ratings are those values beyond which damage to the device may occur. This device contains circuitry to protect the inputs against

damage due to high static voltages or electric fields; however, it is advised normal precautions be taken to avoid application of any voltage

higher than maximum rated voltages to this high impedance circuit. For proper operation it is recommended VIN and VOUT be constrained to

the range VSS ≤ (VIN or VOUT) ≤ VDD.

Rating Symbol Value Unit

DC Supply Voltage VDD –0.5 to +15 V

Input Voltage, All Inputs Except Pin 8 VIN –0.25 to VDD + 0.25 V

DC Current Drain per Input Pin, Except Pin 15 = 1 mA I 10 mA

DC Current Drain per Output Pin I30 mA

Operating Temperature Range TA–10 to +60 °C

Storage Temperature Range TSTG –55 to +125 °C

Reverse Battery Time tRB 5.0 s

–

To Other Units

I/O FEEDBACKVDDVDD 28

45 K

325 K

LOW V SET

DETECT

COMPARATOR OUT

STROBE OUT

280 K

Low-Battery

Comparator

Detect

Comparator

DETECT INPUT

Guard

Amp 14

VDDLO-Z HI-Z

Alarm

Logic

Power-On

Reset

OSC

and

Timing

SILVER

BRASS

5LED

VDD = Pin 6

VSS = Pin 9

VDD

12 7

Sensors

Freescale Semiconductor 3

MC14468

Table 2. Recommended Operating Conditions

(Voltages Referenced to VSS)

Parameter Symbol Value Unit

Supply Voltage VDD 9.0 V

Timing Capacitor —0.1 µF

Timing Resistor —8.2 MΩ

Battery Load (Resistor or LED) —10 mA

Table 3. Electrical Characteristics

(TA = 25°C)

Characteristic Symbol VDD

VDC Min Type(1)

1. Data labelled “Typ'' is not to be used for design purposes, but is intended as an indication of the IC's potential performance.

Max Unit

Operating Voltage VDD —6.0 —12 V

Output Voltage

Piezoelectric Horn Drivers (IOH = –16 mA)

Comparators (IOH = –30 µA)

Piezoelectric Horn Drivers (IOL = +16 mA)

Comparators (IOL = +30 µA)

VOH

VOL

7.2

9.0

7.2

9.0

6.3

8.5

—

8.8

—

0.1

—

0.9

0.5

Output Voltage — LED Driver, IOL = 10 mA VOL 7.2 — — 3.0 V

Output Impedance, Active Guard

Pin 14

Pin 16 LO-Z

HI-Z 9.0

9.0 —

——

—10

1000

kΩ

Operating Current (RBIAS = 8.2 MΩ) IDD 9.0

12.0 —

—5.0

—9.0

12.0 µA

Input Current — Detect (40% R.H.) IIN 9.0 — — ±1.0 pA

Input Current, Pin 8 IIN 9.0 — — ±0.1 µA

Input Current @ 50°C, Pin 15 IIN — — — ±6.0 pA

Internal Set Voltage

Low Battery

Sensitivity VLOW

VSET

9.0

—7.2

47 —

50 7.8

53 V

%VDD

Hysteresis VHYS 9.0 75 100 150 mV

Offset Voltage (Measured at VIN = VDD/2)

Active Guard

Detect Comparator

VOS 9.0

9.0 —

——

—±100

±50

Input Voltage Range, Pin 8 VIN — VSS – 10 — VDD + 10 V

Input Capacitance CIN — — 5.0 —pF

Common Mode Voltage Range, Pin 15 VCM —0.6 — VDD – 2 V

I/O Current, Pin 2

Input, VIH = VDD –2

Output, VOH = VDD –2 IIH

IOH

—

—25

–4.0 —

—100

–16 µA

Sensors

4Freescale Semiconductor

MC14468

Table 4. Timing Parameters

(C = 0.1 µF, Rbias = 8.2 MΩ, VDD = 9.0 V, TA = 25°C, See Figure 7)

Characteristics Symbol Min Typ(1)

1. Data labelled “Typ'' is not to be used for design purposes, but is intended as an indication of the IC's potential performance.

Max Units

Oscillator Period No Smoke

Smoke tCI 1.34

32 1.67

40 20

48 s

Oscillator Rise Time tR8.0 10 12 ms

Horn Output On Time

(During Smoke) Off Time PWON

PWOFF

120

60 160

80 208

104 ms

LED Output Between Pulses

On time tLED

PWON

8.0 40

10 48

12 s

Horn Output On Time

(During Low Battery) Between Pulses tON

tOFF

8.0

32 10

40 12

48 ms

Figure 3. Typical LED Output

I-V Characteristic Figure 4. Typical Comparator Output

I-V Characteristic

Figure 5. Typical P Horn Driver Output

I-V Characteristic

012345678910

0.1

1.0

10.0

100.0

VDS, Drain To Source Voltage (Vdc)

VDD = 7.2 Vdc

VDD = 9.0 Vdc TA = 25°C

012345678910

0.01

0.1

1.0

10.0

VDS, Drain To Source Voltage (Vdc)

ID, Drain Current (mA)

ID, Drain current (mA)

TA = 25°C

VDD = 9.0 Vdc or 7.2 Vdc

P-CH Source

and N-CH

Sink Current

012345678910

1.0

10.0

100.0

1000.0

VDS, Drain To Source Voltage (Vdc)

ID, Drain current (mA)

VDD = 7.2 Vdc

VDD = 9.0 Vdc

TA = 25°C

P-CH Source Current

TA = 25°C

012345678910

1.0

10.0

100.0

1000.0

VDS, Drain To Source Voltage (Vdc)

ID, Drain current (mA)

VDD = 7.2 Vdc

VDD = 9.0 Vdc

N-CH Sink Current

012345678910

Sensors

Freescale Semiconductor 5

MC14468

DEVICE OPERATION

Timing

The internal oscill ator of the MC144 68 operates with a

period of 1.67 seconds during no-smoke conditions. Each

1.67 seconds, internal power is applied to the entire IC and a

check is made for smoke, except during LED pulse, Low

Battery Alarm Chirp, or Horn Modulation (in smoke). Every 24

clock cycles a check is made for low battery by comparing

VDD to an internal zener voltage. Since very small currents

are used in th e oscillator , the oscillator cap acitor should be of

a low leakage type.

Detect Circuitry

If smoke is detected, the oscillator period becomes 40 ms

and the piezoelectric horn oscillator circuit is enabled. The

horn output is modulated 160 ms on, 80 ms off. During the off

time, smoke is again checked and will inhibit further horn

output if no smoke is sensed. During local smoke conditions

the low battery alarm is inhibite d, but the LED pulses at a

1.0 Hz rate. In remote smoke, the LED is inhibited as well.

An active guard is provided on both pins adjacent to the

detect input. The voltage at these pins will be within 100 mV

of the input signal. This will keep surface leakage currents to

a minimum and provide a method of measuring the input

voltage without loading the ioni zation chamber. The active

guard op amp is not power strobed and thus give s constant

protecti on fro m surface leakage currents. Pin 15 (the Detect

input) has internal diode protection ag ainst static damage.

Interconnect

The I/O (Pin 2), in combination with VSS, is used to

interconnect up to 40 remote units for common signaling. A

Local Smoke condition activates a current limited output

driver, thereby sign aling Remote Smoke to interconnected

units. A small current sink improves noise immunity during

non-smoke conditions. Remote units at lower voltages do not

draw excessive current from a sending unit at a higher

voltage. The I/O is disabled for three oscillator cycles after

power up, to eliminate false alarming of remote units when

the battery is changed.

Sensitivity/Low Battery Thresholds

Both the sensitivity threshold and the low batte ry voltage

levels are s et internal ly by a common voltag e divider (pl ease

see Figure 2) connected between VDD and VSS. These

voltages can be altered by external resistors connected from

pins 3 or 13 to either VDD or VSS. There will be a slight

interaction here due to the common voltage divider network.

The sensitivity threshold can also be set by adjusting the

smoke chamber ionization source.

Test Mode

Since the internal op amps and comparators are power

strobed, adjustments for sensitivity or low battery level could

be difficult and/or time-consuming. By forcing Pin 12 to VSS,

the power strobing is bypassed and the output, Pin 1,

constantly shows smoke/no smoke. Pin 1 = VDD for smoke.

In this mode and during the 10 ms power strobe, chip current

rises to approximately 50 µA.

LED Pulse

The 9-volt battery level is checked every 40 seconds

during the LED pulse. The battery is loaded via a 10 mA

pulse for 10 ms. If the LED is not used, it should be replaced

with an equivalent resistor such that the battery loading

remains at 10 mA.

Hysteresis

When smoke is detected, the resistor/divider network that

sets sensitivity is altered to increase sensitivity. This yields

approximately 100 mV of hysteresis and reduces false

triggering.

Figure 6. Typical Application as Ionization Smoke Detector

MC14468

116

Test

+9 V

8.2 MΩ

330 Ω

1.5 MΩ*220 kΩ*

0.1 µF

1 M 1 M

0.1 µF

0.001 µF

*Note: Component values may change

Other

Units

depending on type of piezoelectric horn used.

Sensors

6Freescale Semiconductor

MC14468

Figure 7. Timing Diagram

Notes:

1. Horn modulation is self-completing. When going from smoke to no smoke, the alarm condition will terminate only when horn is off.

2. Comparators are strobed on once per clock cycle (1.67 s for no smoke, 40 ms for smoke).

3. Low battery comparator information is latched only during LED pulse.

4. ~ 100 mV p-p swing.

HYSTERESIS (Internal)

(Pin 13) (Pin 14)

DETECT OUT

(Pin 1)

LOW BATTERY

(Internal)

SAMPLE (Internal)

Smoke

HORN

(Pin 10 and 11)

Low = Disable

High = Enable

LED

(Pin 5)

OSCILLATOR

(Pin 12)

Smoke/No Low Battery Smoke/Low Battery No Smoke/Low Battery

40 ms 10 ms 1.67 s

Standby

No Smoke/

No Low Battery

24 Clock Cycles (0.96 s)

24 Clock Cycles

(40S) 24 Clock Cycles 6 Clock

Suppressed Chirp

Battery Test

(Note 3) (Note 3)

(Note 1)

Cycles (10.0 s)

STROBE OUT

(Pin 14)

I/O (Pin 2)

Output (Local)

I/O (Pin 2)

Input (Remote)

LED

Note: Horn Modulation Not Self-Completing

(Suppressed LED for Remote Only)

Sensors

Freescale Semiconductor 7

MC14468

PACKAGE DIMENSIONS

CASE 648-08

ISSUE T

16-LEAD PLASTIC DIP

Sensors

8Freescale Semiconductor

MC14468

REVISION HISTORY

REVISION DATE DESCRIPTION OF CHANGES

5.0 11/2006 • Implemented Revision History page

• Converted to Freescale format

• Added part number MC14468ED to Ordering Information.

How to Reach Us:

Home Page:

www.freescale.com

Web Support:

http://www.freescale.com/support

USA/Europe or Locations Not Listed:

Freescale Semiconductor, Inc.

Technical Information Center, EL516

2100 East Elliot Road

Tempe, Arizona 85284

+1-800-521-6274 or +1-480-768-2130

www.freescale.com/support

Europe, Middle East, and Africa:

Freescale Halbleiter Deutschland GmbH

Technical Information Center

Schatzbogen 7

81829 Muenchen, Germany

+44 1296 380 456 (English)

+46 8 52200080 (English)

+49 89 92103 559 (German)

+33 1 69 35 48 48 (French)

www.freescale.com/support

Japan:

Freescale Semiconductor Japan Ltd.

Headquarters

ARCO Tower 15F

1-8-1, Shimo-Meguro, Meguro-ku,

Tokyo 153-0064

Japan

0120 191014 or +81 3 5437 9125

support.japan@freescale.com

Asia/Pacific:

Freescale Semiconductor Hong Kong Ltd.

Technical Information Center

2 Dai King Street

Tai Po Industrial Estate

Tai Po, N.T., Hong Kong

+800 2666 8080

support.asia@freescale.com

For Literature Requests Only:

Freescale Semiconductor Literature Distribution Center

P.O. Box 5405

Denver, Colorado 80217

1-800-441-2447 or 303-675-2140

Fax: 303-675-2150

LDCForFreescaleSemiconductor@hibbertgroup.com

MC14468

Rev. 5.0

11/2006

Information in this document is provided solely to enable system and software

implementers to use Freescale Semiconduct or products. There are no express or

implied copyright licenses granted hereunder to design or fabricate any integrated

circuits or integrated circuits based on the information in this document .

Freescale Semiconductor reserves the ri ght to make changes without further notice to

any products herein. Freescale Semiconductor makes no warranty, representation or

guarantee regarding the suitability of its products for any p articular purpose, nor does

Freescale Semiconductor assume any liability arising out of the application or use of any

product or circuit, and specifically disclaims any and all liability, including without

limitation consequen tial or incidental damages. “Typical” parameters that may be

provided in Freescale Se miconductor data sheets and/or specifications can and do vary

in different applications and actual performance may vary over time. All operating

parameters, includin g “Typicals”, must be validated for each customer application by

customer’s technical experts . Freescale Semiconductor does not convey any license

under its patent rights nor the rights of others. Freescale Semiconductor products are

not designed, intended, or authorized for use as components in systems intended for

surgical implant into the body, or other applications intended to support or sustai n life,

or for any other application in which th e failure of th e Freescale Semiconductor product

could create a situation where personal injury or death may occur. Should Buyer

purchase or use Freescale Semiconductor products for any such unintended or

unauthorized application, Buyer shall indemn ify and hold Freescale Semiconductor and

its officers, employees, subsidiaries, affiliates, and distributors harmless against all

claims, costs, damages, and expenses, and reasonable attorney fee s arising out of,

directly or indirectly, any claim of personal injury or deat h associa ted with such

unintended or unauthorized use, even if such claim alleges that Fr eescale

Semiconductor was negligent regarding the design or manufacture of the p art.

Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc.

All other product or service names are the property of their respective owners.

RoHS-compliant and/or Pb-free versions of Freescale products have the functionality

and electrical characterist ics of their non-RoHS-compliant and/or non-Pb-free

counterparts. For further information, see http://www.freescale.com or contact your

Freescale sales representative.

For information on Freescale’s Environmental Products program, go to http://