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RE46C190
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Datasheet RE46C190 Datasheet

RE46C190
RE46C190
SOIC
V
SS
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
IRED
V
DD
TEST
TEST2
IRP
IRN
RLED
LX
V
BST
HS
HB
IO
IRCAP
FEED
GLED
CMOS Low Voltage Photoelectric Smoke Detector ASIC
with Interconnect and Timer Mode
Features
• Two AA Battery Operation
• Internal Power On Reset
• Low Quiescent Current Consumption
• Available in 16L N SOIC
• Local Alarm Memory
• 9 Minute Timer for Sensitivity Control
• Temporal or Continuous Horn Pattern
• Internal Low Battery and Chamber Test
• All Internal Oscillator
• Internal Infrared Emitter Diode (IRED) driver
• Adjustable IRED Drive current
• Adjustable Hush Sensitivity
• 2% Low Battery Set Point
Description
The RE46C190 is a low power, low voltage CMOS photoelectric type smoke detector IC. With minimal external components, this circuit will provide all the required features for a photoelectric-type smoke detector.
The design incorporates a gain-selectable photo amplifier for use with an infrared emitter/detector pair.
An internal oscillator strobes power to the smoke detection circuitry every 10 seconds, to keep the standby current to a minimum. If smoke is sensed, the detection rate is increased to verify an Alarm condition. A high gain mode is available for push button chamber testing.
A check for a low battery condition is performed every 86 seconds, and chamber integrity is tested once every 43 seconds, when in Standby. The temporal horn pat­tern supports the NFPA 72 emergency evacuation sig­nal.
An interconnect pin allows multiple detectors to be connected such that, when one unit alarms, all units will sound.
An internal 9 minute timer can be used for a Reduced Sensitivity mode.
Utilizing low power CMOS technology, the RE46C190 was designed for use in smoke detectors that comply with Underwriters Laboratory Specification UL217 and UL268.
PIN CONFIGURATION
2010 Microchip Technology Inc. DS22271A-page 1
RE46C190
Control
Logic and
Timing
Trimmed Oscilator
POR and
BIAS
+
-
+
-
VDD (3)
IRCAP (11)
IRN (7)
IRED (2)
TEST (4)
R4
R3
LX (16)
FEED (10)
HS (14)
V
BST
(15)
RLED (8)
GLED (9)
HB (13)
IRP (6)
VSS (1)
Interconnect
+
-
Programmable
IRED Current
Programmable
Limits
Photo
Integrator
Precision
Reference
+
-
TEST2 (5)
Horn Driver
Level
Shift
IO (12)
Current
Sense
Boost Control
Boost Comparator
Low Battery Comparator
Smoke
Comparator
Programming
Control
High
Normal
Hysteresis
TYPICAL BLOCK DIAGRAM
DS22271A-page 2 2010 Microchip Technology Inc.
TYPICAL BATTERY APPLICATION
Note 1: C2 should be located as close as possible to the device power pins, and C1 should be located as close
as possible to V
SS
.
2: R3, R4 and C5 are typical values and may be adjusted to maximize sound pressure. 3: DC-DC converter in High Boost mode (nominal V
BST
= 9.6V) can draw current pulses of greater than 1A, and is therefore very sensitive to series resistance. Critical components of this resistance are the inductor DC resistance, the internal resistance of the battery and the resistance in the connections from the inductor to the battery, from the inductor to the LX pin and from the V
SS
pin to the battery. In order to
function properly under full load at V
DD
= 2V, the total of the inductor and interconnect resistances should not exceed 0.3 . The internal battery resistance should be no more than 0.5  and a low ESR capacitor of 10 µF or more should be connected in parallel with the battery, to average the current draw over the boost converter cycle.
4: Schottky diode D1 must have a maximum peak current rating of at least 1.5A. For best results it should
have forward voltage specification of less than 0.5V at 1A, and low reverse leakage.
5: Inductor L1 must have a maximum peak current rating of at least 1.5A.
16
15
14
13
12
11
10
9
8
7
6
5
3
2
1
V
SS
IRED
V
DD
TEST
TEST2
IRP
IRN
RLED
FEED
GLED
IRCAP
IO
HB
HS
V
BST
LX
RE46C190
D2
D3
4
9
D1
4.7 µF
C4
200K
R3
1.5M
R4
1 nF
C5
L1
10 µH
330
R5
33 µF
C6
To other Units
1 µF
C2
100
R1
10 µF
C1
V
DD
Push-to-Test/
Hush
V
BST
330
R6
100
R7
D4
RED
D5
GREEN
C3
Smoke
Chamber
Battery
3V
TP1 TP2
V
BST
100 µF
RE46C190
2010 Microchip Technology Inc. DS22271A-page 3
RE46C190
NOTES:
DS22271A-page 4 2010 Microchip Technology Inc.
RE46C190

1.0 ELECTRICAL CHARACTERISTICS

Absolute Maximum Ratings†
Supply Voltage.....................................VDD=5.5V; V
Input Voltage Range Except FEED, TEST..... V
FEED Input Voltage Range..................... V
TEST Input Voltage Range ......... V
Input Current except FEED ................................... I
Continuous Operating Current (HS, HB, V
Continuous Operating Current (IRED) ...............I
Operating Temperature ...............................T
Storage Temperature ............................T
ESD Human Body Model.................................. V
ESD Machine Model .............................................V
INTEST
= -.3V to VDD +.3V
IN
=-10 to +22V
INFD
=-.3V to V
)...... IO= 40 mA
BST
OIR
= -10 to +60°C
A
= -55 to +125°C
STG
HBM
=13V
BST
+.3V
BST
= 10 mA
IN
= 300 mA
= 750V
= 75V
MM
† Notice: Stresses above those listed under “Maximum ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those indicated in the operation listings of this specification is not implied. Exposure to maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
DC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
= 4.2V, Typical Application (unless otherwise noted)(Note 1, Note 2, Note 3)
V
BST
Parameter Symbol
Supply Voltage V
Supply Current I
Standby Boost
I
DD
DD1
BST1
Test
Pin
Min Typ Max Units Conditions
32 —5.0VOperating
3 — 1 2 µA Standby, Inputs low,
15 — 100 — nA Standby, Inputs low,
Current
IRCAP Supply
I
IRCAP
11 — 500 — µA During smoke check
Current
Boost Voltage V
Input Leakage I
V
INOP
BST1
BST2
15 3.0 3.6 4.2 V IRCAP charging for Smoke
15 8.5 9.6 10.7 V No local alarm,
6 -200 — 200 pA IRP = VDD or VSS
7 -200 — 200 pA IRN = V
I
IHF
I
ILF
Input Voltage Low V
IL1
V
IL2
Note 1: Wherever a specific V
10 — 20 50 µA FEED = 22V; V
10 -50 -15 — µA FEED = -10V;
10 — — 2.7 V FEED, V
12 — — 800 mV No local alarm,
value is listed under test conditions, the V
BST
BST
inductor disconnected and the DC-DC converter NOT running.
2: Typical values are for design information only. 3: Limits over the specified temperature range are not production tested and are based on characterization
data. Unless otherwise stated, production test is at room temperature with guardbanded limits.
4: Not production tested.
= -10 to +60°C, VDD = 3V,
A
No loads, Boost Off, No smoke check
No loads, Boost Off, No smoke check
Check, GLED operation
=40mA
I
OUT
RLED Operation,
= 40 mA, IO as an
I
OUT
input
DD
=10.7V
V
BST
BST
IO as an input
is forced externally with the
or VSS
BST
= 9V
= 9V
2010 Microchip Technology Inc. DS22271A-page 5
RE46C190
DC ELECTRICAL CHARACTERISTICS (CONTINUED)
DC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
V
= 4.2V, Typical Application (unless otherwise noted)(Note 1, Note 2, Note 3)
BST
Parameter Symbol
Input Voltage High V
IO Hysteresis V
Input Pull Down Current
I
I
Output Voltage Low V
Output High Voltage V
Output Current I
I
IODMP
I
IRED50
I
IRED100
I
IRED150
I
IRED2050
IRED Current
TC
IH1
V
IH2
HYST1
I
PD1
PDIO1
PDIO2
OL1
V
OL2
V
OL3
OH1
IOH1
IRED
Test
Pin
Min Typ Max Units Conditions
10 6.2 — — V FEED; V
12 2.0 — — V No local alarm,
12 — 150 — mV
4, 5 0.25 — 10 µA VIN = V
12 20 — 80 µA VIN = V
12 — — 140 µA VIN = 15V
13, 14 — — 1 V I
8— —300mVI
9— —300mVI
13, 14 8.5 — — V I
12 -4 -5 — mA Alarm, V
12 5 30 — mA At Conclusion of Local
2 45 50 55 mA IRED on, V
2 90 100 110 mA IRED on, V
2 135 150 165 mA IRED on, V
2 180 200 220 mA IRED on, V
— 0.5 — %/°C V Temperature Coefficient
Note 1: Wherever a specific V
value is listed under test conditions, the V
BST
BST
inductor disconnected and the DC-DC converter NOT running.
2: Typical values are for design information only. 3: Limits over the specified temperature range are not production tested and are based on characterization
data. Unless otherwise stated, production test is at room temperature with guardbanded limits.
4: Not production tested.
= -10 to +60°C, VDD = 3V,
A
BST
IO as an input
DD
DD
= 16 mA, V
OL
= 10 mA, V
OL
= 10 mA, V
OL
= 16 mA, V
OL
IO
= 0V, V
V
IO
Alarm or Test, V
V
= 5V, IRCAP = 5V,
BST
(50 mA option selected;
=27°C)
T
A
= 5V, IRCAP = 5V,
V
BST
(100 mA option selected; TA=27°C)
= 5V, IRCAP = 5V,
V
BST
(150 mA option selected; TA=27°C)
V
= 5V, IRCAP = 5V,
BST
(200 mA option selected;
=27°C)
T
A
= 5V, IRCAP = 5V;
BST
Note 4
is forced externally with the
= 9V
BST
BST
BST
BST
= 3V or
= 9V
BST
IO
= 1V,
IRED
= 1V,
IRED
= 1V,
IRED
= 1V,
IRED
= 9V
= 9V
= 3.6V
= 9V
=1V
DS22271A-page 6 2010 Microchip Technology Inc.
RE46C190
DC ELECTRICAL CHARACTERISTICS (CONTINUED)
DC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
V
= 4.2V, Typical Application (unless otherwise noted)(Note 1, Note 2, Note 3)
BST
Parameter Symbol
Low Battery Alarm
V
LB1
Test
Pin
Min Typ Max Units Conditions
3 2.05 2.1 2.15 V Falling Edge;
Voltage
Low Battery
V
LB2
V
LB3
V
LB4
V
LB5
V
LB6
V
LB7
V
LB8
V
LBHYST
3 2.15 2.2 2.25 V Falling Edge;
3 2.25 2.3 2.35 V Falling Edge;
3 2.35 2.4 2.45 V Falling Edge;
3 2.45 2.5 2.55 V Falling Edge;
3 2.55 2.6 2.65 V Falling Edge;
3 2.65 2.7 2.75 V Falling Edge;
3 2.75 2.8 2.85 V Falling Edge;
3—100—mV
Hysteresis
IRCAP Turn On
V
TIR1
11 3.6 4.0 4.4 V Falling edge;
Voltage
IRCAP Turn Off
V
TIR2
11 4.0 4.4 4.8 V Rising edge;
Voltage
Note 1: Wherever a specific V
value is listed under test conditions, the V
BST
BST
inductor disconnected and the DC-DC converter NOT running.
2: Typical values are for design information only. 3: Limits over the specified temperature range are not production tested and are based on characterization
data. Unless otherwise stated, production test is at room temperature with guardbanded limits.
4: Not production tested.
= -10 to +60°C, VDD = 3V,
A
2.1V nominal selected
2.2V nominal selected
2.3V nominal selected
2.4V nominal selected
2.5V nominal selected
2.6V nominal selected
2.7V nominal selected
2.8V nominal selected
V
= 5V; I
BST
= 5V; I
V
BST
is forced externally with the
OUT
OUT
= 20 mA
= 20 mA
2010 Microchip Technology Inc. DS22271A-page 7
RE46C190
AC ELECTRICAL CHARACTERISTICS
AC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
= 4.2V, Typical Application (unless otherwise noted) (Note 1 to Note 4).
V
BST
Parameter Symbol Test Pin Min Typ Max Units Condition
Time Base
Internal Clock Period T
PCLK
9.80 10.4 11.0 ms PROGSET,
RLED Indicator
On Time T
Standby Period T
Local Alarm Period T
T
Hush Timer Period T
External Alarm
T
ON1
PLED1
PLED2A
PLED2B
PLED4
PLED0
8 9.80 10.4 11.0 ms Operating
8 320 344 368 s Standby, no alarm
8 470 500 530 ms Local alarm condition
8 625 667 710 ms Local alarm condition
8 10 10.7 11.4 s Timer mode, no local
8 LED IS NOT ON s Remote alarm only
Period
GLED Indicator
Latched Alarm Period T
Latched Alarm Pulse
PLED3
T
OFLED
9 40 43 46 s Latched Alarm Condition,
9 1.25 1.33 1.41 s Latched Alarm Condition,
Train (3x) Off Time
Latched Alarm LED
T
LALED
9 22.4 23.9 25.3 Hours Latched Alarm Condition,
Enabled Duration
Smoke Check
Smoke Test Period with Temporal Horn Pattern
T
PER0A
T
PER1A
T
PER2A
T
PER3A
T
PER4A
2 10 10.7 11.4 s Standby, no alarm
2 1.88 2.0 2.12 s Standby, after one valid
2 0.94 1.0 1.06 s Standby,
2 0.94 1.0 1.06 s Local Alarm
2 235 250 265 ms Push button test,
313 333 353 ms Push button test,
T
PER5A
2 7.5 8.0 8.5 s In remote alarm
Note 1: See timing diagram for Horn Pattern (Figure 5-2).
2: T
PCLK
and T
are 100% production tested. All other AC parameters are verified by functional testing.
IRON
3: Typical values are for design information only. 4: Limits over the specified temperature range are not production tested, and are based on characterization
data.
= -10° to +60°C, VDD = 3V,
A
IO = high
with temporal horn pattern
with continuous horn pattern
alarm
LED enabled
LED enabled
LED enabled
smoke sample
after two consecutive valid smoke samples
(three consecutive valid smoke samples)
>1 chamber detections
no chamber detections
DS22271A-page 8 2010 Microchip Technology Inc.
RE46C190
AC ELECTRICAL CHARACTERISTICS (CONTINUED)
AC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
V
= 4.2V, Typical Application (unless otherwise noted) (Note 1 to Note 4).
BST
Parameter Symbol Test Pin Min Typ Max Units Condition
Smoke Test Period with Continuous Horn Pattern
Chamber Test Period T
Long Term Drift
T
PER0B
T
PER1B
T
PER2B
T
PER3B
T
PER4B
T
PER5B
PCT1
T
LTD
2 10 10.7 11.4 s Standby, no alarm
2 2.5 2.7 2.9 s Standby, after one valid
2 1.25 1.33 1.41 s Standby,
2 1.251.331.41 sLocal Alarm
2 313 333 353 ms Push button test
2 10 10.7 11.4 s In remote alarm
2 40 43 46 s Standby, no alarm
2 400 430 460 s Standby, no alarm
Sample Period
Low Battery
Low Battery Sample Period
T
PLB1
T
PLB2
3 320 344 368 s RLED on
3808692 sRLED on
Horn Operation
Low Battery Horn
T
HPER1
13 40 43 46 s Low battery, no alarm
Period
Chamber Fail Horn
T
HPER2
13 40 43 46 s Chamber failure
Period
Low Battery Horn
T
HON1
13 9.8 10.4 11.0 ms Low battery, no alarm
On Time
Chamber Fail Horn
T
HON2
13 9.8 10.4 11.0 ms Chamber failure
On Time
Chamber Fail
T
HOF1
13 305 325 345 ms Failed chamber,
Off Time
Alarm On Time
T
HON2A
13 470 500 530 ms Local or remote alarm with Temporal Horn Pattern
Alarm Off Time
T
HOF2A
13 470 500 530 ms Local or remote alarm with Temporal Horn Pattern
Alarm On Time
T
HOF3A
T
HON2B
13 1.4 1.5 1.6 s Local or remote alarm
13 235 250 265 ms Local or remote alarm with Continuous Horn Pattern
Alarm Off Time
T
HOF2B
13 78 83 88 ms Local or remote alarm with Continuous Horn Pattern
Note 1: See timing diagram for Horn Pattern (Figure 5-2).
2: T
PCLK
and T
are 100% production tested. All other AC parameters are verified by functional testing.
IRON
3: Typical values are for design information only. 4: Limits over the specified temperature range are not production tested, and are based on characterization
data.
= -10° to +60°C, VDD = 3V,
A
smoke sample
after two consecutive valid smoke samples
(three consecutive valid smoke samples)
LTD enabled
no alarm, 3x chirp option
(Note 1)
(Note 1)
(Note 1)
(Note 1)
(Note 1)
2010 Microchip Technology Inc. DS22271A-page 9
RE46C190
AC ELECTRICAL CHARACTERISTICS (CONTINUED)
AC Electrical Characteristics: Unless otherwise indicated, all parameters apply at T
V
= 4.2V, Typical Application (unless otherwise noted) (Note 1 to Note 4).
BST
Parameter Symbol Test Pin Min Typ Max Units Condition
Push-to-Test Alarm
T
HON4
13 9.8 10.4 11.0 ms Alarm memory active,
Memory On Time
Push-to-Test Alarm
T
HPER4
13 235 250 265 ms Alarm memory active,
Memory Horn Period
Interconnect Signal Operation (IO)
IO Active Delay T
Remote Alarm Delay
IODLY1
T
IODLY2A
12 — 0 — s From start of local alarm
12 0.780 1.00 1.25 s No local alarm, with Temporal Horn Pattern
Remote Alarm Delay
T
IODLY2B
12 380 572 785 ms No local alarm, with Continuous Horn Pattern
IO Charge
T
IODMP
12 1.23 1.31 1.39 s At conclusion of local Dump Duration
IO Filter T
IOFILT
12 — — 313 ms Standby, no alarm
Hush Timer Operation
Hush Timer Period T
TPER
8.0 8.6 9.1 Min No alarm
EOL
End-of-Life
T
EOL
314 334 354 Hours EOL Enabled; Standby
Age Sample
Detection
IRED On Time T
IRON
2 — 100 — µs Prog Bits 3,4 = 1,1 2 — 200 — µs Prog Bits 3,4 = 0,1 2 — 300 — µs Prog Bits 3,4 = 1,0 2 — 400 — µs Prog Bits 3,4 = 0,0
Note 1: See timing diagram for Horn Pattern (Figure 5-2).
2: T
PCLK
and T
are 100% production tested. All other AC parameters are verified by functional testing.
IRON
3: Typical values are for design information only. 4: Limits over the specified temperature range are not production tested, and are based on characterization
data.
= -10° to +60°C, VDD = 3V,
A
push-to-test
push-to-test
to IO active
from IO active to alarm
from IO active to alarm
alarm or test
TEMPERATURE CHARACTERISTICS
Electrical Specifications: All limits specified for V
Electrical Characteristics.
Parameters Sym Min Typ Max Units Conditions
Temperature Ranges
Operating Temperature Range T
Storage Temperature Range T
Thermal Package Resistances
Thermal Resistance, 16L-SOIC (150 mil.) θ
DS22271A-page 10 2010 Microchip Technology Inc.
A
STG
JA
DD
=3V, V
= 4.2V and VSS= 0V, Except where noted in the
BST
-10 — +60 °C
-55 — +125 °C
— 86.1 — °C/W

2.0 PIN DESCRIPTIONS

The descriptions of the pins are listed in Tab le 2 -1 .

TABLE 2-1: PIN FUNCTION TABLE

RE46C190
SOIC
Symbol Function
RE46C190
1V
2 IRED Provides a regulated and programmable pulsed current for the infrared emitter
3V
4 TEST This input is used to invoke Test modes and the Timer mode. This input has an
5 TEST2 Test input for test and programming modes. This input has an internal pull-down.
6 IRP Connect to the anode of the photo diode.
7 IRN Connect to the cathode of the photo diode.
8 RLED Open drain NMOS output, used to drive a visible LED. This pin provides load current
9 GLED Open drain NMOS output used to drive a visible LED to provide visual indication of
10 FEED Usually connected to the feedback electrode through a current limiting resistor. If not
11 IRCAP Used to charge and monitor the IRED capacitor.
12 IO This bidirectional pin provides the capability to interconnect many detectors in a
13 HB This pin is connected to the metal electrode of a piezoelectric transducer.
14 HS This pin is a complementary output to HB, connected to the ceramic electrode of the
15 V
16 LX Open drain NMOS output, used to drive the boost converter inductor. The inductor
SS
DD
BST
Connect to the negative supply voltage.
diode.
Connect to the positive supply or battery voltage.
internal pull-down.
for the low battery test, and is a visual indicator for Alarm and Hush modes.
an Alarm Memory condition.
used, this pin must be connected to V
single system. This pin has an internal pull-down device and a charge dump device.
piezoelectric transducer.
Boosted voltage produced by DC-DC converter.
should be connected from this pin to the positive supply through a low resistance
path.
or VSS.
DD
2010 Microchip Technology Inc. DS22271A-page 11
RE46C190
NOTES:
DS22271A-page 12 2010 Microchip Technology Inc.
RE46C190

3.0 DEVICE DESCRIPTION

3.1 St andby Internal Timing

The internal oscillator is trimmed to ±6% tolerance. Once every 10 seconds, the boost converter is powered up, the IRcap is charged from V the detection circuitry is active for 10 ms. Prior to completion of the 10 mS period, the IRED pulse is active for a user-programmable duration of 100­400 µs. During this IRED pulse, the photo diode current is integrated and then digitized. The result is compared to a limit value stored in EEPROM during calibration to determine the photo chamber status. If a smoke condition is present, the period to the next detection decreases, and additional checks are made.

3.2 Smoke Detection Circuitry

The digitized photo amplifier integrator output is compared to the stored limit value at the conclusion of the IRED pulse period. The IRED drive is all internal, and both the period and current are user programmable. Three consecutive smoke detections will cause the device to go into Alarm and activate the horn and interconnect circuits. In Alarm, the horn is driven at the high boost voltage level, which is regulated based on an internal voltage reference, and therefore results in consistent audibility over battery life. RLED will turn on for 10 ms at a 2 Hz rate. In Local Alarm, the integration limit is internally decreased to provide alarm hysteresis. The integrator has three separate gain settings:
• Normal and Hysteresis
• Reduced Sensitivity (HUSH)
• High Gain for Chamber Test and Push-to-Test
There are four separate sets of integration limits (all user programmable):
• Normal Detection
• Hysteresis
• HUSH
• Chamber Test and Push-to-Test modes
In addition, there are user selectable integrator gain settings to optimize detection levels (see Tab le 4 -1 ).
and then
BST

3.3 Supervisory Tests

Once every 86 seconds, the status of the battery voltage is checked by enabling the boost converter for 10 ms and comparing a fraction of the V an internal reference. In each period of 344 seconds, the battery voltage is checked four times. Three checks are unloaded and one check is performed with the RLED enabled, which provides a battery load. The High Boost mode is active only for the loaded low battery test. In addition, once every 43 seconds the chamber is activated and a High Gain mode and chamber test limits are internally selected. A check of the chamber is made by amplifying background reflections. The Low Boost mode is used for the chamber test.
If either the low battery test or the chamber test fails, the horn will pulse on for 10 ms every 43 seconds, and will continue to pulse until the failing condition passes. If two consecutive chamber tests fail, the horn will pulse on three times for 10 ms, separated by 330 ms every 43 seconds. Each of the two supervisory test audible indicators is separated by approximately 20 seconds.
As an option, a Low Battery Silence mode can be invoked. If a low battery condition exists, and the TEST input is driven high, the RLED will turn on. If the TEST input is held for more than 0.5 second, the unit will enter the Push-to-test operation described in
Section 3.4 “Push-to-Test Operation (PTT)”. After
the TEST input is driven low, the unit enters in Low Battery Hush mode, and the 10 ms horn pulse is silenced for 8 hours. The activation of the test button will also initiate the 9 minute Reduced Sensitivity mode
described in Section 3.6 “Reduced Sensitivity
Mode”. At the end of the 8 hours, the audible indication
will resume if the low battery condition still exists.
voltage to
DD

3.4 Push-to-Test Operation (PTT)

If the TEST input pin is activated (VIH), the smoke detection rate increases to once every 250 ms after one internal clock cycle. In Push-to-Test, the photo amplifier High Gain mode is selected, and background reflections are used to simulate a smoke condition. After the required three consecutive detections, the device will go into a Local Alarm condition. When the TEST input is driven low (V Normal Gain is selected, after one clock cycle. The detection rate continues at once every 250 ms until three consecutive No Smoke conditions are detected. At this point, the device returns to standby timing. In addition, after the TEST input goes low, the device
enters the HUSH mode (see Section 3.6 “Reduced
Sensitivity Mode”).
), the photo amplifier
IL
2010 Microchip Technology Inc. DS22271A-page 13
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