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CS235
CS235
System Photoelectric Smoke Detector
Description
The CS235 System Smoke Detector is a photo electric type with a pulsed infrared LED as the light source and a silicon photodiode as the light detector. The CS235 IC, along with passive external components, controls the system timing and signal processing. Low average current is attained by pulsing the system once every 10 seconds for 20 milliseconds. Bias is applied to the signal processing circuitry for this time interval. During the second half of the pulse, the last 10 milliseconds, the IR LED is pulsed and the unit samples for an alarm level smoke condition. After the first alarm level signal the sample rate increases to a two second interval. After three consecutive alarm level samples the logic drives the output latch signalling the system panel. The signal processing circuit blocks are amplifiers A1 and A2, synchronous detector, voltage comparator and the decode counter. The voltage gain of A2 and the comparator reference voltage are set by external resistors. Additional on-chip features include an ICC current limiter. The current limiter eliminates power-on false alarming. The oscillator controls the IR LED excitation frequency and provides drive to the synchronous detector. The synchronous detection method has very high noise rejection performance. The internal latch is capable of sinking 100 milliamps maximum and will clamp the VCC pin to 5 volts when tripped. The latch current is determined by an external resistor typically located in the master panel and is reset by temporary removal of detector power.
Features
s Synchronous Detection for High Noise Immunity s Pulsed Operation for Low Average Current Drain s System Gain Externally Set s System Sensitivity Externally Adjustable s System Operation Monitored by Means of External Red LED
Package Options
18 Lead PDIP & SOIC Wide
Timer Pulse Width 1 ICC Program 2
18 17 16 15 14
Timer Cap Timer Period Program V REG
Block Diagram
INT OSC TIMER PGM PULSE LED H.L. VR ICC VCC/ Gnd BIAS PGM CAP RES WIDTH PGM OUT
VCC /Output 3 Hi Level GND 4 A1 Input (-) 5 A1 Input (+) 6 LO Level GND 7 A2 Input 8
LED Output Oscillator Program 13 Internal Bias
12 11
NC Detector Output Detector Reference
GATE
POWER UP
MAIN TIMER LED DRIVER
CURRENT LIMITER OUTPUT LATCH CLOCK
A2 Output 9
10
OSCILLATOR
GATE BIAS A1 IN (-) A1 A1 IN (+) A2
POWER UP BIAS
SET
SYNC DETECTOR
COMP
COUNTER
3
L.L. A2 GND IN
A2 OUT
NC DET
OUT
DET REF
Cherry Semiconductor Corporation 2000 South County Trail, East Greenwich, RI 02818 Tel: (401)885-3600 Fax: (401)885-5786 Email: info@cherry-semi.com Web Site: www.cherry-semi.com
Rev. 7/6/98
1
A
Company
CS235
Absolute Maximum Ratings Lead Temperature Soldering Wave Solder (through hole styles only) .....................................................................................10 sec. max, 260C peak Reflow (SMD styles only) ......................................................................................60 sec. max above 183C, 230C peak Storage Temperature Range ..................................................................................................................................-65C to 150C
Electrical Characteristics: TA = 25C, unless otherwise stated.
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
Absolute Maximum Voltage Output Latch Current Operation Temperature Range, TA
(pin 3) 0
38 100 70
V mA C
s 24V System (C2 = 100 F, R7 = 12 M1/2) Operating Voltage (pin 3) Average Supply Current V (pin 3) = 22.5V Peak Supply Current V (pin 3) = 22.5V )(non Ospeed upO) Peak Supply Current V (pin 16) = 12V )(Ospeed upO) Regulator Voltage (pin 16) s 12V System (C2 = 150F, R7 = 12M1/2) Operating Voltage (pin 3) Average Supply Current V (pin 3) = 12V Peak Supply Current V (pin 3) = 12V (non Ospeed upO) Peak Supply Current V (pin 16) = 8V (Ospeed upO mode) Regulator Voltage (pin 16) (V pin 3 = 12V) s Oscillator Output Frequency Sink Current Source Current High Trip Point Voltage Low Trip Point Voltage
13.8
22.5 35 150
12.8
35 60 100 350 15.7
V A A A V
8.7
12 60 100 350 11.85
V A A A V
R6 = 18k1/2, C3 = .0068F (pin 14) (pin 14) (pin 14) (pin 14)
2.1 16 19 1.8 1.2
3.3 26 26 1.9 1.4
4.4 35 32 2.2 1.5
kHz A A V V
s LED Drive (Detector LED and Status LED) Source Current (pin 15) R8=361/2 Detector LED V IR LED = 1.156V Status LED (alarm) V Status LED = 1.99V Regulator Voltage (pin 15) ISOURCE = 30mA s Amplifier A1 Fixed Gain Input Current B1 Input Current B2 Input current (B1-B2) (pin 5) (pin 6)
20 10 3.7
30 4.4
40 5.2
mA mA V
26 500 500
1000 1000 250
dB nA nA nA
2
CS235
Electrical Characteristics: TA = 25C
PARAMETER TEST CONDITIONS MIN TYP MAX UNIT
s Amplifier A2 DC Output (pin 9) Input Bias Current (pin 8) Voltage gain @ 3.5kHz
R3 = 6k1/2, R4 = 5101/2, C5 = .47F (Externally adjusted gain with R3 and R4. Unity DC gain) (Externally adjusted gain with R3 and R4. Unity DC gain)
2.5 250 21.6
V nA dB
s Detector and Reference Output (C4 = .47F) Reference Resistance Reference Voltage (pin 10) Detector Output Resistance Detector Output Voltage (pin 11) (No signal, and at 2X time Constant) s Main Timer (R1 = 20M1/2, R2 = 75k1/2, C1 = .47F) Power Up Pulse Period Standby Mode (pin 1) Power Up Pulse Period Speed Up Mode (pin 1) Power Up Pulse Width (pin 1) Gate Pulse Width Power up pulse width 12 Sink Current (pin 18) Source Current (pin 18) s Output Circuit Output Latch Voltage Leakage Current V (pin 16) = 16V V (pin 16) = 16V
13 1.8 10 1.4
19 3.6 15 2.8
25 5.5 20 4.3
k1/2 V k1/2 V
8 1.5
10 2 20 10 460 -235
12 2.5
Sec Sec ms ms nA A
415 -220
505 -250
(pin 3) ISUPPLY = 100mA V (pin 3) = 38V, V (pins 2, 16) = 0V
4.4
5.2 500
6.1
V A
s Alarm Alarm Reset Supply interruption 5 Sec Power up time 30 Sec System will go into alarm upon detection and transfer of three consecutive alarm level signals into the counter.
3
CS235
Timing Diagrams
Timing Diagram Out of Alarm Timing Diagram In Alarm
10 Sec. 20ms Power Up 20ms
20ms
2 Sec. Power Up
Gate (Clock) 10ms
Gate (Clock) 10ms
3.5KHz
3.5KHz
Oscillator/ LED Driver
Oscillator/ LED Driver
Comp. Ref.
Comp. Ref.
Comp. Ref. Level
Detector Output
Comp. Ref. Level
Detector Output
Data Input (low)
Data Input
Alarm Enable (low)
Alarm Enable
Preset
Preset
4
CS235
Application Diagram
R6 18k 13 14
C3 6.8nF
CS235
1 R2 75k R1 20M C1 18 .47mF
15 R8 36W Status LED IR LED PGnd 4
LED Driver
Oscillator
Gate
Power UP
Main Timer
17
Clock
16 C2 150mF
Current Limit
+
2 R7 12M
1nF C6 R9 270k R12 150k R11 150k
5
A1
Gain =20 6 -
1nF C7
+
Synchronous Detector A2
COMP
Counter 3
Output Latch
3
VCC/Output
R12 R13 150k 150k
-
8
9 R3 6k R4 510W C5 .47mF
11 10 R5 100K C4 .47mF
7 LLGnd
5
CS235
Package Specification
PACKAGE DIMENSIONS IN mm (INCHES) PACKAGE THERMAL DATA
D Lead Count 18L PDIP 18L SO Wide Metric Max Min 23.37 22.35 11.75 11.35 English Max Min .920 .880 .463 .447
Thermal Data RQJC RQJA typ typ
18L SO Wide 21 100
18L PDIP 29 65
uC/W uC/W
Plastic DIP (N); 300 mil wide
7.11 (.280) 6.10 (.240)
8.26 (.325) 7.62 (.300) 3.68 (.145) 2.92 (.115)
1.77 (.070) 1.14 (.045)
2.54 (.100) BSC
.356 (.014) .203 (.008)
0.39 (.015) MIN. .558 (.022) .356 (.014) Some 8 and 16 lead packages may have 1/2 lead at the end of the package. All specs are the same.
REF: JEDEC MS-001
D
Surface Mount Wide Body (DW); 300 mil wide
7.60 (.299) 7.40 (.291)
10.65 (.419) 10.00 (.394)
0.51 (.020) 0.33 (.013)
1.27 (.050) BSC
2.49 (.098) 2.24 (.088)
2.65 (.104) 2.35 (.093)
1.27 (.050) 0.40 (.016)
REF: JEDEC MS-013
0.32 (.013) 0.23 (.009) D 0.30 (.012) 0.10 (.004)
Ordering Information
Part Number CS235GDW18 CS235GDWR18 CS235GN18
Rev. 7/6/98
Description 18L SO 18L SO (tape & reel) 18L PDIP 6
Cherry Semiconductor Corporation reserves the right to make changes to the specifications without notice. Please contact Cherry Semiconductor Corporation for the latest available information.
(c) 1999 Cherry Semiconductor Corporation

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