![](http://datasheet.mmic.net.cn/370000/MAX951EUA_datasheet_16718853/MAX951EUA_12.png)
by the high input impedance op amp of a MAX951
(Figure 6). The comparator and resistor voltage divider
set an alarm threshold to indicate a fire.
Design and fabrication of the connection from the inter-
mediate plate of the ionization chamber to the nonin-
verting input of the op amp is critical, since the
impedance of this node must be well above 50M
. This
connection must be as short and direct as possible to
prevent charge leakage and 60Hz interference. Where
possible, the grounded outer electrode or chassis of
the ionization chamber should shield this connection to
reduce 60Hz interference. Pay special attention to
board cleaning, to prevent leakage due to ionic com-
pounds such as chlorides, flux, and other contaminants
from the manufacturing process. Where applicable, a
coating of high-purity wax may be used to insulate this
connection and prevent leakage due to surface mois-
ture or an accumulation of dirt.
0.084"
(2.134mm)
0.058"
(1.473mm)
V
DD
V
SS
COMPOUT
REF(COMPIN-)
COMPIN+
AMPIN+
( ) ARE FOR MAX953/MAX954
AMPIN-
AMPOUT
M
Ultra-Low-Power, S ingle-S upply
Op Amp + Comparator + Referenc e
______________Ordering Information
___________________Chip Topography
PART
MAX951
C/D
MAX951EPA
MAX951ESA
MAX951EUA
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
TEMP. RANGE
PIN-PACKAGE
Dice*
8 Plastic DIP
8 SO
8 μMAX
* Dice are tested at T
A
= +25°C, DC parameters only.
**Contact factory for availability and processing to MIL-STD-883.
TRANSISTOR COUNT: 163
SUBSTRATE CONNECTED TO V
DD
3
AMPIN+
INPUT
2
5
6
1
8
4
REF
0.1
μ
F
1.20V
V
SS
V
CC
R1
R2
1M
COMPOUT
7
MAX951
MAX952
__________Typic al Operating Circ uit
MAX951MJ A
MAX952
C/D
MAX952EPA
MAX952ESA
MAX952EUA
-55°C to +125°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8 CERDIP**
Dice*
8 Plastic DIP
8 SO
8 μMAX
MAX952MJ A
MAX953
C/D
MAX953EPA
MAX953ESA
MAX953EUA
-55°C to +125°C
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
8 CERDIP**
Dice*
8 Plastic DIP
8 SO
8 μMAX
MAX954
C/D
MAX954EPA
MAX954ESA
MAX954EUA
0°C to +70°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
MAX953MJ A
-55°C to +125°C
8 CERDIP**
Dice*
8 Plastic DIP
8 SO
8 μMAX
MAX954MJ A
-55°C to +125°C
8 CERDIP**
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12
____________________Maxim Integrated Produc ts, 120 S an Gabriel Drive, S unnyvale, CA 94086 408-737-7600
1997 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.