FIC03272 Datasheet, PDF (8/14 Pages) List of Unclassifed Manufacturers – Microprocessor for handling signals from the TGS4161 carbon dioxide sensor

TECHNICAL INFORMATION FOR FIC03272
FIC03272
AIN0 ⁷
AIN1 ⁸
10k
10µ
104
+5V
+3. 8V
12
TH
TLC271CP
3
87
6
24
43
103
+4 .4V ^8.2k
30k 30k
10k ^100p
220k
22k
9
8
10
LM324N
24
R90
47k
10k
1M
6
7
5
104 ^LM324N
100k
1m
Figure 4 - Circuit for driving sensor and processing sensor signal
AIN1 (Pin No. 8) as a thermistor signal for the
temperature compensation circuit.
c) As a first stage, the sensor’s output (pin No. 3),
which is of very high impedance, should be
amplified by 4.5 times with a high impedance
(100MΩ or higher) operational amplifier, such as
Texas Instrument’s Model No. TLC271. This
amplified signal is designed to be further amplified
by ten times in the second stage. The output from
the amplifier is input into port AIN0 (Pin No. 7)
after being adjusted by a regulator (differential
circuit) with a bias signal.
5-2 Power supply circuit
As illustrated in Figure 5, the circuit is designed to
be operated by +5V. The sensor ’s heater, which
requires a large current, is powered directly by +5V.
The microprocessor is powered by +4.4V (down-
stream from a diode). A diode is connected between
the power supply and the microprocessor to protect
the microprocessor from a surge current. Taking the
saturation voltage of the operational amplifiers into
consideration, the analog reference voltage (VAREF)
is set at +3.8V. Voltage is provided downstream from
another diode.
+5V
+4.4V
FIC03272
1SS176
28 _VDD
+3.8V
1SS176
6
5V
VAREF
103 104 220^µ _{6. 2V} 220µ
2. 2k
14 _VSS
Figure 5 - Power supply circuit
Revised 06/04
8