FIC98648 Datasheet, PDF (2/14 Pages) List of Unclassifed Manufacturers – Microprocessor for use with TGS4160 in automatic CO2 monitors

TECHNICAL INFORMATION FOR FIC98648
Introduction
The FIC98648 is a microprocessor for handling signals
from the TGS4160 carbon dioxide sensor, enabling
maintenance-free automation of air quality control
in buildings when connected with appliances such
as ventilation fans, air cleaning systems, etc.
The microprocessor takes in the output voltage, or
electromotive force (EMF), from the TGS4160 sensor
and outputs a signal which corresponds to a
concentration of CO2 in the environment. CO2
concentrations are calculated in the microprocessor
based on ∆EMF, which is the change in the value of
EMF from the value in a normal clean environment.
The microprocessor also contains software to
compensate the sensor’s signal for changes in
temperature and basic environmental factors.
1. Features
1-1 Automatic calibration
The FIC98648 uses the concept of a benchmark value
of EMF in order to provide automatic calibration. The
benchmark value is assumed to be equal to the level
of CO2 which exists in ambient air (approx. 400ppm).
CO2 concentrations are calculated periodically by
determining the change of EMF from the benchmark
level (∆EMF). In order to offset the effects of sensor
signal drift which are caused by environmental
temperature and air contaminants, the micro-
processor automatically renews the benchmark level
to the current EMF value whenever a lower CO2
concentration than the current benchmark is
calculated. Using this method of automatic calibra-
tion, very stable characteristics can be expected for
the sensor, allowing for reliable monitoring of CO2
levels and long term maintenance-free ventilation
control.
1-2 High CO2 sensitivity and wide detectable range of
400~3000ppm
By programming the microprocessor to take into
consideration the unique performance characteristics
of the TGS4160, reliable readings of CO2 concen-
trations within a wide range (400~3000ppm) can be
achieved, satisfying the requirements of building
ventilation control applications.
X-TAL
Input port for
microprocessor reset
Input port for
test mode
Input port for +4.4V
Input port for +3.8V
Gas sensor signal
input port
Thermistor signal
input port
Input port for damper
control thresholds
Input port for setting
warm up period
Input port for setting
benchmark renewal (VL)
Input port for setting
benchmark renewal (TK)
Input port for automatic
benchmark reset (Tr)
GND
1 XOUT
2 XIN
3 RESET
4 R70
5 R71
6 ^VAREF
7 AIN0
8 AIN1
9 AIN2
10 R43
11 R50
12 R51
13 R52
14 VSS
VDD ²⁸
KEO ²⁷
R92 ²⁶
R91 ²⁵
R90 ²⁴
R83 ²³
R82 ²²
R81 ²¹
R80 ²⁰
R63 ¹⁹
R62 ¹⁸
R61 ¹⁷
R60 ¹⁶
R53 ¹⁵
Input port for +4.4V
Input port for manual
benchmark reset
Output port for benchmark
renewal status signal
Output port for CO2
concentration signal
Output port for
bias signal
GND
GND
GND
GND
Output port for green LED
Output port for red LED
Output port for malfunction signal
Output port for damper
control signal
GND
Figure 1 - Pin arrangement for FIC98648
Revised 08/03
2