SMART GAS SENSOR ANALOG FRONT END
SMART GAS SENSOR AFES ON I2C BUS
The LMP91000 together with an external EEPROM repre-
sents the core of a SMART GAS SENSOR AFE. In the
EEPROM it is possible to store the information related to the
GAS sensor type, calibration and LMP91000's configuration
(content of registers 10h, 11h, 12h). At startup the microcon-
troller reads the EEPROM's content and configures the
LMP91000. A typical smart gas sensor AFE is shown in Fig-
ure 8. The connection of MENB to the hardware address pin
A0 of the EEPROM allows the microcontroller to select the
LMP91000 and its corresponding EEPROM when more than
one smart gas sensor AFE is present on the I2C bus. Note:
only EEPROM I2C addresses with A0=0 should be used in
this configuration.
The connection of Smart gas sensor AFEs on the I2C bus is
the natural extension of the previous concepts. Also in this
case the microcontroller starts communication asserting 1 out
of N MENB signals where N is the total number of smart gas
sensor AFE connected to the I2C bus. Only one of the devices
(either LMP91000 or its corresponding EEPROM) in the
smart gas sensor AFE enabled will acknowledge the I2C com-
mands. When the communication with this particular module
ends, the microcontroller de-asserts the corresponding
MENB and repeats the procedure for other modules.
Figure 9 shows the typical connection when several smart gas
sensor AFEs are connected to the I2C bus.
30132580
FIGURE 8. SMART GAS SENSOR AFE
30132582
FIGURE 9. SMART GAS SENSOR AFEs on I2C bus
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