Datasheet

µC
SCL
SDA
GPIO 1
GPIO 2
GPIO N
SMART SENSOR AFE
LMP91000
SDA
SCL
I
2
C EEPROM
SDA
SCL
A0
MENB
LMP91000
SDA
SCL
I
2
C EEPROM
SDA
SCL
A0
MENB
SMART SENSOR AFE SMART SENSOR AFE
LMP91000
SDA
SCL
I
2
C EEPROM
SDA
SCL
A0
MENB
SCL SDA
LMP91000
SDA
SCL
I
2
C EEPROM
SDA
SCL
A0
MENB
MENB
LMP91002
SNIS163A –APRIL 2012–REVISED MARCH 2013 www.ti.com
Figure 24. SMART GAS SENSOR AFE
SMART GAS SENSOR AFES ON I
2
C BUS
The connection of Smart gas sensor AFEs on the I
2
C 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 I
2
C bus. Only one of the devices (either LMP91002 or its
corresponding EEPROM) in the smart gas sensor AFE enabled will acknowledge the I
2
C commands. When the
communication with this particular module ends, the microcontroller de-asserts the corresponding MENB and
repeats the procedure for other modules. Figure 25 shows the typical connection when several smart gas sensor
AFEs are connected to the I
2
C bus.
Figure 25. SMART GAS SENSOR AFEs on I
2
C bus
POWER CONSUMPTION
The LMP91002 is intended for use in portable devices, so the power consumption is as low as possible in order
to ensure a long battery life. The total power consumption for the LMP91002 is below 10µA @ 3.3v average over
time, (this excludes any current drawn from any pin). A typical usage of the LMP91002 is in a portable gas
detector and its power consumption is summarized in Table 2. This has the following assumptions:
-Power On only happens a few times over life, so its power consumption can be ignored
-Deep Sleep mode is not used
-The system is used about 8 hours a day, and 16 hours a day it is in Standby mode.
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