Datasheet

LMP91000
µC
SCL
SDA
GPIO 1 GPIO 2
GPIO 3
GPIO N
SDA
SCL
MENB
LMP91000
SDA
SCL
MENB
LMP91000
SDA
SCL
MENB
LMP91000
SDA
SCL
MENB
LMP91002
www.ti.com SNIS163A –APRIL 2012–REVISED MARCH 2013
APPLICATION INFORMATION
CONNECTION OF MORE THAN ONE LMP91002 TO THE I
2
C BUS
The LMP91002 comes out with a unique and fixed I
2
C slave address. It is still possible to connect more than one
LMP91002 to an I
2
C bus and select each device using the MENB pin. The MENB simply enables/disables the
I
2
C communication of the LMP91002. When the MENB is at logic level low all the I
2
C communication is enabled,
it is disabled when MENB is at high logic level.
In a system based on a μcontroller and more than one LMP91002 connected to the I
2
C bus, the I
2
C lines (SDA
and SCL) are shared, while the MENB of each LMP91002 is connected to a dedicate GPIO port of the
μcontroller.
The μcontroller starts communication asserting one out of N MENB signals where N is the total number of
LMP91002s connected to the I
2
C bus. Only the enabled device will acknowledge the I
2
C commands. After
finishing communicating with this particular LMP91002, the microcontroller de-asserts the corresponding MENB
and repeats the procedure for other LMP91002s. Figure 23 shows the typical connection when more than one
LMP91002 is connected to the I
2
C bus.
Figure 23. More than one LMP91002 on I
2
C bus
SMART GAS SENSOR ANALOG FRONT END
The LMP91002 together with an external EEPROM represents 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 LMP91002's
configuration (content of registers 10h, 11h, 12h). At startup the microcontroller reads the EEPROM's content
and configures the LMP91002. A typical smart gas sensor AFE is shown in Figure 24. The connection of MENB
to the hardware address pin A0 of the EEPROM allows the microcontroller to select the LMP91002 and its
corresponding EEPROM when more than one smart gas sensor AFE is present on the I
2
C bus. Note: only
EEPROM I
2
C addresses with A0=0 should be used in this configuration.
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