Datasheet

RE
CE
WE
VE-
VE+
NC
2-Lead Sensor
such as Oxygen
I2C INTERFACE
AND
CONTROL
REGISTERS
VREF
VDD
AGND
VOUT
C1
SCL
VREF
DIVIDER
C2
SDA
R
Load
DIAGNOSTIC
MENB
DGND
A1
+
-
TIA
+
-
R
TIA
LMP91002
LMP91002
SNIS163A –APRIL 2012–REVISED MARCH 2013 www.ti.com
2-lead Galvanic Cell in Potentiostat Configuration
When the LMP91002 is interfaced to a galvanic cell (for instance to an Oxygen gas sensor) referred to a
reference, the Counter and the Reference pin of the LMP91002 are shorted together and connected to negative
electrode of the galvanic cell. The positive electrode of the galvanic cell is then connected to the Working pin of
the LMP91002.
The LMP91002 is then configured in 3-lead amperometric cell mode (as for amperometric cell). In this
configuration the Control Amplifier (A1) is ON and provides the internal zero voltage. The transimpedance
amplifier (TIA) is also ON, it converts the current generated by the gas sensor in a voltage, according to the
transimpedance gain:
Gain= R
TIA
If different gains are required, an external resistor can be connected between the pins C1 and C2. In this case
the internal feedback resistor should be programmed to “external”.
Figure 22.
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