Datasheet

3-Lead

Electrochemical

Cell

I2C INTERFACE

AND

CONTROL

REGISTERS

VREF

VDD

AGND

VOUT

SCL

VREF

DIVIDER

SDA

Load

DIAGNOSTIC

MENB

DGND

TIA

LMP91002

www.ti.com

SNIS163A –APRIL 2012–REVISED MARCH 2013

GAS SENSOR INTERFACE

The LMP91002 supports both 3-lead and 2-lead gas sensors. Most of the toxic gas sensors are amperometric

cells with 3 leads (Counter, Worker and Reference). These leads should be connected to the LMP91002 in the

potentiostat topology.

3-lead Amperometric Cell In Potentiostat Configuration

Most of the amperometric cell have 3 leads (Counter, Reference and Working electrodes). The interface of the 3-

lead gas sensor to the LMP91002 is straightforward, the leads of the gas sensor need to be connected to the

namesake pins of the LMP91002.

The LMP91002 is then configured in 3-lead amperometric cell mode; in this configuration the Control Amplifier

(A1) is ON and provides the internal zero voltage and bias in case of biased gas sensor. The transimpedance

amplifier (TIA) is 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”. The R

Load

together with the output

capacitance of the gas sensor acts as a low pass filter.

Figure 21. 3-Lead Amperometric Cell

Product Folder Links: LMP91002