Datasheet
Table Of Contents
- Features
- Applications
- Description
- Absolute Maximum Ratings
- Operating Ratings
- Electrical Characteristics
- I2C Interface
- Timing Characteristics
- Timing Diagram
- Typical Performance Characteristics
- Function Description
- Application Information
- Revision History
I2C INTERFACE
AND
CONTROL
REGISTERS
RE
VREF
VDD
AGND
CE
WE
VOUT
C1
SCL
TEMP
SENSOR
VREF
DIVIDER
C2
SDA
R
Load
VARIABLE
BIAS
MENB
DGND
A1
+
-
TIA
+
-
R
TIA
CE
WE
RE
3-Lead
Electrochemical
Cell
LMP91000
LMP91000
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SNAS506H –JANUARY 2011–REVISED MARCH 2013
Figure 29. 3-Lead Amperometric Cell
2-lead Galvanic Cell In Ground Referred Configuration
When the LMP91000 is interfaced to a galvanic cell (for instance to an Oxygen gas sensor) referred to the
ground of the system, an external resistor needs to be placed in parallel to the gas sensor; the negative
electrode of the gas sensor is connected to the ground of the system and the positive electrode to the Vref pin of
the LMP91000, the working pin of the LMP91000 is connected to the ground.
The LMP91000 is then configured in 2-lead galvanic cell mode and the Vref bypass feature needs to be enabled.
In this configuration the Control Amplifier (A1) is turned off, and the output of the gas sensor is amplified by the
Transimpedance Amplifier (TIA) which is configured as a simple non-inverting amplifier.
The gain of this non inverting amplifier is set according the following formula
Gain= 1+(R
TIA
/R
Load
)
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”.
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