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LMP91000
September 12, 2011
Sensor AFE System: Configurable AFE Potentiostat for
Low-Power Chemical Sensing Applications
General Description
The LMP91000 is a programmable Analog Front End (AFE)
for use in micro-power electrochemical sensing applications.
It provides a complete signal path solution between a sensor
and a microcontroller that generates an output voltage pro-
portional to the cell current. The LMP91000’s programmability
enables it to support multiple electrochemical sensors such
as 3-lead toxic gas sensors and 2-lead galvanic cell sensors
with a single design as opposed to the multiple discrete so-
lutions. The LMP91000 supports gas sensitivities over a
range of 0.5 nA/ppm to 9500 nA/ppm. It also allows for an
easy conversion of current ranges from 5µA to 750µA full
scale.
The LMP91000’s adjustable cell bias and transimpedance
amplifier (TIA) gain are programmable through the the I2C in-
terface. The I2C interface can also be used for sensor diag-
nostics. An integrated temperature sensor can be read by the
user through the VOUT pin and used to provide additional
signal correction in the µC or monitored to verify temperature
conditions at the sensor.
The LMP91000 is optimized for micro-power applications and
operates over a voltage range of 2.7V to 5.25V. The total cur-
rent consumption can be less than 10μA. Further power sav-
ings are possible by switching off the TIA amplifier and
shorting the reference electrode to the working electrode with
an internal switch.
Features
Typical Values, TA = 25°C
■ Supply voltage
2.7 V to 5.25 V
■ Supply current (average over time)
<10 µA
■ Cell conditioning current up to
10 mA
■ Reference electrode bias current (85°C) 900pA (max)
■ Output drive current
750µA
■ Complete potentiostat circuit to interface to most chemical
cells
■ Programmable cell bias voltage
■ Low bias voltage drift
■ Programmable TIA gain
2.75kΩ to 350kΩ
■ Sink and source capability
■ I2C compatible digital interface
■ Ambient operating temperature
-40°C to 85°C
■ Package
14 pin LLP
■ Supported by Webench Sensor AFE Designer
Applications
■ Chemical species identification
■ Amperometric applications
■ Electrochemical blood glucose meter
Typical Application
AFE Gas Detector
© 2011 National Semiconductor Corporation 301325
30132505
www.national.com
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