LMP91050 Datasheet, PDF (1/19 Pages) Texas Instruments – Configurable AFE for Nondispersive Infrared (NDIR) Sensing Applications

LMP91050
April 9, 2012
Configurable AFE for Nondispersive Infrared (NDIR)
Sensing Applications
General Description
The LMP91050 is a programmable integrated Sensor Analog
Front End (AFE) optimized for thermopile sensors, as typi-
cally used in NDIR applications. It provides a complete signal
path solution between a sensor and microcontroller that gen-
erates an output voltage proportional to the thermopile volt-
age. The LMP91050's programmability enables it to support
multiple thermopile sensors with a single design as opposed
to the multiple discrete solutions.
The LMP91050 features a programmable gain amplifier
(PGA), “dark phase” offset cancellation, and an adjustable
common mode generator (1.15V or 2.59V) which increases
output dynamic range. The PGA offers a low gain range of
167V/V to 1335V/V plus a high gain range of 1002V/V to
7986V/V which enables the user to utilize thermopiles with
different sensitivities. The PGA is highlighted by low gain drift
(100 ppm/°C), output offset drift (1.2mV/°C at G = 1002 V/V),
phase delay drift (500ns) and noise specifications (0.1
μV_RMS 0.1 to 10Hz) . The offset cancellation circuitry com-
pensates for the “dark signal” by adding an equal and oppo-
site offset to the input of the second stage, thus removing the
original offset from the output signal. This offset cancellation
circuitry allows optimized usage of the ADC full scale and re-
laxes ADC resolution requirements.
The LMP91050 allows extra signal filtering (high pass, low
pass or band pass) through dedicated pins A0 and A1, in or-
der to remove out of band noise. The user can program
through the on board SPI interface. Available in a small form
factor 10–pin MSOP package, the LMP91050 operates from
-40 to +105°C.
Key Specifications
■ Programmable gain
■ Low noise (0.1 to 10 Hz)
■ Gain Drift
■ Phase Delay Drift
■ Power supply voltage range
167V/V to 7986V/V
0.1μV_RMS
100 ppm/°C (max)
500ns (max)
2.7V to 5.5V
Features
■ ^{Programmable gain amplifier}
■ ^{“Dark Signal” offset cancellation}
■ ^{Supports external filtering}
■ ^{Common mode generator and 8 bit DAC}
■ ^{10 pin MSOP package}
Applications
■ ^{NDIR sensing}
■ ^{Demand control ventilation}
■ ^{Building monitoring}
■ ^{CO2 cabin control — Automotive}
■ ^{Alcohol detection — Automotive}
■ ^{Industrial safety and security}
■ ^{GHG & Freons detection platforms}
Block Diagram
Configurable AFE for NDIR
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