The LMP91050 device is a programmable integrated Sensor Analog Front End (AFE) optimized
for thermopile sensors, as typically used in NDIR applications. It provides a complete signal path
solution between a sensor and microcontroller that generates an output voltage proportional to the
thermopile voltage. The programmability of the LMP91050 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 (1.15 V or 2.59 V)
which increases output dynamic range. The PGA offers a low-gain range
of 167 V/V to 1335 V/V plus a
high-gain range of 1002 V/V to 7986 V/V which enables the user to use
thermopiles with different
sensitivities. The PGA is highlighted by low-gain drift (100 ppm/°C),
output offset drift (1.2
mV/°C at G = 1002 V/V), phase delay drift (500 ns) and noise
µVRMS 0.1 to 10Hz).
The offset cancellation circuitry compensates for the by adding an
equal and opposite 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 relaxes ADC resolution
The LMP91050 allows extra signal filtering (high-pass, lowpass or bandpass) through
dedicated pins A0 and A1, in order to remove out of band noise. The user can program through the on
board SPI interface. Available in a small form factor 10-pin package, the LMP91050 operates from
40 to 105°C.