1FEATURES
2• Dual Channel Input
• Programmable Gain Amplifier
• “Dark Signal” Offset Cancellation
• Supports External Filtering
• Common Mode Generator and 8 Bit DAC
• Package 14 Pin TSSOP

APPLICATIONS
• NDIR Sensing
• Demand Control Ventilation
• Building Monitoring
• CO2 Cabin Control — Automotive
• Alcohol Detection — Automotive
• Industrial Safety and Security
• GHG & Freons Detection Platforms

KEY SPECIFICATIONS
• Programmable Gain … 167V/V to 7986V/V
• Low Noise (0.1 to 10 Hz) … 0.1μVRMS
• Gain Drift … 20 ppm/°C (typ)
• Phase Delay Drift … 300 ns (typ)
• Power supply voltage range … 2.7V to 5.5V

DESCRIPTION
The LMP91051 is a dual channel 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 LMP91051’s programmability
enables it to support multiple thermopile sensors with
a single design as opposed to the multiple discrete
solutions.
The LMP91051 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
(20 ppm/°C), output offset drift (230 mV/°C at
G = 1002 V/V), phase delay drift (300 ns) and noise
specifications (0.1 μVRMS 0.1 to 10Hz) . The offset
cancellation circuitry compensates for the “dark
signal” 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 requirements.
The LMP91051 allows extra signal filtering (high
pass, low pass or band pass) 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 14 pin TSSOP
package, the LMP91051 operates from –40 to
+105°C.