1 Features

• Programmable Gain Amplifier
• Dark Signal Offset Cancellation
• Supports External Filtering
• Common-Mode Generator and 8-Bit DAC
• Key Specifications
  • Programmable Gain 167 to 7986 V/V
  • Low Noise (0.1 to 10 Hz) 0.1 μVRMS
  • Gain Drift 100 ppm/°C (Maximum)
  • Phase Delay Drift 500 ns (Maximum)
  • Power Supply Voltage Range 2.7 to 5.5 V

2 Applications

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

3 Description

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 specifications (0.1 μV_RMS 0.1 to 10Hz).

1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application Circuit

Configurable AFE for NDIR