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.