Programmable Analogue Front End creates Smart Sensor Technology 

The LMP91000A, from Alphasense (UK), is a programmable Analogue Front End (AFE) for use in micro power chemical sensing applications. It is intended to be used within the sensor, creating a “smart sensor”. The AFE is designed for three-electrode single gas sensors and for two terminals oxygen sensor. This device provides all of the functionality for detecting changes in gas concentration based on a delta current at the working electrode.

The AFE generates an output voltage proportional to the cell current. Trans-impedance gain is user programmable through an I2C compatible interface from 3.4kOhm to 440kOhm making easy to convert current ranges from 5µA to 650uA full scale. Optimised for micro-power applications, the AFE works over a voltage range of 2.7V to 5.5 V. The cell voltage is user selectable using the on board programmability.

A temperature sensor is embedded and it can be power cycled through the interface. The output of this temperature sensor can be read by the user through the ‘Out’ pin. Together with the coefficients stored in the on board EEPROM, this information can be used to compensate for the sensor sensitivity drift over temperature.Additionally user controlled sensor test will be implemented. This function tests the sensor for proper connection (all 3 terminals) and proper function.

Depending on configuration, total current consumption for the device can be less than 10µA running. For power savings trans-impedance amplifier (TIA) can be turned off and instead a load impedance equivalent to the TIA’s inputs impedance is switched in.

A Technical Data Sheet can be downloaded from the new Alphasense web site.