New-Tech Europe Magazine | Feb 2017

Sensors Special Edition

Discrete vs. Integrated Solutions for Sensor Conditioning

Debbie Brandenburg, Exar

Our world is filled with intelligent (smart) products and technology to make our lives more efficient, convenient, connected and informed. We come into contact with these smart devices every day. More and more cities are employing smart traffic lights that adjust to real-time traffic conditions. Smart street lights and office lighting dim or turn off when no one is around to conserve energy. High efficiency top load washers determine the water level for each load based on the weight of clothing in each load. New smart automobiles respond to adverse conditions and feature parking assist. Cell phones respond not only to your touch but also the force of your touch. Many of these systems incorporate multiple analog sensors that are used to detect pressure, temperature, force,

position, light, flow, sound, speed, heat, etc. Betweentheanalogsensoranddigital signal processing lies an important electronic interface that conditions the electrical signal to ensure it lies within the range of the downstream ADC (analog-to-digital converter). This signal conditioning or sensor interface block is highlighted in Figure 1. Analog sensors produce an electrical signal that is usually very small and surrounded by noise. In many cases, no two sensors are alike, each sensor carries its own unique noise signature, introduces its own offset into the signal path and requires a different gain to meet the requirements of the downstream ADC. Calibrating the system, differentiating signal from noise and amplifying it are crucial to end system performance.

Today’s system designer is faced with choosing between developing a discrete sensor conditioning function or making use of a more integrated sensor interface analog front end (AFE). Unfortunately, there is never a clear choice for all applications. Footprint, ease-of- use, flexibility, performance, price, and functionality are all things to consider. This article will describe some benefits and short-comings of each. Footprint Comparison If real-estate is a concern, then a more integrated solution is usually more desirable. Take for example a system that uses 16 Hall Effect sensors to monitor current in a solar panel application. The XR10910, a 16:1 sensor interface AFE has a 6mm x 6mm footprint

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