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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
Discrete vs. Integrated Solutions for Sensor
Conditioning
Debbie Brandenburg, Exar
Sensors
Special Edition
44 l New-Tech Magazine Europe