Ultra-low power microcontrollers

Ultra-low power microcontrollers
for embedded security applications

Engineers developing modern security systems
like smoke detectors and intruder alarms
have seen quite a change in the methods they
can employ to realize their applications. Fixed
function solutions built from a number of components
have given way to fully integrated fast
response systems. In the past, ASIC solutions
for front-end signal conditioning, data conversion
and, in the case of bus-based systems, for
communication purposes were quite popular
and frequently used. These solutions, however,
did not offer the flexibility to react quickly to
changes in the market environment such as the
introduction of different types of sensors and
new communication standards.
The constraints imposed by fixed-function
ASIC systems mean that adaptive systems, capable
of compensating for temperature fluctuations,
aging sensor behaviour and other external
influences like higher environmental noise
levels, cannot be easily built-in. Miniaturization,
increased networking capabilities and
data logging features are additional drivers for
modern, flexible solutions in this area. A typical
motion detector front-end based on a passive
infrared (PIR) sensor is shown in figure 2.
This system amplifies the signal from the PIR
sensor in two stages, which are compared
using a comparator device. This outputs a high
signal if movement is detected, which is indicated
on a direct user display, or is communicatedto a central unit in a bigger security system.
However, this fixed function does not allow for
on-the-fly adjustment should the parameters
change and, even more importantly, consumes
a current in the range of 80 μA, which does not
help the life-cycle of battery-powered systems.
By contrast, a PIR motion detector system
based on the new MSP430F20x3 microcontroller