Go Analog With Microcontrollers
By Erin Kettwig, product marketing manager, Cypress Semiconductor Corp.
Microcontrollers have long been valued for their ability to perform specific functions that system designers find themselves
requiring in their applications. With a glance through any microcontroller vendor’s broad product catalog, engineers can find
virtually any combination of features to satisfy their design requirements. The explosion of fixed-function devices for specific
applications (brushless dc motor control, for example) has been driven partially by the desire to simplify designs for customers.
With a microcontroller that has been configured for an exact application, engineers need not worry about setting up the
microcontroller. Instead, they often spend time figuring out which external components will be required in addition to the
microcontroller to realize the end product’s design, and then incorporating these devices into the design.
Most microcontrollers are paired with discrete analog components—analog-to-digital converters (ADCs), amplifiers, filters,
digital-to-analog converters (DACs), and comparators, to name a few—to achieve filtering, signal conditioning, and signal
conversion in systems like those that require interfaces to analog sensors or the filtering of noisy signals. To help alleviate the
complicated design challenges often associated with discrete analog component implementation, a trend has emerged among
semiconductor companies to integrate more of these functions into a microcontroller or microcontroller-like device.
The challenges that come with utilizing external analog components include difficulty in making last-minute system changes
that then require a board spin, higher bill of materials (BOM) costs, utilizing devices that are overkill for the design but the “best
fit” available, and requiring the expertise of specialized analog engineers to implement more complex analog systems. With
the proliferation of more complicated, but low-cost, electronics, it is important to make it easy for system designers to select
and implement both analog and digital functions in a quick and easy manner. A new generation of integrated, flexible
microcontroller-based devices mixes familiar digital features with combined analog functionality in a programmable manner.
These devices help to address these challenges while making it easier for designers to implement more complicated designs.
A Hypothetical Case
An example of the number of analog components in a system can be seen in a security system design. A typical security
system will include a number of sensors—temperature, piezo-infrared (PIR), ultrasonic, and gas. While a microcontroller may
be the ultimate destination for the signals, there is often a signal-conditioning circuit in front of the microcontroller to assist in
cleaning up and/or amplifying the analog information coming from each sensor.
A PIR sensor requires high pass and band-pass filters, one or two amplifiers, an ADC, and a comparator. An ultrasonic sensor
requires band-pass and low pass filters, an amplifier, an ADC, and a comparator. A gas (carbon monoxide) sensor requires an
amplifier, a low pass filter, and a comparator. A simple temperature sensor requires a low pass filter, an ADC, and an
amplifier. If it is assumed that most microcontrollers have at least a rudimentary ADC already integrated, the analog
component count is still approximately 15 (Fig. 1).
Go Analog With Microcontrollers
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Figure 1. Without programmable analog, a typical security system with four sensors would require 15 external
components.
System designers must pick all of the components, possibly without knowing all of the parameters, and lay out a board.
Designers also must have knowledge of analog design rules or an available analog design engineer to ensure optimal
performance of the system. If system requirements change after the board has been laid out and spun, designers may be
required to select different analog components, lay out the board again, and do another spin.
Along with the cost of the external components, all of this redesign work includes cost, both monetary and from a time-tomarket perspective, as well. Many of these costs might be eliminated if a programmable analog device were used to integrate
as many of the external components as possible.
While a device with programmable analog may never be able to attain the performance of the highest-end analog
components, programmable analog will provide sufficient performance for most systems. Taking the same security system
example, if a designer used a programmable mixed-signal system-on-a-chip (SoC), up to 13 of the additional discrete analog
functions could also be integrated, leaving just two or three simple functions external to the device (Fig. 2).
Go Analog With Microcontrollers
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Figure 2. With programmable analog, a typical security system with four sensors would only require 2 external
components.
Engineers are recognizing that simplified system design, the ability to program the analog for a close fit to the system’s
performance requirements, and the ability to reprogram a device instead of respinning a board are extremely valuable features
for a microcontroller or programmable SoC, and these features are now being requested more often.
System designers have also realized that the same general design can be used with simple reprogramming to add or subtract
functionality, instead of selecting a whole new device or redeveloping the analog front of their new system. Semiconductor
vendors are also recognizing the value provided to the customer and have begun to make these types of devices available,
with varying levels of integration.
As the number of systems requiring more complex analog functions grows, system designers will be under more pressure to
quickly and cost-effectively release systems. With the advent of more integrated mixed-signal SoCs and microcontrollers,
semiconductor vendors can help system designers achieve their goals faster and with less complexity.
Go Analog With Microcontrollers
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Cypress Semiconductor
198 Champion Court
San Jose, CA 95134-1709
Phone: 408-943-2600
Fax: 408-943-4730
http://www.cypress.com
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Go Analog With Microcontrollers
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