Microcontrollers (MCUs) today are amazing examples of synergy and innovation. Anywhere from 30,000 to 2 million gates are contained on a single chip, and up until very recently, the various integrated components and modules were considered advanced ICs on their own.
For example, currently a typical MCU device (Figure 1, below ) may contain the following components: 120kB Flash, 8kB RAM, (4) 16-bit timers, supply voltage supervisor, Brownout Reset, programmable low-dropout regulator, I2C, SPI, UART, IrDA, Direct Memory Access controller, hardware multiplier (32×32), Analog Comparator, 12 channel 12-bit SAR analog-to-digital converter, 12-bit digital-to-analog converter,3 op amps, and 48 general purpose input/output pins ” all on a 100 pin device!
|Figure 1. Mixed Signal MCU block diagram|
Anyone in the semiconductor industry knows that the rate of integration of new components is accelerating, and not just for MCUs. There are almost an infinite number of permutations of new cores, memory densities, power management and protection systems, communication peripherals, display controllers and data converters.
The industry has been increasing the integration of new technologies and modules in order to reach new markets and reduce costs on existing applications. In the past two years, features such as multi-core, floating point cores, ubiquitous USB (Host, Device, and the adaptable On-The-Go variety), wireless radios, op amps, high performance A/Ds, DACs and advanced display controllers (VGA, QVGA) have all been squeezed onto a single MCU. Within the next two years, we will see even more unique, powerful and innovative components added.
The future may look a bit foggy due to the sheer number of new paths for this integration to take; however, clear skies are ahead with a few technologies that will emerge as game-changers in the market.
These include advanced wireless (such as Zigbee, Bluetooth and WiFi), integrated power management modules (multiple power levels on and off chip), modules that allow chips to harvest some of their own power from the environment (energy harvesting) in addition to application specific modules like medical sensors and analog front ends.
Furthermore, MCUs will start to close the gap with the latest wired communication interfaces like high speed USB 2.0, Ethernet and IEEE 1394 at data rates that were only available on the highest end processors just a few years ago.
Wired and Wireless Communications
Adding wireless communication (RF usually) seems to be the most obvious area for integration, but it's also perhaps the most difficult to implement. Radio Frequency (RF) components are tough to add onto a PCB, and doing this at the chip scale is orders of magnitude more difficult.
There is a reason why only 8051 core-based MCUs have been added to the latest low power RF System-on-Chips (SOCs). The mating of these two completely different systems is complex and difficult because of problems like noisy ground planes, antenna and balun interfacing, data transfer, and accounting for the plethora of different wireless protocols and modulation schemes.
There are some huge technical challenges, but in many cases each successive monolithic RF + MCU chip makes the next one easier to design. This will result in a rapid acceleration of the number of integrated RF solutions as well as increased differentiation in this genre.
Today, MCU vendors have taken the first step by creating multi-chip modules and one or two with integrated RF on CPUs other than the 8051. But, this is just the ramp-up phase for a set of devices which have the potential to enable dozens of new applications that have not even been thought of yet.
In addition, innovations in die stacking and packaging have made it easier to put more diverse silicon on the same chip. Companies like ZeroG Wireless have started created low power WiFi modules and are taking advantage of the intersection of the increased demand for extremely low power consumption in MCUs and the emerging smart grid to gain a lot of support from the big SOC vendors. It is only a matter of time before this technology merges with existing MCUs.
Wired communications interfaces are already very common (Figure2 below ). Several different MCU vendors have already integrated CAN, Ethernet 10/100, and USB full-speed onto a single chip. There are even small 100 MHz MCU that have integrated high speed USB 2.0(480Mbps) onto a microcontroller!
|Figure 2. CC430 Integrated MSP430 + Chipcon Radio|
Not only will these peripherals improve through added hardware acceleration such as PHY layers, MAC layers, integrated isolation and power management, but there will be further integration of other protocols such as IEEE 1394, DALI for lighting, or LIN/FlexRay for vehicles.
Application Specific Integration
Integrating multiple modules for a specific type of end equipment is one trend that has been happening in MCUs for a while, but expect an explosion of many targeted devices within the next 24 months.
Prototyping and designing have become such short and controlled processes and vendors have created such a staggering amount of modular analog content that marketing departments are able to specify exact chips for narrow, high volume applications.
This is mostly due to advancements in manufacturing and design techniques, but it is also a byproduct of the maturity of the MCU market, as more and more companies are looking for ways to be the first to capture sockets in any emerging equipment.
Competition is so fierce that new applications are heavily marketed even before the first actual device for those customers emerges. One example of this can be seen in personal medical devices. Digitized blood glucose and blood pressure monitors have been around for a while, but lately innovations like digital stethoscopes, spirometers, pulse monitors and oximeters all rolled into one system that can fit in a pocket have been driving highly integrated chips.
This wouldn't be possible without several “generations” of integration including op amps for buffering and signal conditioning, high resolution ADCs, programmable gain stages and digital-to-analog converters (DACs).
Many medical companies hope to revolutionize modern health care with portable health monitors as chips shrink and new sensors evolve to replace and improve conventional mechanical sensors.
The ideal medical-focused MCU will be tiny, extremely low power, implantable signal chain with an energy harvester or tiny battery, 8- or 10-bit ADC, op amps for signal conditioning, low speed/low power CPU, and probably a 415 MHz radio in the MICS band.
Another interesting area where application specific integration is happening today is in utility metering. With tremendous buzz around the smart grid, everyone is racing to capture some of the stimulus-inspired smart meter market, and this has resulted in some pretty unique MCUs.
Some companies have produced entire portfolios of highly integrated devices aimed at this market. These parts may have data converters for up to three-phase electricity metering and a secondary programmable processor which speeds up the calculation process while consuming far less power than the primary CPU.
The MCU that will be the heart of tomorrow's smart meters will probably contain even more data converters and sensors, as well as wired and wireless communication interfaces for communicating with all power-consuming devices in the house.
In addition, there will be solutions with multiple dedicated processors on chip for handling measurement, communication, data recording and display. The one MCU solution for future smart meters will truly be a test of engineering capabilities as these devices must be very durable and power efficient.
Power Management and Energy Harvesting
Every single IC in the industry has had to tighten its belt on power consumption as green engineering becomes one of the hottest topics in the industry. MCUs have been ahead of the curve thanks to aggressive design goals to integrate functions that have traditionally been the duty of separate power management chips.
There are already devices with integrated low dropout regulators, brownout detection, voltage converters, and multiple core voltage levels, but these elements have always been passive and non-programmable.
Emerging and future devices will take in and output multiple voltage levels during the course of normal operation, all of which can be dictated and changed through an operating system or state machine programmed into the chip. Integrated power management is a key differentiator for many MCUs as board sizes decrease and more devices appear on PCBs which require different voltage and current levels.
Energy harvesting is a very new and tricky area. The emergence of technologies such as the thin-film solid state energy cells and innovative micro-energy harvesting elements for vibration, solar, heat and RF energy will enable battery-free applications that could last an entire generation without maintenance.
A key element to the efficacy of a battery independent application is the intelligence of a low power MCU. These systems have complex power management circuits built for the extreme outputs of the harvesting element.
An an integrated solution is key for putting these parts into the wireless sensor networks and embedding them into buildings to monitor the environment and structural integrity. In the end, this increasing integration is being driven by several different trends.
First, the CPU and digital parts of a modern SOC take up less than 15 percent of the chip on average. Most space is used for embedded memory, and as new memory technologies emerge and scale down in geometry, there is room for more modules on chip without affecting the overall size of the SOC.
Second, customers want smaller, cheaper products that do more. This creates a conundrum for chip vendors where they have to choose between smaller and more complex systems full of many small chips, or smaller and more complex SOCs to replace five or six chips on an older design.
Finally, fully integrated solutions present a much more reliable and durable way to solve many of today's problems like implantable devices, embedded structural monitoring, and a fully networked home.
So far, we've discussed two trends in embedded processors; Non-volatile memory and advanced, rapid integration. Next, we will look at a trend that could be considered a byproduct of these or even an entirely separate trend enabled by different technological advances.
This is the trend of truly embedded control, which is the addition of electronic control in places that have never before been heard of outside of science fiction.
It's already happening in Formula One racecars, mass transport trains and even credit cards where you see the controller embedded in the material of the product or otherwise made invisible to the user.
To read, Part 1, go to “Memories that last forever.”
Next in Part 3: Deeply Embedded Devices.
Jacob Borgeson is currently a product marketing engineer for microcontrollers at Texas Instruments. He has a special interest in integrating low power functionality with wireless operation in many standard applications; especially biomedical devices. He works with Universities and TI engineers to help enable the best educational environments and next generation products through directed research.