Eco-Friendly Microcontrollers by Renesas Boast Strong Analog Functionality Support
In the realm of embedded computing, there typically exists a pair of overriding requirements: minimal energy usage to maximize battery longevity and a dependable, precise sensor interface to capture environmental data. Renesas has introduced a novel series of microcontrollers (MCUs) aimed at fulfilling these needs by melding exceptionally low power drain with high-precision analog-to-digital conversion (ADC) functionalities.
The new RA2A2 microcontrollers. Image used courtesy of Renesas
Let’s take a look at the new MCUs and the theory behind high-accuracy ADCs.
Announcing the RA2A2 Series MCUs by Renesas
Renesas unveils their RA2A2 microcontroller line, brimming with innovative features perfect for high-precision analog tasks and streamlined wireless upgrades.
The cornerstone of these MCUs (datasheet included) is the power-savvy Arm Cortex-M23 32-bit CPU, striking an optimal balance between computational prowess and energy efficiency, peaking at a 48 MHz operating frequency. Founded on the robust Armv8-M framework, this processor incorporates built-in features to boost security and dependability, furnished with a single-cycle integer multiplier, a 19-cycle integer divider, and an eight-region Arm Memory Protection Unit.
The RA2A2 series is architected with a comprehensive memory setup, boasting up to 512 KB of dual-bank code flash memory, enabling seamless application updates without interrupting ongoing operations. Alongside this feature, an 8-KB data flash memory is provided for high-endurance data retention, as well as 48 KB of SRAM for streamlined data management during active tasks. Renesas highlights that the newcomers’ dual-bank flash memory and bank switch capabilities equip developers to execute firmware updates over the air (FOTA) effectively, which is particularly advantageous for IoT applications—including building management, healthcare devices, and myriad consumer gadgets—that require the convenience of remote updating.
RA2A2 MCU block diagram. Image used courtesy of Renesas
The RA2A2 MCUs come equipped with a wide array of connectivity features. They house five channels for serial communication, a serial peripheral interface, and dual I2C bus interfaces, enabling extensive and flexible communication modes with various integrated circuits, sensors, and supplementary devices.
The RA2A2 series sets itself apart with exceptional analog attributes, notably including a 24-bit Sigma-Delta ADC and a 12-bit ADC. These analog-to-digital converters deliver precise signal measurement capability, suitable for a variety of sampling rates such as 7.813 kHz/8.333 kHz or 3.906 kHz/4.166 kHz, thereby ensuring meticulous analog-to-digital translation. Additionally, the MCUs are crafted for optimal energy efficiency with an ultra-low power footprint, operating at just 100 µA/MHz in active mode and a mere 0.40 µA during software standby.
Understanding Sampling Rates and ADC Precision
In the realm of digital signal processing system architecture, it's crucial to comprehend how the sampling rate interplays with the accuracy of the analog-to-digital converter (ADC).
The sampling rate is the measure of how frequently an analog signal is sampled for digital conversion, and is of critical importance in preserving the integrity of the signal by preventing loss of crucial information. Conversely, the ADC's accuracy—often susceptible to disturbances by noise—dictates how accurately the analog signal is reflected in the digital domain.
At the core of this interplay lies the Nyquist theorem, which prescribes that the sampling rate must at least double the highest frequency contained in the analog signal for an accurate reconstruction free from aliasing. Nevertheless, merely exceeding this minimum sampling rate threshold does not guarantee a direct enhancement in the digital representation's accuracy. Indeed, at augmented sampling rates, various elements can inject noise that might compromise the ADC's precision.
The theory behind sigma-delta ADCs. Image used courtesy of Analog Devices
Utilizing higher sampling rates can mitigate the effects of quantization noise—a kind of distortion that occurs when analog signals are quantized into discrete digital values. This noise is an inevitable aspect of the ADC process and its intensity is inversely related to the resolution of the ADC.
To grasp this concept more clearly, consider oversampling, which entails sampling the analog signal significantly more frequently than the Nyquist criterion's minimum. Oversampling extends the frequency range across which quantization noise is spread, effectively lowering its concentration in any specified bandwidth. This diminishment of noise concentration results in an enhanced signal-to-noise ratio (SNR) within the signal bandwidth, leading to a truer representation of the original signal after digital filter application to eliminate noise beyond the band of interest.
When combined with noise-shaping methods such as sigma-delta modulation, oversampling can redistribute quantization noise from lower (more audible) frequencies to higher ones. Post-digital filtering within the signal bandwidth can then more efficiently reduce this noise, significantly augmenting the ADC's effective resolution and the precision of the signal.
Solutions for Contemporary Embedded Systems
The demands of contemporary embedded applications revolve around consistent and accurate sensor interaction and minimizing energy usage. The Renesas RA2A2 MCUs serve an essential role in today's market, meeting these stringent requirements. With their low-energy operation, high-frequency ADCs, and diverse communication options, these MCUs are poised to be particularly influential in consumer electronics and the burgeoning IoT sector, where they offer a versatile and powerful feature set for a wide array of applications.
