Renesas – 32-Bit RX21A Group of Microcontrollers with Large Memory Capacity and Built-In A/D Converter
The RX21A Group are 32-bit microcontrollers (MCUs) for smart meters with advanced functionality. The new MCUs are the first in the industry to combine large flash memory capacity of 512 KB and a 24-bit delta-sigma (Delta-sigma) A/D converter for high-resolution measurement.
The RX21A Group of MCUs implements in a single chip functions that previously required separate devices, such as power measurement, meter control, calculation of electricity charges, and data encryption. This reduces the number of external components required and helps to lower the overall cost. In addition, the RX21A Group includes product versions for a variety of meter models, allowing common and effective system design.
Recently, the smart meter market has expanded rapidly with the spread of smart grids as a way to increase energy efficiency. The proliferation of smart meters has created demand for MCUs that provide, in addition to reduced power consumption, higher performance to support advanced functions such as complex power calculation, needed for time-of-day rate systems and other diverse power services in many countries, and strong security, including communication data protection and unauthorized access prevention, in addition to reduced power consumption. There is also a greater need for shorter development cycles and improved development efficiency for new meter models, which spurs the need for an extensive lineup of MCUs supporting a wide range of smart meter models. At the same time, the home energy management system (HEMS) market is growing rapidly, driving the trend toward MCUs with enhanced functionality and larger memory capacity.
Renesas already mass produces 8-bit and 16-bit MCUs with on-chip Delta-sigma A/D converter for use in power meters with power calculation and ordinary billing capabilities. The RX21A Group of MCUs expands the product lineups to further meet the market demands. Renesas now offers a full range of Delta-sigma A/D converter-equipped MCU product lineups, allowing designers to scale from the low-end to high-end smart meters more easily.
Key features of the new RX21A Group of MCUs:
-
(1) On-chip peripheral functions for meters, such as 24-bit Delta-sigma A/D converter and encryption engine
The RX21A Group of MCUs integrates a newly-developed 24-bit Delta-sigma A/D converter module that delivers higher resolution than the 16-bit module of existing MCU products. The new MCUs incorporate in a single chip all the main functions required by smart meters, including encryption engine, real-time clock (RTC) with tamper, temperature sensor, and IrDA.3 (Infrared Data Association). This reduces the total number of components required and lowers the overall system cost.The 24-bit Delta-sigma A/D converter achieves conversion accuracy (SNDR) of 85 dB, and the encryption engine supports AES (256-bit key length). This provides smart meters with improved calculation precision and enhanced security functionality, such as communication data protection and unauthorized data access prevention that will be needed for the next- generation smart meters. -
(2) High-performance CPU and large memory capacity to support advanced-functionality smart meters
In addition to the performance boost moving from the existing Delta-sigma A/D converter-equipped 16-bit MCUs to a 32-bit architecture, the operating frequency of the RX21A Group of MCUs has been increased to 50 megahertz (MHz), and DSP functions added for filter calculation. The RX21A Group of MCUs also has a large on-chip flash memory with a capacity of up to 512 KB, twice that of Renesas’ existing products, to accommodate larger programs. -
(3) RX CPU and low-power peripheral functions for the system’s overall reduced power consumption
The new RX21A Group of MCUs is part of the RX200 MCU series that brings new levels of capability and performance to ultra-low-power, low-voltage embedded-system applications. Based on the advanced 32-bit RX CPU core, the RX21A Group of MCUs achieves the industry-leading power consumption of 0.2 mA/MHz. Power consumption in standby mode is only 1.0 microampere (µA) when the RTC is operating and 0.3 µA when the RTC is stopped. These enhancements enable system designers to develop smart meters with reduced power consumption and smaller backup batteries. -
(4) Nine product versions to support wide range of power meters, such as single-phase and poly-phase models
The new RX21A Group of MCUs includes product versions with three, four, and seven 24-bit Delta-sigma A/D converter channels to accommodate both single-phase smart meters, and poly-phase smart meters. System designers can choose from three on-chip flash memory capacities, 256 KB, 384 KB, and 512 KB, to accommodate the differing billing and communication systems in various countries and regions. The nine product versions in total support a variety of meter models, allowing common system design and a shortened development cycle.
Renesas plans to supply a development support environment, including middleware for power measurement and calibration tools, for the new RX21A Group of MCUs. The company will also provide one-stop kit solutions combining the new MCUs with devices such as the PS2513/14 photocouplers to insulate the MCU from the communication interface in smart meter applications.
