RX microcontrollers with built-in analogue front end

The RX23E-A MCUs are the first Renesas solutions to enable such signals to be measured with better than 0.1% precision without calibration. 

The new MCUs achieve AFE precision at the highest class in the industry (offset drift: 10nV/°C, gain drift: 1ppm/°C, and RMS noise: 30nV rms), a level that could previously only be achieved by combining dedicated A/D converter circuits with high-precision operational amplifier ICs.

By integrating this high-precision AFE IP (intellectual property) on a single chip using the same fabrication process technology, Renesas has made it possible to implement high-precision sensor measurement, computation, control, and communications on a single chip.

This allows system manufactures to reduce the number of required components, save space, and simplify system design in a wide range of equipment requiring high-precision measurement, such as sensing, temperature controllers, recording, weighing, and force sensing. It also accelerates endpoint intelligence by enabling distributed processing with MCUs.

“The RX23E-A MCUs will radically evolve the structure of high-precision analogue measurement systems,” said Akira Denda, Vice President, Industrial Automation Business Division, Renesas Electronics Corporation. “Moving forward, Renesas is aiming to deliver an extensive product line, starting with the RX23E-A Group, that integrates MCUs and high-precision analogue on a single chip for programmable logic controllers, distributed control system applications, and test and measurement equipment that require a variety of higher precision measurements.”

With big data-driven quality and productivity improvements, the pressure is on for factories and manufacturing sites to measure a wide variety of sensor data accurately and reliably.

Since users require stability when measuring small signals at high precision over a wide environmental temperature range, it is important to reduce noise characteristics and temperature drift characteristics to low levels. To address to these needs, Renesas has developed a high-precision AFE and integrated it into an RX MCU with an extensive track record with industrial applications. 

The RX23E-A MCUs are based on the RXv2 core, which features operating speeds of 32MHz, a digital signal processor (DSP), and superlative floating point unit (FPU) calculations. This allows the implementation of adaptive control using temperature data and inverse matrix calculations using 6-axis distortion data.

For example, robot arm force sensors require the measurement and calculation of the 6-axis distortion in a small space. The RX23E-A MCUs make it possible to measure the six-axis distortion data and perform the inverse matrix calculations with a single chip.

Key features of the RX23E-A MCUs

AFE block:

• 24-bit delta-sigma A/D converter: Up to 23 bits of effective resolution. Data output rate flexible at 7.6PS to 15.6kPS.
• Two 24-bit delta-sigma A/D converters that can start synchronously, allowing sensor temperature correction to be performed without switching channels.
• PGA (programmable gain amplifier): Rail-to-rail input PGA allows amplification up to 128×. Offset drift: 10nV/°C, gain drift: 1 ppm/°C, and RMS noise: 30nV rms.
• Voltage reference: Low temperature drift characteristics of 4ppm/°C with superlative temperature stabilisation.
• Excitation current source: Programmable current source with required matching required for three-wire resistance temperature detector.
• Analogue inputs: differential inputs: up to 6 channels, pseudo-differential inputs: up to 11 channels, single-ended inputs: up to 11 channels. All can be used as inputs to the two A/D converters.

MCU block:

• CPU: 32-bit RXv2 core operating at 32MHz.
• Digital signal processing can be implemented with DPS instructions and FPU.
• ROM/RAM: ROM: 128 to 256 KB, RAM: 16 to 32 KB.
• Communication interfaces: SPI (1 channel), UART (4 channels), I2C (1 channel), CAN (1 channel).
• Functional safety: software load reduced by Self-diagnostic and disconnection-detection assistance functions for the A/D converter, clock frequency accuracy measurement circuit, independent watchdog timer, RAM test assistance functions using the DOC and other circuits.
• Supply voltage: five volts, independent power supplies can be used for the AFE block and microcontroller. Voltages of 1.8 to 5.5V can be supported.
• Operating temperature: -40 to +85°C, -40 to +105°C
• Package: 48-pin QFP with seven millimetre square. 40-pin QFP with six millimetre square.

Samples of the RX23E-A Group of MCUs are available now with mass production planned for December 2019.