32-Bit MCUs Integrate High-Precision Analog Front End

Renesas Electronics Corporation introduced the RX23E-A Group 32-bit RX MCUs that combine a high-precision analog front end (AFE) and an MCU on a single chip.

The company designed the MCUs for manufacturing and test and measurement equipment applications that demand high-precision measurements of analog signals for temperature, weight, pressure, and flow.

Renesas says that the RX23E-A MCUs are the first Renesas solutions to enable such signals to be measured with a precision of better than 0.1% without calibration. The new MCUs boast AFE precision at the highest class in the industry. They have an offset drift of 10nV/°C, gain drift: 1ppm/°C, and RMS noise of 30nVrms.

Previously this RMS noise level could only be achieved by combining dedicated ac-dc converter ICs with high-precision operational amplifier ICs.

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The MCUs integrate this high-precision AFE IP on a single chip using the same fabrication process technology, Renesas enabling implementation of high-precision sensor measurement, computation, control, and communications on a single chip.

Analog Front End diagram (Click on image to enlarge)

These MCUs allow a reduction in the number of required components and space savings as well as a simplified system design for a wide range of equipment requiring high-precision measurement, including sensing, temperature controllers, weighing, recording, and force sensing. It also enables distributed processing with MCUs for endpoint intelligence.

"The RX23E-A MCUs will radically evolve the structure of high-precision analog 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 analog 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."

In order to measure small signals at high precision over a wide environmental temperature range, noise characteristics should be reduced and temperature drift characteristics should be kept to low levels. To address to these demands, Renesas developed a high-precision AFE and integrated it into an RX MCU.

The company based the RX23E-A MCUs on the RXv2 core, which features operating speeds of 32 MHz, a digital signal processor, and floating point unit calculations.

RX 32-Bit Core (Click on charts to enlarge)

These features allow 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 can measure the 6-axis distortion data and perform the inverse matrix calculations with a single chip.

Key features

AFE block

• 24-bit delta-sigma ac-dc converter: Up to 23 bits of effective resolution. Data output rate flexible at 7.6PS to 15.6kPS.
• Two 24-bit delta-sigma ac-dc 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: 1ppm/°C, and RMS noise: 30nVrms.
• Voltage reference: Low-temperature drift characteristics of 4ppm/°C with superlative temperature stabilization.
• Excitation current source: Programmable current source with required matching required for 3-wire resistance temperature detector.
• Analog 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 ac-dc 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: 128KB to 256KB, RAM: 16KB to 32KB.
• 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 ac-dc converter, clock frequency accuracy measurement circuit, independent watchdog timer, RAM test assistance functions using the DOC and other circuits.
• Supply voltage: 5V. Independent power supplies can be used for the AFE block and microcontroller. Voltages of 1.8V to 5.5V can be supported.
• Operating temperature: -40°C to +85°C, -40°C to +105°C
• Package: 48-pin QFP with 7mm square. 40-pin QFP with 6mm square.

Availability

Samples of the RX23E-A Group of MCUs are available now with mass production planned for December 2019. (Availability is subject to change without notice.)