How does RISC-V fit into automotive systems?

RISC-V is being used in a surprising range of automotive systems ranging from ASIL-D safety rated controllers and security co-processors, artificial intelligence (AI) accelerators, controllers for advanced electric vehicle (EV) battery chargers based on gallium-nitride (GaN) power semiconductors, and even in high-voltage monolithic motor drive controllers for light EVs. The following is a sampling of the automotive applications for RISC-V.

Europe’s GaNext project (short for next-generation GaN power modules), aims to make designing power converters with GaN power semiconductors easier while at the same time improving the efficiency and compactness of GaN-based power modules for systems such as electric vehicle chargers. The primary focus on GaNext is on the development of an intelligent power module (IPM) based on GaN power switches. A key part of GaNext is developing a custom RISC-V controller with a high-resolution timer, integrated front-ends, and an external SPI interface.

The IPM will combine the RISC-V controller with gate drivers and a programmable, fail-safe PWM control unit with integrated protection circuits and safety functions, filter units, a wide range of programmable timing to enable optimal adaptation to the drive demands of the GaN power components. Key specifications of the GaNext IMP include:

• 650V GaN HEMTs with 55mΩ on-resistance
• 15A, RMS output current rating
• Integrated sensors for voltage, current, and temperature
• Module dimensions of 35.0 x 35.0 x 3.0 mm
• Silicon on insulator (SOI) gate driver with integrated bootstrap circuitry
• Custom RISC-V controller with integrated front-end’s, external SPI interface, and a high-resolution timer

GaN is a wide bandgap semiconductor material that enables high efficiency and high-density power conversion systems. The performance improvements supported by GaN are a result of lower on-resistances (reducing conduction losses), much lower switching losses, and faster switching times compared with silicon-based power devices. As a result, GaN-based power converters are lighter, smaller, substantially more efficient, and lower in cost than alternative designs based on silicon power switches.

The IPM being developed by GaNext is designed to simplify the adoption of GaN power conversion technology enabling more users to adopt GaN and realize the multiple performance improvements it enables. While EV chargers are the initial target application for the GaNext IPM, they could also find use in EV motor drives and industrial motor drives, and inverters.

RISC-V in a monolithic HV motor driver

RISC-V is also being incorporated into a new family of motor drives targeting light electric vehicles and other motor drive applications. The new drives are also the first RISC-V implementation in a monolithic high voltage technology, allowing direct driving of N-channel MOSFETs controlling brushless dc (BLDC), stepper, brushed dc, permanent magnet synchronous motors (PMSMs), and voice-coil motors.

The first two RISC-V-based motor drives are a dedicated BLDC/PMSM driver with 6 integrated gate drivers and a driver IC for stepper motors and stepper servos with 8 integrated drivers. Both drives include integrated diagnostics and a selection of interfacing options, and both are based on a 32-bit RISC-V core which provides hardware-based field-oriented control. The drives include serial interfaces, USB, CAN-FD, and integrated drivers for 2-phase or 3-phase motors. Integrated switching regulators enable one-chip drive solutions, and 128k EEPROM non-volatile memory plus 32k SRAM memory make the drives powerful enough to implement a range of high-level industrial protocols such as CANopen or CANopen-FD as well as standalone system designs.

MCUs, whether ARM or RISC-V, are at the core of embedded systems and motion controllers. They provide the application control layer, execute bus communications protocols and provide a user interface. However, in a typical design, actuators, motors, and other mechanical components have a much longer product lifetime compared with the control and drive electronics. RISC-V is viewed as a good platform for long product lifetimes: the RISC-V ISA is stable and reliable. There are no obligations or license agreements that could limit long-term product roadmaps or technology developments.

DOCK5 motor controller evaluation board with integral RISC-V core. (Image: Trinamic Motion Control)

Data flow processor

A RISC-V-based data flow processor (DFP), the DR1000C that meets the ASIL D safety requirement level of the ISO 26262 functional safety standard for vehicles, has been developed. A DFP is a type of hardware accelerator. It’s a parallel processor optimized to offload the intensive computing that vehicle control microcontrollers (MCUs) are otherwise required to perform. The DFP operates using a multithreading mechanism and vector instructions.

By incorporating the DR1000C with the vehicle microcontroller in an SoC, automotive systems will handle advanced control algorithms more efficiently, such as model predictive control, and meet ever-tighter performance designs and legal regulations.

RISC-V data flow processor is designed to work with automotive MCUs to implement advanced control algorithms such as model predictive control.

In addition to being used in SoCs with vehicle MCUs, The DR1000C is suitable for various embedded systems such as industrial equipment and factory automation, and sensor processing, including LIDAR and radar. The DR1000C was developed by NSITEXE, Inc., a group company of DENSO Corporation that develops and sells high-performance semiconductor IPs.

Crypto manager for secure automotive applications

A fully programmable, ISO-26262 ASIL-D ready hardware security core offering security by design for automotive applications has been announced. Called the Root of Trust RT-645 (formerly the CryptoManager RT-645), it protects against a wide range of failures such as permanent, transient, and latent faults and hardware and software attacks with anti-tamper and security techniques.

Automotive device and system designers face a growing array of threat vectors as the connected capabilities of systems continues to grow. One constraint across a wide range of automotive applications, including vehicle-to-external systems (V2X) connections, ADAS, even infotainment, and other systems, is the need for a hardware root of trust-based security implementation.

The RT-645 is a security co-processor optimized for automotive uses. Built on a custom 32-bit, RISC-V siloed and layered secure co-processor, along with dedicated secure memories, the RT-645 features several high-capability cryptographic accelerators like AES (all modes), HMAC, SHA-2 (all modes), RSA up to 4096 bits, ECC up to 521 bits, a NIST-compliant Random Bit Generator, AXI Multi-Issue Out-of-Order, and Fast DMA capability. Additional algorithms such as Whirlpool (SHE), SHA-1 (legacy), AES-CMAC, SHA-3, Poly1305 & ChaCha, and OSCCA SM2-3-4 are available as optional HW crypto accelerators.

Fully programmable ISO-26262 ASIL-D security core with a custom RISC-V processor.

The RT-645 is from Rambus and is certified by TÜV-SGS as ISO26262 ASIL-D ready, satisfying the ASIL-D Single Point Fault Metric (SPFM ≥ 99 % of faults detected) and Latent Fault Metric (LFM ≥ 90 % of faults detected).

High-performance RISC-V cores optimized for automotive applications are being widely pursued. In one instance, they are being developed by an international partnership to expand high-end SoC and MCU capabilities to continue advancing innovative and trusted automotive solutions. Targeted applications including ADAS, Autonomous Driving (AD), Electric Vehicles (EV), and Connected Gateways (CoGW) by combining RISC-V cores with microcontrollers (MCUs) and system-on-chips (SoCs), as well as analog and power ICs, all of which could potentially benefit from the RISC-V technology.

This partnership to develop automotive applications for RISC-V includes SiFive licensing the use of their RISC-V core IP portfolio to Renesas Electronics. SiFive’s roadmap of advanced, high-performance RISC-V processor cores and AI accelerators is expected to deliver significant core performance increases with the capabilities needed to meet automotive application requirements, along with enhanced AI capabilities to power scalable, workload-accelerated solutions.

Summary

RISC-V is a good fit for a range of automotive systems. This article has provided an overview of several of the more important developments, including ASIL-D safety-rated controllers and security co-processors, AI accelerators, controllers for advanced EV battery chargers based on GaN power semiconductors, and high-voltage monolithic motor drive controllers for light electric vehicles.