Chip-level tweaks give automotive SoC performance boost
Domain and zone architectures in the car are becoming reality – and require adequate high-performance infrastructure in the car. Renesas now has pimped its existing gateway SoC range. At the current International Solid-State Circuits Conference (ISSCC) in San Francisco, the company announced its latest tweaks at the semiconductor level.
SoCs for automotive gateways provide both high performance data path and routing capabilities to implement new applications such as cloud services. When not in use, they must reduce their power consumption to a minimum, especially when they are installed in BEVs. They also need to deliver fast CAN response to support instant start-up. Additionally, these SoCs need to provide power-efficient communication technology that enables network functions as a gateway using limited power and security technology to enable safe communication outside the vehicle. To meet these requirements, Renesas has developed
- an architecture that dynamically changes the circuit timing to match vehicle conditions with optimised performance and power consumption,
- fast start-up technology by partitioning and powering essential programs only,
- a network accelerator that achieves a power efficiency of 10 gigabits per second/watt (Gbps/W), and
- security technology that prevents communication interference by recognizing and protecting vital in-vehicle communication related to vehicle control.
Faster data exchange through chip-level improvements: Renesas R-Car S4
Details of the new technologies include:
- Architecture that optimizes processing performance and power consumption depending on vehicle conditions: Communication gateway SoCs need to deliver processing performance exceeding 30,000 Dhrystone million instructions per second (DMIPS) when running, while also keeping standby power consumption to 2 mW or less in order to maintain battery life. However, high-performance SoCs typically also have high power consumption in standby mode, while low-power SoCs with small standby power consumption have performance issues. To resolve this tradeoff, Renesas combined in a single chip a high-performance application system and a control system optimized for ultralow standby power consumption. The architecture controls the power supplies of these two subsystems and changes the timing of circuit operation to achieve an optimal balance between performance and power efficiency.
- Fast start-up technology with external flash memory achieving the same fast speed as embedded flash memory: Since communication gateway SoCs manage processing of critical functions related to vehicle control, they must be able to respond to CAN within 50 milliseconds of start-up. However, if the SoC uses a process that does not support embedded flash memory, the start-up program must be encrypted and stored in external flash memory. This means that it takes additional time to load program data and decrypt it. To solve this issue, Renesas developed technology that splits the program into sections and initially loads and decrypts only an essential portion for start-up, while continuing to load the rest of the program in parallel. This enables a fast response to CAN of 50ms or less, even when using external flash memory.
- Highly efficient network accelerator with 10 Gbps/W communication efficiency: To allow air cooling and heat dissipation for ECUs, communication gateway SoCs must keep power consumption to 7 W or less. Since performance of 30,000 DMIPS or higher requires approximately 6 W of power, only around 1 W can be used for network processing. This presents a challenge as the total communication of 10 Gbps must be achieved using 1 W of power, with a processing efficiency of only around 3 Gbps/W when processed by the CPU. To work around this issue, Renesas offloaded processing from the CPU to a custom network accelerator, achieving higher efficiency at 9.4 Gbps/W. Additionally, Renesas boosted efficiency to 11.5 Gbps/W by switching the routing method from a conventional TCAM approach to a hash table in SRAM.
- Security technology to prevent interference with communication requiring high reliability: Communication gateway SoCs perform a mixed set of tasks such as data processing related to vehicle control that requires a high level of reliability, and large amounts of random data communication with cloud services and others. Since vehicle control is essential to ensuring safety, protecting and separating mission-critical data is important. However, despite the differences in data types, all data is transmitted through the same in-vehicle network, leading to physical intersections and raising security issues. To address this challenge, Renesas developed security technology that analyzes incoming packets to the SoC. It determines whether or not they contain essential data, and assigns them to different pathways and control functions within the network accelerator. This prevents interference with data that requires high reliability and safeguards in-vehicle data communication from a variety of security threats.
These technologies have been incorporated into Renesas’ current R-Car S4 vehicle communication gateway SoC. With the latest iteration of the chip, developers can accelerate advances in E/E architectures, implement secure connection with cloud services, and ensure safe and reliable vehicle control at the same time.
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