“Although today’s vehicles have achieved automation in a variety of driving scenarios, it is not automakers that really push cars from partially automated driving to fully automated driving, but mobile service providers, such as taxi companies, car rental companies, and delivery companies. Cargo service companies and cities that need to provide safe, efficient, convenient, and economical public and private transportation.
Although today’s vehicles have achieved automation in a variety of driving scenarios, it is not automakers that really push cars from partially automated driving to fully automated driving, but mobile service providers, such as taxi companies, car rental companies, and delivery companies. Cargo service companies and cities that need to provide safe, efficient, convenient, and economical public and private transportation.
Before a fully autonomous self-driving car can drive on public roads, it must go through six different levels of automation, from level 0 (no automation) to level 5 (full automation), as shown in Figure 1. Every increase in the level of automation requires significant improvements in advanced driver assistance system (ADAS) technology and proper management of all safety-critical functions.
Figure 1: Autonomous driving level
Self-driving cars use multiple sensor technologies, including cameras, radar, and lidar. According to different environmental conditions and distances, these sensors have their own advantages and disadvantages. The sensor fusion box will analyze these sensor signals and data from GPS and car networking systems to create accurate three-dimensional environmental mapping and send appropriate action signals. Figure 2 is a block diagram of such an autonomous system.
Figure 2: Autonomous driving system
With the increasing level of vehicle automation, hardware and software subsystems have become more and more complex. In order to prevent drivers, passengers, and pedestrians from facing dangerous situations, the functional safety of these subsystems has become critical. These subsystems need to meet ultra-high-level functional safety standards, because any failure can be fatal. According to the automation level divided by ISO 26262, the functional safety of road vehicles must meet the highest ASIL-D automotive safety integrity level (ASIL).
In order to achieve a high level of ASIL functional safety requirements, these subsystems need to significantly reduce the failure rate and increase the coverage rate of failure detection by using appropriate diagnostic monitoring mechanisms and parallel redundant circuits. They need to measure and identify potential faults related to different power rails, detect whether there are any abnormalities in the voltage or current consumption of different power supplies, and whether there are any fluctuations in the system temperature. After diagnosing these faults, appropriate measures must be taken in time. Figure 3 shows a conceptual block diagram of this function.
Figure 3: Power rail and temperature diagnostic monitoring system
An easier way to use a standalone analog-to-digital converter (ADC) for diagnostic monitoring is becoming more and more popular. Functional safety goals may vary depending on safety criticality and implementation. In addition, the number of channels for each project or platform may vary, because the number of measurements may vary from project to platform.
To facilitate the realization of this diagnostic monitoring function, Texas Instruments (TI) has developed the ADS7038-Q1 and ADS7142-Q1. ADS7038-Q1 is an ultra-small (3mmx 3mm), 8-channel, 12-bit, ADC that meets the Automotive Electronics Council (AEC)-Q100 level 1 standard, with integrated general-purpose input and output pins (GPIO) and programmable fault detection Comparator, analog watchdog and 8-bit cyclic redundancy check code for data read/write operation and power-on configuration. ADS7142-Q1 is an ultra-small (2mmx3mm), dual-channel, 12-bit, AEC-Q100 Class 1 ADC with a programmable fault detection comparator. Figure 4 shows the block diagram of ADS7038-Q1, and Figure 5 shows the block diagram of ADS7142-Q1.
Figure 4: Simplified block diagram of ADS7038-Q1
Figure 5: Simplified block diagram of ADS7142-Q1
With the continuous improvement of the automation level of vehicles, Tier 1 suppliers and original equipment manufacturers increasingly need the above-mentioned ADCs that provide diagnostic monitoring to achieve their functional safety goals.