The required performance level for both stationary and mobile use case is Pld. PLd can be achieved by either using Category 2 (Cat 2) or Category 3 (Cat 3) architecture (see Figure 3-9) as defined per ISO 13849-1.

With "Category" the ISO 13849-1 standard specifies the resistance to faults. For a Cat 2 this would be a Single channel plus diagnostics as seen in Figure 3-11. For a Cat 3, this would be a dual channel plus diagnostics architecture and no accumulation of faults.

The designated architectures cannot be considered only as circuit diagrams but also as logical diagrams. For category 3, this means that not all parts are necessarily physically redundant but that there are redundant means of assuring that a fault cannot lead to the loss of the safety function. Main relevant understanding of a Cat 3 architecture is that every single failure does not lead in a loss of the safety function. A change into a safe state in case of a fault is okay. Therefore, for a fail-safe application the requirement for single-fault tolerance does not necessarily mean that a two-channel system must be implemented. Also, a single channel system with a high standard of monitoring that responds to a fault with a dedicated deactivation path sufficiently quickly for a dangerous state to be avoided can be fulfill Cat 3.

At the sensor level, there are two main possible architectures for PLd:

• A logical dual-channel approach, leveraging IWR6843 unique hardware architecture in combination with the safety PMIC LP87745, which would allow a CAT 3
• A SW diversity approach and higher diagnostics in combination with the safety PMIC LP87745, which would allow at least CAT 2