ASIL B
Understanding ASIL B
ASIL B is the most common safety classification for vehicle radar and RF systems that provide driver assistance warnings. These systems detect potential hazards and alert the driver, but do not directly control the vehicle — the driver retains ultimate control.
ASIL B Requirements
Compared to ASIL A, ASIL B increases rigor in several areas:
- Latent fault metric: LFM ≥80% (vs. 60% for ASIL A) — more internal faults must be detectable by diagnostic monitoring.
- Software methods: Semi-formal specification methods become recommended, and structural test coverage requirements increase.
- Safety validation: More comprehensive testing of the safety function under fault conditions.
Radar Systems at ASIL B
Blind-spot detection, rear cross-traffic alert, and parking radar systems are commonly classified ASIL B. These systems operate in scenarios where failure could lead to a collision, but the severity is moderated by low vehicle speeds and the driver's ability to visually verify the situation. The radar MMIC must incorporate sufficient self-diagnostic capability to detect failures and alert the driver that the function is degraded.
Key Equations
ASIL B is the second-lowest Automotive Safety Integrity Level in ISO 26262, applying to safety-related functions with moderate risk classification. For RF and radar systems,...
Key specifications:
90 % | 80 % | 60 % | 32.44 dB | 60 km
Power: P(dBm) = 10log(PmW), 0dBm = 1mW
Comparison
| Aspect | ASIL B Spec | Typical Range | Impact | Design Note |
|---|---|---|---|---|
| Primary function | ASIL B is the second-lowest Automotive S... | Application-dep. | Critical | Verify in sim |
| Operating range | Understanding ASIL B ASIL B is the most... | Application-dep. | Critical | Verify in sim |
| Performance | These systems detect potential hazards a... | Application-dep. | Critical | Verify in sim |
| Integration | ASIL B Requirements Compared to ASIL A,... | Application-dep. | Critical | Verify in sim |
| Trade-off | 60% for ASIL A) — more internal faults m... | Application-dep. | Critical | Verify in sim |
Frequently Asked Questions
Can ASIL B be achieved through decomposition?
Yes. An ASIL D function can be decomposed into two ASIL B subsystems if they are sufficiently independent. For example, a lateral collision avoidance system (ASIL D) might use a radar sensor (ASIL B) and a camera sensor (ASIL B) as independent sensing channels. The combined system achieves ASIL D through diversity and independence, even though each sensor individually meets only ASIL B.
What self-diagnostics does an ASIL B radar need?
Typical ASIL B radar self-diagnostics include: transmitter power monitoring (detecting PA failure), receiver noise floor monitoring (detecting LNA degradation), MMIC internal loopback testing (verifying the complete signal chain), timing reference monitoring (detecting clock failures), and antenna integrity monitoring (detecting physical damage through reflection coefficient measurement). These diagnostics must achieve the required diagnostic coverage percentage within the specified fault detection time interval.
How does ASIL B affect radar MMIC selection?
ASIL B requires MMIC devices with built-in self-test (BIST) capabilities that ASIL A and QM-rated applications do not require. Major automotive radar MMIC suppliers (Texas Instruments, NXP, Infineon) offer ASIL B-qualified variants of their 77 GHz radar chipsets with integrated safety monitoring features specifically designed to meet ISO 26262 hardware metrics.