Vec-643 [repack] May 2026
Project/Issue Write‑Up – VEC‑643
Prepared on 16 April 2026
6.4 Safety & Timing Re‑analysis
- WCET: Run static analysis with Polyspace Code Prover on
Task_TorqueVectoring. - Timing Model: Update Simulink model, run Monte‑Carlo simulations (10 000 runs) to confirm ≤ 5 ms worst‑case.
- ASIL‑D Argument: Produce a new Safety Case section (VEC‑SCC‑004) showing compliance.
2. Switch Mode Power Supplies (SMPS)
In high-power SMPS units (500W+), the VEC-643 serves as a primary-side filter. Its high voltage rating ensures it can handle rectified mains electricity in 480V three-phase systems without failing. VEC-643
3. Problem Statement
- Latency Jitter – The existing torque‑vectoring command processing exhibits non‑deterministic latency (3 ms ± 9 ms) under peak bus load.
- Resource Contention – The polling loop monopolises the single CPU core, starving lower‑priority tasks (e.g., diagnostics, OTA update handler).
- Safety Margin Erosion – The ISO‑26262 safety analysis assumes ≤ 5 ms deterministic response; the observed jitter exceeds this, impacting ASIL‑D compliance.
Root Cause (pre‑liminary) – The VEC firmware uses a blocking while (!msgReady) construct that prevents the scheduler from pre‑empting the loop, and the CAN driver runs in interrupt‑latency mode without proper priority inversion handling. Project/Issue Write‑Up – VEC‑643 Prepared on 16 April
2. Background & Context
| Item | Detail |
|------|--------|
| System | VEC Suite (v4.7.2) – the core software stack that runs on the Vehicle Embedded Controller (VEC) for power‑train, chassis and ADAS coordination. |
| Stakeholders | • Product Management (PM – Jane Doe)
• Firmware Engineering (FE – John Smith)
• Quality Assurance (QA – Emily Zhang)
• Safety & Compliance (SC – Mark Patel)
• End‑Customer (OEM – AutoMotiveX) |
| Relevant Documents | • VEC‑ARCH‑001 – System Architecture
• VEC‑REQ‑018 – Functional Requirements for Torque‑Vectoring
• VEC‑TEST‑023 – Regression Test Matrix
• ISO‑26262 ASIL‑D Safety Plan |
| Current State | The VEC controller currently processes CAN‑bus torque‑vectoring commands using a single‑threaded, polling‑based loop (≈ 3 ms latency). Field data shows occasional jitter spikes up to 12 ms, leading to NVH (Noise‑Vibration‑Harshness) complaints on Model‑X2025. |
| Business Impact | • OEM has issued a Service Bulletin (SB‑2025‑07) requesting a fix for all vehicles delivered after Q2‑2025.
• Failure to address may result in warranty claims estimated at US $4.2 M and a potential loss of future platform contracts. | WCET : Run static analysis with Polyspace Code
Where to Buy
- Authorized Distributors: Digi-Key, Mouser, or Arrow (Limited stock, often rebranded equivalents).
- Aftermarket Specialists: Octopart, FindChips, or 1-source components.
- Caution: Avoid eBay or Alibaba for VEC-643. Counterfeit units often use 400V dies relabeled as 643V. This is a fire risk.
Electrical Characteristics
- Operating Voltage Range: 3.3V to 5.5V DC (with transient over-voltage protection up to 6.8V)
- Current Consumption: Idle: 12mA; Active: 210mA (typical); Peak: 450mA
- Impedance: 50 Ohms nominal (RF applications)
- Isolation Rating: 1.5kV RMS (reinforced isolation for industrial safety)
2. Visible Cracking
Due to thermal cycling (constant heating and cooling), the epoxy casing may crack. This allows moisture ingress, which causes a short circuit or "flashover" across the leads.