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Physical Design & Signoff

Timing Signoff Across Corners: Why One Timing Run Isn't Enough

A chip that meets timing under perfect, average manufacturing conditions can still fail in the real world, where every chip comes off the manufacturing line with slightly different transistor characteristics, and operates across a range of voltages and temperatures.

VIDYUTT• August 3, 2026• 2 min read
Figure 1: Timing must close across multiple process, voltage, and temperature (PVT) corners, not just typical conditions.
Figure 1: Timing must close across multiple process, voltage, and temperature (PVT) corners, not just typical conditions.

What Multi-Corner Timing Signoff Involves

Chips are analyzed across multiple 'corners' representing combinations of process variation (e.g., slow-slow or fast-fast transistors), supply voltage, and operating temperature. A design must meet setup and hold timing requirements in every one of these corners – a slow, cold, low-voltage corner might be the hardest for setup timing, while a fast, hot, high-voltage corner might be hardest for hold timing.

Why It Matters

Manufacturing variation is unavoidable – no two chips off the same production line are perfectly identical. Signing off timing only at nominal, 'typical' conditions all but guarantees that some fraction of manufactured chips will fail to meet timing once real-world variation and operating conditions are accounted for.

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