AC Testing is an electrical test that measures the dynamic (time-dependent) performance of an integrated circuit — verifying timing parameters such as propagation delay, setup/hold times, and maximum operating frequency under switching conditions.

What Is AC Testing?

• Definition: Tests performed while the circuit is actively switching.
• Key Measurements:
• Propagation Delay ($t_{pd}$): Time from input change to output change.
• Setup Time ($t_{su}$): Data must be stable this long before the clock edge.
• Hold Time ($t_h$): Data must be stable this long after the clock edge.
• Rise/Fall Time ($t_r$, $t_f$): Edge transition speed.
• $F_{max}$: Maximum clock frequency at which the device operates correctly.
• Equipment: High-speed ATE with timing generators and comparators.

Why It Matters

• Speed Binning: Sorting chips into speed grades (e.g., 2.0 GHz, 2.4 GHz, 3.0 GHz) based on AC results.
• Signal Integrity: Verifying that outputs meet spec under load.
• Margin: Ensuring timing margins are sufficient for reliable system-level operation.

AC Testing is the speed test for silicon — determining how fast a chip can reliably operate under real-world switching conditions.