ac testing

**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.