slow-fast (sf) corner

**Slow-Fast (SF) corner** is the **opposite of FS corner** — NMOS slow while PMOS fast, completing the asymmetric corner coverage to catch timing failures on the opposite transition direction. **What Is SF Corner?** - **Definition**: NMOS slow + PMOS fast (or opposite convention). - **Purpose**: Verify opposite edge from FS corner, complete asymmetric coverage. - **Use**: Complement to FS corner for full verification. **SF Corner Characteristics** **NMOS**: Slow process, low mobility, high Vth. **PMOS**: Fast process, high mobility, low Vth. **Result**: Opposite imbalance from FS corner. **Why SF Corner Matters?** - **Complete Coverage**: Catches failures FS corner misses. - **Opposite Edge**: Verifies the other transition direction. - **Analog Balance**: Tests differential pairs from other side. - **Symmetry**: Ensures both edges are verified. **What Gets Verified** **Opposite Transition**: Check edge not covered by FS. **Hold Time**: Verify no violations on this edge. **Analog Circuits**: Test from opposite imbalance direction. **Level Shifters**: Verify both polarity combinations. **Applications**: Complete corner coverage, analog verification, differential circuit analysis. SF corner is **the mirror image** — proving every transition works even when the opposite polarity dominates.