What is IR drop and how is it analyzed?

IR drop is voltage reduction across power distribution network due to resistance and current flow (V = I*R). Static IR: DC current through PDN resistance. Dynamic IR: Switching current causes transient voltage drop. Effects: Timing degradation (cells slower at lower voltage), functional failures (logic levels compromised), and reliability issues. Analysis: Vectorless (statistical switching activity) or vector-based (specific test patterns). Mitigation: Wider power straps, more vias, decoupling capacitors, and power mesh optimization. Signoff criteria: typically 5-10% VDD maximum drop.