Design Margins in SRAM Design

To basic types:

• Self Timed: Does not vary with frequency, process, temperature, voltage
• Frequency Dependent: Varies with each timing, process corner

Self-Timed Margin (STM) can be of two sub-types:

• STM(Functional): Not meeting this margin breaks your functionality and the design is broken. For Example: Setup and Hold Violations.
  Typically 15% pre-layout and 10% post-layout

• STM(Crowbar): Not meeting this margin, causes a crow-bar current. You lose performance and power, but the design is correct functionally. For Example: Turning off pre-charge clock after the word-line turns on, causes the bit-line to discharge very slowly and there is a huge crow-bar current flowing through it. This impacts your clk2q and also is a huge power drain.
  Typically 0-10% pre-layout and 10% post-layout