Standard Cell Characterization

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Cell Characterization

• a technical brief

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What is Characterization?

• Circuit characterization is a process of
  analyzing a circuit using static and dynamic
  methods to create models suitable for chip
  implementation flows.

• Software analyzes circuit characters to create
  models
• circuit (spice format)
• character (cdf format)
• analysis (guna software)
• model (libertyTM format)

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Why Characterization?

• No digital chip is possible without cell models.
• These cell models are produced by cell
  characterization using commercial softwares like
  guna.
• rtl-to-gdsII flow requires cell models for
  analysis
• (logic simulation, verification, timing, power,
  noise etc),
• implementation (synthesis, test insertion,
  placement, clock tree synthesis, routing) and
• fixing (engineering change order, rule fixing
  etc).

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Software - guna

• guna is a fast and flexible standard cells, I/O
  pad and complex cell characterization platform.
  It is built on BEST in class analysis engines,
  performing Boolean, Electrical, Structural
  Stimulus and Temporal analysis of circuits.

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guna Benefits

• BEST engines provide
• Smart worst case stimulus search improves
  correlation and avoids silicon failure.
• Automatic function recognition, acquisition,
  specification.
• Compact waveforms to maintain accuracy with min
  space.
• High throughput with massively parallel fine
  grained distributed computing.
• Built-in proprietary spice engine.
• Productivity gains with incremental
  characterization.
• Comprehensive support for all cell types with
  proprietary circuit description format (CDF).

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Characterization Flow

• acquire or recognize cell's function,
• generates stimulus appropriate to determine
  characteristic (like delay, transition time etc),
  
• simulates it using circuit simulator,
• gather simulations output to measure
  characteristic and
• finally writes this data into a standard like
  libertyTM, veriog or IBIS.

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Typical Coverage
Cell Type Sim Type

• delay
• tristate
• input cap
• hidden power
• glitch power
• dynamic power
• leakage power
• setup
• hold
• recovery
• removal
• mpw

• CCS delay
• CCS cap
• CCS power
• PG currents
• Leak currents
• CCS noise
• CCSN VIVO
• CCSN Volt
• CCSN propagation
• CCSN Miller

• Standard cells including single- and multi-output
  combinational cells
• Flip-flops and complex latches
• Tri-state cells, bus holder cells
• Multiplexers, including one-hot MUXes
• Multi-voltage cells and I/Os
• I/Os with differential inputs
• Bidirectional I/Os
• Multi-mode cells

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• paripath.com