Standard Cell Characterization
Post date: Aug 31, 2014 2:15:09 PM
What is cell characterization?
Cell characterization is a process of analyzing a circuit using static and dynamic methods to generate models suitable for chip implementation flows.
Why is cell characterization needed?
No digital chip is possible without cell models. These cell models are produced by cell characterization using commercial softwares like guna. Every digital chip implementation (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).
How is cell characterization performed?
Cell characterization typically takes cell design extracted as spice circuit and spice technology models. Characterization software like guna from Paripath, analyzes this information to
- 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, verilog or IBIS.
This entire flow is depicted into the picture shown below
Figure: cell characterization flow
Cell characterization output
Cell characterization produces following outputs, in no particular order
- verilog
- IBIS
- libertyTM Format
- Delay
- Transition Time
- Tristate
- Input Capacitance
- Hidden Power
- Glitch Power
- Dynamic Power
- Leakage Power
- Setup Time
- Hold Time
- Recovery Time
- Removal Time
- Minimum Pulse Width
- Output Current Waveform
- Input Receiver Capacitance
- Power Supply Waveforms
- Ground Waveforms
- Leakage Current
- Gate Leakage Current
- CCB Output VIVO
- CCB Output Voltage Waveform
- CCB Input Miller Capacitance
- CCB Noise Propagation Model
- ... and other
Summary
This article answers main questions on standard cell characterization and model generation. Scope of this topic is VLSI cell/circuits. Please google for solar cell characterization and bio-cell characterization. Read more on VLSI characterization on Paripath Blog.