ACTIVE DRIVER Characterization

026_cell : ACTIVE DRIVER Characterization

Minimum Required Versions: AccuCell 2.6.0.R, SmartSpice 4.6.2.R

This example explains the basics of AccuCell's ACTIVE DRIVER characterization and modeling options for an inverter using the embedded SmartSpice SPICE engine to perform characterization.

The use of ACTIVE DRIVER characterization replaces the input RAMP stimulus with an actual buffer cell to generate a realistic input stimulus curve. For critial applications, the differences between the edge shapes can result in unacceptable timing difference due to edge shape sensitivity. The use of this feature often provides a better match to the actual cell library output drive characteristics when the pre-driver buffer cell is chosen appropriately.

The libray level .cfg file commands DRIVER_*, BUF_SUBCKT, LOAD_SUBCKT, SLEW_LOAD_TABLE, TRUE_DRIVER_SLOPE specify and control the process. A pre-characterization step is initially performed in an interactive manner to establish the proper characterization conditions to match the desired slope tables and the results are saved for later use during the characterization phase. This pre-driver pre-characterization work need only occur ONCE as long as all need slopes are pre-characterized for each coner of characterization. To eliminate device under test loading effects the actual cell inputs are isolated and driven by an ideal SPICE "E" element that is driven with the pre-characterization pre-driver stimulus results.

For additional details on the ACTIVE DRIVER commands and there use, please refer to the AccuCell Reference Manual and AccuCell Uer's Manual.