For different voltage threshold groups, cell leakage is different. A common way to reduce leakage power is to swap LVT cells to HVT cells. LVT & HVT cells usually have the same area, pin, and layout.
Voltage threshold group setting:
The voltage threshold group is a string attribute set to library or library cell.
- For library, the attribute name is default_threshold_voltage_group.
- For library cell, the attribute name is threshold_voltage_group
You can using set_attribute to set the attribute to library and library cell. If you set the attribute both on library and library cell, the lib cell's attribute will override the default.
The attribute should be saved in .lib file, and compiled into .db files.
How to identify voltage threshold groups:
There is no easy way to deside it based on area & leakage value.
Following is an example for LMP/LXP/SXP/HXP cells:
-- EOF-TRUEVUE --
Lib Cell VTH Area Leakage
SEDFPRQX1HXP VT: 1 10.36800003 0.69336277
SEDFPRQX1SXP VT: 2 10.36800003 1.35262072
SEDFPRQX1LXP VT: 3 10.36800003 3.90733600
SEDFPRQX1LMP VT: 4 10.36800003 16.62232399