Power Switch cells and strategy in Power aware design and UPF

Overview:

• Power Switch cells are used for Power distribution in Power aware design. 
• These are typically inserted by Placement and routing tool (i.e ICC).
• To let tool insert a PSW cells in the design , At RTL stage user needs to define Power switch strategy in UPF using create_power_switch command.

Types of Power switch cells:

Depending on liberty attribute:

1. Fine grain :

• Liberty attribute : switch_cell_type : fine_grain;

2. Coarse grain :

• Liberty attribute : switch_cell_type : coarse_grain;

Depending on Power/Ground Routing:

1. Header switch :

• This is for routing Power Net. PMOS is used for constructing this type of PSW cells as PMOS is good to pass logic 1 .

2. Footer switch :

• This is for routing Ground Net. NMOS is used for constructing this type of PSW cells as NMOS is good to pass logic 1 .

Example: 

UPF:

create_power_switch sw_1 -domain TOP

-output_supply_port {psw_out VDD_PSW}

-input_supply_port {psw_in VDD}

-control_port {ctrl_psw sw_en}

-on_state {PSW_on vin { ctrl_psw }}

-off_state {PSW_off { ! ctrl_psw}}