A rail or power rail refers to a group of
supplies or power rails. In this section, a supply or power supply refers to an
individual device power supply such as Vccint and Vccram. An auxiliary power supply can
have voltage regulators that are fed by multiple sources in different phases. To handle
this, user may need to add a power rail in multiple groups to account for voltage
sources drawing current from different phases. Power rail definitions, the number of
phases for a power rail as well as phase distribution on a rail and their current
budgets are typically supplied with the target board files. Xilinx supports Tcl commands to overwrite board data or to create rail
definitions, update phase information, and current budgets. Following are some useful commands:
- create_power_rail
- Creates a new power
rail.
create_power_rail <power rail name> -power_sources {supply1, supply2 ,..} create_power_rail <power rail name> -power_sources {supply1, supply2 ,..} -num_phases <number of phases> create_power_rail <power rail name> -power_sources {supply1, supply2 ,..} -phased_power_source {<power rail name with phase info> <num_phase>} - delete_power_rail
- Deletes an existing power
rail.
delete_power_rail <power rail name> - add_to_power_rail
- Add power sources to an existing power
rail.
add_to_power_rail <power rail name> -power_sources {supply1, supply2, ..} add_to_power_rail <power rail name> -power_sources {supply1, supply2, ..} -phased_power_source { <power_rail_with_phase_info> <num_phases> } - remove_from_power_rail
- Removes power sources from a power
rail.
remove_from_power_rail <power rail name> -power_sources {supply1, supply2, ..}
When defined, the supply current budget can be specified for the Power Rails along with the Rail voltage. The power budget of the Rail is the supply current budget multiplied by the Rail voltage. Use the following command to specify the power and supply current budget:
set_operating_conditions -supply_current_budget {<supply rail name> <current budget in Amp>} -voltage {<supply rail name> <voltage>}
Important: Power rail reporting is not supported in the Report Power GUI, to
view the complete results, ensure to generate a .txt output file.
Report Power compares the current on each Power Rail against their current budget and indicates positive and negative margin in the power text report as discussed in the previous section. The following figure shows a power text report with Power Rails and their budgets.
Figure 1. Power Text Report
