Capacitance Report (Power Rail Summary)

When processing a design, NetBom will automatically generate a power rail summary report. This report consists of one page for each power rail that was able to be identified in the design, and each page contains a list of the capacitor parts and information related to them.

For browser report help and information, see the Web Report Features documentation.

Here is an example report:

Open

Features

Power Rail Identification

All of our reports that display net voltage use our NetBom Voltage Matching system. In absence of net voltage properties, our voltage matching system uses the net name to extract the real voltage property of the net. The smart extraction is configurable using regular expressions; click the link above for more information.

After we identify all the nets that carry a voltage in the design, we comb through the list of potential power rails (nets carrying a voltage) and trim down the list by testing each one according to a specific rule set. Some of the rules we use are:

• Minimum number of ground-connected capacitors on the net

• Minimum capacitance value for a part to be included in the total capacitor count

• Minimum total capacitance (sum of all capacitors) on the net

• Maximum resistor Ohms to be traced through to find capacitors (e.g. if a capacitor is on the other side of a high-ohm resistor it will not be counted as a capacitor on the power rail)

See the configuration settings section for more detailed information about these rules and how to configure them to suit your design needs.

Rail Summary Navigator

At the top of the report is a power rail summary table. Each row in this table contains top-level information related to this rail. The voltage value is editable on each row. The total capacitance is the sum of all the total capacitance on the associated rail (accounts for cap derating).

Voltage Derating

The voltage derating is configurable inside NetBom and can be edited in the report. Changing this field will change the styling of the part voltage field on the associated row.

Cap Derating

The cap derating is also configurable inside NetBom with a default value of 90%. This number is used to multiply the part capacitance, which is then multiplied by the number of caps on that row and is then displayed as the total part capacitance. In the example above, the first row has a capacitance value of 10uF, multiplied by the number of parts (in this case, just a single part), times 90%, resulting in the total capacitance for that row of 9uF.

Configuration Settings

The power rail identification method is configurable using the following list of CSets:

In addition to those settings, there are CSets that govern some of the behavior inside of the report. Those are the following: