8.5. Power pins and Power flags

8.5. Power pins and Power flags

It is common to have an error or a warning on power pins, even though all seems normal. See example above. This happens because, in most designs, the power is provided by connectors that are not power sources (like regulator output, which is declared as Power out).

The ERC thus won’t detect any Power out pin to control this wire and will declare them not driven by a power source.

To avoid this warning you have to place a “PWR_FLAG” on such a power port. Take a look at the following example:

The error marker will then disappear.

Most of the time, a PWR_FLAG must be connected to GND, because usually regulators have outputs declared as power out, but ground pins are never power out (the normal attribute is power in), so grounds never appear connected to a power source without a pwr_flag.