I have an application for the C5515 where it is only sometimes connected to USB. The device draws 90 mA after boot; when it is connected to USB, and then disconnected (theoretically returning it to the same state as after initial boot) it only draws 70 mA! As you can imagine, I am eager to recover this 20 mA.
I found that setting the ENSUSPM bit in the POWER register lowers the power consumption. However, if I set this immediately during USB configuration, the controller becomes inoperable and does not respond to insertion. If I wait one second later, the controller works just fine.
So, I have a workaround, but waiting one second is really cheesy. Does anyone know what is happening during that second? Is the LDO stabilizing or something? Is there some register I can query to know that it will be safe to activate suspend mode?