I'm in the process of designing a mixed signal circuit powered by USB. Power supply requirements: 0-5V and 0-3.3V for a microcontroller and an audio codec (ADC/DAC), -5V to +11.5V (ground at +5V)to an analog IC. A step-up converter boosts +5V to 11.5V I understand that between the digital and analog supply a ferrite bead filters high frequency noise. The analog and digital ground are connected to their own ground planes. An LM137 converts 5V to 3.3V. Would this circuit work? Is there a way to improve it?