An on-chip USB-powered three-phase up/down DC/DC converter in a standard 3.3 V CMOS process

Some USB powered applications, like PC cameras, require an accurate and low-ripple 5 V supply for sensitive circuits, such as image sensor and video processing. Therefore an on-chip USB powered DC/DC converter with a regulated low-ripple 5 V output is needed for this USB application. As the USB supply voltage can range from 4.0 V to 5.5 V, the required DC/DC converter is of the up/down type. Known solutions are, e.g., the SEPIC converter, which requires a transformer, and the combination of an upconverter and a linear regulator, which results in a low efficiency. The presented on-chip DC/DC converter needs only an external coil and output capacitor. A digitally-controlled three-phase switching scheme is employed for easy implementation with high efficiency. A two-phase switching scheme would require a more complex duty cycle and up/down switching control.