A simplified single-inductor dual-output DC-DC buck converter architecture with a fully digital Σ-Δ based controller

In this paper, a fully digital single-inductor dualoutput (SIDO) DC-DC Buck converter architecture is presented. The proposed converter features a simplified control loop that eliminates duplication of the controller sub blocks and allows for use of a single Pulse Width Modulator (PWM), compensator, and comparator to regulate the two outputs, therefore reducing overall system complexity. A 3^rd order ΣΔ modulator was adopted for the implementation of the PWM generator resulting in spurious tone free operation. The ΣΔ modulator is implemented digitally with a minimum response delay time topology and reduced hardware complexity achieved through error masking and dithering. In addition, digitization of error signals in the control loop is achieved using non-feedback firstorder ΣΔ frequency Discriminators (SDFD) that are combined in an arrangement robust to process, voltage and temperature (PVT) variations. The design was implemented in 14nm technology and validated with simulations. Output voltage ripple is ~20mV and conversion efficiency 91%.