Digital V2 Constant On-time Control Buck Converter with Adaptive Voltage Positioning and Automatic Calibration Mechanism

This article presents a digital V2 constant on -time control buck converter with adaptive voltage positioning (AVP) and automatic closed-loop output impedance ( Z oc) calibration for advanced system-on-a-chip processors. To ensure that the output voltage deviation remains within the desired range, the system is equipped with AVP. For an optimal AVP design, the system includes a second-order digital inductor current sensor for deriving a constant Z oc within a wide bandwidth. A detailed system-level analysis was performed to design the proposed control architecture. Considering the inevitable variation and aging of power stage components, the system is equipped with an online real-time Z oc calibration mechanism established to ensure the performance of AVP control. A prototype chip was fabricated using a 90-nm complementary metal–oxide–semiconductor (CMOS) process. The digital controller was fully realized using a standard cell library. Under a 0.9-A load transient, the measured output voltage could be adequately constrained within a specified 1.1-V and 110-mV AVP window.