NEWS
Congratulations to Sundaramoorthy Sridhar, PhD!
Jul 02, 2026
Sundar defended his dissertation titled, “Modeling and Stability Analysis for Multiphase Constant On-Time (COT) Control With Phase Overlapping”, conducted under the guidance of CPES Professor Qiang Li. This work delivers a rigorous small-signal framework that enables reliable design of high-performance multiphase voltage regulators, a critical component of today’s AI-driven processors.
Sridhar’s dissertation tackles a pressing limitation in power-management for multi-core AI chips: as the number of buck-converter phases grows, the on-time windows begin to overlap, causing non-linear interactions that existing single-phase models cannot predict. By extending the describing-function method to capture these dynamics, the research provides designers with frequency-domain tools (Bode, Nyquist) that were previously unavailable for overlapping-phase systems. The results are directly applicable to next-generation data-center and mobile processors that demand tighter voltage tolerances and faster transient response.
Key Technical Contributions:
- Developed the first generalized small-signal model for multiphase COT buck converters with phase overlap.
- Identified and characterized potential instability mechanisms across varying phase-overlap ratios.
- Derived closed-form stability boundaries for both current-mode and voltage-mode COT architectures.
- Demonstrated a 30% increase in control-bandwidth and a 25% reduction in design-iteration time via analytical design vs. pure simulation.
- Delivered a practical design-guide that integrates the new models into standard EE-CAD workflows.
Reflecting on his experience, Sundar said, “I am grateful to have been part of CPES, working with Dr. Qiang Li and alongside so many talented researchers and support staff. This journey helped me grow both as a researcher and as a person, teaching me patience, resilience, critical thinking, and effective communication.”
Sundar has joined Texas Instruments in Dallas, TX as a Systems Engineer on the Multiphase Processor Power (MPP) team.
Please join us in congratulating Dr. Sridhar on this outstanding achievement and wishing him success in his new role!
