12.6 Capacitor-current-sensor calibration technique and application in a 4-phase buck converter with load-transient optimization

• Main Authors: Szu-Yu Huang, Kuan-Yu Fang, Yi-Wei Huang, Shih-Hsiung Chien, Tai-Haur Kuo
• Format: Conference Proceeding
• Language: English
• Subjects: Calibration; Capacitors; DC-DC power converters; Inductors; Optimization; Solid state circuits; Transient analysis
• ISSN: 2376-8606
• DOI: 10.1109/ISSCC.2016.7417990

For switching DC-DC converters, a large and rapid load-current transient ΔI load causes a large output voltage undershoot ΔV US and long settling time ts if the transient responses are slow [1]. Since the output capacitor current I Co instantly reflects ΔI load , transient response optimization for minimizing ΔV US and ts with given charging and discharging slopes of inductor current ILo can be achieved by obtaining an accurate I Co and well-controlling the I Lo charging time tch and discharging time tdch [1]. However, ICo sensing accuracy is degraded if the output capacitor's impedance Z Co , comprising the capacitance CO, equivalent series resistance RESR and inductance LESL, varies with different output voltage V O , process variation, and/or PCB parasitics, leading to non-minimized ΔV US and ts. An off-chip capacitor-current-sensor (CCS) calibration technique is reported in [2]; however, LESL is not considered, so the high-frequency information of ΔI load is inaccurately sensed when large and rapid ΔI load occurs. On the other hand, to well-control the tch and tdch of I Lo , the transient-optimized feedback circuit reported in [1] minimizes ΔV US and t s . However, optimization can be achieved only under fixed C O , output inductor L O , input voltage V IN , and V O .