Karthik Padmanabhan

Integration of a Monolithic Buck Converter Power IC and Bondwire Inductors With Ferrite Epoxy Glob Cores

In this letter, we report a concept of integrating a monolithic buck converter power IC with in-package bondwire inductors. The power IC containing all switching devices, driver circuitry, and control logic was designed and fabricated with a standard 0.5-μm CMOS process. Mutliturn bondwires with and without ferrite epoxy glob cores are used as the filter inductor in the buck converter. A prototype system-in-package converter with an output voltage and current of 2.5 V and 120 mA was built to operate at frequencies up to 5 MHz. The power level of the prototype buck converter is scalable by increasing the size of the active power switches.

Modeling, Design, and Characterization of Multiturn Bondwire Inductors With Ferrite Epoxy Glob Cores for Power Supply System-on-Chip or System-in-Package Applications

The concept of coupled multiturn bondwire inductors with ferrite epoxy glob cores is investigated both experimentally and numerically to offer a cost-effective approach realizing power supply system-on-chip (PSoC) or system-in-package (PSiP). Improvement in total inductance and Q factor is demonstrated for the multiturn bondwire inductors due to the coupling effect. An empirical calculation method is developed to help determine the self and mutual inductance of the proposed bondwire inductors. The bondwire magnetic components can be easily integrated into IC packaging processes with minimal changes, and open possibilities for realizing cost-effective, high-current, and high-efficiency PSoCs or PSiPs.

A novel trench shielded MOSFET with buried field ring for tunable switching and improved ruggedness

In this paper, a novel trench shielded 600V MOSFET with buried field ring is proposed and demonstrated. The proposed structure achieves an active area die shrink of 35-55% compared to a conventional 600V planar MOSFET. Furthermore, it almost doubles the Unclamped Inductive Switching (UIS) rated current and improves 0.3% of the efficiency compared to the Superjunction device. It also shows better diode reverse recovery performance than Superjunction device.

A novel Trench Fast Recovery Diode with injection control

A novel Trench Fast Recovery Diode (FRD) structure with injection control is proposed in this paper. The proposed structure achieves improved carrier profile without the need for excess lifetime control. This substantially improves the device performance, especially at extreme temperatures (-40 °C to 175 °C). The device maintains low leakage at high temperatures, and its Qrr and Irm do not degrade as is the usual case in heavily electron radiated devices. A 1600 diode using this structure is proposed in this paper, with a low Vf and good reverse recovery properties. The experimental results show that the structure maintains its performance at high temperatures.

MHz-frequency operation of flyback converter with monolithic self-synchronized rectifier (SSR)

Synchronous rectification offers an effective solution to improve efficiency of low-output-voltage flyback converters. Conventional synchronous flyback topologies using discrete synchronous rectifier face challenges in precise timing control on the secondary side. In this paper, MHz-frequency operation of a flyback DC-DC converter using a new monolithic self-synchronized rectifier (SSR) is investigated and demonstrated. The SSR IC, acting solely on its own drain-source voltage instead of external control signals, considerably simplifies converter design, improves system efficiency, and enables MHz operating frequency. Analysis, modeling, and experimental results are presented.

Robust Trench Buried-Guard-Ring-Based Termination for Charge Balanced Devices

A major limitation on the performance of high-voltage power semiconductor is the edge termination of the device. It is critical to maintain the breakdown voltage of the device without compromising the reliability of the device by controlling the surface electric field. A good termination structure is critical to the reliability of the power semiconductor device. The proposed termination uses a novel trench MOS with buried guard ring structure to completely eliminate high surface electric field in the silicon region of the termination. The proposed termination scheme was applied toward a 1350-V fast recovery diode and showed excellent results. It achieved 98% of parallel plane breakdown voltage, with low leakage and no shifts after high-temperature reverse bias testing due to mobile ion contamination from packaging mold compound.