John David Weld

Channel equalization and blocking filter utilizing microelectromechanical mirrors

This paper describes the design and performance of a 64-channel equalization and blocking filter. It utilizes a free space lens and grating multiplexer with micromechanical tilt mirrors providing variable attenuation. The module achieves a 5-dB insertion loss with a 3-dB passband of 87 GHz for 100-GHz spaced channels. The attenuation range achieved is in excess of 35 dB, making it suitable for wavelength blocking in switching applications. The device has been demonstrated to be compatible with 10- and 40-Gb/s transmission.

Optical MEMS devices for telecom systems

As telecom networks increase in complexity there is a need for systems capable of manage numerous optical signals. Many of the channel-manipulation functions can be done more effectively in the optical domain. MEMS devices are especially well suited for this functions since they can offer large number of degrees of freedom in a limited space, thus providing high levels of optical integration. We have designed, fabricated and tested optical MEMS devices at the core of Optical Cross Connects, WDM spectrum equalizers and Optical Add-Drop multiplexors based on different fabrication technologies such as polySi surface micromachining, single crystal SOI and combination of both. We show specific examples of these devices, discussing design trade-offs, fabrication requirements and optical performance in each case.

A 20MHz monolithic DC-DC converter manufactured with the first commercially viable silicon magnetics technology

This paper presents a Power System on Chip (Power-SoC), switch-mode DC-DC synchronous buck converter with switching frequency of 20 MHz, which monolithically integrates high-speed power MOSFET switches, controller and drive circuits, the compensation network, and more importantly, a silicon-based inductor. The new device implements a type III voltage mode control scheme with wide loop bandwidth, which offers ultra-fast transient with tiny small ceramic capacitor and ultra-low ripple (> 8mV peak-peak). The compact design facilitates encapsulation in a 3×4.5×0.9 mm DFN package, while its high efficiency eliminates the necessity of a heat sink. The fully integrated design only requires input and output capacitors, and offers an excellent size and cost-effective alternative to a comparable LDO for high-speed transient and noise sensitive applications. The controller chip is fabricated in a standard 0.25µm CMOS process including high speed, high voltage LDMOS devices used for the integrated power switches. The proprietary magnetics-on-silicon inductor is implemented using a magnetic alloy on silicon die mounted on a substrate coil-in-package to achieve an ultrasmall solution. Performance results show that the new converter can provide up to 1000mA of continuous DC output current, at up to 90% peak efficiency in Pulse-Width-Modulation (PWM) mode. The device is in production with the first commercially viable silicon magnetics technology deployed in a standard foundry.

Integrated magnetic-semiconductor components

We have taken a component view of packaging techniques to achieve high density, low profile power converters. In this work, we have focused on the simultaneous z-axis mounting and plastic encapsulation of the power magnetic device and the power semiconductors into one integrated package. In this effort we study the impact on power density, electrical and thermal performance as well as manufacturability.