DesignCon 2023 Paper Presentation: High-Speed Loopback Applications by Utilizing a Differential DPDT MEMS Switch

Authors:
Stewart Yang, Menlo Micro
Jangwoo Lee, Advantest Korea Co., Ltd.

Abstract:

Ever increased electronic system performance are forcing faster communications between chipsets and memories. Precision high-speed testing of chipsets on design-in-boards is forcing test engineers to Utilizing higher precision components on loopback paths with switches to route the signals back into the DUT becomes widely adopted on design-in-boards method for precision high-speed testing of chipsets. Many of these paths include PCIe 4.0/5.0, Serdes, Ethernet, USB3.x/4, and HDMI.

One of the limiting factors with increasing data rates, such as for PCIe 5.0 specifications, is the switch performance at higher frequencies., The MEMS switch has switching speed of 10s due to its tiny dimension versus milli seconds range for a bulky EM relays. This allows for a significant increase in test speed and DUT throughput. The small size of the device enables higher test site density so again increasing DUT throughput. The lifespan of the MEMS switch is 3 billion cycles, compared to up to 10 million life cycles for EM relays could help reduce the test system down time.

Design for Signal integrity is critical for optimized PCB layout and fabrication. The session will present details of 2x Through fixture design, PCB design parameters, and how to minimize  impedance discontinuity. The session will cover the differential signaling scheme, microwave de-embedding techniques, eye diagram test setup and test conditions, and present measured eye-diagram performance. The eye-diagram performance of the PCIe 5.0 loopback using differential DPDT MEMS switches is optimal both for its eye height and eye width without enabling any pre-emphasis and equalization.

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