On-chip oscilloscopes for noninvasive time-domain measurement of waveforms

High-speed digital design is becoming increasingly analog. In particular, interconnect response at high frequencies can be non-monotonic with "porch steps" and ringing. Crosstalk (both capacitive and inductive) can result in glitches on wires that can produce functional failures in receiving circuits. Most of these important effects are not addressed with traditional ATPG and BIST techniques, which are limited to the binary abstraction. In this work, we explore the feasibility of integrating primitive sampling oscilloscopes on-chip to provide waveforms on selective critical nets for test and diagnosis. The oscilloscopes rely on subsampling techniques to achieve sub-10 psec timing accuracy. High speed samplers are combined with DLLs and a simple 8-bit ADC to convert the waveforms into digital data that can be incorporated as part of the chip scan chain. We will describe the design and measurement of a chip we have fabricated to incorporate these oscilloscopes with a high frequency interconnect structure in a TSMC 0.25 μm process