Rambus Inc.

Nvidia Corporation

Arash Zargaran-Yazd

Masum Hossain

Nhat M Nguyen

Yikui Jen Dong

Wendemagegnehu Beyene

Sunil Rao Sudhakaran

Seema Kumar

Santhosh Kumar Gude

Decision feedback equalization (DFE) is used to help reduce inter-symbol interference (ISI) from a data signal received via a band-limited (or otherwise non-ideal) channel. A first PAM-4 DFE architecture has low latency from the output of the samplers to the application of the first DFE tap feedback to the input signal. This is accomplished by not decoding the sampler outputs in order to generate the feedback signal for the first DFE tap. Rather, weighted versions of the raw sampler outputs are applied directly to the input signal without further analog or digital processing. Additional PAM-4 DFE architectures use the current symbol in addition to previous symbol(s) to determine the DFE feedback signal. Another architecture transmits PAM-4 signaling using non-uniform pre-emphasis. The non-uniform pre-emphasis allows a speculative DFE receiver to resolve the transmitted PAM-4 signals with fewer comparators/samplers.

PAM-4 DFE architectures with symbol-transition dependent DFE tap values

A system includes a transmitter to transmit a set of bits associated with signaling having one or more levels. The system includes a receiver coupled to the transmitter, the receiver to receive the set of bits and generate a first plurality of digital values, each digital value generated at a first timing value and a plurality of reference voltages, the reference voltage incremented based at least in part on generating a digital value of the first plurality of digital values. The receiver is to generate a second plurality of digital values at a second timing value and the plurality of reference voltages, the first timing value incremented to the second timing value based at least in part on generating the first plurality of digital values. The system includes a controller to determine an amplitude associated with each the first and second plurality of digital values.

On-chip virtual oscilloscope using high-speed receiver sampler readback

A receiver serial data streams generates a local timing reference clock from an approximate frequency reference clock by phase-aligning the local clock to transitions in the data stream. This process is commonly known as clock and data recovery (CDR). Certain transitions of the data signals are selected for use in phase-aligning the local clock, and certain transitions are ignored. Phase-error signals from multiple receivers receiving the multiple serial data streams are combined and used to make common phase adjustments to the frequency reference clock. These common adjustments track jitter that is common to the received data streams. Local adjustments that better align each respective local clock to the transitions of its respective serial data stream are made using a local phase-error signal. These local adjustments track jitter that is more unique to each of the respective serial data streams.

Collaborative clock and data recovery

Growing community of inventors

Sunnyvale, CA, United States of America

Arash Zargaran-Yazd