Digital systems engineering
Coding schemes for chip-to-chip interconnect applications
IEEE Transactions on Very Large Scale Integration (VLSI) Systems
Concatenated convolutional codes with interleavers
IEEE Communications Magazine
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Increasing demand for high-speed inter-chip interconnects requires faster links that consume less power. Channel coding can be used to lower the required signal-to-noise ratio for a specific bit error rate in a channel. There are numerous codes that can be used to approach the theoretical Shannon limit, which is the maximum information transfer rate of a communication channel for a particular noise level. However, the complexity of these codes prohibits their use in high-speed inter-chip applications. A low-complexity signaling scheme is proposed here. This method can achieve 3-5-dB coding gain over uncoded four-level pulse amplitude modulation (PAM). The receiver for this signaling scheme along with a regular 4-PAM receiver was designed and implemented in a 0.18-µm standard CMOS technology. Experimental results show that the receiver is functional up to 2.5 Gb/s. This was verified with a bit error rate tester (BERT) and we were able to achieve error free operation at 2.5-Gb/s channel transfer rate. The entire receiver for this scheme consumes 22 mW at 2.5 Gb/s and occupies an area of 0.2 mm2.