serdes design high-speed
**High-Speed SerDes Design** creates **multi-gigabit serial transceivers converting parallel data to high-speed serial streams**, using equalization, clock recovery, and signal processing for reliable transmission at 10-200+ Gbps per lane.
**Architecture**:
| Block | TX | RX |
|-------|----|---------|
| Data path | Serializer (MUX) | Deserializer (DEMUX) |
| Equalization | FFE | CTLE + DFE |
| Clocking | PLL | CDR |
| Driver/Receiver | Current-mode | Linear EQ front-end |
| Adaptation | TX preset optimization | Eye monitor + loops |
**Signaling Evolution**:
| Standard | Rate | Modulation | Loss | Application |
|----------|------|------------|------|-------------|
| PCIe 5.0 | 32 GT/s | NRZ | ~30 dB | CPU-GPU |
| PCIe 6.0 | 64 GT/s | PAM4 | ~36 dB | CPU-CXL |
| 112G Ethernet | 112 Gbps | PAM4 | ~30 dB | Data center |
| 224G Ethernet | 224 Gbps | PAM4 | ~36 dB | Next-gen DC |
**PAM4**: 4 voltage levels encoding 2 bits/symbol. ~9.5dB SNR penalty versus NRZ. TX requires precise level spacing; RX typically ADC-based with digital EQ at 100+ Gbps.
**Equalization**: **TX FFE** — 2-5 tap FIR pre-distortion compensating channel loss; **RX CTLE** — analog high-frequency boost; **RX DFE** — decision feedback canceling post-cursor ISI without noise amplification; **ADC-DSP RX** — 6-8 bit ADCs with 20+ digital taps, enabling MLSE and ML-based equalization.
**CDR**: Bang-bang or linear phase detectors driving digital loop filter controlling fractional-N PLL. Jitter tolerance and transfer characteristics are critical specs.
**SerDes design operates at the intersection of RF circuit design, signal processing, and digital communication — each speed generation pushes closer to the Shannon limit of copper channels.**