This paper describes a 28-Gb/s receiver IC with self-contained adaptive equalization and sampling point control using an on-chip stochastic sigma-tracking eye-opening monitor (SSEOM). The proposed SSEOM accurately detects the bit-error-rate (BER)-related eye contour efficiently without the use of an external microcontroller. The SSEOM determines the BER-optimal sampling point and equalizer coefficients on the basis of pattern-filtered eye diagrams. It also features a background adaptation scheme for robust long-term operation by tracking temperature variations and device aging. The proposed SSEOM is integrated in a 28-Gb/s receiver that is designed to compensate for channel loss up to 25 dB at the Nyquist rate by using a continuous time linear equalizer (CTLE) and a one-tap decision feedback equalizer (DFE) together with an one-tap pre-emphasis at a transmitter. The time required for complete adaptation and the total power consumption are 364 ms and 43.9 mW, respectively. The proposed 28-Gb/s receiver is fabricated in 40 nm CMOS.

A 28-Gb/s Receiver With Self-contained Adaptive Equalization and Sampling Point Control Using Stochastic Sigma-Tracking Eye-Opening Monitor

This paper presents a complete 50–64 Gb/s serializing transmitter including a 4-tap equalizer. An LC-based FFE structure is proposed. The FFE improves the bandwidth of the delay line and the output combiner by applying the design methodology of LC-ladder filters. Proper arrangement of the output combiner reduces the required number of inductors and hence reduces the area. In addition, a novel 4:1 multiplexer (MUX) is used as the final stage of the serializer to reduce power. Designed and fabricated in 65 nm CMOS technology, the transmitter achieves a maximum data rate of 64.5 Gb/s with an energy efficiency of 3.1 pJ/bit.

A 50–64 Gb/s Serializing Transmitter With a 4-Tap, LC-Ladder-Filter-Based FFE in 65 nm CMOS Technology

This paper presents a quad-lane serial transceiver that supports virtually all data center communication standards around 8.5–13 Gbps, implemented in 28 nm CMOS technology. The transmitter consists of 20:2 mux followed by a half-rate source-series terminated (SST) driver embedded with a 4 tap FFE and an analog equalizer. The receiver has an adaptive CTLE, 5 tap DFE, and fully digital CDR followed by 2:20 demux. At 13 Gbps, the transceiver can equalize 35 dB Nyquist loss at BER of 10-12. At 1.0 V supply, the transceiver consumes 49 mW/lane at 13 Gbps rate with full equalization capability. An LC VCO-based fractional PLL provides the clocking to quad TX/RX lanes using a low-power inductively tuned clock routing channel. The transceiver architecture not only enables the baud rate operation from 8.5 to 13 Gbps but also supports a wide range of oversampled subrates. This work represents the lowest reported power in its class to date, and the transceiver is suitable for many applications due to its comprehensive flexibility and power efficiency.

A 3.8 mW/Gbps Quad-Channel 8.5–13 Gbps Serial Link With a 5 Tap DFE and a 4 Tap Transmit FFE in 28 nm CMOS

As processing and network speeds are accelerated to support data-rich services, the bandwidth of backplane interconnects needs to be increased while maintaining the channel length and multi-rate links. However, channel losses and impedance discontinuities increase at high data-rates, making it difficult to compensate the channel. In this work, we target serial links from auto-negotiation in 100G-KR4 of 0.3Gb/s to 32GFC of 28.05Gb/s in 40dB backplane architecture [1-3]. To achieve this challenge, there are two key techniques. First, we introduce a 36-tap decision-feedback equalizer (DFE) to cancel reflections due to connectors because these reflections close the eye. To operate the 36-tap DFE, we need to fix a CDR lock-point and calculate 36-tap coefficients accurately. Thus, we develop a pattern-captured CDR with a 4b pattern filter to fix the lock-point, and a 3b pattern-matched adaptive equalizer (AEQ) to optimize 36 tap coefficients. These techniques enable our chip to compensate 40dB channel loss. Second, we target 100G-KR4/40G-KR4/10G-KR/25G-KR and 32GFC/16GFC/8GFC/4GFC. To operate across a wide range of data-rates, from 0.3 to 28.05Gb/s, with low jitter, we develop a PLL architecture with two LC-VCOs and one ring VCO with a data-rate-adjustment technique by controlling an LDO. Our test chip is fabricated in 28nm CMOS. Our signal conditioner is the demonstration to achieve the BER <1012 PRBS31 at 100G-KR4 in a 40dB chip-to-chip backplane with two connectors by using the 36-tap DFE to cancel the reflection and to operate across a wide range of data-rates from 0.3 to 28.05Gb/s.

3.2 multi-standard 185fs rms 0.3-to-28Gb/s 40dB backplane signal conditioner with adaptive pattern-match 36-Tap DFE and data-rate-adjustment PLL in 28nm CMOS

Demand for increasing performance is far outpacing the capability of traditional methods for performance scaling. Disruptive solutions are needed to advance beyond incremental improvements. Traditionally, processors reside inside packages to enable PCB-based integration. We argue that packages reduce the potential memory bandwidth of a processor by at least one order of magnitude, allowable thermal design power (TDP) by up to 70%, and area efficiency by a factor of 5 to 18. Further, silicon chips have scaled well while packages have not. We propose packageless processors - processors where packages have been removed and dies directly mounted on a silicon board using a novel integration technology, Silicon Interconnection Fabric (Si-IF). We show that Si-IF-based packageless processors outperform their packaged counterparts by up to 58% (16% average), 136%(103% average), and 295% (80% average) due to increased memory bandwidth, increased allowable TDP, and reduced area respectively. We also extend the concept of packageless processing to the entire processor and memory system, where the area footprint reduction was up to 76%.

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A Case for Packageless Processors

A half-duplex serial link design that is capable of 22 Gbps operation over PCB channels with up to 20 dB of loss is presented. A current-mode transmitter can be configured either as a pre-cursor or post-cursor 2-tap FIR filter. The receiver consists of a trans-admittance-trans-impedance single-stage linear equalizer that can provide 10 dB of high-frequency gain without the use of peaking inductors. The CTLE is followed by an half-rate 2-tap decision feedback equalizer with direct feedback. To mitigate long-tail intersymbol interference in a power-efficient manner, a third DFE tap employs a single-pole IIR filter. A 15-22 GHz LC-PLL provides quadrature clocks to a 16-lane macro. The 16-lane macro occupies 1.66 mm × 1.6 mm in a 28 nm CMOS process and is packaged in a 45 mm × 45 mm flip-chip MCM module. The link operates from two power supplies at 1.35 V and 0.9 V with a BER and a power efficiency of 6.5 mW/Gbps at 20 Gbps.

A 15–22 Gbps Serial Link in 28 nm CMOS With Direct DFE

As the processing power and clock rate of CPUs and GPUs increase, there is a need for increased I/O bandwidth to enable chip-to-chip communication. I/O pin limitations demand faster links at low power to enable integration of high chip-to-chip bandwidth. However, the channel losses and impedance discontinuities increase at high data rates making it difficult to equalize the channel at low power. In this work, we target reliable, differential, bi-directional links at 20 Gb/s over 6” FR4 PCB trace and flip-chip packages with a total loss budget of 20 dB at Nyquist. In a half-duplex link, one TX and RX are connected on each side and the link direction can be turned around by the controller. A link-turnaround latency of <;10 ns is achieved by placing several key circuits on standby when not in use and by designing fast bias circuits. When fast turnaround is not required, the circuits not in use are powered down permanently and the link is reduced to the simplex case. The top-level transceiver architecture is shown. An LC-VCO-based PLL oscillates at 20 GHz and generates quadrature I/Q clocks at 10 GHz. Both TX and RX use a half-rate architecture to optimize power. The clocks are distributed through an on-chip transmission line to 16 I/O lanes arranged in 2 rows. The links are capable of data rates as low as 14 Gb/s to save power when full bandwidth is not required.

26.1 A 130mW 20Gb/s half-duplex serial link in 28nm CMOS

An apparatus including a receiver coupled to receive an input signal from a communication link and operable to employ decision feedback equalization to the input signal of the communication link and generate an edge sample signal. The apparatus also includes a timing recovery module coupled to the receiver and operable to receive the edge sample signal and use the edge sample signal to generate a data sampling phase signal, wherein the edge sample signal influences a settling point of the data sampling phase signal.

Influence clock data recovery settling point by applying decision feedback equalization to a crossing sample

A sampler circuit for a decision feedback equalizer and a method of use thereof. One embodiment of the sampler circuit includes: (1) a first sampler portion including a series-coupled first master regeneration latch and first slave latch, (2) a second sampler portion including a series-coupled second master regeneration latch and second slave latch, and (3) a first feedback circuit coupled to a first node between the first master regeneration latch and the first slave latch and operable to provide a feedback signal to the second master regeneration latch to cause a bias charge to be built up therefor.

Sampler circuit for a decision feedback equalizer and method of use threof

Apparat, aufweisend: ein erstes Modul (220, 222), welches an ein Eingabe-Signal (224) gekoppelt ist und operabel ist, ein Kante-Signal (248) unter Benutzung eines ersten Takt-Signals (270) zu erzeugen, wobei das erste Modul (220, 222) ferner aufweist: einen ersten Pfad (350), welcher mit dem Eingabe-Signal (224) gekoppelt ist, wobei der erste Pfad (350) aufweist: einen ersten Vorverstarker (242); einen ersten Summations-Knoten (242), welcher mit dem ersten Vorverstarker (242) gekoppelt ist; und einen ersten Latch (240), welcher mit dem ersten Summations-Knoten (242, 349) und dem ersten Takt-Signal (270) gekoppelt ist; einen zweiten Pfad (352), welcher mit dem Eingabe-Signal (224) gekoppelt ist, wobei der zweite Pfad (352) aufweist: einen zweiten Vorverstarker (242); einen Summations-Knoten (349), welcher mit dem zweiten Vorverstarker (242) gekoppelt ist und operabel ist, Ruckkopplung (370) auf sein Eingabe-Signal anzuwenden basierend auf einer zuvor erzeugten Daten-Abtastung; und einen zweiten Latch (240), welcher mit dem zweiten Summations-Knoten (349) gekoppelt ist; und einen Multiplexer (222), welcher mit dem ersten Latch (240) und dem zweiten Latch (240) gekoppelt ist, wobei der Multiplexer (222) operabel ist, eine Ausgabe zwischen dem ersten Latch (240) und dem zweiten Latch (240) auszuwahlen basierend auf einem exklusiven OR einer ersten und einer zweiten vorher erzeugten Daten-Abtastung; und ein zweites Modul (400), welches operabel ist, das Kante-Signal (248) zu empfangen und ferner operabel ist, ein Daten-abtastendes Phase-Signal (464) zu erzeugen, wobei das Kante-Signal (248) einen Setzpunkt des Daten-abtastenden Phase-Signals (464) beeinflusst.

Arif Al Amin

Papers

A 15–22 Gbps Serial Link in 28 nm CMOS With Direct DFE

26.1 A 130mW 20Gb/s half-duplex serial link in 28nm CMOS

Influence clock data recovery settling point by applying decision feedback equalization to a crossing sample

Sampler circuit for a decision feedback equalizer and method of use threof

Beeinflussen von Taktdaten-Rückgewinnungs-Setzpunkt mittels Anwendens von Entscheidung-Rückkopplung-Equalisierung auf eine Kreuzungs-Abtastung