Matthias Braendli

A 3.1 mW 8b 1.2 GS/s Single-Channel Asynchronous SAR ADC With Alternate Comparators for Enhanced Speed in 32 nm Digital SOI CMOS

Next-generation digital high-speed links require fast, yet energy-efficient ADCs at minimum area. Recent years saw impressive progress in SAR ADC designs towards higher sampling speed. Asynchronous clocking, redundant capacitive DACs (CDAC), multi-bit decisions per step and interleaved designs have been presented. We present an asynchronous redundant single-channel ADC achieving 1.2GS/s at 1V supply by using two comparators in alternation to relax comparator reset timing. The ADC achieves 39.3dB SNDR and 34fJ/conversion-step with a core chip area of 0.0015mm2.

22.1 A 90GS/s 8b 667mW 64× interleaved SAR ADC in 32nm digital SOI CMOS

Forthcoming optical communication standards such as ITU OTU-4 and 100/400Gb/s Ethernet require ADCs with more than 50GS/s and at least 5 ENOB to enable complex equalization in the digital domain. SAR ADCs and interleaved ADCs made impressive progress in recent years. First CMOS ADCs with at least 6b and conversion rates exceeding 20GS/s were presented, proving that interleaved SAR ADCs are an optimal choice for high-speed ADCs with moderate resolution. We present an interleaved CMOS ADC architecture based on an asynchronous redundant SAR ADC core element. It was measured up to a sampling rate of 100GS/s and can be operated from a single supply voltage. At 90GS/s, the measured SNDR stays above 36.0dB SNDR up to 6.1GHz and 33.0dB up to 19.9GHz input frequency while consuming 667mW. The ADC is implemented in 32nm digital SOI CMOS and occupies 0.45mm2.

A 28Gb/s source-series terminated TX in 32nm CMOS SOI

Upcoming standards such as OIF CEI-25LR and CEI-28SR demand transmitter circuits above 20Gb/s [1]-[3] with stringent jitter requirements. The SST driver topology, which has been previously demonstrated at lower data rates [4], is an attractive solution as it enables multiple termination options and low power consumption. In addition, its single-ended topology facilitates an architecture in which the delay mismatch between true and complementary output can be adjusted, as is desirable for data transmission over long cables. In this contribution, the architecture and design of the key components of a half-rate 28Gb/s SST TX are presented.

A 14Gb/s high-swing thin-oxide device SST TX in 45nm CMOS SOI

The limited supply voltage of todays state-of-the-art CMOS technologies makes the design of high-speed transmitters at signaling swings above the typical 1V supply a challenging task. Higher-voltage TX amplitude is not only required in older I/O standards and legacy applications, but also in emerging electro-optical extensions where high voltage swing combined with high-speed operation is desired. Higher swing also helps meet certain I/O standards in applications where losses introduced by high-density package constraints can be compensated to some extent. The source-series terminated (SST) driver is a versatile building block in a multistandard I/O TX thanks to its potential for low-power operation, its low area consumption, high CMOS-style circuit content, and flexible termination capability [1]. Also, the SST driver supports single-ended output and differential operation.

Room-temperature THz imaging based on antenna-coupled MOSFET bolometer

We report on the design, fabrication and measurements of a new THz sensor concept based on an antenna-coupled MOSFET bolometer for room-temperature passive THz imaging for security and medical-diagnostic applications. The device is fabricated in a 180-nm CMOS SOI technology followed by a post-CMOS MEMS process. In this sensor, the antenna absorbing the THz electromagnetic field is directly coupled to the bolometer for maximum energy collection, whereas its design aims at minimizing its thermal mass as is necessary for fast frame rates. DC measurements before and after the MEMS process as well as thermal time constant and THz antenna measurements are presented.

10.6 continuous-time linear equalization with programmable active-peaking transistor arrays in a 14nm FinFET 2mW/Gb/s 16Gb/s 2-Tap speculative DFE receiver

The authors report the implementation of a continuous-time linear equalizer (CTLE) featuring a new technique to control the high-frequency gain peaking and to interface to current-summing stages usually implemented as interleaved slices for the linear analog superposition of the coefficients of decision-feedback equalizers (DFE). The circuits are implemented in 14nm FinFET SOI CMOS technology and are included in a prototype receiver targeted to 16Gb/s serial I/O links for multi-core microprocessors off-chip communication. The architecture is shown in the paper. Power efficiency and compactness are among the primary goals of the study together with an equalization capability sufficient to recover at bit-error rate (BER) levels below 10-12 data transmitted across smooth channels with losses in excess of 25dB at 8GHz.

A 3.6pJ/b 56Gb/s 4-PAM receiver with 6-Bit TI-SAR ADC and quarter-rate speculative 2-tap DFE in 32 nm CMOS

This paper describes the implementation of a 4-level pulse-amplitude-modulation (4-PAM) receiver consisting of a 6-bit time-interleaved successive-approximation analog-to-digital converter (TI-SAR ADC), followed by a fully digital speculative 2-tap decision-feedback equalizer (DFE) operating at one-fourth of the modulation rate. The receiver, implemented in an experimental chip fabricated in 32 nm SOI CMOS, is designed to recover data at 56Gb/s over a channel with an attenuation of 11 dB at 14 GHz. The power consumption of the receiver is 202.7 mW at a supply of 1.2 V, achieving an overall energy efficiency of 3.62 pJ/b. The DFE along with area-optimized register arrays and memory-control buffers occupies an area of 0.154×0.169 mm2. Experimental results demonstrating a BER<;10-8 are obtained using a (27-1)-bit pseudo-random binary sequence (PRBS-7).

Design of a wide-bandwidth on-chip antenna for uncooled passive THz imaging

The design of a broadband on-chip antenna for passive THz imaging in the frequency range of 0.6 THz to 1.4 THz is reported. The antenna design has to fulfill the requirements of the IBM CMOS process and the MEMS post CMOS processing. The antenna is coupled directly to the sensor, a MOSFET bolometer. Because of this direct coupling and the need for real time imaging, only extremely physically small antennas are feasible. Hence, typical broadband antennas like the toothed log-periodic antenna are not useable for this application and new antenna approaches have to be examined.

28.5 A 10b 1.5GS/s pipelined-SAR ADC with background second-stage common-mode regulation and offset calibration in 14nm CMOS FinFET

High-speed SAR ADCs became popular with modern CMOS technologies because of their mostly digital logic, making them highly suitable for compact and power-efficient multi-GS/s time-interleaved ADCs. As many applications cannot tolerate input swings ≥1Vppd, comparator noise limits the SNDR of SAR ADCs, making gain stages necessary for higher SNDR - either as comparator pre-amplifiers or between pipelined stages. Pre-amplifiers significantly reduce the conversion speed of the ADC, but they provide maximum SNDR because linearity of the amplifier is irrelevant. An interstage amplifier for pipelining best suits mid-resolution SAR ADCs, where the required linearity is limited. Moreover, pipelining results in higher conversion speeds and power efficiency because the gain stage is used only once per conversion [1]. This work presents a pipelined-SAR ADC architecture that exceeds the conversion speed of previous pipelined and single-stage SAR ADCs. The ADC achieves 50dB SNDR and 950MS/s at 2.26mW, and 1.5GS/s at 6.92mW on an area of 0.0016mm2.

A 12b 61dB SNDR 300MS/s SAR ADC with inverter-based preamplifier and common-mode-regulation DAC in 14nm CMOS FinFET

A 300MS/s 12b SAR ADC achieving 61.6dB peak SNDR is presented. It reaches 60.5dB SNDR and 78.7dB SFDR with 0.8Vpp,diff input amplitude at Nyquist. The key elements are a comparator with inverter-based preamplifier and a SAR-based common-mode regulation. The regulation adjusts the common mode on a sample-by-sample basis to improve common-mode rejection. The ADC consumes 7.0mW from a single 0.85V supply, where 3.7mW is contributed by the reference buffer.