A 1-V 1.25-GS/S 8-Bit Self-Calibrated Flash ADC in 90-nm Digital CMOS

We present an 8-bit 1.25-GS/s flash analog-to-digital converter (ADC) in 90-nm digital CMOS with wide analog input bandwidth and low power dissipation. The ADC employs two key techniques: a self-biased track-and-hold amplifier which enhances the ADC full-scale voltage and enables the converter operating under a single 1-V supply; and an improved calibration scheme based on reference pre-distortion to enhance the ADC linearity without sacrificing its sampling speed. The prototype converter thus achieves 7-, 6.9-, 6.5–bit ENOB at 1.25 GS/s for input signal frequencies of 10 MHz, 600 MHz, and 1.3 GHz, respectively, and better than 52-dB SFDR across the full Nyquist-band, while dissipating 207 mW from a single 1-V supply.      

A 0.5-V 8-bit 10-Ms/s Pipelined ADC in 90-nm CMOS

This paper presents a pipelined analog-to-digital converter (ADC) operating from a 0.5-V supply voltage. The ADC uses true low-voltage design techniques that do not require any on-chip supply or clock voltage boosting. The switch OFF leakage in the sampling circuit is suppressed using a cascaded sampling technique. A front-end signal-path sample-and-hold amplifier (SHA) is avoided by using a coarse auxiliary sample and hold (S/H) for the sub-ADC and by synchronizing the sub-ADC and pipeline-stage sampling circuit. A 0.5-V operational transconductance amplifier (OTA) is presented that provides inter-stage amplification with an 8-bit performance for the pipelined ADC operating at 10 Ms/s. The chip was fabricated on a standard 90 nm CMOS technology and measures 1.2 mm times 1.2 mm. The prototype chip has eight identical stages and stage scaling was not used. It consumes 2.4 mW for 10-Ms/s operation. Measured peak SNDR is 48.1 dB and peak SFDR is 57.2 dB for a full-scale sinusoidal input. Maximal integral nonlinearity and differential nonlinearity are 1.19 and 0.55 LSB, respectively.     

4- and 6-GS/s 4-bit frequency-translating hybrid ADCs in 90-nm CMOS

Two frequency-translating hybrid analog-to-digital converters (FTH-ADCs) are implemented using building blocks that are designed and fabricated in a 90-nm CMOS technology. These blocks include a mixer, a filter, and an ADC that are cascaded to build each analog processing path of the FTH-ADC. The mixer-filter path is designed with sufficient linearity and signal-to-noise-and-distortion ratio (SNDR) to accommodate for the desired resolution of the path ADC. A 4-bit flash ADC structure is used in each path. This path has a signal bandwidth of 0.5 GHz and frequency-translates the input signal into baseband and digitizes it with the sample rate of 2 GHz. Multiple such mixer-filter-ADC paths are then combined together with proper mixing frequencies in order to implement two- and three-channel ADC systems. The two- and three-channel systems have overall input bandwidths of 2 and 3 GHz and effective conversion rates of 4 and 6 GS/s, respectively, while maintaining their single-path resolution across their entire input bandwidths. The implemented architecture provides an extendible solution to improve the speed of ADCs by incorporating them in an FTH-ADC architecture.     

A 1.2-V 250-mW 14-b 100-MS/s Digitally Calibrated Pipeline ADC in 90-nm CMOS

This paper describes a digitally calibrated pipeline analog-to-digital converter (ADC) implemented in 90 nm CMOS technology with a 1.2 V supply voltage. A digital background calibration algorithm reduces the linearity requirements in the first stage of the pipeline chain. Range scaling in the first pipeline stage enables a maximal 1.6$ {rm V}_{rm pp}$ input signal swing, and a charge-reset switch eliminates ISI-induced distortion. The 14b ADC achieves 73 $~$dB SNR and 90 dB SFDR at 100 MS/s sampling rate and 250$~$mW power consumption. The 73 dB SNDR performance is maintained within 3 dB up to a Nyquist input frequency and the FOM is 0.68 $~$pJ per conversion-step.      

A 1.8-V 11-bit 40-MS/s 21-mW pipelined ADC

A set of low-power techniques is proposed to realize low power design in pipeline analog-to-digital converter (ADC). These techniques include removing the active S/H (i.e., SHA-less), sharing the opamp between the adjacent multi-bit-per-stages, low-power high-efficiency high-swing amplifier technique. Also, a new sampling topology is proposed to minimize aperture error by matching the time constant between the two input signal paths. All these skills are verified by simulation in the design of the 1.8-V 11-bit 40-MHz ADC in a 0.18-μm CMOS process with power dissipation 21-mW, signal-to-noise-and-distortion ratio (SNDR) 65-dB, effective number of bit (ENOB) 10.5-bit, spurious free dynamic range (SFDR) 78-dB, total harmonic distortion (THD) −75.4-dB, signal-to-noise ratio (SNR) 65.4-dB and figure-of-merit (FOM) 0.18 pJ/step.     

A 1.8-V 22-mW 10-bit 30-MS/s Pipelined CMOS ADC for Low-Power Subsampling Applications

This paper describes a 10-bit 30-MS/s subsampling pipelined analog-to-digital converter (ADC) that is implemented in a 0.18 mum CMOS process. The ADC adopts a power efficient amplifier sharing architecture in which additional switches are introduced to reduce the crosstalk between the two opamp-sharing successive stages. A new configuration is used in the first stage of the ADC to avoid using a dedicated sample-and-hold amplifier (SHA) circuit at the input and to avoid the matching requirement between the first multiplying digital-to-analog converter (MDAC) and flash input signal paths. A symmetrical gate-bootstrapping switch is used as the bottom-sampling switch in the first stage to enhance the sampling linearity. The measured differential and integral nonlinearities of the prototype are less than 0.57 least significant bit (LSB) and 0.8 LSB, respectively, at full sampling rate. The ADC exhibits higher than 9.1 effective number of bits (ENOB) for input frequencies up to 30 MHz, which is the twofold Nyquist rate (fs/2), at 30 MS/s. The ADC consumes 21.6 mW from a 1.8-V power supply and occupies 0.7 mm², which also includes the bandgap and buffer amplifiers. The figure-of-merit (FOM) of this ADC is 0.26 pJ/step.     

A 69-mW 10-bit 80-MSample/s Pipelined CMOS ADC

A 10-bit 80-MS/s analog-to-digital converter (ADC) with an area- and power-efficient architecture is described. By sharing an amplifier between two successive pipeline stages, a 10-bit pipeline is realized using just four amplifiers with a separate sample-and-hold block. The proposed feedback signal polarity inverting (FSPI) technique addresses the drawback of the conventional amplifier sharing technique. A wide-swing wide-bandwidth telescopic amplifier and an early comparison technique with a constant delay circuit have been developed to further reduce power consumption. The ADC is implemented in a 0.18-/spl mu/m dual-gate-oxidation CMOS process technology, achieves 72.8-dBc spurious free dynamic range, 57.92-dBc signal-to-noise ratio, 9.29 effective number of bits (ENOB) for a 99-MHz input at full sampling rate, and consumes 69 mW from a 3-V supply. The ADC occupies 1.85 mm/sup 2/.     

A 14-mW 6.25-Gb/s Transceiver in 90-nm CMOS

This paper describes a 6.25-Gb/s 14-mW transceiver in 90-nm CMOS for chip-to-chip applications. The transceiver employs a number of features for reducing power consumption, including a shared LC-PLL clock multiplier, an inductor-loaded resonant clock distribution network, a low- and programmable-swing voltage-mode transmitter, software-controlled clock and data recovery (CDR) and adaptive equalization within the receiver, and a novel PLL-based phase rotator for the CDR. The design can operate with channel attenuation of -15 dB or greater at a bit-error rate of 10^-15 or less, while consuming less than 2.25 mW/Gb/s per transceiver.     

A 55-mW, 10-bit, 40-Msample/s Nyquist-rate CMOS ADC

A low-power 10-bit converter that can sample input frequencies above 100 MHz is presented. The converter consumes 55 mW when sampling at f_s=40 MHz from a 3-V supply, which also includes a bandgap and a reference circuit (70 mW if including digital drivers with a 10-pF load). It exhibits higher than 9.5 effective number of bits for an input frequency at Nyquist (f_in=f_s/2=20 MHz). The differential and integral nonlinearity of the converter are within ±0.3 and ±0.75 LSB, respectively, when sampling at 40 MHz, and improve to a 12-bit accuracy level for lower sampling rates. The overall performance is achieved using a pipelined architecture without a dedicated sample/hold amplifier circuit at the input. The converter is implemented in double-poly, triple-metal 0.35-μm CMOS technology and occupies an area of 2.6 mm²     

A 6-bit 600-MS/s 5.3-mW Asynchronous ADC in 0.13-μm CMOS

An asynchronous analog-to-digital converter (ADC) based on successive approximation is used to provide a high-speed (600-MS/s) and medium-resolution (6-bit) conversion. A high input bandwidth (>4 GHz) was achieved which allows its use in RF subsampling applications. By using asynchronous processing techniques, it avoids clocks at higher than the sample rate and speeds up a nonbinary successive approximation algorithm utilizing a series nonbinary capacitive ladder with digital radix calibration. The sample rate of 600 MS/s was achieved by time-interleaving two single ADCs, which were fabricated in a 0.13-mum standard digital CMOS process. The ADC achieves a peak SNDR of 34 dB, while only consuming an active area of 0.12mm² and having power consumption of 5.3 mW     

A digitally enhanced 1.8-V 15-bit 40-MSample/s CMOS pipelined ADC

A 1.8-V 15-bit 40-MSample/s CMOS pipelined analog-to-digital converter with 90-dB spurious-free dynamic range (SFDR) and 72-dB peak signal-to-noise ratio (SNR) over the full Nyquist band is presented. Its differential and integral nonlinearities are 0.25 LSB and 1.5 LSB, respectively, and its power consumption is 400 mW. This performance is enabled by digital background calibration of internal digital-to-analog converter (DAC) noise and interstage gain errors. The calibration achieves improvements of better than 12 dB in signal-to-noise plus distortion ratio and 20 dB in SFDR relative to the case where calibration is disabled. Other enabling features of the prototype integrated circuit (IC) include a low-latency, segmented, dynamic element-matching DAC, distributed passive input signal sampling, and asymmetric clocking to maximize the time available for the first-stage residue amplifier to settle. The IC is realized in a 0.18-/spl mu/m mixed-signal CMOS process and has a die size of 4mm/spl times/5 mm.     

Highly Interleaved 5-bit, 250-MSample/s, 1.2-mW ADC With Redundant Channels in 65-nm CMOS

This successive approximation register ADC uses time-interleaving to gain the energy advantage of slower circuits (reduced supply voltage and improved bias points) without sacrificing high speed operation. The drawbacks of interleaving are addressed through architectural solutions. Channel redundancy counteracts the severe yield loss that parallel circuits experience due to local variation. Clock partitioning restricts the distribution of the precise, high-speed sampling clock to three centrally located sampling networks. Only a low frequency clock is distributed across the majority of die area. The skew-resistant global top-plate sampling network is extended to allow overlapped sampling windows without introducing extra sources of crosstalk. The 36-way interleaved 5-bit ADC operates with a core voltage of 800 mV and consumes 1.20 mW total power at 250 MS/s. At Nyquist, the SNDR is 28.4 dB. The 6 redundant channels (17% overhead) increase the yield of the 24 measured chips from 42% to 88%.      

A 1.8-V 67-mW 10-bit 100-MS/s pipelined ADC using time-shifted CDS technique

A time-shifted correlated double sampling (CDS) technique is proposed in the design of a 10-bit 100-MS/s pipelined ADC. This technique significantly reduces the finite opamp gain error without compromising the conversion speed, allowing the active opamp blocks to be replaced by simple cascoded CMOS inverters. Both high-speed and low-power operation is achieved without compromising the accuracy requirement. An efficient common-mode voltage control is introduced for pseudodifferential architecture which can further reduce power consumption. Fabricated in a 0.18-/spl mu/m CMOS process, the prototype 10-bit pipelined ADC occupies 2.5 mm/sup 2/ of active die area. With 1-MHz input signal, it achieves 65-dB SFDR and 54-dB SNDR at 100MS/s. For 99-MHz input signal, the SFDR and SNDR are 63 and 51 dB, respectively. The total power consumption is 67 mW at 1.8-V supply, of which analog portion consumes 45 mW without any opamp current scaling down the pipeline.     

A 65-fJ/Conversion-Step 0.9-V 200-kS/s Rail-to-Rail 8-bit Successive Approximation ADC

An 8-bit successive approximation (SA) analog-to- digital converter (ADC) in 0.18 mum CMOS dedicated for energy-limited applications is presented. The SA ADC achieves a wide effective resolution bandwidth (ERBW) by applying only one bootstrapped switch, thereby preserving the desired low power characteristic. Measurement results show that at a supply voltage of 0.9 V and an output rate of 200 kS/s, the SA ADC performs a peak signal-to-noise-and-distortion ratio of 47.4 dB and an ERBW up to its Nyquist bandwidth (100 kHz). It consumes 2.47 muW in the test, corresponding to a figure of merit of 65 f J/conversion-step.     

A 1-V 6-b 50-MSamples/s current-interpolating CMOS ADC

CMOS analog-to-digital converters (ADC's) require either bootstrapping techniques or low-threshold devices to function at low supply voltages. A 6-b 50-MSamples/s ADC in normal-threshold CMOS operates with a single battery cell as low as 0.9 V without bootstrapping. A current-interpolation approach is taken to configure a 1-V ADC system that does not allow more than one V_GS plus one V_DSsat between the supply rails. The prototype takes a rail-to-rail input and works with a single system clock. The chip fabricated in 0.35-μm CMOS occupies an area of 2.4×2 mm² and consumes 10 mW each in analog and digital supplies     

A 1-V 100-MS/s 8-bit CMOS Switched-Opamp Pipelined ADC Using Loading-Free Architecture

A 1-V, 8-bit pipelined ADC is realized using multi-phase switched-opamp (SO) technique. A novel loading-free architecture is proposed to reduce the capacitive loading and to improve the speed in low-voltage SO circuits. Employing the proposed loading-free pipelined ADC architecture together with double-sampling technique and a fast-wake-up dual-input-dual-output switchable opamp, the ADC achieves 100-MS/s conversion rate, which to our knowledge is the fastest ADC ever reported at 1-V supply using SO technique, with performance comparable to that of many high-voltage switched-capacitor (SC) ADCs. Implemented in a 0.18-mum CMOS process, the ADC obtains a peak SNR of 45.2 dB, SNDR of 41.5 dB, and SFDR of 52.6 dB. Measured DNL and INL are 0.5 LSB and 1.1 LSB, respectively. The chip dissipates only 30 mW from a 1-V supply     

A Programmable 0.8-V 10-bit 60-MS/s 19.2-mW 0.13-$mu$ m CMOS ADC Operating Down to 0.5 V

This work describes a programmable 10- to 100-MS/s, low-power 10-bit two-step pipeline analog-digital converter (ADC) operating at a power supply from 0.5- to 1.2-V. MOS transistors with a low-threshold voltage are employed partially in the input sampling switches and differential pair of the SHA and MDAC for a proper signal swing margin at a 0.5-V supply. The integrated adjustable current reference optimizes the static and dynamic performance of amplifiers at 10-bit accuracy with a wide range of supply voltages. A signal-isolated layout improves the capacitor mismatch of the multiplying digital-to-analog converter, while a switched- bias power-reduction technique reduces the power dissipation of comparators in the flash ADCs. The prototype ADC in a 0.13-mum CMOS process demonstrates the measured differential nonlin- earity and integral nonlinearity within 0.35 and 0.49 least significant bits. The ADC, with an active die area of 0.98 mm², shows a maximum signal-to-noise distortion ratio and spurious free dynamic range of 56.0 and 69.6 dB, respectively, and a power consumption of 19.2 mW at a nominal condition of 0.8 V and 60 MS/s.     

A 10-Bit 500-MS/s 55-mW CMOS ADC

A pipelined ADC incorporates a digital foreground calibration technique that corrects errors due to capacitor mismatch, gain error, and op amp nonlinearity. Employing a high-speed, low-power op amp topology and an accurate on-chip resistor ladder and designed in 90-nm CMOS technology, the ADC achieves a DNL of 0.4 LSB and an INL of 1 LSB. The prototype digitizes a 233-MHz input with 53-dB SNDR while consuming 55$~$mW from a 1.2-V supply.      

A 90-nm CMOS, 8-bit pipeline ADC with 60-MHz bandwidth and 125-MS/s or 250-MS/s sampling frequency

In this paper a dual operating mode 8-bit, 1.1-V pipeline ADC for Gigabit Ethernet applications is presented. In the two operating modes, the ADC features different sampling frequency (125 and 250 MHz) and power consumption (9.4 and 22.8 mW). Considering a signal bandwidth of 60 MHz in both operating modes, as required by the Gigabit Ethernet standard, the ADC achieves a SNDR always larger than 39.4 dB at 125 MHz and 38.7 dB at 250 MHz (6.25-bit and 6.13-bit ENOB, respectively), with a FoM of 0.84 pJ/conv at 125 MHz and 2.2 pJ/conv at 250 MHz. The ENOB achieved is mainly limited by clock jitter. The ADC is fabricated with a 90-nm CMOS technology, with an active area of 1.25 × 0.65 mm².