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This paper presents an overview for low-power successive approximation register (SAR) analog-to-digital converters (ADCs). It covers the operation principle, error analysis, and practical design issues. Furthermore, this paper provides a comprehensive survey of state-of-the-art low-power design techniques for every circuit block in the SAR ADC, including comparator, capacitive digital-to-analog converter (DAC), and SAR logic. The goal of this paper is to provide a useful overview to SAR ADC designers who want to improve the energy efficiency targeting low-to-medium speed applications. [ABSTRACT FROM AUTHOR]

This paper presents a mixed-signal SRAM-based in-memory computing (IMC) macro for processing binarized neural networks. The IMC macro consists of $128\times 128$ (16K) SRAM-based bitcells. Each bitcell consists of a standard 6T SRAM bitcell, an XNOR-based binary multiplier, and a pseudo-differential voltage-mode driver (i.e., an accumulator unit). Multiply-and-accumulate (MAC) operations between 64 pairs of inputs and weights (stored in the first 64 SRAM bitcells) are performed in 128 rows of the macro, all in parallel. A weight-stationary architecture, which minimizes off-chip memory accesses, effectively reduces energy-hungry data communications. A row-by-row analog-to-digital converter (ADC) based on 32 replica bitcells and a sense amplifier reduces the ADC area overhead and compensates for nonlinearity and variation. The ADC converts the MAC result from each row to an N-bit digital output taking 2N-1 cycles per conversion by sweeping the reference level of 32 replica bitcells. The remaining 32 replica bitcells in the row are utilized for offset calibration. In addition, this paper presents a pseudo-differential voltage-mode accumulator to address issues in the current-mode or single-ended voltage-mode accumulator. A test chip including a 16Kbit SRAM IMC bitcell array is fabricated using a 65nm CMOS technology. The measured energy- and area-efficiency is 741-87TOPS/W with 1-5bit ADC at 0.5V supply and 3.97TOPS/mm2, respectively. [ABSTRACT FROM AUTHOR]

This paper presents a tunable new deadtime control circuit providing an optimal delay for power converter optimization. Our method can reduce the deadtime loss while improving the efficiency and power density of a given power converter. The circuit presents a reconfigurable delay element to generate a wide range of deadtime for different power conversion applications with varying loads and input voltages. The optimal deadtime equation for buck converters is derived, and its dependency on the input voltage and load is discussed. Experimental results show that the presented circuit can provide a wide range of deadtime delays, ranging from 9.2 ns to 1000 ns. The power consumption of the presented circuit is measured for different capacitive loads ($\text{C}_{\mathrm {L}}$) and operating frequencies (${f}_{\mathrm {s}}$). The circuit consumed a power between 610 $\mu \text{W}$ and $850~\mu \text{W}$ across the measured deadtime ranges while $\text{C}_{\mathrm {L}} =12$ pF, $\text{V}_{\mathrm {dd}} =3.3$ V, and $\text{f}_{\mathrm {s}}=200$ kHz. The proposed deadtime generator can operate up to 18 MHz when the minimum deadtime of 9.2 ns is selected. The presented circuit occupies an area of $150\mu $ m $\times 260\mu \text{m}$. The fabricated chip is connected to a buck converter to validate the operation of the proposed circuit. The efficiency of a typical buck converter with minimum $\text{T}_{\mathrm {DLH}}$ and optimal $\text{T}_{\mathrm {DHL}}$ at $\text{I}_{\mathrm {Load}} =25$ mA is improved by 12% compared to a converter with a fixed deadtime of $\text{T}_{\mathrm {DLH}} =\,\,\text{T}_{\mathrm {DHL}} =12$ ns. [ABSTRACT FROM AUTHOR]

Primary-side regulation (PSR) flyback topology with discontinuous conduction modulation (DCM) mode has been widely used in low-power application due to its high stability, wide input voltage range, low cost, and low standby power. To improve the output power, continuous conduction modulation (CCM) mode is always introduced. However, in CCM mode, conventional PSR voltage-sampling method cannot realize high precision of output voltage or the voltage sampling method requires complex control of high cost. In this paper, a simple digital voltage sampling scheme with two reference voltages outputted from a digital-to-analog converter (DAC) is put forward to trace the “accurate-point” voltage for DCM and CCM modes. In CCM mode, the sampling voltage error of the “knee-point” voltage can be compensated just by inserting DCM switching cycle to obtain the “accurate-point” voltage. Voltage difference between DCM mode and CCM mode will be eliminated, and high precision is easily realized. The proposed method is verified in a 20V, 65W PSR flyback converter. The sampling method only requires a low speed DAC, three comparators and a digital controller. The output voltage precision is within 0.6% with universal input voltage. [ABSTRACT FROM AUTHOR]

This paper presents a fully differential wake-up receiver (WuRX) with ultra-low power and high sensitivity. Implementing the fully differential framework achieves differential signal processing without an off-chip balun, which achieves noise suppression and sensitivity improvement. The low voltage baseband signal processing (LVBSP) is proposed to cut down the power consumption, which is achieved by the low-voltage fast-response differential amplifier (LFDA) and the time-domain signal processing circuit. Moreover, the periodic offset cancellation technique (POCT) in the baseband circuit is proposed to alleviate the offset and low-frequency noise impacts. This WuRX is implemented in the TSMC 65-nm CMOS process occupying an active area of 0.18 mm2. When operating at 434 MHz, the proposed WuRX has a −75-dBm sensitivity at 250 bps while consuming 6.4 nW from 0.4 V supply voltage. [ABSTRACT FROM AUTHOR]

This paper introduces the utilization of two different input-referred offset voltage correction methods applied to multiple amplifiers within a front-end sensing circuit of a buck regulator for the first time. The multi-amplifier system under investigation contains an instrumentation amplifier consisting of three folded cascode stages and an additional amplifier configured as a unity-gain buffer for a reference voltage. The first method in this work alleviates voltage offsets in this 4-amplifier system based on a shared auxiliary amplifier correction circuit that switches between different target amplifiers; whereas the second method applies a chopping-based auto-zero procedure to cancel the input-referred offset voltage of the same amplifiers. Since the instrumentation amplifier is designed for feedback sensing in integrated power management applications, it has a relatively high bandwidth requirement. For this reason, the chopping technique does not involve a low-pass or band-pass filter. Instead, a successive approximation register (SAR) analog-to-digital converter is used to sense the output. Measurements of the amplifiers fabricated in a 130nm CMOS technology demonstrate that the auxiliary auto-zero offset cancellation method leads to lower input-referred offset voltage standard deviation ($\sigma = 1.31\,\,\mu \text{V}$) compared to the chopping technique ($\sigma = 184.67\,\,\mu \text{V}$), and that the die area requirement and power consumption with the auxiliary amplifier-based offset cancellation (0.105 mm2, 1.32 mW) are lower than with the chopping method (0.25 mm2, 1.72 mW). [ABSTRACT FROM AUTHOR]

In this paper, a single-channel two-step voltage-time hybrid domain analog-to-digital converter (ADC) is proposed. To achieve high sampling rate and high accuracy, 3.5-bit voltage domain MDAC and 7-bit high-speed time domain ADC (TD-ADC) are combined into a 10-bit hybrid ADC. In the first stage MDAC, a low-power push-pull amplifier is used to improve settling speed, and 1-bit redundancy is designed for calibration and dither injection. The TD-ADC with selective time domain quantization is implemented by a constant-current voltage to time converter (VTC) array and a direct positive feedback time domain comparator. The proposed VTC array can maintain high linearity with a large input swing in high-speed application. The prototype ADC was fabricated in a 28-nm CMOS process and occupied a core area of 0.074 mm2. Under a 0.95-V power supply, the chip achieves a measured peak SNDR of 53.2 dB and SFDR of 61.7 dB respectively at conversion rate up to 2.5 GS/s. The FOM is 48.2 fJ/conversion-step. [ABSTRACT FROM AUTHOR]

This paper presents a buffer-embedded noise-shaping SAR ADC, whose input buffer separates the capacitive DAC (CDAC) and the sampling capacitor (CS) at the input and output of the input buffer. This compensates for the non-linearity of the input buffer and reduces the CS value, resulting in a significant power saving in the input buffer. This buffer-embedded architecture enables the effective implementation of the following passive loop filter and enhances energy efficiency. A bootstrapping switch in the feedback CDAC is coupled to the output of the buffer, thereby avoiding a signal dependency due to the parasitic capacitance of the switch. The buffer-embedded noise-shaping SAR ADC occupies 0.08mm2 in a 65 nm CMOS process and features a parasitic input capacitor of 0.2 pF. It achieves 73.8 dB SNDR, 77 dB DR and 87.3 dB SFDR in a 2 MHz bandwidth without any calibration. Including the power consumption of the input buffer, the ADC consumes only 2.1 mW. [ABSTRACT FROM AUTHOR]

A novel Resistive random access memory (ReRAM)-based Compute-in-memory (CIM) macro is proposed to overcome the limited accuracy and throughput of a conventional ReRAM-based CIM macro that results from to the low R-Ratio and large variation of ReRAM. The proposed structure consists of 1T2R1C bit-cells and 4-kb ReRAM-based nvCIM architecture with ternary weight and ternary input. Ternary multiplication is implemented with voltage division between paired ReRAM devices within a bit-cell to make the output voltage variation tolerant and less sensitive to low R-ratios. An accumulation operation is realized with capacitive coupling so that linearity can be guaranteed for a large number of operands, allowing accurate and fast multiply-and-accumulate (MAC) operations. For comprehensive validation of the proposed CIM macro, the Verilog-A models for ReRAM devices with an adjustable R-ratio and adjustable variations are adopted to perform simulation on various R-ratio and variation conditions. With the peripheral circuits designed in 180-nm CMOS technology, the proposed CIM macro is confirmed to have high variation tolerance, high throughput, and less sensitivity to a low R-ratio, resulting in a high ternary DNN accuracy of 99.07% (0.01% drop) for the MNIST and 83.79% (0.38% drop) for the CIFAR-10 data sets with an R-ratio as low as 38 and 20%/40% low/high resistance variation. [ABSTRACT FROM AUTHOR]

Memristive technology has experienced explosive growth in the last decade, with multiple device structures being developed for a wide range of applications. However, transitioning the technology from the lab into the marketplace requires the development of an accessible and user-friendly design flow, supported by an industry-grade toolchain. In this work, we demonstrate the behaviour of our in-house fabricated custom memristor model and its integration into the Cadence Electronic Design Automation (EDA) tools for verification. Various input stimuli were given to record the memristive device characteristics both at the device level as well as the schematic level for verification of the memristor model. This design flow from device to industrial level EDA tools is the first step before the model can be used and integrated with Complementary Metal-Oxide Semiconductor (CMOS) in applications for hybrid memristor/CMOS system design. [ABSTRACT FROM AUTHOR]