On-chip Calibration Technique Research Articles

A 16b 120MS/s Pipelined ADC Using an Auxiliary-Capacitor-Based Calibration Technique Achieving 90.5dB SFDR in 0.18 μm CMOS

A 16-bit 120 MS/s sample-hold-amplifier-less(SHA-less) pipelined analog-to-digital converter (ADC) with an on-chip calibration technique in a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18~\mu \text{m}$ </tex-math></inline-formula> CMOS process is presented. A switched capacitor circuit with an auxiliary unit capacitor in the multiplying-digital-to-analog converter (MDAC) of the first stage is proposed. The auxiliary-capacitor based calibration technique eliminates the need for a dedicated reference buffer to generate the calibration voltages at all the comparator thresholds. By switching the auxiliary capacitor and doing some simple calculation work, all the capacitor mismatches in the first and second stages are corrected in the digital domain, thereby significantly improving the ADC performance. Measurement results show that, with 70.1 MHz input, the signal-to-noise-and-distortion-ratio (SNDR) is improved from 75.5 dB to 77.8 dB, and the spurious-free-dynamic-range (SFDR) is improved from 81.9 dBc to 90.5 dBc with the proposed calibration technique.

Neuromorphic Low-Power Inference on Memristive Crossbars With On-Chip Offset Calibration

Monolithic integration of silicon with nano-sized Redox-based resistive Random-Access Memory (ReRAM) devices opened the door to the creation of dense synaptic connections for bio-inspired neuromorphic circuits. One drawback of OxRAM based neuromorphic systems is the relatively low ON resistance of OxRAM synapses (in the range of just a few kilo-ohms). This requires relatively large currents (many micro amperes per synapse), and therefore imposes strong driving capability demands on peripheral circuitry, limiting scalability and low power operation. After learning, however, a read inference can be made low-power by applying very small amplitude read pulses, which require much smaller driving currents per synapse. Here we propose and experimentally demonstrate a technique to reduce the amplitude of read inference pulses in monolithic neuromorphic CMOS OxRAM-synaptic crossbar systems. Unfortunately, applying tiny read pulses is non-trivial due to the presence of random DC offset voltages. To overcome this, we propose finely calibrating DC offset voltages using a bulk-based three-stage on-chip calibration technique. In this work, we demonstrate spiking pattern recognition using STDP learning on a small 4×4 proof-of-concept memristive crossbar, where on-chip offset calibration is implemented and inference pulse amplitude could be made as small as 2mV. A chip with pre-synaptic calibrated input neuron drivers and a 4×4 1T1R synapse crossbar was designed and fabricated in the CEA-LETI MAD200 technology, which uses monolithic integration of OxRAMs above ST130nm CMOS. Custom-made PCBs hosting the post-synaptic circuits and control FPGAs were used to test the chip in different experiments, including synapse characterization, template matching, and pattern recognition using STDP learning, and to demonstrate the use of on-chip offset-calibrated low-power amplifiers. According to our experiments, the minimum possible inference pulse amplitude is limited by offset voltage drifts and noise. We conclude the paper with some suggestions for future work in this direction.

A 4-b 7-$\mu$ W Phase Domain ADC With Time Domain Reference Generation for Low-Power FSK/PSK Demodulation

This paper presents a 4-b phase-domain analog-to-digital converter (ADC) that utilizes the time-domain reference generation scheme for low-power operation. Rather than prior arts that rely on power-hungry resistive/current combiners or the IQ-assisted binary-search algorithm with large power T&H circuits for the reference generation, this design benefits from the fully dynamic power characteristic of the time-domain operation, thus leading to an energy-efficient phase ADC design. By introducing several on-chip calibration techniques, the design achieves good robustness with the proposed time-domain operation. The prototype is fabricated in the standard 65-nm CMOS technology, achieving an ENOB of 3.42 bits at 1 MS/s with near Nyquist input, while dissipating 7 μW from a 1-V supply. It leads to a 1.36-pJ/conversion-step Walden Figure of Merit at Nyquist input (FoM@Nyquist).

An 85-MHz-BW ASAR-Assisted CT 4-0 MASH $\Delta\Sigma$ Modulator With Background Half-Range Dithering-Based DAC Calibration in 28-nm CMOS

This paper presents a continuous-time 4-0 MASH $\Delta \Sigma $ modulator with high power efficiency for wide-bandwidth wireless communication systems. An asynchronous successive-approximation-register (ASAR) is used as the quantizer in the $\Delta \Sigma $ modulator to reduce the power consumption and to cancel the comparator mismatch of the conventional flash quantizer. An on-chip background half-range dithering-based calibration technique is proposed to improve the multi-bit feedback digital-to-analog converter matching, with limited overhead cost in terms of power consumption and area. To alleviate the metastability error of the ASAR and to increase the bandwidth, a zero-order loop is added to further quantize the intrinsic quantization error of the ASAR. The design is fabricated in a 28-nm bulk CMOS process. Clocked at a frequency of 1.7 GHz, the modulator achieves 68.5-dB SNDR and 83.6-dB spurious-free dynamic range over an 85-MHz bandwidth, while consuming 23.9-mW power, leading to an excellent Walden figure-of-merit of 64.9 fJ/step and a Schreier figure-of-merit of 164 dB.

An Automatic On-Chip Calibration Technique for Static and Dynamic DAC Error Correction in High-Speed Continuous-Time Delta-Sigma Modulators

Calibration is preferred over dynamic element matching (DEM) techniques to correct nonlinearity in digital-to-analog converters (DACs) in high-speed multi-bit continuous-time (CT) delta-sigma modulators (DSMs) to avoid introducing extra excess loop delay. The state-of-the-art calibration techniques, however, involve substantial external control, making it difficult for a complete on-chip realization. In this paper a highly automated on-chip technique for calibrating differential nonlinearity (DNL) and inter-symbolinterference (ISI) errors of a multi-bit DAC in a CTDSM is presented. The proposed technique implements a Calibration Control System (CCS), equipped with a Finite State Machine (FSM) logic, that automates the entire calibration process with minimal intervention. The calibration loop utilizes the modulator itself to produce the digital estimates of the DNL and the average ISI errors of each unit element of the DAC. These digital estimates are then used to configure auxiliary DACs for correction of the errors in the main DAC. For every unit element in the main DAC, an 8-bit dynamic auxiliary DAC injects a calibrated compensation current in the loop at every up-transition of the input data to cancel the average ISI error, and a 5-bit constant current source array corrects its DNL error. Design considerations and post-layout simulation results for a 50-MHz bandwidth, 1.8GS/s 4 th -order CTDSM are presented. The modulator has a 4.8 dB and a 10.8 dB improvement in SNDR and SFDR respectively with calibration, leading to a dynamic range of 71 dB with a total power consumption of 37.7 mW from 1.3 V and 1 V supplies.

Analysis and Compensation of the Effects of Analog VLSI Arithmetic on the LMS Algorithm

Analog very large scale integration implementations of neural networks can compute using a fraction of the size and power required by their digital counterparts. However, intrinsic limitations of analog hardware, such as device mismatch, charge leakage, and noise, reduce the accuracy of analog arithmetic circuits, degrading the performance of large-scale adaptive systems. In this paper, we present a detailed mathematical analysis that relates different parameters of the hardware limitations to specific effects on the convergence properties of linear perceptrons trained with the least-mean-square (LMS) algorithm. Using this analysis, we derive design guidelines and introduce simple on-chip calibration techniques to improve the accuracy of analog neural networks with a small cost in die area and power dissipation. We validate our analysis by evaluating the performance of a mixed-signal complementary metal-oxide-semiconductor implementation of a 32-input perceptron trained with LMS.

An On-chip Calibration Technique for Reducing Supply Voltage Sensitivity in Ring Oscillators

A technique for reducing the supply voltage sensitivity of a ring oscillator using on-chip calibration is described. A 1-V 0.13-mum CMOS PLL demonstrates robust performance against VCO supply noise over operating frequencies of 0.5 to 2 GHz. In the presence of a 10-mV 1-MHz VCO supply noise, the measured rms jitter of the proposed PLL with on-chip calibration is 3.95 ps at a 1.4-GHz operating frequency, while a conventional design measures 8.22 ps rms jitter. For 10-MHz VCO supply noise, the measured rms jitter is improved from 16.8 ps to 3.97 ps. The total power consumption of the PLL is 9.6 mW at 1.4 GHz, and the combined core die area of the PLL and the calibration circuitry is 0.064 mm2

S-parameter measurement prediction for bipolar transistors using a physical device simulator

S-parameter data characterizing bipolar IC test structures (including layout parasitics) are derived from two-dimensional device simulations of a submicrometer emitter bipolar transistor (BJT). The modeling used for the calculation of the BJT test structure S-parameter response is reported. The effects of interconnect and bond pads used in the IC test structure layout are evaluated. In addition, a two-layer metal interconnect-based test structure with very low signal loss is proposed. This result has applications in: (1) designing BJT test structures for IC technologies, (2) supplementing existing two-port S-parameter measurements to provide three-port characterization, and (3) evaluating the accuracy of on-chip S-parameter calibration techniques for specific IC test structure layouts. >