Giorgio Cristiano

Last Name

Cristiano

First Name

Giorgio

ORCID

0000-0002-6322-519X

Organisational unit

09757 - Wang, Hua / Wang, Hua

Show all metadata

Search Results

Publications 1 - 10 of 13

17.3 A 1.25GHz Fully Integrated DC-DC Converter Using Electromagnetically Coupled Class-D LC Oscillators
Novello, Alessandro; Atzeni, Gabriele; Cristiano, Giorgio; et al. (2021)
Digest of Technical Papers / IEEE International Solid State Circuits Conference ~ 2021 IEEE International Solid- State Circuits Conference (ISSCC)
Over the past years, the constant reduction in the size of consumer electronics has strengthened the demand for fully integrated power management circuits. Buck converters offer high efficiency, but they cannot satisfy the stringent size requirements because bulky off-chip inductors are required [1]. Switched-capacitor (SC) approaches provide fully integrated power management solutions; however, their power density is limited by the on-chip capacitance density [2]. Resonant switched capacitor (ReSC) converters need 3D die-stacked inductors or PCB-integrated inductors to achieve appropriate power density values, posing challenges for monolithic integration [3]. A fully integrated ReSC has been presented [4], which implements an on-chip resonator, avoiding any external or 3D stacked passive components. However, the switching losses associated with the four transistors driving the resonator limit the switching frequency to 10s of MHz, bounding the power density scaling to 0.097W/mm 2.© 2021 IEEE.
A 2.3GHz Fully Integrated DC-DC Converter based on Electromagnetically Coupled Class-D LC Oscillators achieving 78.1% Efficiency in 22nm FDSOI CMOS
Novello, Alessandro; Atzeni, Gabriele; Cristiano, Giorgio; et al. (2021)
IEEE Solid-State Circuits Letters
This letter introduces a fully integrated DC-DC converter based on electromagnetically coupled class-D LC oscillators featuring on-chip stacked 8-shaped transformers in a 22nm FDSOI CMOS process. The GHz-range resonant frequency of the proposed converter enables high integration of the passive components, achieving up to 3.2W/mm2 power density. The on-chip 8-shaped stacked transformers reach 16.9 quality factor and 0.91 coupling coefficient, demonstrating 78.1% converter efficiency. Furthermore, the twisted nature of the 8-shaped transformers introduces a magnetic field cancellation mechanism that minimizes the parasitic coupling between the transformers, saving 25% area in one single converter unit and 47% in the converter array, with respect a spiral transformer implementation. In addition, the field intensity is reduced by 27dB outside of the transformer borders compared with a spiral implementation, which helps to mitigate issues such as parasitic magnetic coupling with neighbouring circuits and EMI.
Design of Ultra-Low Power Pulse-Driven MEMS Oscillator
Seok, Seonho; Cristiano, Giorgio; Jang, Taekwang (2020)
2020 Symposium on Design, Test, Integration & Packaging of MEMS and MOEMS (DTIP)
This paper presents an energy efficient pulse-driven on-chip MEMS oscillator which consists of MEMS resonator and sustaining CMOS circuit. Conventional oscillators are driven by means of an inverter-based amplifier low-pass filtered through a series resistor. However, this architecture suffers from multiple energy losses. Firstly, the inverter amplifier is driven by a sinusoidal input, thus consuming significant static power. Additional power is also consumed by the series resistance. The proposed pulsed driver provides a 180° degree shift, effectively replacing the amplifier. The driver injects energy in the oscillator by periodically switching one oscillator end to V DD when the other end reaches the bottom voltage, and to V SS when the other end reaches the peak voltage. The proposed configuration reduces the static power consumption, as the switch is driven by two rectangular voltages and reduces leakage by activating only one of the two switches at a time. This pulse-driven oscillator, running at 33.14kHz, is simulated to consume 835pW when driven at 0.8V, leading to more than ×15 power saving with respect to the traditional configuration, which consumes 13.2nW.
A 1.25-GHz Fully Integrated DC-DC Converter Using Electromagnetically Coupled Class-D LC Oscillators
Novello, Alessandro; Atzeni, Gabriele; Künzli, Jonas; et al. (2021)
IEEE Journal of Solid-State Circuits
Fully integrated power management circuits are promising candidates to provide small form factors and meet high power density demand of modern computing platforms. This article presents a new fully integrated dc-dc converter topology based on electromagnetically coupled class-D LC oscillators that enables up to 2.5 GHz switching frequency, allowing aggressive scaling of the on-chip passives. On-chip transformers and flying capacitors are designed to electromagnetically couple the two oscillators, and gigahertz-range switching frequency is achieved by the quasi-adiabatic switching of the parasitic capacitors. The proposed converter is implemented in a 0.18-μm CMOS process occupying 1.61 mm² for 7.8 nH inductance (high efficiency version) and 0.37 mm² for 3.1 nH (high power density version), achieving 1 W/mm² peak power density. This work also proposes a duty-cycling scheme that improves the efficiency under light loads, which stays close to the peak from 4 μW up to 0.5 W, and in continuous operation mode the output voltage ripple is 12 mV without attaching any output capacitor thanks to the four-phase electromagnetic power delivery scheme.
RC Oscillators with Non-linear Temperature Compensation
Cristiano, Giorgio; Livanelioglu, Can; Ji, Youngwoo; et al. (2023)
Biomedical Electronics, Noise Shaping ADCs, and Frequency References. Advances in Analog Circuit Design 2022
Various IoT applications require on-chip time references to achieve a small form factor. An on-chip RC oscillator is one of the most promising candidates, thanks to its full compatibility with standard CMOS technology. Conventional on-chip RC oscillators combine resistors with complementary temperature coefficients to achieve a low-temperature coefficient (TC). While this can successfully eliminate the first-order temperature dependency after a two-point trim, it leaves a residual non-linear dependency, which ranges from 20 to 50 ppm/°C. Consequently, several techniques have been proposed to eliminate this residual temperature dependency to achieve less than 10 ppm/°C temperature stability. This chapter reviews two recent designs, an R-RC oscillator (Ji et al., Second-order temperature-compensated on-chip R-RC oscillator achieving 7.93ppm/°C and 3.3pJ/Hz in −40°C to 125°C temperature range. In: 2022 IEEE international solid-state circuits conference (ISSCC), vol 65, pp 1–3. https://doi.org/10.1109/ISSCC42614.2022.9731730, 2022) and a non-linearity-aware dual phase-locked loop (Cristiano et al., A 8.7ppm/°C, 694nW, one-point calibrated RC oscillator using a nonlinearity-aware dual phase-locked loop and DSM-controlled frequency-locked loops. In: 2020 IEEE symposium on VLSI circuits, pp. 1–2. https://doi.org/10.1109/VLSICircuits18222.2020.9162838, 2020), which achieve 7.9 ppm/°C and 8.7 ppm/°C temperature stability using analog and digital techniques, respectively.
An Impedance-boosted Switched-capacitor Low-noise Amplifier Achieving 0.4 NEF
Atzeni, Gabriele; Incandela, Rosario; Ji, Youngwoo; et al. (2022)
2022 IEEE Symposium on VLSI Technology and Circuits (VLSI Technology and Circuits)
This paper presents an impedance-boosted analog front-end (AFE) for mm-scale ultra-low power sensor nodes. The proposed AFE employs a discrete-time low noise amplifier (LNA) based on noise-efficient switched-capacitor stages. The input impedance, ZIN, is boosted through a 27-step multiphase soft-charging technique of the bottom-plate capaci-tance, achieving ZIN > 10 MΩ at 4.5 MHz sampling frequency. The LNA achieves 0.4 NEF and 0.15 PEF, the smallest values reported to date, while consuming 0.28 μW.
A 0.0014 mm2, 1.18 TΩ Segmented Duty-Cycled Resistor Replacing Pseudo-Resistor for Neural Recording Interface Circuits
Livanelioglu, Can; Choi, Woojun; Kim, Donghwan; et al. (2022)
2022 IEEE Symposium on VLSI Technology and Circuits (VLSI Technology and Circuits)
This paper proposes a segmented duty-cycled resistor (SDR) that replaces the pseudo-resistor for neural recording amplifiers. To the authors’ best knowledge, the proposed design, for the first time, achieves higher than 1 TΩ resistance and a switching frequency above the signal bandwidth at the same time. Therefore, it eliminates in-band switching artifacts and output DC drift. The SDR achieves up to 1.18TΩ with only 6.5% temperature variation and 1.5% chip-to-chip variation among 10 samples. Hence it offers sufficiently low and stable cut-off frequencies for both action potential and local field potential recordings, while only occupying an area of 0.001375mm 2 .
A 8.7ppm/°C, 694nW, One-Point Calibrated RC Oscillator using a Nonlinearity-Aware Dual Phase-Locked Loop and DSM-Controlled Frequency-Locked Loops
Cristiano, Giorgio; Liao, Jiawei; Novello, Alessandro; et al. (2020)
2020 IEEE Symposium on VLSI Circuits
This paper presents an on-chip timer composed of two DSM-controlled RC oscillators, locked through a non-linearity aware digital dual phase-locked loop. The proposed design achieves an accurate temperature coefficient below 8.7ppm/degrees C from 10 samples from two different wafer lots with only one-point calibration and an Allan deviation floor of 4ppm. The power consumption is 694nW at 116kHz.
A High-Order-Temperature-Compensated 328kHz On Chip RC Timer Using Time-Interleaved Resistors Achieving 1.5pJ/Cycle and 5.86ppm°C
Liao, Jiawei; Omdeh Ghiasi, Hesam; Cristiano, Giorgio; et al. (2023)
2023 IEEE Custom Integrated Circuits Conference (CICC)
Wireless IoT nodes can be ubiquitously applied for environmental and biomedical sensing. They are typically duty-cycled to save power consumption, thus requiring ultra-low power consumption and stable frequency. At the same time, they need to occupy a small area for the miniaturization of the nodes. Consequently, monolithic RC os-cillators have gained popularity instead of bulky crystal oscillators for their low power and CMOS compatibility [1]– [7]. Conventional RC oscillators exploit resistors with complementary temperature coefficients (TC) to compensate for the resistor’s temperature drift. They normally need precise trimming with many resistors and switch arrays, but their parasitics and off-leakage limit the TC [1] [2]. A lower TC can be achieved by applying polynomial correction with a temperature sensor, but they have relatively higher energy per cycle and normally require power-hungry digital processing [3] [4]. An alternative is to use a switched resistor [5] [6], but in [5], it either is limited only to first-order TC cancellation or requires more than 3-point trimming, while [6] has a high power and area overhead due to the two PLLs used. Time-domain trimming is proposed in [7], but it requires extensive calibration and has a large frequency ripple.
Analog-to-Digital Conversion With Reconfigurable Function Mapping for Neural Networks Activation Function Acceleration
Giordano, Massimo; Cristiano, Giorgio; Ishibashi, Koji; et al. (2019)
IEEE Journal on Emerging and Selected Topics in Circuits and Systems

Publications 1 - 10 of 13

Giorgio Cristiano

Last Name

First Name

ORCID

Organisational unit

Filters

Search Results