Philippe Flatresse

A 3 GHz Dual Core Processor ARM Cortex TM -A9 in 28 nm UTBB FD-SOI CMOS With Ultra-Wide Voltage Range and Energy Efficiency Optimization

This paper presents the implementation details and silicon results of a 3 GHz dual-core ARM Cortex TM -A9 (A9) manufactured in the 28 nm planar Ultra-Thin Box and Body Fully-Depleted CMOS (UTBB FD-SOI) technology. The implementation is based on a fully synthesizable standard design flow. The design exploits the important flexibility provided by the FD-SOI technology, notably a wide Dynamic Voltage and Frequency Scaling (DVFS) range, from 0.52 V to 1.37 V, and Forward Body Bias (FBB) techniques up to 1.3 V. Detailed explanations of the body-biasing techniques specific to this technology are largely presented, in the context of a multi- VT co-integration, which enable this energy efficient silicon implementation. The system integrates all the advanced IPs for energy efficiency as well as the body bias generator and a fast (μs range) dynamic body bias management capability. The measured dual core CPU maximum operation frequency is 3 GHz (for 1.37 V) and it can be operated down to 300 MHz (for 0.52 V) in full continuous DVFS. The obtained relative performance, with respect to an equivalent planar 28 nm bulk CMOS chip, shows an improvement of +237% at 0.6 V, or +544% at 0.61 V with 1.3 V FBB.

UTBB FD-SOI: a process/design symbiosis for breakthrough energy-efficiency

UTBB FD-SOI technology has become mainstream within STMicroelectronics, with the objective to serve a wide spectrum of mobile multimedia products. This breakthrough technology brings a significant improvement in terms of performance and power saving, complemented by an excellent responsiveness to power management design techniques for energy efficiency optimization. The symbiosis between process and design is key in this achievement enabling to provide already at 28nm node a real differentiation in terms of flexibility, cost and energy efficiency with respect to any process available on the market.

Ultra-wide body-bias range LDPC decoder in 28nm UTBB FDSOI technology

This paper presents an IEEE 802.11n Low-Density Parity-Check (LDPC) decoder implemented in 28nm Ultra-Thin Body and BOX Fully Depleted SOI (UTBB FDSOI), and demonstrates the performance gains of this circuit vs. 28nm LP high-κ metal-gate CMOS bulk technology. It also introduces extended body bias (BB) design techniques to take advantage of specific features of the UTBB technology to overcome the +/-300mV BB range limitation of conventional bulk technologies [1].

A predictive bottom-up hierarchical approach to digital system reliability

This work has introduced a new electrical aging assessment framework for digital systems, based upon strong physics-based foundations and an adequate bottom-up approach which enables propagating accurate reliability knowledge at system level. This work opens new ways to optimize high level digital systems with respect to aging with great accuracy.

Switching energy efficiency optimization for advanced CPU thanks to UTBB technology

This paper presents the superior performance of UTBB (Ultra-Thin Box and Body) technology for providing high speed at low voltage. We evidence the transistor capability to sustain full forward-body-biasing solution thanks to a planar back-side gate scheme. Silicon measurements on low complexity circuits show that the dynamic power consumption can be reduced by 90% without any speed degradation by simply selecting the appropriate power supply and body bias couple (Vdd; Vbb). A simple switching energy efficiency model is then proposed allowing the (Vdd; Vbb) couple prediction reaching the minimum energy point. Finally, we demonstrate on a full CPU Core implementation with UTBB a total power reduction of -30% and a +40% energy efficiency at identical speed with respect to bulk technology thanks to back side gate biasing efficiency.

A 460 MHz at 397 mV, 2.6 GHz at 1.3 V, 32 bits VLIW DSP Embedding F MAX Tracking

Wide voltage range operation for DSPs brings more versatility to achieve high energy efficiency in mobile applications. This paper describes a 32 bits DSP fabricated in 28 nm Ultra Thin Body and Box FDSOI technology. Body Biasing Voltage (VBB) scaling from 0 V up to ±2 V decreases the core VDDMIN to 397 mV and increases clock frequency by +400%@500 mV and +114%@1.3 V. The DSP frequency measurements show 2.6 GHz@1.3 V(VDD)@2 V(VBB) and 460 MHz@397 mV(VDD)@2 V(VBB). The lowest peak energy efficiency is measured at 62 pJ/op at 0.53 V. In addition to technological gains, maximum frequency tracking design techniques are proposed for wide voltage range operation. On silicon, at 0.6 V, those techniques allow high energy gain of 40.6% w.r.t. a worst case corner approach.

A RISC-V vector processor with tightly-integrated switched-capacitor DC-DC converters in 28nm FDSOI

This work demonstrates a RISC-V vector microprocessor implemented in 28nm FDSOI with fully-integrated non-interleaved switched-capacitor DCDC (SC-DCDC) converters and adaptive clocking that generates four on-chip voltages between 0.5V and 1V using only 1.0V core and 1.8V IO voltage inputs. The design pushes the capabilities of dynamic voltage scaling by enabling fast transitions (20ns), simple packaging (no off-chip passives), low area overhead (16%), high conversion efficiency (80-86%), and high energy efficiency (26.2 DP GFLOPS/W) for mobile devices.

6T SRAM design for wide voltage range in 28nm FDSOI

Unique features of the 28nm ultra-thin body and buried oxide (UTBB) FDSOI technology enable the operation of SRAM in a wide voltage range. Minimum operating voltage limitations of a high-density (HD) 6-transistor (6T) SRAM can be overcome by using a single p-well (SPW) bitcell design in FDSOI. Transient simulations of dynamic failure metrics suggest that a HD 6T SPW array with 128 cells per bitline operates down to 0.65V in typical conditions with no assist techniques. In addition, a wide back-bias voltage range enables run-time tradeoffs between the low leakage current in the sleep mode and the short access time in the active mode, making it attractive for high-performance portable applications.

A RISC-V Vector Processor With Simultaneous-Switching Switched-Capacitor DC–DC Converters in 28 nm FDSOI

This work demonstrates a RISC-V vector microprocessor implemented in 28 nm FDSOI with fully integrated simultaneous-switching switched-capacitor DC-DC (SC DC-DC) converters and adaptive clocking that generates four on-chip voltages between 0.45 and 1 V using only 1.0 V core and 1.8 V IO voltage inputs. The converters achieve high efficiency at the system level by switching simultaneously to avoid charge-sharing losses and by using an adaptive clock to maximize performance for the resulting voltage ripple. Details about the implementation of the DC-DC switches, DC-DC controller, and adaptive clock are provided, and the sources of conversion loss are analyzed based on measured results. This system pushes the capabilities of dynamic voltage scaling by enabling fast transitions (20 ns), simple packaging (no off-chip passives), low area overhead (16%), high conversion efficiency (80%-86%), and high energy efficiency (26.2 DP GFLOPS/W) for mobile devices.

Impact of CMOS Technology Scaling on SRAM Standby Leakage Reduction techniques

This paper investigates leakage reduction techniques for a conventional 6T SRAM cell in advanced technologies. The most promising leakage reduction techniques that have been proposed are presented and compared for the 130-nm and 65-nm technology nodes. More specifically, the impact of the evolution of the gate tunneling and substrate currents is studied considering the efficiency of those techniques. Finally, the best techniques for leakage reduction in sub 100-nm SRAM cell, and guidelines on how to merge them in order to reach an optimum, are proposed