Chip gallery


DAC with graceful degradation

First DAC architecture with digital-like shrinking under scaled technologies, and exhibiting graceful degradation under voltage/frequency overscaling

The proposed DAC allows very low design effort, enables digital-like shrinkage across CMOS generations, low area at down-scaled technologies, and operation down to near-threshold voltages. The proposed DAC can operate at supply voltages that are significantly lower and/or at clock frequencies that are significantly greater than the intended design point, at the expense of moderate resolution degradation. In a 12-bit 40-nm testchip, graceful degradation of 0.3bit/100mV is achieved when  is over-scaled down to 0.8V, and 1.4bit/100mV when further scaled down to 0.6V. 
The proposed DAC enables dynamic power-resolution tradeoff with 3X (2X) power saving for 1-bit resolution degradation at iso-sample rate (iso-resolution).

Relaxation oscillator for sensor nodes with lowest power to date (pW-range), operating under 0.3V-1.8V unregulated supply without any reference/bias circuitry

A pW-power versatile relaxation oscillator operating from sub-threshold (0.3V) to nominal voltage (1.8V) is presented, having Hz-range frequency under sub-pF capacitor. The wide voltage and low sensitivity of frequency/absorbed current to the supply allow the suppression of the voltage regulator, and direct powering from harvesters (e.g., solar cell, thermal from machines) or 1.2-1.5V batteries. A 180nm testchip exhibits a frequency of 4Hz, 10%/V supply sensitivity at 0.3-1.8V, 8-18pA current, 4%/°C thermal drift from -20°C to 40°C.


The first microcontroller (MSP430) that can operate at the minimum-energy or the minimum-power point, with minimum power of 595pW (purely harvested in minimum-power mode)

This work presents an MSP430-compatible microcontroller with dual-mode standard cells enabling minimum-power and minimum-energy mode in 180nm. Minimum-power mode with sub-leakage power (595pW) allows purely energy harvested operation with sub-mm2 harvester. Minimum-energy mode (14-33pJ/cycle) maximizes battery lifetime, when battery-powered. Power management with ripple power gating self-startup allows cold start with on-chip 0.54mm2 solar cell at 55lux light condition.


First sub-mW feature extraction engine for ubiquitous computer vision and IoT

An energy-quality scalable (EQSCALE) feature extraction accelerator for IoT vision applications is presented. Knobs are introduced to dynamically adjust the tradeoff between energy and feature extraction quality, leveraging the intrinsic redundancy in video frames and the robustness of object recognition against missing features. The active area of the accelerator is 0.55mm2. EQSCALE enables at least 5.7X energy improvement and 1.8X area reduction over state-of-the-art accelerators. To the best of our knowledge, EQSCALE is the first feature extraction accelerator operating in the sub-mW range (0.51mW at VGA resolution and 30 fps, and 0.19mW at 5 fps).


First fully-synthesizable PUF ("PUF design in a day") and active temperature compensation with native 2.8% BER, 1.02fJ/b at 0.8-1.0V in 40nm

A fully-synthesizable Physically Unclonable Function (PUF) with hysteresis-enhanced stability and active compensation of temperature variations is proposed. To reduce undesired bit flips, hysteretic behavior is obtained through the insertion of a Muller C-element output stage. A feedback scheme is also introduced to compensate the effect of temperature variations at run time. Native worst-case BER of 2.8% is measured under 0.8-1.0V and 25-85°C, with instability degradation with temperature being 0.15% per 10°C. The PUF bitcell consumes 1.02fJ/b at 0.9V. This PUF can be designed with fully automated standard cell-based flows, thus enabling substantial design effort reduction compared to prior art based on custom design styles.


First reconfigurable microarchitecture down to the pipestage level for wide energy/voltage scaling (demonstration on FFT engine)

Dynamically adaptable pipelines with its full integration with automated digital flows at design time and with dynamic voltage scaling schemes at run time is demonstrated with a 256-point radix-4 fixed-point FFT engine on a 40-nm test chip. Measurements show energy savings up to 30% (38%) at iso throughput (iso-voltage). Area and worst-case performance penalty are 5% and 11%, respectively.


First demonstration of reconfigurable clock networks for adaptation under wide voltage scaling

A reconfigurable clock network design for operation from sub-threshold to nominal voltage is presented. The number of levels is adjusted with more levels at nominal voltage to mitigate the impact of wire delay, and fewer in sub-threshold to mitigate the dominant random skew due to repeaters. Clock skew is reduced by up to 2.5 standard deviations and enables 110mV Vmin reduction at 1.8% area penalty in an FFT 40nm testchip, compared to traditional clock networks.

PUF chip (2014)

15-fJ/bit Static Physically Unclonable Functions for Secure Chip Identification with <2% Native Bit Instability and 140X Intra/Inter PUF Hamming Distance Separation in 65nm

A static class of Physically Unclonable Functions for secure key generation and chip identification is presented. Energy down to 15 fJ/bit is achieved, key reproducibility and uniqueness meet inter/intra-PUF Hamming distance separation of 140X or greater, randomness passes all NIST tests. Native unstable bits are less than 2% at nominal conditions and less than 5% in 0.7-1 V voltage and 25-85 oC temperature range, before applying any further post-silicon technique for stability enhancement.