An Auto-Zero Stabilized Voltage Buffer with a Quiet Chopping Scheme and Constant Input Current

The readout of high-impedance sensors and sampled voltage references [1] requires amplifiers that can achieve both low offset and low input current. Recently, it has been shown that this unique combination can be achieved by an auto-zero (AZ) stabilized buffer [2]. However, its low-frequency noise density is surd 5 times higher than the...

A 15nW per Button Noise-Immune Readout IC for Capacitive Touch Sensor

This paper presents a readout IC that uses an asynchronous charge-redistribution-based capacitance-to-digital-converter (CDC) to digitize the capacitance of a touch sensor. Thanks to the power efficient tracking algorithm, the CDC consumes negligible power consumption in the absence of touch events. To facilitate stand-alone or wake-on-touch...

A 6800-μm² Resistor-Based Temperature Sensor in 180-nm CMOS

A resistor-based temperature sensor has been realized in 180 nm CMOS for SoC thermal management applications. Occupying only 6800 μm², it is the smallest resistor-based temperature sensor ever reported. This is achieved by employing a compact highly-digital VCO-based ADC. After a 2-point trim, the sensor achieves an inaccuracy of ...

A 0.53pJK27000μm2resistor-based temperature sensor with an inaccuracy of ±0.35°C (3σ) in 65nm CMOS

In microprocessors and DRAMs, on-chip temperature sensors are essential components, ensuring reliability by monitoring thermal gradients and hot spots. Such sensors must be as small as possible, since multiple sensors are required for dense thermal monitoring. However, conventional BJT-based temperature sensors are not compatible with the sub...

A ±4A high-side current sensor with 25V input CM range and 0.9% gain error from -40°C to 85°C using an analog temperature compensation technique

This paper presents a fully integrated ±4A current sensor that supports a 25V input common-mode voltage range (CMVR) while operating from a single 1.5V supply. It consists of an on-chip metal shunt, a beyond-the-rails ADC [1] and a temperature-dependent voltage reference. The beyond-the-rails ADC facilitates high-side current sensing without...

A 280μW dynamic-zoom ADC with 120dB DR and 118dB SNDR in 1kHz BW

Micro-power ADCs with high linearity and dynamic range (DR) are required in several applications, such as smart sensors, biomedical imaging, and portable instrumentation. Since the signals of interest are then often small (tens of μν) and slow (<1kHz BW), such ADCs should also exhibit low offset and flicker noise. Noise-shaping SAR [1] and...

A CMOS Dual-RC frequency reference with ±250ppm inaccuracy from -45°C to 85°C

To comply with wired communication standards such as USB, SATA and PCI/PCI-E, systems-on-chip require frequency references with better than 300ppm accuracy. LC-based references achieve 100ppm accuracy [1], but suffer from high power consumption (∼20mW). Thermal diffusivity (TD) references require less power (∼2mW), at the expense of less...

Energy-Efficient Bridge-to-Digital Converters

This paper presents an overview of energy-efficient analog-to-digital converters (ADCs) specifically intended for the readout of Wheatstone bridge sensors. Apart from achieving good energy-efficiency, such bridge-to-digital converters (BDCs) must achieve low input-referred offset, drift and noise; high gain accuracy, stability and linearity;...

A 0.25mm² Resistor-Based Temperature Sensor with an Inaccuracy of 0.12°C (3σ) from -55°C to 125°C and a Resolution FOM of 32fJK²

Temperature sensors based on Wheatstone bridges, e.g. [1,2], have recently achieved higher resolution and greater energy efficiency than conventional BJT-based sensors [3]. However, this comes at the expense of area, making them less attractive in industrial applications. This paper presents a Wheatstone-bridge sensor that uses a zoom-ADC...

A phase-domain readout circuit for a CMOS-compatible thermal-conductivity-based carbon dioxide sensor

The measurement of carbon-dioxide (CO2) concentration is very important in home and building automation, e.g. to control ventilation in energy-efficient buildings. This application requires compact, low-cost sensors that can measure CO₂ concentration with a resolution of <200 ppm over a 2500ppm range. Conventional optical (NDIR...

A Quiet Digitally Assisted Auto-Zero-Stabilized Voltage Buffer with 0.6pA Input Current and 0.6μV Offset

The readout of high impedance sensors and sampled voltage references [1]<br/>requires amplifiers with both low offset and low input current. Chopper amplifiers<br/>can achieve low offset, but the switching of their input chopper gives rise to<br/>significant input current (40 to 110pA) [2-4]. Auto-zero (AZ) amplifiers require<br/>less input...

A Resistor-Based Temperature Sensor with a 0.13pJ·K2 Resolution FOM

Temperature sensors are often used for the temperature compensation of frequency references [1-5]. High resolution and energy efficiency are then critical requirements, the former to minimize jitter and the latter to minimize power dissipation in a given conversion time. A MEMS-resonator-based sensor meets both criteria [1], but requires two...

A CMOS Temperature Sensor with a 49fJ·K2 Resolution FoM

This paper presents the most energy-efficient CMOS temperature sensor ever reported, with a resolution FoM of 49fJ·K2, 2.7× better than the state-of-the-art. It consists of a Wheatstone bridge made from poly-silicon resistors, which is readout by a 2nd-order Continuous-Time Delta-Sigma modulator (CTDSM). This approach leads to a high resolution ...

A CMOS temperature sensor with a voltage-calibrated inaccuracy of ±0.15°C (3σ) from -55 to 125°C

This paper describes an energy-efficient CMOS temperature sensor intended for use in RFID tags. The sensor achieves an inaccuracy of ±0.15°C (3σ) over the military temperature range (-55 to 125°C) and dissipates only 27nJ/conversion: over 20× less than a previous sensor with comparable accuracy and resolution [2]. This energy efficiency is...

DRIE and Bonding Assisted Low Cost MEMS Processing of In-plane HAR Inertial Sensors

We present a simple, flexible and low cost MEMS fabrication process, developed using deep reactive ion etching (DRIE) and wafer bonding technologies, for manufacturing in-plane high aspect ratio (HAR) inertial sensors. Among examples, the design and fabrication results of a two axis inertial device are presented. Fabricated device thickness...