Comparison and design of VCOs for ultra-low power CMOS temperature sensors

Arshad, Waseem; Ramzan, Rashad; Beg, Azam; Bastaki, Nabil

doi:10.1109/iccspa.2015.7081297

Cited by 6 publications

(7 citation statements)

References 13 publications

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“…The prevalent trend has been to digitize the sensed temperature signal on-chip, and some approaches employ direct thermal sigma-delta for digital conversions, 41 while some approaches have adopted the voltage-tofrequency conversion using temperature-sensitive voltage-controlled oscillators (VCOs). 24,33 This paper presents a wirelessly powered ultralow-power TS designed in CMOS 150-nm process. The WPT circuits employ a high-efficiency diode-less rectifier with the help of a two-inductor-based quadrature oscillator.…”

Section: Discussionmentioning

confidence: 99%

“…The delay cells that are used to implement the ring‐oscillator based VCO are differentially cross‐coupled (DCC) delay cells, as shown in following Figure . As demonstrated in Arshad et al, DCC delay cells have a reasonable temperature sensitivity of 1.66 Hz/°C with a good supply isolation of 0.17 mV Hz/mV.…”

Section: Design Descriptionmentioning

confidence: 99%

“…This results in a more robust implementation from process perspective, and also, it does not put extra constraints on a single VCO as analog difference may lead to a singular zero-frequency scenario for the VCO. The delay cells that are used to implement the ring-oscillator based VCO are differentially cross-coupled (DCC) delay cells, 33 as shown in following Figure 9. As demonstrated in Arshad et al, 33 DCC delay cells have a reasonable temperature sensitivity of 1.66 Hz/ C with a good supply isolation of 0.17 mV Hz/mV.…”

Section: Temperature Sensormentioning

confidence: 99%

“…However, the subthreshold designs are prone to considerable process variations due to the exponential relationship between drain current and other process parameters therefore special provisions for process gradient cancellation should be kept in the design. The prevalent trend has been to digitize the sensed temperature signal on‐chip, and some approaches employ direct thermal sigma‐delta for digital conversions, while some approaches have adopted the voltage‐to‐frequency conversion using temperature‐sensitive voltage‐controlled oscillators (VCOs) …”

Section: Introductionmentioning

confidence: 99%

“…Another design challenge with wirelessly powered systems is the size and storage density of the on‐chip capacitor, which is defined by the load, the ripple, and wireless link frequency and efficiency; typically, this capacitor can be in hundreds of pico‐Farads taking huge area on chip . The presented design increases the charge storage efficiency by making a time‐limited energy‐efficient back‐scattering communication scheme, which increases the refresh rate of the charge storage capacitor through the WPT link.…”

Section: Introductionmentioning

confidence: 99%

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A wirelessly powered low‐power digital temperature sensor

Amin

Shahbaz

Jawed

et al. 2020

Circuit Theory & Apps

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Summary A wirelessly powered temperature sensor is presented in complementary metal‐oxide‐semiconductor (CMOS) 180‐nm process. The wireless power transfer (WPT) is performed using resonant magnetic coupling, and a diode‐less AC to DC conversion is achieved through a quadrature‐oscillator with native‐MOS. The quadrature‐signals are subsequently used to control the diode‐less rectifier switches. The on‐chip temperature sensor exploits the subthreshold region temperature, and the sensed temperature is converted to frequency using a ring‐oscillator, which is implemented using differential cross coupled oscillator‐based delay cells. The temperature sensor architecture also employs a temperature‐insensitive replica circuit to minimize process dependence and enhance power‐supply rejection ratio (PSRR) of the sensing process. The application‐specific integrated circuit has been designed and fabricated in 180‐nm CMOS process and has dimensions of 2 mm × 2 mm. The measurement results demonstrate that the WPT circuit generates a DC voltage of 1V with a power transfer efficiency of 85% for distances 2 to 8 mm with settling time of microseconds to milliseconds. The temperature sensor demonstrates a resolution of < ±0.6C with a sensitivity of 0.52 mV/C and 126.9 Hz/C along with PSRR of −63dB and Integral Non‐Linraity (INL) of 5% measured across six different dies. The back‐scattering communication demonstrates a −53‐dB signal at a distance of 4 mm without affecting the WPT efficiency. The total power consumption of the temperature sensor along with the integrated biases is 120 nW.

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Section: Discussionmentioning

confidence: 99%

Section: Design Descriptionmentioning

confidence: 99%