A 40nm-CMOS, 18 μW, temperature and supply voltage independent sensor interface for RFID tags

Temperature- and Supply Voltage-Independent Time References for Wireless Sensor Networks

“…By using the ratio of two time values within a ring oscillator, the impact of temperature and supply voltage variations on the digital output value is lowered drastically. Furthermore, by the use of a low-noise oscillator with high control linearity, the SNR and the SNDR at the output and the power-efficiency are comparable to other state of the art implementations [58,59,61,[263][264][265]279].…”

Towards Energy-Efficient CMOS Integrated Sensor-to-Digital Interface Circuits

“…Compared to the first design example, it is independent of supply-voltage and temperature variations [19]. This is done by building a ring oscillator of which the stage delay is differentially modulated: each half of the stage delays is increased and decreased simultaneously.…”

“…In order to digitize the PWM sensor signal, the signal is single-bit sampled by a clock of 50 MHz. In [19], it has been calculated that for an accuracy of 8 bits, at least 64 periods of the oscillator need to be sampled by this clock. Under the assumption that 100 periods are needed to accurately digitize the PWM sensor signal, this results in a FoM of the sensor-to-digital conversion of 6.6 pJ/bit-conv.…”

“…11. To quantify the temperature and supply-voltage resilience, measurements have been performed on the chip [19]. The maximum temperature error is 79 ppm/°C over a -20 to 100°temperature range.…”

“…To decrease the power consumption of the oscillator, unused stages are turned off. The interface circuit has been prototyped in 40 nm CMOS technology [19]. The performance of the sensor interface is evaluated by measuring the output spectrum when applying a 100 kHz input (Fig.…”