A 0.13μm CMOS low power wake-up radio is presented. The wake-up radio operates with -41dBm sensitivity at 915MHz using OOK modulation with a data rate of 100kbps while consuming 98nW active power, 11pW sleep power, and has an energy efficiency of 0.98pJ/bit. The wake-up radio occupies 0.03mm 2 and uses two off-chip components (an inductor and a capacitor). All biasing and calibration for process variation and mismatch is included on-chip. The entire radio operates from a single 1.2V supply.Index Terms -Wakeup radio, low power radio, body area networks, wireless sensor networks.
Most systems require a voltage reference independent of variation of power supply, process, or temperature, and a bandgap voltage reference (BGR) often serves this purpose. For ultra-low power (ULP) systems, the BGR may constitute a significant component of standby power, and the system start-up voltage is often determined by the voltage, V in , at which the BGR becomes operational. Lowering V in can also allow an ULP system to continue operation longer as its battery or energy harvested input voltage decreases. The minimum V in for state-of-the-art BGRs is restricted by V EB +V DS [1], where V EB is the emitter-base voltage of a pnp transistor, and V DS is the drain-source saturation voltage of a MOS transistor. Recent work brings the V in voltage down to 700mV [2]. There is a need to reduce the standby power and V in of a BGR to increase the lifetime of ULP systems. This paper presents a BGR circuit with measured minimum operating V in of 500mV, reducing the V in of [2] by 1.4×. Further, the power consumption of the proposed circuit is 32nW, which is 1.6× lower than the non-duty cycled BGR reported in [2]. A 2×-charge pump based bandgap core, a switched-capacitor network (SCN), and a current controlled oscillator and clock doubler circuit enable a BGR with a temperature variation of 75ppm/°C and power supply rejection (PSR) of up to -52dB at DC.
A boost converter for thermoelectric energy harvesting in 130 nm CMOS achieves energy harvesting from a 10 mV input, which allows wearable body sensors to continue operation with low thermal gradients. The design uses a peak inductor current control scheme and duty cycled, offset compensated comparators to maintain high efficiency across a broad range of input and output voltages. The measured efficiency ranges from 53% at mV to a peak efficiency of 83% at mV. A cold-start circuit starts the operation of the boost converter from 220 mV, and an RF kick-start circuits starts it from 14.5 dBm at 915 MHz RF power.
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