This brief presents an 8-bit successive approximation register analog-to-digital converter (ADC) implemented within a system-on-chip (SoC) for autonomous flapping-wing microrobots. The ADC implements hybrid split-capacitor sub-digital-to-analog converter (DAC) techniques to achieve 35.72% improvement in a capacitor bank energy-area product. The device also implements an extended single-ended input voltage range allowing a direct connection to sensors while maintaining low-power operation. This technique allows 51.7% DAC switching energy reduction compared to the state of the art. The SoC, fabricated in 40-nm CMOS, includes four parallel 0.001 mm 2 1 MS/s ADC cores multiplexed across 13 input ports. It enables 0 to 1.8-V input range while operating off of a 0.9 V supply. At 1 MS/s, the ADC achieves a signal-to-noise and distortion ratio of 45.6 dB for a 1.6-V pp input signal and consumes 10.4 μW.

Piezoelectric actuators are used in a growing range of applications, e.g., haptic feedback systems, cooling fans, and microrobots. However, to fully realize their potential, these actuators require drivers able to efficiently generate high-voltage (>100V pp ) low frequency (<;300Hz) analog waveforms from a low-voltage source (3-to-5V) with small form factor. Certain applications, such as piezoelectric (PZT) cooling fans, further demand low distortion waveforms (THD+N <; 1%) to minimize sound emission from the actuator. Existing solutions for small PZT drivers typically rely on designs comprising a power converter to step up a low voltage followed by a high-voltage amplifier [1,2,3]. Although envelope tracking can help reduce amplifier power [3], none of these designs can recover the energy stored on the actuator to maximize efficiency. And while a differential bidirectional flyback converter [4] can recover energy, it requires four inductors, thereby incurring large size penalty. This paper introduces a single-inductor, highly integrated, bidirectional, high-voltage actuator driver that achieves 12.6× lower power and 2.1× lower THD+N at a similar size to the currently available state-of-the art solution [1]. Measured results from an IC prototype demonstrate 200Hz sinusoidal waveforms up to 100V pp with 0.42% THD+N from a 3.6V source while dissipating 57.7mW to drive a 150nF capacitor. Beyond PZT actuators, the IC can also drive any type of capacitive load, e.g., electrostatic and electroactive polymer actuators.

We demonstrate a battery-powered multi-chip system optimized for insect-scale flapping wing robots that meets the tight weight limit and real-time performance demands of autonomous flight. Measured results show open-loop wing flapping driven by a power electronics unit and energy efficiency improvements via hardware acceleration.