Particle detection can be done with many different sensors. In this case, the particle detector is based on avalanche photodiodes (APDs) integrated on standard CMOS technology. The integration of the sensors allows the possibility to integrate also the processing circuitry, reducing the volume of components, the complexity, and also the cost of the total device. The sensor is based on a double sensor detection to discriminate the inherent noise of APDs. An electrical model of the sensor, including noise modeling of dark counts and afterpulsing, based on fabricated component, has been developed to proof the suitability of the proposed detector circuit.
Microrobots were proposed more than 20 years ago but it has proven challenging to integrate a power system and actuators into some few mm 3 . There have been some attempts to create an autonomous mobile microrobot but any has been successful. Moreover, the proposed microrobots were simply mobile platforms incapable of sensing its environment and taking decisions. I-SWARM has been designed to be a real autonomous microrobot. It is powered by solar cells and provided with a locomotion unit for moving, an IR module for communicating and a contact tip for detecting near objects. Those modules are managed by an ASIC designed specifically for I-SWARM. All the electronics (power electronics, buffers, ADCs, DACs, control unit, analog transducers and an oscillator) have been embedded in the ASIC due to the limited area, 3 x 3 mm 2 . The ASIC is a complete System On Chip (SoC) that has several features not reported before in any circuit for microrobots: communicate and act cooperatively with other I-SWARM microrobots, detect near objects, measure distance to an object, light trailing and reprogramability. This paper gives some guidelines to design integrated circuits for microrobots. A Fig. 1. Block diagram of the major electronics circuits for a microrobot.
This work presents low noise readout circuits for silicon pixel detectors based on Geiger mode avalanche photodiodes. Geiger mode avalanche photodiodes offer a high intrinsic gain as well as an excellent timing accuracy. In addition, they can be compatible with standard CMOS technologies. However, they suffer from a high intrinsic noise, which induces false counts indistinguishable from real events and represents an increase of the readout electronics area to store the false counts. We have developed new front-end electronic circuitry for Geiger mode avalanche photodiodes in a conventional 0.35 µm HV-CMOS technology based on a gated mode of operation that allows low noise operation. The performance of the pixel detector is triggered and synchronized with the particle beam thanks to the gated acquisition. The circuits allow low reverse bias overvoltage operation which also improves the noise figures. Experimental characterization of the fabricated front-end circuit is presented in this work.
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