In this study, we propose an advanced architecture of a smart electrode for neural stimulation of a retinal prosthesis. A feature of the proposed architecture is embedding CMOS microchips into the core of the stimulus electrodes. Microchip integration without dead space on the array is possible. Additionally, higher durability can be expected because the microchips are protected by the stimulus electrodes like a metal casing. Dedicated circular-shaped CMOS microchips were designed and fabricated. The microchip measured 400 μm in diameter. Stimulus electrodes that had a microcavity for embedding the microchip were also fabricated. In the assembly process, the CMOS microchip was mounted on a flexible substrate, and then the stimulus electrode was mounted to cover the microchip. The microchip was completely built into the inside of the electrode. By performing an ex-vivo experiment using the extracted eyeball of a pig, stimulus function of the electrode was demonstrated successfully.

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In this paper, we propose a high-resolution all-digital complementary metal-oxide semiconductor (CMOS) temperature sensor with a ring oscillator for temperature sensing and power supply immunity, a time amplifier for process variation compensation, and serial digital output for low area consumption. Because of the linearity of its high output cycle-temperature, the sensor has excellent measurement accuracy; the architecture of the sensor effectively decreased power supply sensitivity, and the parallel-to-serial converter considerably reduced area consumption. In addition, the high resolution is determined by the time amplifier with external digital codes. The determination of resolution using the time amplifier and the process variation compensation were accomplished simultaneously. The temperature sensor was fabricated using 0.18-μm standard CMOS technology, and the core circuit occupies an area of 0.001 mm 2 . The experimental results indicated that the energy per conversion rate was only 10 nJ at a supply voltage of 1.8 V; the conversion rate was 15-30 k samples/s, and the error in temperature sensing ranged from −1.58 to +1.6 °C with a resolution higher than 0.1 °C after one-point calibration in the −40 to +130 °C range. With these advantages, the temperature sensor is suitable for application in large integrated circuit (IC) systems and three-dimensional ICs.