Abstract
This paper presents a fully integrated voltage-reference circuit for implantable devices such as retinal implants. The recently developed retinal prostheses require a stable supply voltage to drive a high-density stimulator array. Accordingly, a voltage-reference circuit plays a critical role in generating a constant reference voltage, which is provided to a low-voltage-drop regulator (LDO), and filtering out the AC ripples in a power-supply rail after rectification. For this purpose, we use a beta-multiplier voltage-reference architecture to which a nonlinear current sink circuit is added, to improve the supply-independent performance drastically. The proposed reference circuit is fabricated using the standard 0.35 µm technology, along with an LDO that adopts an output ringing compensation circuit. The novel reference circuit generates a reference voltage of 1.37 V with a line regulation of 3.45 mV/V and maximum power-supply rejection ratio (PSRR) of −93 dB.
Highlights
Short-distance wireless communication for retinal prosthetic systems plays a critical role in delivering a radio-frequency (RF) power carrier and data from the external world to an implant inside the eyeball
The recent advances in submicron complementary metal oxide semiconductor (CMOS) technologies have facilitated the reduction of the size of the implanted hardware such as an inductive coil receiver, digital controller, or high-density stimulator array
Back telemetry is utilized to observe the operating status of load-shift keying (LSK) technique is used for back telemetry, which is fully controlled by the reverse the implanted device
Summary
Short-distance wireless communication for retinal prosthetic systems plays a critical role in delivering a radio-frequency (RF) power carrier and data from the external world to an implant inside the eyeball. The implanted device consists of a rectifier, regulator, over-voltage–protection circuit, demodulator, reverse telemetry controller, global digital controller, and stimulator array. LDO1 and LDO2 is shown, where +REF and −REF, respectively generate positive and negative reference supply constant voltages to analog and digital circuits in the implanted devices respectively. LDO1 and LDO2 supply constant voltages to analog and digital circuits in command data modulated on the RF carrier are recovered using the demodulator and sent to the the implanted devices respectively. The command data modulated on the RF carrier are recovered using global digital controller that decodes the demodulated data in order to activate the stimulator array. Back telemetry is utilized to observe the operating status of load-shift keying (LSK) technique is used for back telemetry, which is fully controlled by the reverse the implanted device.
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