Integrated High-Voltage Inductive Power and Data-Recovery Front End Dedicated to Implantable Devices

Abstract

In near-field electromagnetic links, the inductive voltage is usually much larger than the compliance of low-voltage integrated-circuit (IC) technologies used for the implementation of implantable devices. Thus most integrated power-recovery approaches limit the induced signal to low voltages with inefficient shunt regulation or voltage clipping. In this paper, we propose using high-voltage (HV) complementary metal-oxide semiconductor technology to fully integrate the inductive power and data-recovery front end while adopting a step-down approach where the inductive voltage is left free up to 20 or 50 V. The advantage is that excessive inductive power will translate to an additional charge that can be stored in a capacitor, instead of shunting to ground excessive current with voltage limiters. We report the design of two consecutive HV custom ICs-IC1 and IC2-fabricated in DALSA semiconductor C08G and C08E technologies, respectively, with a total silicon area (including pads) of 4 and 9 mm(2), respectively. Both ICs include HV rectification and regulation; however, IC2 includes two enhanced rectifier designs, a voltage-doubler, and a bridge rectifier, as well as data recovery. Postlayout simulations show that both IC2 rectifiers achieve more than 90% power efficiency at a 1-mA load and provide enough room for 12-V regulation at a 3-mA load and a maximum-available inductive power of 50 mW only. Successful measurement results show that HV regulators provide a stable 3.3- to 12-V supply from an unregulated input up to 50 or 20 V for IC1 and IC2, respectively, with performance that matches simulation results.

An Integrated Chip High-Voltage Power Receiver for Wireless Biomedical Implants

“…A continuous low current stimuli in the magnitude of order 30 µA at 100 Hz [4,12,13] is provided for longer intervals of time powered from the battery. The high stimulation current of magnitude range 0.8-2 mA [3,4,12,13] is supplied for shorter time intervals. Though conventional LV schemes are favorable for high current stimulation at the initial stages of implant, over the course of time, the cuff-nerve electrode interface impedance of the implant rises [3,4,12,13] and the LV schemes become unsuitable.…”

“…To ensure long-term reliability and to improve device portability, these devices demand for power-efficient and compact physical design. In biomedical devices, such as neural stimulator aiding nerve repair and cochlear implant, power is transmitted by inductive links to enhance the operational lifetime of the implant batteries [1][2][3][4]. The inductive near-field link supplies essential power to the bio-microsystem, which requires high stimulation currents for the large cuff-electrode interface nerve impedance (cuff-electrode nerve interface impedance at time of implant: 0.7 KΩ [4], 4.5 KΩ [5], 0.35 KΩ [6], 0.4 KΩ [7]).…”

“…Ref [3] Ref [4] Ref [5] Ref [6] Ref [7] In consideration of a real-time system for a neural stimulator (current >800 µA from 3.7 V for a control system, 2-mA stimulation pulses from 10 V for nerve stimulation [14]), a dual supply is necessary for the system. Generally, there are two approaches to generate dual supplies for inductive power receivers employing a shunt regulator topology: (1) the step down and (2) the step up approach [3].…”

“…Generally, there are two approaches to generate dual supplies for inductive power receivers employing a shunt regulator topology: (1) the step down and (2) the step up approach [3]. Referring to the theoretical studies published in [15] and the system requirements [14], the step down approach proves to be more efficient, if the converter preceding the rectifier has more than 40% efficiency and the output impedance of the DC-DC converter is less than 10 KΩ.…”

“…In [3,16], IC based on the HV process for receivers in implantable device showed improved power efficiency based on simulation results. An HV IC power recovery system for contact-less memory card [17] reported 50% power efficiency at a higher supply voltage.…”