An Inductive Power and Data Telemetry Subsystem With Fast Transient Low Dropout Regulator for Biomedical Implants

Abstract

This paper presents a capacitorless low-dropout (LDO) regulator with fast transient response and data reverse telemetry circuit for fully implantable wireless transmission applications. We propose a novel hybrid feedback structure using high-frequency compensation technology to achieve a rapid transient response for the LDO regulator. To reduce the size of the implant and transmit neural recordings through the same coil without interfering with power transmission, the load-shift-key (LSK) modulation technique is adopted for back data telemetry. The proposed implantable chip, fabricated using commercial 0.18 μm complementary metal oxide semiconductor technology, yielded an output power of 15 mW. Under 1.15 V operation voltage, the maximum overshoot and undershoot voltages were less than 45 mV and 55 mV, respectively, for a 15 mA full-load current whose rising and falling time were less than 100 ns. The proposed LSK transceiver uses a digitized demodulator to improve bandwidth efficiency for low carrier frequency operation.

Evaluation and Perspective of Analog Low-Dropout Voltage Regulators: A Review

“…In addition to the edge time in FoM9, the recovery time, TRc, is also a key parameter in evaluating the performance of an OCL-LDO. The authors of [50] claimed that an FoM that considers the response time is not sufficient for evaluating the performance and proposed a modified FoM that includes the recovery time factor, RRc, leading to the following definition:…”

“…In this case, the settling time is not less harmful and critical than the response time. In the application of highdensity SoC, which is crucial for IoE, IoT and RFID, a better slewing performance is preferred [44], where the settling time becomes the key factor since OCL-LDO is preferred [50] for reduced pin count, smaller form factor and footprint [22].…”

“…It may cover more metrics, such as phase margin or Q, but it also makes the other terms in the FoM difficult to tradeoff, while maintaining the same performance. Although the scalability of FoM19 may not be as good as FoM1, in the application of high-density SoC, where OCL-LDO is preferred, the settling/recovery time becomes the key factor [50].…”

“…Although the edge time (or equivalently, K) does not scale linearly with either the TRc or TRs, the edge time is a key parameter in affecting the performance for OCL-LDO [38]. Whilst In high-density SoC, a better slew performance is preferrable [44], where TRc is another key factor [50]. Hence, to evaluate OCL-LDO in the application for high-density SoC, the parameters Tedge and TRc should be accounted in evaluating the performance of the architecture.…”

“…Instead, the edge time, Tedge, becomes the key parameter in affecting the performance [38]. Besides that, an improved slewing performance is preferred in high-density SoC [44], where TRc is another key factor [50]. Hence, to evaluate OCL-LDO in the application for high-density SoC for IoE, IoT and RFID, the parameters Tedge and TRc should be incorporated in evaluating the performance of the architecture.…”