IEEE Trans Biomed Circuits Syst. 2023 Oct;17(5):1166-1176. doi: 10.1109/TBCAS.2023.3287294. Epub 2023 Nov 21.
This article presents a multichannel neurostimulator implementing a novel charge balancing technique to achieve maximal integration. Safe neurostimulation demands accurate charge balancing of the stimulation waveforms to prevent charge build-up on the electrode-tissue interface. We propose digital time-domain calibration (DTDC), which adjusts the second phase of the biphasic stimulation pulses digitally, based on a one-time characterization of all stimulator channels with an on-chip ADC. Accurate control of the stimulation current amplitude is loosened in exchange for time-domain corrections, relieving circuit matching constraints and consequentially saving channel area. A theoretical analysis of DTDC is presented, establishing expressions for the required time resolution and the new, relaxed circuit matching constraints. To validate the DTDC principle, a 16-channel stimulator was implemented in 65 nm CMOS, requiring only 0.0141 mm area/channel. Despite being implemented in a standard CMOS technology, 10.4 V compliance is achieved for compatibility with high-impedance microelectrode arrays typical for high-resolution neural prostheses. To the authors' knowledge, this is the first stimulator in a 65 nm low-voltage process achieving over 10 V output swing. Measurements after calibration show the DC error is successfully reduced below 96 nA on all channels. Static power consumption is 20.3 µW/channel.
这篇文章介绍了一种多通道神经刺激器，它采用了一种新颖的电荷平衡技术，以实现最大的集成度。安全的神经刺激需要精确的刺激波形电荷平衡，以防止电极-组织界面上的电荷积累。我们提出了数字时域校准（DTDC），它根据片上 ADC 对所有刺激器通道进行的一次性特性化，在数字上调整双相刺激脉冲的第二阶段。以放宽对刺激电流幅度的精确控制为代价，进行时域校正，从而减轻电路匹配约束，并因此节省通道面积。提出了 DTDC 的理论分析，建立了所需的时间分辨率和新的、放宽的电路匹配约束的表达式。为了验证 DTDC 原理，我们在 65nm CMOS 中实现了一个 16 通道的刺激器，每个通道仅需 0.0141mm 面积。尽管是在标准 CMOS 技术中实现的，但为了与高分辨率神经假体中典型的高阻抗微电极阵列兼容，实现了 10.4V 的合规性。据作者所知，这是第一个在 65nm 低压工艺中实现超过 10V 输出摆幅的刺激器。校准后的测量结果表明，所有通道的直流误差都成功降低到 96nA 以下。静态功耗为 20.3µW/通道。
