神经植入物与人类安全：直流耦合记录前端的单故障检测
Neural implants and human safety: single-fault detection for DC-coupled recording front ends
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中文总结 AI 辅助
本文针对直流耦合神经植入物记录前端的组织安全风险，提出一种基于电流饥饿型弛张振荡器的单故障检测机制，可在规定时间内解析故障并禁用放大器，符合相关安全标准。
中文摘要 AI 辅助
用于神经植入物的直流耦合模拟前端（AFE）是一种低面积解决方案。然而，移除耦合电容会消除保护皮层组织的固有屏障：单故障事件（例如低噪声放大器（LNA）输入晶体管的栅氧击穿）可能会在电源轨与大脑之间形成直接直流路径。在刺激方面，该危害已被充分认识，且通过串联直流阻断电容强制实现单故障容错；但在记录方面，直流耦合前端放弃了这一等效保护措施，其保护机制几乎未被研究。本文提出一种单故障检测机制，该机制监测LNA因此类故障产生的直流不平衡，并在故障电流造成组织不可逆损伤前禁用放大器。该不平衡被编码为电流饥饿型弛张振荡器的占空比，并读取为时间数字测量值。该机制采用65 nm工艺设计，可在0.81 ms内解析所有工艺角下最坏情况的6.4 nA故障，符合ISO 14708-3标准中针对8533 μm²电极的限值，为直流耦合记录的安全问题展开更广泛讨论。
英文摘要
DC-coupled analogue front ends (AFEs) for neural implants provide a low-area solution. However, removing the coupling capacitor eliminates the intrinsic barrier that protects cortical tissue: a single-fault event, such as gate-oxide breakdown of a low-noise amplifier (LNA) input transistor, can open a direct DC path from the supply rail into the brain. On the stimulation side this hazard is well understood, and single-fault tolerance is enforced by a series DC-blocking capacitor; on the recording side, DC-coupled front ends discard the equivalent safeguard, yet their protection has gone almost unexamined. This paper presents a single-fault detection mechanism that monitors the LNA for the DC imbalance produced by such a failure and disables the amplifier before the resulting fault current can irreversibly damage tissue. The imbalance is encoded in the duty cycle of a current-starved relaxation oscillator and read out as a time-to-digital measurement. Designed in 65 nm, the mechanism resolves a worst-case fault of 6.4 nA across all corners within 0.81 ms - compliant with the ISO~14708-3 limit for an 8533 um2 electrode - opening a broader discussion of safety in DC-coupled recording.
