A 22 V Compliant 56 μW Twin-Track Active Charge Balancing Enabling 100% Charge Compensation Even in Monophasic and 36% Amplitude Correction in Biphasic Neural Stimulators
A 22 V Compliant 56 μW Twin-Track Active Charge Balancing Enabling 100% Charge Compensation Even in Monophasic and 36% Amplitude Correction in Biphasic Neural Stimulators
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DOI：
10.1109/jssc.2018.2828823
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发表时间：
2018-08-01
影响因子：
5.4
通讯作者：
Kuhl, Matthias
中科院分区：
文献类型：
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作者：
Butz, Natalie;Taschwer, Armin;Kuhl, Matthias
闭环电荷平衡器对安全可靠的电刺激做出了巨大贡献，并且还提供了笨重隔直电容器的替代方案。这款 CMOS 集成、22 V 兼容双轨有源电荷平衡器可实现瞬时和长期平衡条件。长期电荷平衡是通过对剩余电极电压进行基于原因的 PI 控制的偏移补偿来实现的。仅 1.5 nS 的 Gm 仅需一个 12 pF 电容器即可提供大 (8 ms) 时间常数，并导致第一个用于神经植入中偏移补偿的集成 PI 控制器。瞬时自主平衡是通过第二个概念实现的，即基于结果的脉冲间充电控制。它采用 B 类架构来提供补偿电流。因此，不需要额外的参考来定义剩余电极电压的安全窗口。空闲状态下功耗为 31.8 μW，而输出功率可高达 11 mW。这两种互补的方法可以组合到一个系统中，从而提供实现更好性能的机会。该系统功耗为 56 μW，双相刺激振幅具有 36% 失配校正，并且在最大补偿振幅 500 μA 时可自主 100% 电荷去除，这使其成为单相刺激器的合适补充。
Closed-loop charge balancers make a considerable contribution to a safe and secure electrical stimulation and additionally present an alternative to bulky blocking capacitors. This CMOS-integrated, 22 V compliant Twin-Track active charge balancer accomplishes both instantaneous and long-term balanced conditions. Long-term charge balancing is achieved by a cause-based PI-controlled offset compensation of the remaining electrode voltage. A Gm of only 1.5 nS offers a large (8 ms) time constant with only a 12 pF capacitor and leads to the first integrated PI-controller for offset compensation in neural implants. Instantaneous autonomous balancing is realized by a second concept, the consequence-based Inter-Pulse Charge Control. It uses a class-B architecture to supply the compensation currents. Thus, no additional references are required to define the safety window of the remaining electrode voltage. It consumes 31.8 mu W in the idle state, while the delivered output power can be as high as 11 mW. The two complementary approaches can be combined to one system, providing the opportunity to achieve a better performance. The system consumes 56 mu W and features a 36% mismatch correction in biphasic stimuli amplitude, as well as an autonomous 100% charge removal at maximum compensation amplitudes of 500 mu A, which makes it a suitable complement to monophasic stimulators.