A 12 V Compliant Multichannel Dual Mode Neural Stimulator With 0.004% Charge Mismatch and a 4×VDD Tolerant On-Chip Discharge Switch in Low-Voltage CMOS

This letter presents a 12 V-compliant 4-channel neural stimulator fabricated in a low-voltage bulk CMOS process. Arrays of current memory cells are used to implement anodic and cathodic current sources to generate anodic and cathodic current ratios that are robust to process-voltage-temperature variations. A novel, fully integrated discharge switch is presented that tolerates an output voltage up to $4\times V_{DD}$ , which is the highest reported for low-voltage bulk CMOS monopolar stimulators. The proposed neural stimulator can operate in both constant current mode (CCM) with a $1~\mu $ -1.2 mA output current range and constant voltage mode (CVM) with a 1–11 V output voltage range. The output waveform is fully programmable, including cathodic and anodic amplitudes and ratios designed to have excellent charge balancing with only 0.004% charge mismatch.