This paper presents a highly miniaturized and low-power CMOS electrochemical potentiostat based on a fully digital design. The potentiostat functionality has been evaluated through dopamine detection using proper microelectrodes. The system drives an electrochemical cell in a three-electrode configuration and implements the chronoamperometric technique to minimize both power consumption and required area. The circuit has been fabricated using TSMC 180 nm CMOS technology. Supplied at 0.4 V, the potentiostat alone consumes the up-to-date smallest power of 1.2 nW and occupies the up-to-date smallest ever area of 260 μm2. Together with its voltage reference and oscillator, the entire system consumes 9.2 nW and occupies 370 μm2. The potentiostatic voltage maintains an accuracy of ±10% (180 mV to 220 mV) for a 200 mV reference and supply voltage ranging from 0.4 V to 0.56 V, at a frequency of 25 kHz, driven by the ring oscillator. In-vitro experiments demonstrate dopamine detection with a sensitivity of 18.74 pulses/μM and a limit of detection of 0.525 μM. Results demonstrate the huge advantage of using the proposed fully-digital design, making this potentiostat well-suited for implantable devices where size and energy efficiency are critical (e.g., Neural Dust).