Disclosed are biosensor devices, systems, and methods for point-of-care applications. In some aspects, a biosensor system includes a biosensor chip device to measure impedance at an electrode-electrolyte interface, which includes an electrochemical sensor comprising a first electrode including a functionalization layer exposing a molecular binding site to bind a target molecule for detection and a second electrode that does not include the binding site, and an electronic circuit unit corresponding to each electrode of the electrochemical sensor including a transimpedance amplifier, a phase detector to determine a relative phase shift in the detected electrical signal caused by an impedance change from a binding event of the target molecule at the molecular binding site, and a time-to-digital converter to quantize and average phase data points in time to remove uncorrelated noise from the detected electrical signal; and a signal generator to produce an electrical excitation signal applied across the electrode-electrolyte interface.