Frequency to current circuit

Aspects of the present disclosure include a frequency-to-current (F2I) circuit and systems, methods, devices, and other circuits related thereto. The F2I circuit is implemented with a delta-modulator-based control loop to settle and maintain an operating point on a bias node. The control loop provides an integral of an output of a comparator, and the comparator compares it to a self-built voltage reference. Upon powering on the circuit, an integrator in the control loop starts to integrate the charge on both a bias voltage and an internal voltage to provide a settling process for the internal voltage to approximate the reference voltage and for the bias voltage to approximate a predetermined operating point of the bias node. After the circuit has settled, the comparator's output charge toggles and the internal voltage and bias voltage become sawtooth-like waveforms at the reference voltage and operating points, respectively.