Example apparatus, systems, and methods receive, by a current digital-to-analog converter (DAC) of a shunt regulator, a first digital code indicative of a first programmable power supply command specifying a first programmable output voltage (Vbus) to be delivered to a voltage bus of a USB-compatible device. The programmable power supply command is compatible with a universal serial bus—power delivery (USB-PD) standard. Responsive to receipt of the first digital code, adjust, by the current DAC, a sink current delivered to a feedback node to adjust an output voltage to the first Vbus for dynamic programmability. The feedback node is coupled to a first input of an amplifier of the shunt regulator and the first Vbus is programmable.