This disclosure relates generally to digital bus interfaces. In one embodiment, a bus interface system includes a master bus controller and a slave bus controller coupled along a bus line. The master bus controller is configured to generate an input data signal that is received by the slave bus controller along the bus line. The slave bus controller includes power conversion circuitry that includes a power converter configured to convert the input data signal from the master bus controller into a supply voltage. The power conversion circuitry is also configured to generate a charge current from the input data signal. In this manner, the charge current can be used to regulate the supply voltage and maintain the appropriate charge.