Abstract: A circuit for regulating a current provided by a power supply to drive a load in response to an input signal, is provided. The circuit contains a current source that has a specified current value and is coupled to the power supply. In addition, the circuit also comprises a controller that generates a reference voltage and is coupled to the current source. Furthermore, the circuit also includes a comparator that compares the reference voltage and a voltage at a node. To this node, controller is coupled. In addition, the load is coupled between the node and the power supply. In response to the input signal, the controller regulates the current to drive the load. This current has a first current-value that is proportional to the specified current value of the current source when the voltage at the node is greater than the reference voltage and a second current value that is based on the power supply when the voltage at the node is less than the reference voltage.

Abstract: An apparatus having a power supply terminal, a capacitor terminal, and a load terminal for distributing power from the power supply terminal to the capacitor terminal. The apparatus has a driver which supplies load current to the load terminal in response to a control signal, a controller which generates the control signal, and is coupled to the capacitor terminal, and a switching device. The switching device couples the power supply terminal to the controller and the capacitor terminal when the driver does not supply the load current to the load terminal, and decouples the power supply terminal from the controller and the capacitor terminal when the driver supplies the load current to the load terminal. As a result, the controller is effectively isolated from the noisy power supply.