1. Field of the Disclosure
The present invention relates generally to control circuits, and more specifically, the present invention relates to control circuits that are responsive to an impedance at a control circuit terminal.
2. Background
Integrated circuits may be used for a multitude of purposes and applications. Many applications have cost goals that limit the functionality of the integrated circuit in order to meet these goals. The package in which the integrated circuit is housed can significantly contribute to its cost. The number of pins or terminals that it uses in turn influences the cost of the integrated circuit package. The number of pins that can be used to meet cost goals therefore often limits the number of features or options that can be provided to customers using an integrated circuit.
An example of this can be appreciated with respect to an over-voltage protection feature commonly provided by control circuits used in power conversion applications. Depending on the customer, the desired response to an over-voltage fault condition may be for the power converter to stop operating and require the power converter to be reset by, for example, removing and reapplying the input voltage before the power converter starts to operate again. In other cases a customer may wish the response to an over-voltage condition to be an automatic restart after a shutdown period, an operation often referred to as auto-restart.
In order to provide customers with these different responses to the same operating condition, it is often necessary to manufacture two versions of the same integrated circuit with the response to an over-voltage condition as the only difference. This introduces additional manufacturing costs and overhead associated with holding inventory of two integrated circuit types with a single distinguishing feature. Alternatively the same integrated circuit could have multiple separate terminals to accommodate the various responses to an operating condition, which increases the cost of the package used to house the integrated circuit.