Methods and apparatus for protecting a physical unclonable function (PUF) generator are disclosed. In one example, a PUF generator is disclosed. The PUF generator includes a PUF cell array, a PUF control circuit and a reset circuit. The PUF cell array comprises a plurality of bit cells. Each of the plurality of bit cells is configurable into at least two different stable states. The PUF control circuit is coupled to the PUF cell array and is configured to access each of the plurality of bit cells to determine one of the at least two different stable states upon a power-up of the plurality of bit cells, and generate a PUF signature based on the determined stable states of the plurality of bit cells. The reset circuit is coupled to the PUF cell array and is configured to set the plurality of bit cells to represent their initialization data based on an indication of a voltage tempering event of a supply voltage of the PUF cell array.