An integrated circuit includes an energy detection circuit, a switching circuit, and a tamper response circuit. The integrated circuit has an input for receiving a radio frequency (RF) signal, a first output for providing a demodulated signal, and a second output for selectively providing a detect signal. The detect signal is provided in response to detecting that an energy of an internal signal exceeds a first threshold when the integrated circuit is in a secure mode. The switching circuit is used to alternatively switch the input of the energy detection circuit to an RF input terminal in a normal mode and to an internal antenna in a secure mode. The tamper response circuit disables a function of the integrated circuit in response to an activation of the detect signal in the secure mode.