An electronic monitoring circuit for detecting a variation in the power or current absorbed by an electronic circuit under test is disclosed. The circuit includes an input terminal adapted to receive a pulse-width modulation control signal, a resistor having a first terminal connected to the input terminal, and a capacitor having a first terminal connected to a second terminal of the resistor. The output terminal is adapted to generate an output signal as a function of the value of the voltage drop at the ends of the capacitor, said output signal being representative of a variation of the pulse width of the pulse-width modulation control signal. The variation of the pulse width is a function of the power or current absorbed by the electronic circuit under test.