1. A method of measuring the electrical impedance of at least one power distribution network of a programmable logic device, comprising: providing a programmable logic device connected in an electric circuit comprising at least one power distribution network; configuring a plurality of configurable logic blocks of the said programmable logic device to function as power supply sinusoidal current load with waveform aberrations less than 40% on at least one power supply, and having activate and frequency control features; configuring a plurality of configurable logic blocks of the said programmable logic device to function as programmable frequency generator that controls the frequency of the said power supply sinusoidal current load; configuring a plurality of configurable logic blocks of the said programmable logic device to function as ring oscillator powered from the same power supply as the said power supply sinusoidal current load; configuring a plurality of configurable logic blocks of the said programmable logic device to function as frequency counter that measures the oscillation frequency of the said ring oscillator; programming a frequency value of the said programmable frequency generator, activating the said power supply sinusoidal current load and measuring a first average frequency of the said ring oscillator over a time interval, deactivating the said power supply sinusoidal current load and measuring a second average frequency of the said ring oscillator over a time interval, and calculating the electrical impedance of the said power distribution network at the said frequency value by processing the values of the said first average frequency, the said second average frequency, and a plurality of design and functionality characteristics of the said programmable logic device and the said electric circuit; repeating the above step for multiple frequency values programmed in the said programmable frequency generator to provide an impedance versus frequency information of the said power distribution network.