A continuous time Delta-Sigma (CT-ΔΣ) modulator has an input node configured to receive an input signal and an output node configured to output a digital output signal. The CT-ΔΣ modulator includes a feedback loop with a summation circuit configured to sum the digital output signal with a jitter perturbed test signal to generate a signal supplied to an input of a digital to analog converter circuit. A single tone signal is injected with a jitter error of a clock signal to generate the jitter perturbed test signal. A processing circuit processes the digital output signal to detect a signal to noise ratio of the CT-ΔΣ modulator. The detected signal to noise ratio is indicative of presence of jitter in the clock signal.