On-chip waveform measurement

A circuit for measuring a transition time of a digital signal, said circuit comprising:

• a window detector comprising a comparator circuitry arranged for generating a first signal based on comparing said digital signal with a first reference voltage and for generating a second signal based on comparing said digital signal with a second reference voltage;
• and
• a time-difference-to-digital converter operable for converting a delay between an edge of said first signal and an edge of said second signal into a digital value, said digital value characterizing said transition time of said digital signal, wherein said time-difference-to-digital converter comprises a first programmable delay line and/or a second programmable delay line,
• wherein said time-difference-to-digital converter comprises a phase detector, said first programmable delay line being arranged to forward said first signal to said phase detector with a first programmable delay applied and/or said second programmable delay line being arranged to forward said second signal to said phase detector with a second programmable delay applied, and
• wherein said phase detector comprises a control circuit operable iteratively adjusting said first and/or said second delay until a phase difference detected by said phase detector is below a predefined threshold value and for determining said transition time from said first and/or second delay.