A successive approximation logic frequency-to-code converter

A new frequency-to-code converter (fDC) circuit in which an input frequency f
i
is processed by successive approximation logic (SAL) to generate a proportional digital number is described in this letter. Several ingenious subcircuits plus the conventional sequencer clocked by the input hertz constitute the SAL fDC. Conversion time is equal to nT
i
where n is the number of bits in the output digital word and T
i
is the period of the input hertz.