Sigma-delta converter for performing an attenuation function and having a transfer function insensitive to the rise and fall time mismatch of the switching components

摘要

A sigma-delta converter including a switching component (313) controlled by a first clock (308) having determined transitions for generating a train of sigma-delta code pulses corresponding to an analog input value. The sigma-­delta includes means (306, 310, 311) for generating a second clock (350) of a same frequency than the first clock and having a negative transition followed after a defined period of time (d2) by a positive transition. The determined transi­tions of the first clock controlling the swithing element occur during said de­fined period of time. There is also included means (305) controlled by the sigma-delta code pulse train and said second clock for generating a train of sigma-delta pulses being insensitive to the mismatch of the rise and fall times of said switching element (313) whereby improving the linearity and the signal-to-noise ration of the converter. The control of the said period of time allows the varying of the energy of the pulses in order to provide pulses train which, when applied to a sigma-delta decoder, provides an analog output value representative but attenuated with respect to the analog input value.