Voltage offset compensation method for time-interleaved multi-path analog-to-digital sigma-delta converters and respective circuit

摘要

A multi-path time-interleaved analog-to-digital converter (MP-ADC) exploits an additional reference ADC cyclically connected in parallel to each ADC component part to be calibrated of the multi-path ADC, which can be of any kind, in particular sigma-delta, to whom conventional calibration techniques cannot be applied because of its stochastic behaviour. For each ADC component part the algebraic differences between successive digital outputs of the reference ADC and the ADC under calibration are forwarded to an accumulator circuit (13) which integrates them over a given time slot, obtaining a digital word (CH1',...,CH4') proportional to the difference between the offset of the two paths. A digital adder adds up the digital word so obtained to the output of the ADC component part under calibration multiplied by a scale factor which depends on the length of the given time slot. After a reasonable time the voltage offset of each individual path is proportional to the voltage offset of the only reference path, not necessarily zero. Optionally, the outputs of the digital adder are de-scaled by the same scale factor, restoring the original value. The time-interleaved ADC is continuously running and the voltage offset calibration is performed in background without affecting the normal operation (fig.7). <IMAGE>