Automatic coefficients design for high-order sigma-delta modulators

摘要

An automatic-design methodology for designing high-tolerancenmodulator coefficients for high-order sigma-delta modulators (SDMs) fromnsystem specifications is presented. The methodology covers many designnconcerns including SDM coefficient tolerances for circuit componentnmismatch, stability, reduction of in-band tones, design tradeoffs amongnin-band noise suppression, oversampling ratio, and modulator order.nMoreover, a high-order SDM synthesis tool (HOST) based on thenmethodology has been implemented in a C language program. Even forninexperienced designers, reliable and high-tolerance SDM coefficientsnfor various applications can be automatically and efficiently generatednusing HOST. For synthesized SDM's with orders from three to eight andnoversampling ratios from 32 to 256, coefficient variations within 2% (1%nfor the eighth order) are allowed and the resulting peak signal-to-noisenratio degradation is less than 3 dB. Several design examples synthesizednby HOST are included