Low harmonic distortion flash A/D converters incorporating dynamic element matching techniques

Abstract

New dynamic element matching techniques are shown to reduce the harmonic distortion and improve the spurious-free dynamic range of flash ADCs. Resistor chain mismatch errors are negated by randomly rearranging the resistors each sample by utilizing 5(2{dollar}\sp{b}{dollar}-1) digital switches and b + 1 random control signals for a b-bit flash ADC. The integral and differential nonlinearity of a non-ideal flash ADC are derived for three common resistor chain mismatch errors; namely, geometric mismatches, linear gradient mismatches, and dynamic mismatches. The transfer function of a non-ideal flash ADC is also derived and the converter output is shown to consist of a scaled copy of the input, a DC gain, and conversion noise that is a function of the resistor mismatches. A comprehensive summary of dynamic element matching techniques given in literature is provided. In addition, the DEM network introduced by Galton and Jensen is shown to be equivalent to the generalized-cube network used in parallel processing architectures. An alternative version of this network that uses logic gates is also proposed

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