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Dynamic Element Matching Method for D/A Converters

IP.com Disclosure Number: IPCOM000022637D
Original Publication Date: 2004-Apr-25
Included in the Prior Art Database: 2004-Apr-25
Document File: 3 page(s) / 172K

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Abstract

To achieve low nonlinear distortion results for D/A (Digital-to-Analog) conversions, the use of dynamic element matching (DEM) methods is essential. Apart from the element mismatches, the glitch signals introduced by the switches of the converter add an additional noise floor to the quantization noise floor. Therefore, the number of switches necessary to output a given sequence should be as low as possible. This becomes increasingly significant for new process technologies and in high speed D/A converters. So far, to minimize the glitch signal energy, a restricted randomization technique is used. The disadvantage of this method is that the element mismatch noise is not shaped, resulting in a low signal-to-noise ratio (SNR) in the signal bandwidth. Therefore, it is proposed to incorporate into the restricted randomization technique a mechanism to limit the span of time a single switch can be in one state. All the current sources are summed up and mapped to a voltage at the output. As the control mechanism guarantees that no switch remains in one state (on or off) longer than a predetermined time (number of samples), the spectrum of the output signal of a single switch gets more high frequency components. Thus, the element mismatch noise is changed to a colored high pass noise and the SNR in the signal bandwidth is higher.