Coded data generation or conversion – Converter compensation
Patent
1992-04-17
1993-10-26
Williams, Howard L.
Coded data generation or conversion
Converter compensation
341143, 36472410, H03M 106
Patent
active
052570266
ABSTRACT:
A calibration method and apparatus to calibrate for non-linearities in a multi-level delta-sigma modulator (12) includes a calibration multiplexer (10) on the input for selecting in a calibration mode a zero voltage for input to the delta-sigma modulator (12). The delta-sigma modulator (12) has three levels, +1, 0, -1, the +1 level input to a processor (32) and the -1 level input to a processor (34). The processor (34) has the output thereof input to an compensation circuit (14) that offsets the value generated by the -1 processor (34) by a coefficient .delta.. The output of the compensation circuit (14) is then input to the minus input of a summation junction (36), which also receives the output of the processor (32), the output of summation junction (36) providing the digital output. The processors (32) and (34) are realized with a separate accumulator that switches between an associated filter coefficient and ground, the filter coefficient stored in a ROM (35). The .delta. coefficient is stored in a block (16) and is generated during a calibration cycle by a .delta. processor (39). The .delta. processor (39) receives the output of the compensation circuit (14) and the digital output from the summing junction (36) when the calibration multiplexer (10) sets the input to zero. A control circuit (40) controls the overall operation, with the calibration operation initiated in response to either an external signal on a line (30) or an internally generated signal. After calibration, the value of the .delta. coefficient is frozen and the calibration multiplexer (10) selects the analog input.
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"Adaptive Selfcalibrating Delta-Sigma Modulators" by S. Abdennadher, S. Kiaei, G. Temes and R. Schreier, Electronics Letters, Jul. 2, 1992, vol. 28, No. 14.
"On-Line Adaptive Digital Correction of Dual-Quantisation Delta-Sigma Modulators" by Yaohua Yang, R. Schreier, G. C. Temes and S. Kiaei, Electronics Letters, Jul. 30, 1992, vol. 28, No. 16.
Bernadas Salvador R.
Swanson Eric J.
Thompson Charles D.
van Bavel Nicholas R.
Crystal Semiconductor, Inc.
Howison Gregory M.
Williams Howard L.
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