A signal processing circuit comprising a sigma delta analog to digital converter
A technology of signal processing circuits and digital converters, applied in the direction of analog conversion, code conversion, electrical components, etc., can solve the problem of the overall operation of the Sigma Delta A/D converter, the influence of manufacturing distribution is unavoidable, and it is difficult to control Filter circuit bandwidth and other issues
Active Publication Date: 2008-11-12
NXP BV
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Problems solved by technology
[0007] However, in the case of using such different analog circuit elements (such as capacitors and resistors), the influence of manufacturing spread cannot be avoided
As a result, it is difficult to control the bandwidth of the filter circuit and thus the overall operation of the sigma delta A / D converter
Method used
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[0016] figure 1 Represents a basic sigma delta A / D converter. It should be understood that the circuits described are shown by way of example: the invention is not limited to this particular circuit. The converter comprises an input 10 , a subtractor 12 , a filter circuit 14 , a digitization circuit 16 , a digital-to-analog conversion circuit 17 , a frequency band detector 18 and a control circuit 19 . The subtractor 12 has a positive input coupled to the input 10 and a negative input coupled to the output of the digital-to-analog conversion circuit 17 . The output of the subtractor 12 is coupled via a filter circuit 14 to an input of a digitization circuit 16 . The output terminal of the digitization circuit 16 is coupled to the input terminal of the digital-to-analog conversion circuit 17 . Band detector 18 has an input coupled to the output of digitization circuit 16 and an output coupled to control circuit 19 . The control circuit 19 has an output coupled to the contro...
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A signal processing circuit comprising a sigma delta analog to digital converter with a feedback loop that comprises an analog filtering circuit (14) that has a controllable time constant. In a calibration mode a detector (18) detects a signal strength in a band (34) of frequencies at an output of the sigma delta analog to digital converter. A bandwidth control circuit (19) has an output coupled to a control input of the analog filtering circuit (14), and is arranged to control said time constant dependent on a signal strength in a band (34) of frequencies at the output of the sigma delta analog to digital converter. The band (34) of frequencies is selected so that noise shaped quantization noise density (32) of the sigma delta analog to digital converter rises with frequency. Thus, detection output depends on the time constant, shifts in the time constant affecting the rise of quantization noise. In this way a simple calibration of the time constant can be realized.
Description
technical field [0001] The invention relates to a circuit comprising a sigma delta analog-to-digital conversion circuit. Background technique [0002] Sigma delta analog-to-digital conversion circuits are well known. A sigma delta analog-to-digital conversion circuit can be obtained, for example, from the paper entitled "Alow-power 10-bitcontinuous-time CMOS sigma- delta A / D converter" article. Furthermore, a general background on sigma delta analog-to-digital conversion circuits can be found, for example, in the book entitled "Delta Sigma Data Conversion" by S. Norsworthy (ISBN 0-7803-1045-4, 174 -182 pages). [0003] A simple sigma delta A / D converter includes digitization circuitry with an integrated feedback loop from output to input. The digitizing circuit digitizes a signal resulting from the difference between the signal obtained from the input signal and the integration of the output signal of the digitizing circuit. [0004] The advantage of sigma delta analog-...
Claims
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Login to View More IPC IPC(8): H03M3/00
CPCH03M3/382H03M3/458H03M3/00H03M3/02
Inventor 凯瑟琳·菲利普斯
Owner NXP BV