High performance switched-capacitor filter for oversampling Sigma-Delta digital to analog converters
First Claim
1. A filter for oversampling Sigma-Delta digital-to-analog converter circuits, comprising:
- a SINC filter that decimates a digital data input signal by a predetermined factor of an over-sampling ratio utilized by a Sigma-Delta modulator, the SINC filter being defined by a cascaded architecture; and
a switched-capacitor biquad filter having a programmable cut-off frequency which tracks the over-sampling ratio.
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Abstract
A SINC filter for an oversampling Sigma-Delta digital to analog converter (OSDAC) having a cascaded construction that results in reduced sensitivity to capacitor mismatch. Specifically, the SINC filter circuit filter may be defined by a transfer function H(z), which is further defined by first constituent transfer functions H1(z) and H2(z). The constituent transfer functions may be implemented in a cascaded fashion. Preferably, one of the cascaded sections includes a resistor string that defines a plurality of reference voltages. A plurality of switching elements are configured to controllably switch these reference voltages to a capacitor of a tap.
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Citations
19 Claims
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1. A filter for oversampling Sigma-Delta digital-to-analog converter circuits, comprising:
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a SINC filter that decimates a digital data input signal by a predetermined factor of an over-sampling ratio utilized by a Sigma-Delta modulator, the SINC filter being defined by a cascaded architecture; and
a switched-capacitor biquad filter having a programmable cut-off frequency which tracks the over-sampling ratio. - View Dependent Claims (7, 8, 9, 10, 11)
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- 2. The filter of claim Error! Bookmark not defined., wherein the cascaded SINC filter is defined by first and second cascaded sections, wherein the SINC filter is defined by a transfer function H(z), which is further defined by first and second constituent transfer functions H1(z) and H2(Z).
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12. A SINC filter for an oversampling Sigma-Delta digital-to-analog converter circuit, comprising:
first and second cascaded sections, wherein the SINC filter is defined by a transfer function H(z), which is further defined by first and second constituent transfer functions H1(z) and H2(z) a switched-capacitor biquad filter having a cut-off frequency which tracks the over-sampling ratio. - View Dependent Claims (13, 14, 15, 16, 17, 18)
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19. A filter for oversampling Sigma-Delta digital-to-analog converter circuits, comprising:
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a SINC filter that decimates a digital data input signal by a predetermined factor of an over-sampling ratio utilized by a Sigma-Delta modulator, the SINC filter being defined by a cascaded architecture that is defined by first and second cascaded sections having first and second constituent transfer functions H1(z) and H2(z), wherein;
a switched-capacitor biquad filter having a programmable cut-off frequency, which tracks the over-sampling ratio.
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Specification