Chopper stabilized delta-sigma analog-to-digital converter
AssigneeCrystal Semiconductor Corporation
InventorAdrian B. Early
Life of this patent
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Abstract
A chopper stabilized analog-to-digital converter includes an analog modulator (10) and a digital filter (12). The analog modulator (10) is comprised of two integrators (20) and (22). The first integrator (20) is a chopper stabilized integrator which is comprised of a chopper stabilized differential amplifier (32) and a capacitively switched input. The amplifier (32) is operable to receive a chopping frequency F.sub.CH that is one-half the sampling frequency F.sub.S and synchronized thereto. The amplifier (32) is operable to modulate the noise up to the chopping frequency F.sub.CH, which frequency is in the rejection portion of the filter response for the digital filter (12), thus rejecting 1/f noise.
Claims19
An analog-to-digital converter, comprising:
- a delta sigma analog modulator operating at a predetermined sampling frequency for receiving an analog input signal, and converting the received analog input signal to a digital output signal which is representative of the analog input signal, said analog modulator having undesirable low frequency noise associated therewith, said analog modulator including at least one stage of amplification;
- a digital filter for receiving the digital output of said analog modulator and having a predetermined frequency response and sampling rate for providing a predetermined amount of attenuation over a predetermined frequency range to reject unwanted signal;
- and
- means for transposing the low frequency noise in the analog modulator to said predetermined frequency range.
An analog-to-digital converter, comprising:
- a delta-sigma modulator for receiving an analog input signal and converting the received analog input signal to a digital signal output that has a value proportional to the analog input signal, said delta sigma modulator operating at a predetermined sampling frequency;
- a digital filter for receiving the digital signal output of said modulator and having a predetermined frequency response for providing a predetermined amount of rejection over a defined frequency range of rejection to reject unwanted signals;
- and
- said delta-sigma modulator having at least one stage of amplification, said one stage of amplification having low frequency noise associated therewith and being chopper stabilized at a predetermined chopping frequency such that the energy in the low frequency noise is transposed upward in frequency by said chopping frequency and the harmonics thereof, with the harmonics of said chopping frequency being within the defined frequency range of rejection of said digital filter.
A method for converting an analog input signal to a digital signal, comprising:
- passing the analog input signal through an oversampled analog modulator operating at a predetermined sampling frequency to convert the analog input signal to a digital output signal proportional to the analog input signal;
- filtering in the digital domain the digital output signal of the analog modulator to provide a predetermined amount of attenuation over a predetermined frequency range to reject unwanted signals;
- and
- transposing the energy of low frequency noise energy generated by the analog modulator proximate to a frequency within the predetermined frequency range to reject unwanted frequencies.
A method for converting an analog input signal to a digital signal, comprising:
- passing the analog input signal through an analog modulator operating at a predetermined sampling frequency to convert the analog input signal to a digital output signal proportional to the analog input signal, the analog modulators having at least one stage of amplification;
- filtering in the digital domain the digital output signal of the analog modulator to provide a predetermined amount of attenuation over a predetermined frequency range to reject unwanted signals;
- chopper stabilizing the one stage of amplification to transpose the low frequency noise up in frequency such that the low frequency noise is disposed about the harmonics of a chopping frequency, the harmonics of the chopping frequency being disposed within the predetermined frequency range to reject unwanted frequencies;
- and
- synchronizing the chopping frequency with the sampling frequency of the analog modulator, such that the harmonics of the chopping frequency are disposed at a predetermined relationship with respect to the harmonics of the sampling frequency.
Dependencies are inferred from the claim text.