Circuit and method for implementing an integrated continuous-time smoothing filter

A central office digital subscriber line transmission unit comprising:

• a first low-pass filter having a programmable cut-off frequency;
• a second low-pass filter having a programmable cut-off frequency, the first and second low-pass filters configured to remove images introduced at multiples of a sampling rate used in converting a digital data stream in a digital to analog conversion;
• and
• an output stage amplifier having a low output impedance.

An integrated circuit comprising:

• a first low-pass filter having a programable cut-off frequency;
• a second low-pass filter having a programmable cut-off frequency, the first and second low-pass filters configured to remove images introduced at multiples of a sampling rate used in converting a digital data stream in a digital to analog conversion;
• and
• an output stage amplifier having a low output impedance.

A method for providing continuous-time smoothing in an analog front end, comprising:

• processing a digital to analog converter generated output signal with a first 3rd order low-pass filter;
• processing a first output signal provided by the first 3rd order low-pass filter with a second 3rd order low-pass filter;
• and
• processing a second output signal provided by the second 3rd order low-pass filter with a low-output impedance amplifier.