PAM4 transceivers for high-speed communication
A communication device includes an AFE configured to track and hold a first driving signal to produce a plurality of sample signals, a shift and hold module configured to store the plurality of sample signals, and an ADC configured to respectively convert the plurality of sample signals to a plurality of digitized sample signals, the ADC including a plurality of ADC slices. A DSP is configured to calibrate the AFE based on the plurality of ADC slices corresponding to the plurality of digitized sample signals and generate an output data stream comprising the plurality of digitized samples. A skew management module is configured to detect a skew of the plurality of digitized sample signals in the output data stream generated by the DSP module, generate a programmable skew offset based on the detected skew, and correct the skew in the output data stream based on the programmable skew offset.
1. A communication device comprising:
an analog front end (AFE) comprising:
a track and hold (T/H) module configured to track and hold a first driving signal to produce a plurality of sample signals, the first driving signal being based on an input data stream;
a shift and hold (S/H) module configured to store the plurality of sample signals; and
an analog-to-digital converter (ADC) module configured to respectively convert the plurality of sample signals to a plurality of digitized sample signals, the ADC module including a plurality of ADC slices respectively corresponding to the plurality of digitized sample signals;
a digital signal processing (DSP) module configured to calibrate the AFE based on the plurality of ADC slices corresponding to the plurality of digitized sample signals and to generate an output data stream comprising the plurality of digitized samples; and
a skew management module configured to (i) detect a skew of the plurality of digitized sample signals in the output data stream generated by the DSP module, the skew corresponding to either one of a timing skew between respective signals of the plurality of digitized sample signals and a logical skew of pulses in the respective signals, (ii) generate a programmable skew offset based on the detected skew, and (iii) correct the skew in the output data stream based on the programmable skew offset.
2. The device of claim 1 further comprising a phase lock loop module for recovering a clock signal from the input data stream, the skew management module being further configured to detect the skew based on the recovered clock signal.
3. The device of claim 1 wherein the DSP module is configured to:
calibrate the AFE by:
adjusting reference voltages of the plurality of ADC slices; and
correcting a residual gain error of the AFE that remains after adjustment of the reference voltages.
4. The device of claim 1 wherein the DSP module comprises a set of parallel feed forward equalizers configured to perform channel equalization.
5. The device of claim 1 , T/H module being configured to track and hold the first driving signal at a first frequency that is about twice a frequency of the input data stream.
6. The device of claim 1 further comprising a power regulator coupled to a power source, the power regulator configured to regulate power supplied to the AFE by performing feed-forward injection of a frequency tuned to attenuate noises associated with the power source.
7. The device of claim 1 wherein the DSP module comprises a baud rate timing recovery module configured to recover a clock signal from the input data stream.
8. The device of claim 1 further comprising a clock generation module configured to generate a clock signal based at least on the input data stream and to provide the clock signal to at least one of the AFE and the DSP module.
9. A method for processing an input data stream, the method comprising:
receiving the input data stream;
generating a first driving signal by amplifying the input data stream;
tracking and holding the first driving signal at a second frequency to produce a plurality of sample signals;
converting the plurality of sample signals to a plurality of digitized sample signals using a plurality of ADC slices respectively corresponding to the plurality of digitized sample signals;
generating an output data stream using the plurality of digitized sample signals;
detecting a skew of the plurality of digitized sample signals in the output data stream, the skew corresponding to either one of a timing skew between respective signals of the plurality of digitized sample signals and a logical skew of pulses in the respective signals;
generating a programmable skew offset based on the detected skew; and
correcting the skew in the output data stream based on the programmable skew offset.
10. The method for processing an input data stream of claim 9 further comprising modulating the output data stream to transmit the output data stream in a pulse amplitude modulated (PAM) format.
11. The method for processing an input data stream of claim 9 further comprising generating a clock signal based on the input data stream.