User-configurable high-speed line driver
An adaptive line driver circuit configured to transmit a signal over a wired link includes a delay-locked loop (DLL) circuit, which includes a phase detector (PD) circuit, charge pump (CP) circuit, and voltage-controlled delay line (VCDL) circuit operatively coupled together. The delay-locked loop circuit provides pre-emphasis and feed-forward equalization of the signal. The delay locked loop circuit also provides a user-configurable parameter including at least one of pre-data tap amplitude, data tap amplitude, post-data tap amplitude, pre-data tap duration, post-data tap duration, pre-data tap quantity, and post-data tap quantity. The adaptive line driver circuit further includes a source-series terminated (SST) driver circuit operatively coupled to the delay-locked loop circuit.
1. An adaptive line driver circuit configured to transmit a signal over a wired link, the adaptive line driver circuit comprising:
a delay-locked loop circuit, providing sub unit interval (UI) user-configurable durations adapted to form pre-emphasis and feed-forward equalization of the signal by retiming the signal, the delay locked loop circuit providing a user-configurable quantity of pre-emphasis taps to retime the signal;
a signal retiming circuit providing pre-emphasis data tap outputs comprising a main data signal referenced to delayed clock outputs from the delay-locked loop circuit; and
a plurality of source-series terminated (SST) driver circuits, the source-series terminated (SST) driver circuits operatively coupled in groups to the signal re-timing circuit, a quantity of SST drivers in a group defining coefficients of pre-emphasis, groups of SST drivers operating in parallel with ganged outputs providing the signal to be transmitted.
2. The adaptive line driver, as defined by claim 1 , wherein the delay locked-loop circuit further comprises a phase detector circuit, charge pump circuit, and voltage-controlled delay line circuit operatively coupled together.
3. The adaptive line driver, as defined by claim 1 , further comprising a false lock correction circuit, the false lock correction circuit operatively coupled to the delay-locked loop circuit.
4. The adaptive line driver, as defined by claim 3 , wherein the false lock correction circuit indicates a false lock condition in response to a total delay associated with the voltage-controlled delay line exceeding one unit interval (UI) in a locked state, the false lock correction circuit entering a shutdown mode in response to determining that taps associated with an interpolator circuit do not indicate the false lock condition, the false lock correction circuit entering a startup mode in response to the DLL circuit being reset.
5. The adaptive line driver, as defined by claim 1 , further comprising an external pre-emphasis parameter optimization circuit, the external pre-emphasis parameter optimization circuit operatively coupled to the line driver.
6. The adaptive line driver, as defined by claim 5 , wherein the external pre-emphasis parameter optimization circuit iteratively calculates an optimal value of the user-configurable parameter based on a value of an eye opening.
7. The adaptive line driver, as defined by claim 1 , further comprising an interpolator circuit, the interpolator circuit operatively coupled to the delay-locked loop circuit.
8. The adaptive line driver, as defined by claim 7 , wherein the interpolator circuit configures at least one of the pre-data tap duration and post-data tap duration, thereby providing time delayed signals from the DLL equal to a fraction of the UI, the UI being equal to a transmitting symbol interval.
9. A method of transmitting a signal over a wired link, the method comprising:
providing sub unit interval (UI) user-configurable durations adapted to form pre-emphasis and feed-forward equalization of the signal by retiming the signal using a delay-locked loop circuit;
providing a user-configurable quantity of pre-emphasis taps to retime the signal using the delay locked loop circuit;
providing pre-emphasis data tap outputs comprising a main data signal referenced to delayed clock outputs from the delay-locked loop circuit using a signal retiming circuit; and
defining coefficients of pre-emphasis using a quantity of source-series terminated (SST) drivers in a group, a plurality of SST driver circuits operatively coupled in groups to the signal re-timing circuit, the groups of SST drivers operating in parallel with ganged outputs providing the signal to be transmitted.
10. A hardware device constructed to implement the method of claim 9 .