Data recovery architecture (CDR) for low-voltage differential signaling (LVDS) video transceiver applications
The present invention discloses data recovery architecture (CDR) to improve a multi-link system's tolerance to delay mismatches (or skewing effect) in its different links. The architecture is entirely digital and usable in any multi-link transceiver implementation that makes use of a separate clock link and requires timing synchronization between the different data links.
1. A low voltage differential signaling (LVDS) system comprising:
a plurality of incoming LVDS channels providing data signals and a source synchronous clock signal;
a plurality of analog differential receivers, each adapted for receiving one of the plurality of incoming LVDS channels;
a phase locked loop (PLL) circuit for generating a PLL clock signal having a plurality of clock phases; and
a plurality of oversampling clock data recovery (CDR) circuits, each coupled to a corresponding one of the differential receivers and having a synchronizing circuit adapted to synchronize an oversampled signal on a respective LVDS channel to a single phase of the PLL clock signal,
wherein detection of a predetermined edge of the source synchronous clock signal determines an initial phase for the CDR circuits receiving the data signals.
2. The LVDS system of claim 1 wherein the source synchronous clock signal comprises a pixel clock.
3. The LVDS system of claim 1 further comprising a matrix of XOR gates, associated with the CDR circuit receiving the source synchronous clock signal, to locate a rising edge of the source synchronous clock signal.
4. The LVDS system of claim 3 wherein a pinpoint is defined from an initial set of multiphase clock samples such that two consecutive phase samples bracket a transition of the source synchronous clock signal.
5. The LVDS system of claim 3 wherein the rising edge of the source synchronous clock signal determines an initial phase for the CDR circuits receiving the data signals.
6. The LVDS system of claim 5 wherein a phase farthest from a pinpointed clock transition is selected as an initial operating condition for data synchronization in other channels.
7. The LVDS system described in claim 1 wherein a number of clock phases provided by the PLL is an even integer.
8. The LVDS system described in claim 1 wherein the PLL circuit generates a multi-phase clock at a same frequency as a data rate.
9. The LVDS system described in claim 1 wherein the PLL circuit generates a clock signal, the frequency of which is a multiple of a data rate.
10. The LVDS system described in claim 1 wherein the LVDS channel associated with the source synchronous clock signal is re-timed by a dedicated CDR circuit.
11. The LVDS system described in claim 1 wherein the CDR circuit receiving the source synchronous clock signal further comprises a circuit for indicating a phase change update to the CDR circuit associated with each of the LVDS channels receiving data signals.
12. The LVDS system described in claim 11 wherein the circuit for indicating the phase change generates a forcedown signal and a forceup signal whenever timing of the LVDS channel associated with the source synchronous clock signal changes.
13. A system comprising:
a plurality of incoming LVDS channels providing data signals and a source synchronous clock signal;
a plurality of analog differential receivers, each adapted for receiving one of the plurality of incoming LVDS channels; and
a phase locked loop (PLL) circuit for generating a PLL clock signal having a plurality of clock phases,
the system further including a tangible computer readable storage medium, which stores software for implementing a plurality of oversampling clock data recovery (CDR) circuits, each coupled to a corresponding one of the differential receivers and having a synchronizing circuit adapted to synchronize an oversampled signal on a respective LVDS channel to a single phase of the PLL clock signal,
wherein detection of a predetermined edge of the source synchronous clock signal determines an initial phase for the CDR circuits receiving the data signals.
14. The system of claim 13 further comprising a matrix of XOR gates, associated with the CDR circuit receiving the source synchronous clock signal, to locate a rising edge of the source synchronous clock signal.
15. The system of claim 13 further comprising a dedicated CDR circuit for the LVDS channel associated with the source synchronous clock signal.