JAJSP85A December 2023 – February 2025 LMK5C33216A
PRODUCTION DATA
The DPLL supports an internal ZDM synchronization option to achieve a known and deterministic phase relationship between the selected DPLL reference input and OUT0, OUT4, or OUT10 clock depending on configuration and selected DPLL for ZDM.
With ZDM enabled, users can attain zero phase delay between the selected DPLL reference input clock and the selected zero-delay feedback clock. Figure 8-32 shows how the OUT0 clock can internally feedback to any DPLL as the zero-delay output clock. ZDM is primarily implemented to achieve deterministic phase relationship between an input and selected outputs such as 1PPS input to 1PPS outputs or 156.25MHz input to 156.25MHz outputs.
There is no need to route external clock signals from output to input as the zero-delay feedback clock from OUT0 is routed internally to the device ; OUT4 can also be used for DPLL2 internal ZDM feedback and OUT10 can be used for DPLL3 internal ZDM feedback.
1PPS phase alignment is able to re-establish with the phase slew control and ZDM. The phase slew control can reduce the phase build-out back to 0 at a controlled rate. To lock to a 1PPS signal using ZDM mode, the output static delay or DPLLx_PH_OFFSET can be programmed to zero out the phase error between the 1PPS input and 1PPS feedback clock. Hitless switching must be disabled when ZDM is used for 1PPS.
See DPLL Programmable Phase Delay for an example of how input to output phase error in the DPLLx_PH_OFFSET field is calculated to apply fine adjustments less than 1ps.