SNAS668E August 2015 – September 2024 LMK03328
PRODUCTION DATA
All output dividers and PLL post dividers can be synchronized using the active-low SYNCN signal. This signal can come from the GPIO0 pin (in soft pin mode only) or from R12.6. The most common method to execute the output synchronization is to toggle the GPIO0 pin. When R56.1 and/or R71.1 are set to 1, to enable synchronization of outputs that are derived from PLL1 and/or PLL2, and GPIO0 pin is asserted (VGPIO0 ≤ VIL), the corresponding output driver or drivers are muted and divider is reset.
Output-to-output skew specification can only be verified when PLL post divider is greater than 2 and after an output synchronization event.
The latency to reset VCO divider is a sum of:
GPIO0 / R12.6 | OUTPUT DIVIDER AND DRIVER STATE |
---|---|
0 | Output driver or drivers is tri stated and divider is reset |
1 | Normal output driver/divider operation as configured |
Minimum SYNCN pulse width = 3 negative clock edge of slowest output clock cycle + “x” nano second of propagation delay + 3 VCO clock cycle. The synchronization feature is particularly helpful in systems with multiple LMK03328 devices. If SYNCN is released simultaneously for all devices, the total remaining output delay variation is ±1 VCO clock cycles for all devices configured to identical output mux settings. Output enable and disable events are synchronous to minimize glitch and runt pulses. In Soft Pin Mode, the SYNCN control can also be used to disable any outputs to prevent output clocks from being distributed to down stream devices, such as DSPs or FPGAs, until devices are configured and ready to accept the incoming clock.