SNAS669E September 2015 – April 2018 LMK03318
PRODUCTION DATA.
All output dividers and the PLL post divider 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 way to execute the output synchronization is to toggle the GPIO0 pin. When R56.1 is set to 1, to enable synchronization of outputs that is derived from the PLL, and GPIO0 pin is asserted (VGPIO0 ≤ VIL), the corresponding output driver(s) are muted and divider is reset.
NOTE
Output-to-output skew specification can only be assured 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(s) 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 prop delay + 3 VCO clock cycle. The synchronization feature is particularly helpful in systems with multiple LMK03318 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/disable events are synchronous to minimize glitch/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 they are configured and ready to accept the incoming clock.