SNAS835 September 2022 LMK5B33414
PRODUCTION DATA
The SYSREF divider output signals can be replicated on either GPIO1 and GPIO2 to provide additional single ended 3.3V CMOS clocks after start-up if desired. To configure the SYSREF/1-PPS output replication the GPIO must be enabled as an output (GPIOx_OUTEN = 1) and one of the SYSREF output to GPIO replication sources must be active. The SYSREF replication source comes from any one of the SYSREF dividers in use from OUT0/1, OUT4/5, OUT6/7, OUT/9, OUT10/11 or OUT12/13 by register programming (OUT_x_y_SR_GPIO_EN = 1). The GPIOx replicated SYSREF output is after static digital delay but before the analog and digital delay and pulser. The output will be a continuous frequency as pulsed SYSREF mode is not supported for the GPIOx replica.
There will be some small fixed delay skew between the normal SYSREF and GPIO replicated SYSREF. An LVCMOS output clock is an unbalanced signal with large voltage swing, therefore it can be a strong aggressor and couple noise onto other jitter-sensitive differential output clocks.