9.3.3 Recommendations for Unused Input and Output Pins
CLK_SEL and CLK_EN: CLK_EN must be held low until a valid reference clock is provided before the engineer can use the pin to enable the outputs. These inputs both have an internal pullup (PU) according to Table 10. Table 10 shows the default floating state of these inputs:
Table 10. Input Floating Default States
INPUT
FLOATING STATE SELECTION
CLK_SEL
CLK_P/CLK_N selected
CLK_EN
Synchronous outputs enable
CLK_P/CLK_N Inputs: See Figure 12 for the internal connections. When using a single-ended input, take note of the internal pullup and pulldown to make sure the unused input is properly biased. To interface a single-ended input to the CLK_P/CLK_N input, the configuration shown in Figure 14 is recommended.
LVCMOS_CLK Input: See Figure 12 for the internal connection. The internal pulldown (PD) resistor ensures a low state when this input is left floating.