SNAS838A October 2022 – November 2022 LMK04832-SEP
PRODUCTION DATA
The CLKIN and OSCIN pins can be driven using a single-ended reference clock source, for example, either a sine wave source or an LVCMOS/LVTTL source. CLKIN supports both AC coupling or DC coupling. OSCin must use AC coupling. In the case of the sine wave source that is expecting a 50-Ω load, TI recommends using AC coupling as shown in Figure 9-4 with a 50-Ω termination.
The signal level must conform to the requirements for the CLKin or OSCin pins listed in the Electrical Characteristics table.
To support LOS functionality, CLKinX_BUF_TYPE must be set to MOS mode (CLKinX_BUF_TYPE = 1) when AC-coupled. When AC coupling, if the 100-Ω termination is placed on the IC side of the blocking capacitors, then the LOS functionality will not be valid.
If the CLKin pins are being driven with a single-ended LVCMOS/LVTTL source, either DC coupling or AC coupling may be used. If DC coupling is used, the CLKinX_BUF_TYPE should be set to MOS buffer mode (CLKinX_BUF_TYPE = 1) and the voltage swing of the source must meet the specifications for DC-coupled, MOS-mode clock inputs given in the Electrical Characteristics table. If AC coupling is used, the CLKinX_BUF_TYPE should be set to the bipolar buffer mode (CLKinX_BUF_TYPE = 0). The voltage swing at the input pins must meet the specifications for AC-coupled, bipolar mode clock inputs given in the Electrical Characteristics table. In this case, some attenuation of the clock input level may be required. A simple resistive divider circuit before the AC-coupling capacitor is sufficient.