TMC5062 has an internal clock but can be used with an external, user-provided clock as well. This slide provides some general guidelines on how to select the clock source and frequency. If the internal clock is used, the CLK pin must be tied to ground, not left floating. If an external clock is used, the first rising edge on the CLK pin switches the device to external clock. It is important that the external CLK input is always present during operation.