Silicon Labs has two types of LVPECL drivers for Timing products. Please see below for the recommended LVPECL terminations for these two types of LVPECL drivers.
These LVPECL outputs only support AC coupling but not DC coupling. Customers must use AC coupling for these LVPECL output terminations as shown below:
The termination at the receiver depends on the receiver’s requirements. The only termination requirement from Si534x/7x/8x/9x is seeing an equivalent differential load impedance of 100ohm for signal integrity.
These LVPECL outputs support both DC and AC coupling. Please refer to the below information.
For AC coupling, please note we use different Rb values in different products as shown below:
Recommended Rb value for different Timing products and power supplies
The purpose of this KB is a reminder that different Timing products at Silicon Labs may have different LVPECL structures and therefore different termination requirements. Please refer to the product datasheets, reference manuals and application notes for more detailed termination information when starting designs with Silicon Labs Timing products.