The Si534x/7x/8x/9x clock generators and jitter attenuators can generate clocks compatible with HCSL receivers. However, the designer must be careful not to use conventional HCSL termination networks but rather follow the recommended HCSL termination in the reference manual.
Conventional HCSL relies on steering a 15mA current across two 50 ohm resistors to ground, which generates the high and low levels of roughly 750mV and 0mV respectively. In contrast, the Si534x/7x/8x/9x driver generates the proper HCSL voltage swing on the driver side and then AC couples that signal to a 50 ohm (Thevenin) resistor divider network to set the proper HCSL common-mode level of about 0.375V at the receiver side.
Figure 1 shows proper HCSL termination for Si534x/7x/8x/9x devices, copied from the reference manual. Figures 2-4 show examples of commonly used HCSL termination networks which should not be used for Si53x4/x7/x8/9x devices.
*Please note that other product families in the Silabs timing portfolio may have different methods of terminating HCSL clocks, and the documentation will provide the proper termination network.
Proper HCSL Termination Networks
Examples of Improper HCSL Termination Networks