When measure differential signal phase noise/jitter performance, an balun must  be added to convert differential signal to single end then connect to equipment(eg E5052B). Never connect one of differential signal end to equipment directly, which will has big difference with reality performance. 

For example, Si545's real jitter performance of LVPECL 156.25MHz is about 90fs(12KHz~20MHz ). But if you connect one of differential end to E5052B then the test result of jitter is about 250fs.

Please see the attached PDF for the answers to the following questions: 

1      What is the main difference between the Si5334, Si5335, and Si5338?

2      Where is the RoHs, REACH, or other material related compliance information for the Si5334, Si5335, and Si5338?

3      Where is the FIT information for the Si5334, Si5335, and Si5338?

4      How can I get a Si5334, Si5335, and Si5338 with a custom startup frequency?

5      What is the default I2C Address of the Si5338 when the part does not have an I2C_LSB pin or a custom address?

6      What finish is used on the contacts of the Si5334, Si5335, or Si5338?

7      How can I burn the NVM on a blank Si5338 part?

8      Will the ClockBuilder Pro Field Programmer (CBPROG-DONGLE) work with the Si5334, Si5335, or Si5338?

9      Where can I find software for the Si5338 Field Programmer?

10    How can I use a CBPro project file with the Field Programmer?

11   Does the Si5338 support in-circuit NVM programming?

12   Can I import a Si5338 ClockBuilder Desktop NVM file into ClockBuilder Pro?

13   How do I control the Si5338-EVB?

14   What if I want a feature in my custom Si5334, Si5335, or Si5338 that is not configurable in ClockBuilder Pro?

15   What is the minimum slew rate for the power supply ramp on Vdd?

16   What power supply sequence/delay is required for Vdd and VDDOx?

17   What should unused VDDOx pins be connected to?

18   When an LOS or LOL occurs, will the outputs be  squelched?

19   What do I need to communicate to a Si5338 via I2C?

20   How do I configure a Si5338 via I2C?

21   What is the Input-Output delay of the Si5335 in ZDB and NZDB modes?

22   Can the Si5335/Si5338 clock generators support spread spectrum inputs?

Si53156 is internal termination for maximum integration which the output buffers in Si53156 are push-pull buffers that integrate the 33-ohms series resistance and the 50 ohms to ground. Please refer to AN781 Alternative Output Termination for Si5211x, Si5213x, Si5214x, Si5216x,Si522xx, Si5310x, Si5311x, and Si5315x PCIe Clock Generator and Buffer Families

For inputs, they are not self-biased. The buffer also expects a DC coupling HCSL input. A bias voltage needs to be provided if the input is AC coupled.

The I2C of Si5332 is compatible with rev6 of the I2C specification, including Standard, Fast, and Fast+ modes. That standard and user manual is here: https://www.nxp.com/docs/en/user-guide/UM10204.pdf