Clock Module Rev A rework - need output pull downs on the Crystal oscillator buffer.

[Tom-McDermott]

U6 (LT6957-1) outputs pins 10 and 11 are AC coupled to the Si5345, but do not have a DC path to ground. They are open-emitter devices and need to source current. A couple of ways to rework the device are possible.

One way is to put 120 ohm resistor from pin 10 to ground, and 120 ohm resistor from pin 11 to ground.

Another approach is to short out the AC coupling capacitors, and put a 50 ohm resistor across the common-mode bypass capacitor C39. This assumes that the DC levels from the LT6957-1 are within compliance range of the Si5347 (probably, but TBD).

[Tom-McDermott]

The inputs to the synthesizer must be AC-coupled according to the documentation - they self-bias at about 0.87 volts. Thus the rework needs to use the 120-ohm pull downs. This rework was done on one unit and verified to solve the problem.