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LMK01020: LMK03318 to LMK01020 coupling and termination

Part Number: LMK01020
Other Parts Discussed in Thread: LMK03318,


I want to drive the LMK01020 clock input (CLKin0/CLKin0*) with the LMK03318 output driver 0 (OUT0_P/N) configured in AC-LVDS.

The LMK03318 datasheet (Figure 66 reproduce below) show how to interface the AC-LVDS output:

The LMK01020 datasheet state that the CLKin/CLKin* inputs must be AC-coupled and that "the DC blocking capacitors are placed between the termination and the OSCin/OSCin* pins" (p. 16). Furthermore, the LMK01020 datasheet (Figure 13 reproduce below) show how to interface the LVDS clock input:

On the other hand, the post

From those reading, I understand that the following topologies (Interface #1 and Interface #2) should be valid. My primary concern is for the LMK01020 in the Interface #2 below. For Interface #2, is it right to have a single pair or DC-blocking capacitor between the LMK03318 driver and the termination resistor and not between the termination resistor and the LMK01020 receiver ? This seem to violate the datasheet recommendation.

If both interface are valid, which Interface would you recommend for best performance ?

Thank You.


  • Hi Nicolas,

    Both interfaces are valid, but I would recommend Interface 2 because you save 2 capacitors and since there is less capacitance on the transmission line, the performance will improve slightly as well.

    The key point to keep in mind when designing the LMK010x0 input termination is that the input stage has an internal DC bias. AC coupling is required to prevent any external DC current flow which can damage the device.