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DAC3482: The DAC3482's LVPECL pull-up and pull-down?

HENRY JUNG
Expert 2030 points
Part Number: DAC3482
Other Parts Discussed in Thread: LMK04806

DEARS.

The LVPECL characteristics are different based on the resistance value.

On the same PCB, the resistance value should be set in two cases at 240 Ohm and 150 Ohm.

Does the LVPECL pull-up pull-down value change under the same PCB condition?

When using 1.2Ghz What is the resistance value of LVPECL?

Guide for pull-up and pull-down of LVPECL is necessary.

Thank you.

  • 0
    TI__Guru* 91947 points

    Henry,

    The termination is determined by the device driving the LVPECL inputs. If using the LMK04806 in LVPECL mode, I would just use 120 Ohms to GND on both legs after the LMK but before the AC caps. Since you are AC coupling, you do not have to worry about the common mode level. If you were DC coupled, a pull-up resistor is usually required to get the correct common mode level at the receiver.

    Regards,

    Jim