Post Go back to editing

Clarification on Input Buffer Control in HMC7044 Datasheet

Category: Datasheet/Specs
Product Number: HMC7044


I'm working with the HMC7044 product.
I am a bit confused regarding the input buffer control and the graphical representation and register settings shown in the datasheet.

In Figure 48 on page 38, the input buffer switches are shown as below:

However it's unclear how these switches in the figure correlate with the settings in the Input Buffer Control registers, detailed in Table 32 on page 54.

Could you provide clarity on this matter?
For instance, I'm interested in understanding which specific switch (as shown in Figure 48) is activated when the AC coupling input mode is enabled through the registers mentioned in Table 32.
And what happens if we activate high-Z input mode?

Thank you very much for your time and help.

  • Hi Bahadır,

    Please see the truth table to see which register corresponds to which switch. 

    X: Dont Care

    Condition A B C D
    Enable internal 100Ohm Termination = 1 X Open 50Ohm 50Ohm
    Enable AC Coupling = 1 Closed X X X
    Enable LVPECL input mode X Closed 100Ohm !00Ohm
    Enable Hi-Z Input Mode X Open 1kOhm 1kOhm