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TS3DV520 Unused I/O

LeonardEllis
Guru 71526 points

Page 4 of the datasheet states:  (1) All unused inputs of the device must be held at VCC or GND to ensure proper device operation. Refer to the TI application report, Implications of Slow or Floating CMOS Inputs, literature number SCBA004.

and then in the test section, page 10 states:  All unused analog I/O ports are left open.

and page 11 states: All unused analog input (A) ports are left open, and output (B) ports are connected to GND through 50-Ω pulldown resistors. 

These statements are conflicting.  Should the unused pins be left open, or connected/terminated?

~Leonard

 

  • 0
    TI__Genius 9860 points
    Hi Leonard, the statement on page 4 refers to logic inputs, like select pins, enable pins, or control pins. It does not refer to analog I/Os.

    I agree that this statement is confusing, and should say instead "Logic/Control inputs of the device must be held at VCC or GND." For this device, the best option would probably be to terminate the unused pins, although leaving them open or grounding them are both valid options too.
  • 0 in reply to C. Ryan Land
    TI__Guru 71526 points

    I've always considered DVI (DIGITAL Video) the same as a logic signal, it is not analog. It does seem that the overall performance of the device is affected by the unused 'A' signals being terminated, as it shows up in the cross-talk test, yet in the and ISOLATION and BW tests, 'A' is open.  I think some clarity is needed in this regard!

    ~Leonard

     

       

  • 0 in reply to LeonardEllis
    TI__Genius 9860 points
    I agree. For a high-speed switch like this, some AC parameters may be affected by termination of other pins (termination resistors can bleed coupled charge off unwanted channels, for example).

    This statement is a generic guideline used by nearly all standard logic gate devices, and a few switches, so we will need to modify it in future DS updates to apply more specifically to these types of high-speed devices.