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Altera_Forum's avatar
Altera_Forum
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18 years ago

Interfacing Cyclone III to a 1.8V LVDS device

Hi,

How can I interface the Cyclone III to a 1.8V ADC that has 1.8V LVDS outputs?

Should I design a PCB for the 2.5V LVDS standard or should I design the PCB with a bank voltage of 1.8V but instantiate the IOs as LVDS pairs within Quartus?

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    18 years ago

    I would use a VCCIO of 1.8V and assign the IOs as LVDS in Quartus (or maybe even 1.8V differential).

    (I've done the same thing with LVDS and a 3.3V VCCIO and it worked)

    ...no guarantees.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    18 years ago

    Hello,

    to my knowledge, the LVDS standard is specified in terms of common mode range and minimum/maximum voltage differntial independent of a particular supply voltage. An ADC with 1.8V output supply should be expected to comply the standard, I knew certainly that the Analog Devices parts do. At the Altera side, the manual tells the VCCIO range applicable for LVDS. For Cyclone III LVDS inputs, this is 2.5V only. 2.5V VCCIO would also fit for single ended 1.8V-LVCMOS-level inputs, if there are any.

    Regards,

    Frank