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Altera_Forum
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11 years ago

No ground pin in Max V 5M80ZE64I5N CPLD

We are planning to use Altera Max V 5M80ZE64I5N CPLD in oneof our designs.

We need 54 user I/O’s in the design. As per the link https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/dp/max-v/5m80z.pdf (https://www.altera.com/content/dam/altera-www/global/en_us/pdfs/literature/dp/max-v/5m80z.pdf)

5M80ZE64 does not have any Ground pins. Below note is givenin the data sheet.

“(2) The E64 package has an exposed pad at the bottom of thepackage. This exposed pad is a ground pad that must be connected to the groundplane on your PCB.

This exposed pad is used for electrical connectivity and notfor thermal purposes.”

Can you please clarify this note? Will we still get 54 userI/O’s ? Any special precautions need to be taken while doing the schematic and PCBlayout?

6 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hi Sinora, there is no Groung "GND" pin on this EQFP package. The exposed pad is an extra pad underneath the EQFP package that may act as a ground connection and/or as a heat sink for the package. The pad size is indicated by E2*D2 in package outline, and with the pad soldered down onto the ground plane heat is passed into the PCB. This exposed pad also gives a solid ground connection.

  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hi,

    As I understand it, the exposed pad at the bottom of the package serves similarly as the GND pins. You will need to connect the exposed pad to your GND in your PCB.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Hi Sinora,

    Yea, you will need to connect the GND pad. Also you will have the 54 IOs... If it was mentioned in the pin out it should have. In the case you do not have 54 IOs... You might need to get back to Altera and check what is the reason for the inconsistency between the documentation and the actual product.

    Some of the consideration to take in is the power, the IO standard, the inputs and outputs. Dedicated clk pins for the refclk input.
  • Altera_Forum's avatar
    Altera_Forum
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    11 years ago

    Most IC have a ground pad on the bottom. Even some op-amps have it.

    Basically it is recommended to connect it to the PCB grounding so that your IC have the lowest impedance path to system GND.

    It does not relate with your available IO pins. You will still have 54 I/Os.

    I dont really agree that "not for thermal purposes" as we use it for thermal dissipation too, though not effective unless you have a multi layer board with vias to the another big piece of GND plane.