Forum Discussion

Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

Problem between VCCINT and GND

Hello everyone im working with an EP2C20Q240C8 (Cyclone II). This FPGA is being hand soldered and I have connected the probes of my multimeter between ground and vccint while i'm soldering each pin in order to hear a sound if there is continuity, in a moment I noticed that a resistor value appears between the VCCINT and GND, at the begining I believed that was a "joint" between the pads but later I realised that exists a resistance between VCCINT and GND pins (I tested the FPGA alone). Does it is normal to exist a resistance value between does pins? Another thing is that after using compressed air that value raises from 189 ohm to 220 ohm.

Does anyone have any idea about what is going on?

Thanks in advance

5 Replies

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

    Perhaps you see resistance when board is off because you charge those capacitors while measuring resistance with your tester.

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

    Thanks everyone, I can confirm that while the board has no power exists that resitance value. After powering the board it works ok. And yes, cioma, I have capacitors between VCCINT and GND.

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

    Does your board have capacitors between VCCINT and GND when you perform measurements?

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

    Thanks very much for your reply ironmoose. Looking for temperature issues I found another post that says that when the FPGA is unpowered VCCINT and GND have a little reistance.

    alterauserforums.org/forum/showthread.php?p=8286

    Thanks again, i will take into cosideration the your comment about the continuity.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    16 years ago

    I noticed the same thing on an Arria GX. I was looking for shorts before powering up a new board and that puzzled me. The boards worked fine after powering up. This may be normal, but without looking at the electrical model of VCCINT, some of this is guess work. Be careful though that multi-meters produce a voltage to check for continuity. That voltage may be above what VCCINT can handle.