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Altera_Forum's avatar
Altera_Forum
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15 years ago

Low impedance in supply pins ALTERA HARDCOPYII

Hello to all

This is my first time in the forum and I would like to explain my problem.

I am working with the ALTERA HARDCOPY II device and we are testing the boards using an ICT. The units are failing of low impedance (25 ohms) related to the supply pins from the ALTERA device.

In a board that pass the ICT test, the measure of this impedance is around 50 ohms but in others is around 90 ohms.

The test that is perform the ICT is a SHORT test.

I do not if this is an issue related to the component or not, why the impedance in supply pins of the ALTERA component is variable.

The supply pins affected are related to 1.8v.

If the unit is powered up, the current consumption is the same than a good board.

At this moment we are replacing the components, but this action is very expensive, I would like to know if this is a real issue or this is a normal condition of the semiconductor for the supply pins of the ALTERA.

Thanks a LOT for your support.

Regards.

3 Replies

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Probably the voltage range of the ICT-test pins is very close to the expected voltage on those power pins. On some devices you will get more conduction (in fact the device is partially powering up) than on others giving different values.

  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    Thank you Josyb

    Let me check that on ICT.

    But, I forgot comment that, if you check the impedance with a multimeter we are measuring the same than ICT (25 ohms around).

    Can you explain me why some other devices get more conduction.

    Thank you for you support.
  • Altera_Forum's avatar
    Altera_Forum
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    15 years ago

    I guess that the measuring circuit of the ICT is very much alike that of a multimeter (using same components?). If you put a multimeter to a low ohmic range and then measure the open circuit voltage with another multimeter you will probably measure 1.2V or more. This 1.2V will try to power up the device, and thus report a low voltage. E.g. on an EP2SGX60 I measure 3.0 ohms on VccInt.

    Maybe we could try this : add an 100 ohm resistor in series and put also 100 ohm in parallel with the power pins to ground. This will halve the voltage over the power pins so they won't try to power up?