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Altera_Forum's avatar
Altera_Forum
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10 years ago

Cyclone IV fails to configure below -20C

I have a Cyclone IV design that operates correctly down to -20C but fails to configure below that temp. I have attached the schematic for the configuration block along with a scope trace showing configuration at room temp. I unfortunately don't have a complete scope trace at cold temp yet, however conf_done never goes high below -20C. If the temperature is ramped up from -40C the device starts working correctly around -20C. Can anyone have a quick look and see if I have botched the configuration set up. This is my 1st experience with Altera devices and I'm at a loss. All devices are rated at -40C or better.

Thanks

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  • Altera_Forum's avatar
    Altera_Forum
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    10 years ago

    The reset controller looks like the culprit to me, or the 3.3V rail (which you didn't measure above). Just to isolate the problem, can you lift a lead on the reset controller so it can't pull nCONFIG low, then configure the part via JTAG in the failing temperature range?

    One other thing to note is that you've got the MSEL pins set for the fast POR delay. According to the CIV handbook: "The fast POR time option has stricter power-up requirements when compared with the standard POR time option." This could be something to look at, but it would not cause the reset controller to keep pulling nCONFIG low. That still points to the reset controller.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    10 years ago

    --- Quote Start ---

    The reset controller looks like the culprit to me, or the 3.3V rail (which you didn't measure above). Just to isolate the problem, can you lift a lead on the reset controller so it can't pull nCONFIG low, then configure the part via JTAG in the failing temperature range?

    One other thing to note is that you've got the MSEL pins set for the fast POR delay. According to the CIV handbook: "The fast POR time option has stricter power-up requirements when compared with the standard POR time option." This could be something to look at, but it would not cause the reset controller to keep pulling nCONFIG low. That still points to the reset controller.

    --- Quote End ---

    Yeah, that's what we have found also. It turns out the tolerance on 3.3V, the tolerance of the reset controller, and the hysteresis of the controller combined to make it marginal at -40C. We have replaced the reset controller with a lower threshold version and all is good.

    Thanks everyone for time and suggestions.