3 Replies Latest reply on Jul 24, 2020 1:39 AM by SudheeshK_26

    How might a NOR Flash component be degraded if Vio exceeds Vcc?

    GrCa_1363456

      How might a NOR Flash component be damaged or degraded if Vio exceeds Vcc?

      To know if parts should be replaced, is there any data on the magnitude or duration of Vio exceeding Vcc before degradation or damage occurs?

       

      For Cypress S29GL01GT/S29GL512T parallel NOR Flash:

      Section 10.4.2 of the Datasheet shows Vio can exceed Vcc by 200mV: "Vio = 1.65V to Vcc + 200mV"

      Section 10.4.3 of the Datasheet then states, "During power-up or power-down VCC must always be greater than or equal to VIO (VCC  VIO)."

       

      Reference:

      Datasheet @ https://www.cypress.com/file/218336/download

      Re: In S29GL512T, during flashing do we need to follow power sequencing? since it has two voltages (I/O-1.8v and Core-3.…

      NOR Flash FAQs - KBA222273

       

      Greg

        • 1. Re: How might a NOR Flash component be degraded if Vio exceeds Vcc?
          SudheeshK_26

          Hello,

           

          Please see the " Absolute Maximum Ratings" for the part given on page 68 of the datasheet. Our device will get damaged if operated outside of the absolute maximum ratings. As you can see from the below table, VCC and VIO voltages can go up to 4V without damaging the device. But, we can guarantee the datasheet specs (DC characteristics and timing specs) only within the operating voltage (VCC: 2.7 V to 3.6 V, VIO: 1.65 V to VCC) range.

           

           

          Regarding VIO and VCC voltages.

          1. During power-up and power-down VCC must always be greater than or equal to VIO. Violation of this condition may cause POR failure.
          2. After power-up VIO can be up to VCC+200mV during normal operation of the flash device, but it should be less than absolute maximum rating (4V).

           

          I hope the above information answers your query. Please feel free to ask if you have any related queries.

           

          Thanks and Regards,

          Sudheesh

          • 2. Re: How might a NOR Flash component be degraded if Vio exceeds Vcc?
            GrCa_1363456

            Sudheesh,

             

            Thanks for the quick response.

             

            For the case I'm concerned with, Vio comes up to 1.8v, while Vcc hangs for some time at 1.0v until it eventually rises to 3.3v. We're working on ways to limit Vio until Vcc passes 1.8v. We want to know if we've permanently damaged all product where Vio temporarily exceeded Vcc on power up. Neither Vio or Vcc violated Absolute Maximum Ratings.

             

            Is POR = Power On Reset ?? If so, does POR failure mean the device may not function per specifications, or are there specific failure modes?

            If POR failure is a permanent condition, what are the symptoms?

             

            If POR is a temporary condition, can it be corrected with a power cycle, (assuming Vio stays below Vcc)?

             

            Greg

            • 3. Re: How might a NOR Flash component be degraded if Vio exceeds Vcc?
              SudheeshK_26

              Hello,

               

              Yes, POR means power on reset.

               

              As mentioned in my previous response, during power-up and power-down VIO should always be less than or equal to VCC. Violating this condition will cause POR failure. Device behavior after POR failure is unpredictable. POR failure is not permanent, device can be recovered by a power cycle (VIO less than VCC). During power cycle, please make sure both VCC and VIO goes below VRST voltage level for tPD time for the part to initialize correctly when VCC and VIO again rise to their operating ranges again.

               

               

              Thanks and Regards,

              Sudheesh

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