8 Replies Latest reply on Jul 20, 2017 3:08 AM by BacemD_61

    S29GL01GP Random bits erased

      I have recently received 3 boards back from the field that have a few random bits erased. We believe that the units were possibly installed in a platform that may have power supply issues. Does anyone know of any conditions that can be applied to the part that may cause this issue. For example Vcc and Vio differences or I/O fluctuations during power down or power up. I would like to correct the boards to prevent this in the future.

        • 1. Re: S29GL01GP Random bits erased
          BacemD_61

          Hello Steven,

             

          The behavior you're seeing might be caused by some cells loosing some charges, which is normally unlikely to happen.

             

          The most likely scenario is an interrupted erase or program operation.

             

          You could make sure to have a stable VCC during these operations or use any sort of flags to detect such interrupted operations and restart them after the next power up.

             

          If your system is suffering from non coherent power on sequence, you might issue a HW reset pulse once the power supply becomes stable. This will solve the issue.

             

          Best regards,

             

          Bacem Daassi

             

          Cypress Semiconductor Corp.

          • 2. Re: S29GL01GP Random bits erased

            Bacem;

               

                               Thank-you for your response. When this occurs the device is locked down (No writes). We do believe that is power supply sequencing related though and we are trying different sequences including brown-outs. This only happens on one installation the rest have been working for years without issue. Would you know of any power sequencing that we need to protect against. Any help would be greatly appreciated.

            • 3. Re: S29GL01GP Random bits erased
              ZhiF_31

              Hi Steven,

                 

              One thing you need to pay attention to brown-out situations is the VLKO parameter in the datasheet. In GL-P devices, VLKO is defined as 2.3V min. If the voltage drops to this level, it is required to do a proper Power On Reset. That means you need to bring the voltage all the way to 0, then start power-up. If the voltage is not dropped sufficient enough before coming back high, you may get  a brown-out situation and the device may have undefined behaviors. 

                 

              Best regards,

                 

              Zhi

              • 4. Re: S29GL01GP Random bits erased

                Zhi;

                   

                                 Thank-you! We do believe that we are getting drop-outs on the Vcc and in these cases (I believe) we may see unfortunate behavior.

                • 5. Re: S29GL01GP Random bits erased

                  I have added plots of power ramps of Vcc and Vio

                  • 6. Re: S29GL01GP Random bits erased
                    BacemD_61

                    Hi Steven,

                       

                    There seems to be quite some noise on the VCC and VIO.

                       

                    In case, this casues VCC to drop below VLKO, you will likely end up having a brown-out situation and only a full POR will recover the situation in this case.

                       

                    Please refer to the following Knowledge Base Article (KBA) for more details about the flash behavior when it comes to voltage irregularities: http://www.cypress.com/knowledge-base-article/65-nm-flash-family-behavior-during-voltage-irregularities-kba219071

                       

                    The KBA is referring to another device family but the behavior should be the same.

                       

                    Best regards,

                       

                    Bacem

                    • 7. Re: S29GL01GP Random bits erased

                      Bacem;

                         

                                     I guess the question is: Will brown-out conditions cause permanent bit changes in the device?

                         

                      Thank-you in advance

                      • 8. Re: S29GL01GP Random bits erased
                        ZhiF_31

                        Hi Steven,

                           

                        Brown out may cause the device to go into an unresponsive state. However, if you perform a proper POR again, the device should be functional again. The memory contents should not be affected by the brown out. 

                           

                        Thanks,

                           

                        Zhi