1 2 Previous Next 23 Replies Latest reply on Nov 6, 2019 5:54 AM by ScGr_289066

    CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply

    ScGr_289066

      Hi All,

       

      I believe we are experiencing a Silicon design problem with the CYUSB3064 chip.  This is the second generation of the design.  We noticed the same issue on the 1st generation, but never got to the bottom of it.  This design appears to be worse (e.g. more leakage).

       

      We have a CX3 design that runs VDDIO1 & VDDIO2 from 1.8V, VDDIO3, CVDDQ from 3.3 volts, TXVDD/RXVDD, AVDD, MIPI_VDD and VDD from 1.2V.  The board contains four voltage regulators powered by USB's VBUS (5V) whose outputs are: 1.2, 1.8, 2.5 and 3.3V.  All the regulator outputs are nominally correct except the 1.8V regulator is 2.7V and appears to be back-fed.  The 1st generation boards supply was around 2.1 volts.

       

      With all the components except the CX3 removed from the 2nd generation PCBA, including the 1.8V regulator, the 1.8V supply still sits at about 2.7V.  If I connect an ammeter between the 1.8V supply and ground, I measure 15.7 mA, so this is not a dead-short.  After removing the CX3 the 1.8V measures zero.

       

      Are we misusing the CX3 in some manner to explain this leakage current?

       

      Thanks,

      Scott

        • 1. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
          YashwantK_46

          Hi Scott,

           

          Can you please share the schematics of your board so that we can get a better understanding as to what could be going wrong in your design?


          Also, without any component on board, except the regulator, can you please check the voltage and if there's any leakage current then also?

           

          Regards,

          Yashwant

          • 2. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
            ScGr_289066

            Hi Yashwant,

             

            I forgot to mention several key details.

             

            First, nothing is attached to any of the connectors except the USB connector for power.  With all the parts on the board, the 1.8V supply sits at nearly 2.7V on several boards.  This caught my attention because the boot flash is only rated for 1.9V.  The CX3 enumerates on USB correctly, and I can load its firmware into RAM or SPI Flash using Control Center.  With code loaded, the CX3 fails to initialize the I2C bus with error 0x55 (see case 210047).

             

            Yesterday, I experimented with one of the boards trying to locate the source of leakage current by removing key components one-at-a-time until the leakage disappeared.  Here's what I did.  I first removed the 1.8V regulator, VR6.  The 1.8V node remained at 2.7V.  I then removed, in this order: U2, U6, M3, R8 & R16.  At this point nothing had changed, the 1.8V node was still sitting at 2.7V.  I then connected an ammeter between 1.8V and ground.  I measured 15.7 mA.

             

            Finally with no other components connected to 1.8, I removed the CX3 (U8).  The 1.8V node dropped to zero.  Then I replaced VR6, per your request today.  The 1.8V node now measures 1.8V (for the first time on this board).

             

            Best,

            Scott

            • 3. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
              YashwantK_46

              Hi Scott,

               

              Did you follow the schematics of the CX3 RDK by e-con systems? If not, please go to this website and download the schematics and the hardware design guidelines for CX3.

               

              Can you power the board with all the components along with CX3 and check the GPIO's in the VDDIO1 and VDDIO2 power domain from the CX3 datasheet and check which of them are high when you are measuring 2.7V on the 1.8V line?

               

              Some of the problems that i found are:

              1.) In the schematics, J2- Type-C Receptacle( or is it plug?? ) is connected in a wrong way. The SSTXM, SSTXP of CX3 should be connected to TX-, TX+ of the connector and same goes for RX- and RX+.

              2.) Is CX3 enumerating as a 2.0 or a 3.0 device?

              3.) Why are PG's of all the regulators connected to a single 10K resistor instead of connected individual PG's of regulators to their respective OUT's ?

              4.) The reset switch SW1 needs to be pulled up using a suitable resistor to 1.8V, or else, if SW1 is pressed, it will cause the PG of VR3 to provide a low-impedence path and will make the 1.2V regulator to ground ( since 1.2V is less than 1.8V at PG).

              5.) Why are you using higher capcitance for AVDD, VBUS instead of the recommended values (Is there any specific reason) ?

               

              Regards,

              Yashwant

              • 4. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                ScGr_289066

                Hi Yashwant,

                 

                I'll address your "problems" first.

                 

                1&2) We are using a receptacle.  It works, the PC communicates with the CX3 as a USB3 device.  It is sensitive to which direction the connector is plugged, but please stick to the leakage issue.

                 

                3) The PG outputs are open-collector and are wire-ORed to the CX3 reset pin.  This holds the CX3 in reset if *any* of the regulators are not operating correctly.  The CX3's RESET input is powered by 1.8V, hence these open-collector signals are pulled-up by R30 to 1.8V.

                 

                4) I'm afraid you have misinterpreted the design.  The reset switch is pulled-up through R30 a 10K resistor to 1.8V  Closing the reset switch does indeed pull all the PG open-collector outputs to ground, but doing so has no effect on any of the four regulator outputs.  I suggest you read TI's TPS74801 data sheet to find out how these regulator's operate.

                 

                5) There is second board that attaches to this board.  This board draws a substantial amount of extra current, hence the additional filtering.  As I said in the original post, we have not connected the second board because of this leakage issue.

                 

                I did refer to e-CON's documentation.  The reason they are not seeing this leakage problem is because they run VDDIO1 and VDDIO2 at the same voltage level as VDDIO3 and CVDDQ, namely 3.3V.

                 

                I am postulating that there is a leakage path through the CX3 from VDDIO3 or CVDDQ to VDDIO1 or VDDIO2.  Since we have VDDIO1 and VDDIO2 tied together, we can't know if the leakage affects one or both of these supplies.  e-CON's design would not have this issue because they run all these supplies at the same potential.

                 

                Are you saying the CX3 does not meet it's specifications which says these supplies can run from 1.8, 2.5 or 3.3 and the only successful way to use it is to connect all these supplies to 3.3?

                 

                To directly answer your earlier question: SDA, SCL are both pulled to the 1.8V supply which is being back-fed by the CX3 to 2.7V.  Similarly, DBG_TX is also at 2.7.  The 1.8V supply *always* measures 2.7V even before the CX3's firmware is loaded, it does not changed after firmware is loaded.

                 

                Thanks,

                Scott

                • 5. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                  ScGr_289066

                  Hi Yashwant,

                   

                  Here's an update.  Your comments about USB is correct.  The device is enumerating, but not as a super speed device.  It communicates, but will not stream video even though the sensor is streaming to the CX3 and the CX3 appears to be receiving the video correctly (HSYNC/VSYNC test points appear correct).

                   

                  I now understand your USB connection comment, I've reversed the pairs.  I thought you meant I'd reversed the "1" and "2" sides (which was intentional).

                   

                  This board also has problems initializing its I2C interface (a block error 0x55 is reported).  I have a case for this: https://community.cypress.com/message/210346?et=watches.email.thread#210346

                   

                  The experiment we did was to connect the 1.8V supply to 3.3V.  All the parts on 1.8V are 3.3V compliant, so running everything at 3.3V is OK.  After doing this, the I2C problem is gone (I2C initializes OK), so this is perhaps another symptom of the CX3's leakage issue.

                   

                  However, none of this changes the fact that the CX3 leaks to VDDIO1/2 is they are connected to a lower potential than VDDIO3/CVDDQ.

                   

                   

                   

                  Thanks,

                  Scott

                  • 6. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                    ScGr_289066

                    Hi All,

                    Has anyone been able to reproduce this?

                     

                    Scott

                    • 7. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                      YashwantK_46

                      Hi Scott,

                       

                      Sorry for being late but i am still trying to figure out as to what is going wrong.

                       

                      One main thing that i can point out is that the eCon CX3 RDK uses a different type of regualator for 1.8V than compared to the regulator that is used for all the other power domains ( 1.2V, 2.5V, 3.3V). If you can refer to the schematics of the RDK board, you can notice it.

                      I am trying to get a hold of the exact reason as to why that's being done in the RDK.

                      Will update you as soon as I figure it out.

                       

                      I had a question about one of your comments,

                      >>The experiment we did was to connect the 1.8V supply to 3.3V.  All the parts on 1.8V are 3.3V compliant, so running everything at 3.3V is      OK.  After doing this, the I2C problem is gone (I2C initializes OK), so this is perhaps another symptom of the CX3's leakage issue.

                       

                      -->So, after doing this, did you still find the 1.8V at 2.7V? or was it at 1.8V?

                       

                      Regards,

                      Yashwant

                      • 8. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                        ScGr_289066

                        Hi Yashwant,

                         

                         

                        After connecting the 1.8V and 3.3V supplies they all sit at 3.3.

                         

                         

                        Best,

                         

                        Scott

                        • 9. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                          ScGr_289066

                          Hi Yashwant,

                           

                          I'm not sure the RDK using a different type of 1.8V regulator is significant since 1.8V isn't connected to the CX3.  All it's IO runs at 3.3.

                           

                          Best,

                          Scott

                          • 10. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                            YashwantK_46

                            Hi Scott,

                             

                            If possible, can you please share the layout of your board as well?

                            And share if you have any update on your side.


                            Regards,

                            Yashwant

                            • 11. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                              ScGr_289066

                              Hi Yashwant,

                               

                              If you provide me with a private email address I can share the layout.  The design is a commercial product I cannot post it to a public forum.

                               

                              Best,

                              Scott

                              • 12. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                                YashwantK_46

                                Hi Scott,

                                 

                                Private message has been received and i will get back to you with results shortly.


                                Regards,Yashwant

                                • 13. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                                  YashwantK_46

                                  Hi Scott,

                                   

                                  Can you please take off the accelerometer U6 ( MMA8652FC) from your board or remove the power connection for the part and then check if you still face the same issue?

                                   

                                  I suspect that accelerometer may be the part that's causing the leakage issue as we had seen some issues in the past where an accelerometer was the cause of finding some back-feeding issues in customer boards?

                                   

                                  Please keep all the components on the board intact and only remove the power to U6 and then measure the 1.8V volt power domain.

                                  Please get back to us with the findings.


                                  Regards,
                                  Yashwant

                                  • 14. Re: CYUSB3064 Silicon is backfeeding VDDIO1 or VDDIO2 supply
                                    ScGr_289066

                                    Hi Yashwant,

                                     

                                     

                                        Sorry you missed my September 24'th post.  I did exactly this,

                                        removed components one-at-a-time and monitored the effect on the

                                        1.8V supply starting with the 1.8V regulator.  The second component

                                        I removed was the accelerometer.  It is not the source of

                                        leakage.  I removed all components from the 1.8V supply until all

                                        that remained was the CX3.  The 1.8V supply node was still raised to

                                        2.7V.  In spite of removing all the other components, the 1.8V node

                                        had not dropped in potential until I removed the CX3.

                                     

                                     

                                        Before removing the CX3, I placed an ammeter across 1.8 and ground

                                        and measured 15.7 mA leaking through the CX3.

                                     

                                     

                                        Best,

                                     

                                        Scott

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