1 Reply Latest reply on May 7, 2020 9:18 PM by JayakrishnaT_76

    CYUSB3064/5 USB boot mode




      We are using CYUSB3064/5 as in USB self powered mode.

      What is the minimum detection voltage level of VBUS?

      "I found this comment from EZ-USB FX3/FX3S Hardware Design Guidelines and Schematic Checklis:

      VBATT can be connected to the system battery or a stable 3.2 V–6 V voltage rail from the PMIC. If VBUS and VBATT are both present and in their specified ranges, VBUS becomes the primary supply to the USB I/O unless there is a software/firmware override. If VBUS is less than 4.1 V, then FX3 behaves as if no VBUS is connected to it. If this happens when the FX3 is powered, then FX3 does not enumerate at all. If this happens somewhere during the operation of FX3, then the FX3 firmware will turn off the USB PHY and disconnect from the host."

      We have seen detection fails when trying to enter USB boot loader mode when VBUS is just over 4.0V (4.05V).

      We are able to increase supply to 4.2V, should this be enough in all cases?



        • 1. Re: CYUSB3064/5 USB boot mode



          Please refer to page 10 of CX3 datasheet. The link to the same is given below:



          The minimum required VBUS for CX3 is 4V from the datasheet. But for stable enumeration, voltage on VBUS should be above 4.1V as mentioned in AN70707. So 4.2V on VBUS should be enough provided that the voltage never go below 4.1V during operation. To be on a safer side, we recommend to keep the VBUS at 5V. In addition to this, you need to follow the power up sequence correctly as shown in Figure 4 of the datasheet.


          Best Regards,