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USB as boot source and as a Charging point - design guidelines

K Md Feroz Irfan
Expert 7225 points
Other Parts Discussed in Thread: AM3352, TPS2543

Dear Champs,

We have a question regarding the Boot mode settings of Am3352.

We plan to implement the boot mode sequence in the order of USB -> NAND -> SPI -> MMC.  And also we are planing to use the charge profile IC TPS2543.


The USB0 port of processor shall be used for boot mode and the power switch used shall be TPS2543.
Do you foresee any risk in using the Power switch because i think the logic ( assume no code in the flash memory) is a little complicated for the charge profile IC.

Best Regards

Feroz

  • 0
    TI__Guru**** 393215 points

    Hi Feroz,

    You will need to ensure that the USB data lines are connected and VBUS is connected to USB0_VBUS pin when the processor tries to boot from USB0.

  • 0 in reply to Biser Gatchev-XID
    TI__Guru 62855 points

    The USB PHY implemented in AM335x expects less than three ohms of series resistance inserted in DP/DM signal paths.  The TPS2543 has a maximum DP/DM switch on resistance of 6 ohms.  So inserting this device in the USB signal path could cause signal integrity issue for USB.

    The AM335x USB PHY has a charger detect circuit.  Is there a reason they are not using this feature?

    Regards,
    Paul
     

  • 0 in reply to peaves
    Prodigy 100 points

    Hi,

    I have a few queries regarding the implementation of DRA60x USB PHY Charger Detect Circuit.

    1. How do we connect the USB0_DRVBUS and USB0_CE Signal of DRA60x. Can USB0_CE be used instead of USB0_DRVBUS to enable the Power switch or do you suggest any other methods.

    2. Can we limit the current depending on SDP (0.5/0.9A) or CDP/DCP (1.5A) connected to USB0 port if DRA60x's Charger detect circuit is used. 

    3. Will the data communication happen if CDP is connected to the USB port as secondary detection between DCP and CDP is not supported by DRA60x.

    4. Do you suggest any Power Management IC/Power Switch that can be used with DRA60x for charging the devices connected to the USB0 port.

    Thanks

    Justin 

    4.