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SYS power required for 4DCAPE LCD

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  • SYS power required for 4DCAPE LCD

    Looks like 4D LCD cape (7") is use SYS_5V and VDD_3V3(B) as power source which generated by BBB's PMIC. For SYS_5V maximum suply current for capes is 250mA. For VDD_3V3(B) maximum suply current for capes is 250mA.

    Question is how many current left for secondary cape if we use 4D LCD 7" cape?

  • #2
    Hi Kzsolt,

    Yes the 4DCape-70 is using the VDD_3V3B for the LCD power and SYS_5V for the backlight driver.
    The VDD_3V3B has a total of 500mA as provided by the TL5209A. Also, the VDD_3V3B is being shared by the 4DCape-70 and the BBB. Doing a quick test the 4DCape-70T drew about ~110 mA on the VDD_3V3B.

    However, for the SYS_5V the available current for this power source is dependent on the power supply used on the BBB. The 4DCape-70T is drawing ~455mA from a 1A power supply. This current draw is particularly due to the backlight circuit.


    As for available current for secondary capes, if a USB supply is used then that would mean 500mA max. If a DC power supply is used then the available current is equal to the specified rating of the power supply.

    I would suggest that for a secondary cape power should be connected to the SYS_5V.

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