SIM900R – USB Device

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This topic contains 0 replies, has 1 voice, and was last updated by  Mista 5 years, 10 months ago.

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    Mista

    Hi,

    I have a problem with degign of SIM900R USB device.
    SIM900R has 2A pick current and SIMCOM advices 2x1500uF for SIM900R suplly voltage. Also advices LM2596 with output current 3A.
    If I put 2x1500uF capacitor for supply voltage, I should also add current limiter for protection of USB port because of the inrush current of capacitors. Beside this, the USB port has 50mA current limiter, how can I get supply current from USB port? Also I wonder how USB 2G/3G modems can get enough power from the USB port?

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