Maximum output current on 3.3V pin Lopy4

  • Hi,

    I wanted to know the maximum output current available from the 3.3V pin on Lopy4. On Lopy4 data sheet it says max output current Iout is 1.2A, not sure if that is when using Vin pin or 3.3V pin.

  • @robert-hh Thanks for that information robert.

  • @pvstejeswar The regulator chip is the LM3281. It can provide the high current down to an input voltage of 3.7V. At 3.4V it switches to a bypass mode.
    A few notes:

    • the 1.2A with peaks to 1.4A is the total current. You have to deduct from that the current used by the LoPy4, ~200mA with peaks to 400mA.
    • The device will supply that current when properly cooled. At high load the temperature of the regulator increases, which reduces the ability to supply the current. And the regulator has a thermal protection.
    • When supplied via LiPo battery, the charging circuitry also is in the line. I have no information about that. So that may be a show stopper.

  • @robert-hh Thanks for your response robert, yes I understand I cannot expect 1.2A when connected to standard USB port that provides 500mA current. I want to know whether the 3.3V pin on Lopy4 would be able to source 1.2A current to a Load connected on that pin if I power Lopy4 using a 3.7V Lipo battery that is capable of providing more than 1.2A.

  • @pvstejeswar The 3.3V regulator on the xxPy can have an output current of over 1 A. That requires an appropriate input supply an Vin. If connected to a standard 500mA USB port, then you cannot expect 1.2A from the 3.3V Output. Since it is a high efficiency switching regulator, the output current can be higher than the input current. Obviously the output power is lower than the input power. But that does not take into account the current drawn by the xxPy device.

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