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BQ500212A: Dynamic Power Limit

Patrick Blake
Prodigy 20 points
Part Number: BQ500212A

Hi,

I am working with BQ500212A-EVM board for testing wireless power transfer. I am using B51013B-EVM as receiver. I want to confirm that I can source 1A from the RX module before I continue. I use a variable current load circuit to load the output of the RX, which works well up until c.900mA, where I cannot source any more from the board. When I am above c. 550mA current on RX module, LEDs on TX EVM board indicate the device is in Dynamic Power Limit. I am powering from a standard bench supply which should have enough power, so I do not see why the power is being limited in this way. 

  • 0
    TI__Guru* 75886 points

    Hello

    Check the 5V going into BQ500212A and make sure it is not dropping at higher loads.  Input voltage can be increased to 5.5V for additional margin.

    For output load of 1A it is best to use and external power supply with good connections to input terminals.  UBS power supplies are good for lower power levels.

  • 0 in reply to Bill Johns
    Prodigy 20 points

    Hi Bill,

    Thanks for the quick response. I increased the input voltage to 5.5V and now I can source 5W on the RX side. 
    Can you explain further what is causing the voltage drop? I intend to design with a fixed 5V supply and will not be able to increase the supply. 

  • 0 in reply to Patrick Blake
    TI__Guru* 75886 points

    Hello

    The voltage drop will be due to leads and connections between power source and input to EVM.  At high RX output currents input to TX will be higher and this aggravates any resistive losses in connections.   

    The device does have a power limit feature that detects input voltage dropping to the 4.5V range.  At this point it will limit output power to prevent input voltage from dropping further.