LTC4125 delivers power without load


I made a simple PCB based on the reference design of the board with LTC4120 as receiver. Schematic is absolutely the same.

I didn't still couple two systems and I tested the trasmitter without load. Often LTC4125 during optimal power search delivers power without reason, there is not a receiver.

This appen quite often, and I found that Tx coil placement take a role in this process, like it interfers with the power search. I tried to move it away from the chip but is even worse. To the other side of the PCB is now the better position but Tx still delivers power, sometimes it sinks from the power also 1A without load!

I can't understand why. Lowering the over current protection from the supply to about 500-600 mA resolve this issue, but only for testing, in the real world should be still there.

I don't know if this is related to faulty exit conditions or the strenght of magnetic field, lower with lower current, so less interference.

Better explanation
[edited by: mtx4 at 9:10 AM (GMT -5) on 22 Jan 2021]