ADuM4070EBZ Eval-Board – Isolated Output supply current differs to the released data-sheet values


I bought the Eval-Board ADuM4070EBZ directly from AnalogDevices.

My desired operation-mode corresponds with the default-mode of the Eval-Board.

(Switching frequency 500kHz; Transformer Coilcraft CR7983-CL; Vinput 5VDC; VISOoutput 5VDC).

I need for my application an isolated output current of 350mA!

The datasheet of the ADuM4070 guarantees for this operation-mode a minimum load-current of 400mA  (typical 500mA)!

In fact, the board starts degrading the VISOoutput voltage at a load current of 310mA (tested with purely resistive load under cold start conditions – no chip overheating). The board input-source remains stable at 5VDC and is able to deliver enough current under all isolated-side load-conditions. At a load-current of 300mA, I measured a primary-source current of 540mA – this values represents an obviously worser efficency than the published value of 72% typical - in the data sheet of ADuM4070!

Has anybody an idea or some hints what is going wrong on the eval-board – in fact, the handling and external wiring seems very simple!?

Thanks for your help!