We are attempting to use the TPS54061 in a power supply for a 4/20mA loop device. We are finding that around 4.8mA the part changes in operating efficiency. The change has proven difficult to model on the digital side of the system. Does anyone have any thoughts as to why TI would recommend a part for a 4/20mA application and not provide a stable operating profile through the 4-20mA range of the power supply. Is this a known issue with a fix?