Document 328-1 Planar Magnetics For National Semiconductor LM5041 IC This planar transformer and inductor pair were designed specifically for National Semiconductor’s LM5041 IC. The A9786-A transformer is engineered for use in highcurrent telecom power supply applications that require high efficiency in a low-profile package.The auxiliary winding can be used to control input current to PWMs. It offers very high current handling capability and extremely low DC resistance in a low profile package.