This is an engineering report for an automotive 12V, 1A Switching Mode Power Supply (SMPS) designed in a

flyback topology. It is mainly intended for 48V to 12V applications, but the results can be reused also for other

voltage domains. The document is intended to provide a technical guideline for desigining the SMPS starting

from a collection of the specifications, their circuit implementation and finally the validation results.

The AECQ-100 OPTIREG™ TLE8386-2EL is used as a flyback controller in combination with the primary switch

IPD50N08S4-13 OptiMOS™-T2. The extended power supply range of the controller make it suitable for harsh

automotive applications, its current mode control loop make it suitable for a wide bill of material variation

thanks to a dedicated compensation pin. Finally the controller embeds some protection features such as output

overvoltage protection, over current protection and over temperature shutdown that improve the reliability of

the system.

The IPD50N08S4-13 OptiMOS™-T2 is an AECQ-101 qualified N-channel enhanced mode MOSFET. It is 80V capable

and it is 100% avalanche tested.

The reference design board operates at 400 kHz switching frequency in the [0-1]A load range at 12V nominal

output, the functional input voltage range is [6-35]V. The secondary side output voltage control is implemented

via an auxialiary winding that avoids the using of galvanic isolated devices (e.g. optocouplers) to feed the sensed

voltage.