Low Cost Hardware Design Techniques for Robust and Reliable Power-Supply Circuits for Automotive ECUs

Power-supply forms a key hardware block for every automotive ECU. Apart from delivering robust and reliable logic supply voltages it is also burdened with many auxiliary tasks like transient protection, good EMI/EMC performance, Power-hold function, Analog Sensor supply voltage etc. It also needs to meet all automotive norms including short to battery/ground etc.

This paper discusses low cost implementation techniques which maximize the value delivered to the vehicle application at minimal cost. Innovative techniques are described for combining sensor and logic supplies wherever applicable. Hurdles faced during such circuit optimization are clearly explained along with the solutions adopted to overcome hurdles yet meeting automotive test norms. A novel low cost concept which combines transient protection as well as power-hold function (without using the conventional relay based technique) further adds value to the end application. The paper also includes lessons learnt during EMI/EMC tests and low cost solutions devised for the same. The paper ends with a case study for a real life ECU application and lists the relevant test-results to confirm that the circuit meets automotive norms including wave-forms during transient tests as well as power-hold tests.