Validation of USB peripheral checklist a challenging requirement for SoC

As of now semiconductor companies only ensure peripheral checklist in design and perform compliance testing at silicon. Compliance tests are essential to verify if design targets are met according to the planned specification. USB implementer's forum (USB-IF) has instituted a compliance program which provides reasonable measures of acceptability. Test equipment vendors provide ready-to-use compliance test suites which have been used for several years but the reality is that surprises and issues have also been consistent at real silicon making life of post silicon activities quite difficult. Simple traditional designs might not face suffocating issues but in current high speed complex designs, problems (electrical or logical) are inevitable. Unpredictability of such issues impacts cycle time to such an extent that companies have no choice but to delay their date of deliverables which could result in financial or market share loss. To avoid these unexpected problems we need to perform low level testing. This paper describes case studies of some issues which escaped compliance testing and were observed at silicon only after validating the tests given in peripheral checklist. It also elaborates the challenges faced in checklist validation.