An EMI Evaluation Method for Integrated Circuits in Mobile Devices

This paper presents an electromagnetic interference (EMI) evaluation method for ICs in mobile devices. The evaluation method consists of a noise measurement method for ICs and a qualification specification, which has a direct correlation with system-level radiated emissions. The 1-Omega direct coupling method, which belongs to the IEC 61967 standard, is adopted to measure the conducted emission from a specially designed low-voltage differential signaling loop-back test IC. To devise the specification for the IC-level EMI evaluation, a definite correlation between the conducted emission from the IC and the radiated emission from a test system, which consists of a printed circuit board with the IC and an attached power cable, was obtained as a radiation transfer function (RTF). By combining the RTF with the system-level regulation specification provided by CISPR or FCC, an EMI evaluation specification for the test IC was derived. For several test cases, we measured the conducted emissions from the IC to assess the noise level and pass/fail statement. Compared with the radiated emissions from the test system, it was observed that there is a meaningful correlation in terms of the emission peak level and the pass/fail decision. The proposed methodology can be applied to component-level EMI assessment at the early design stage of modern high-speed mobile devices and will be very helpful in reducing system-level EMI problems and design failures in advance.