By Stephan Gerlach and Juergen Strohal
Standardization activities focused on electromagnetic compatibility (EMC) at the IC level are evolving to keep pace with current and future interference scenarios. With the long-term trend toward the concentration of functions in fewer active devices, a tiny amount of silicon housed in a small plastic package can produce an increasingly significant level of disturbance, making reliable testing more important than ever.
Most established electromagnetic surface scanning test standards are limited to frequencies up to 1GHz, or sometimes 2GHz. But with the prevalence of technologies such as WLAN and Bluetooth, test methods for reliably measuring frequencies of 3GHz or higher are needed. Two evolving standards for measuring higher frequencies are the IC stripline and the local injection horn antenna. In addition, the proven techniques of printed circuit board (PCB) scanning are helpful for locating sources of distortion, even at the sub-IC level.
- The stripline standard (ISO11452) is widely used in module-level testing, with the wiring harness placed inside a stripline. The forthcoming IC stripline standards cover both aspects of radiated EMC tests for ICs: IEC61967-8 standardizes emission measurements, and IEC62132-8 standardizes immunity measurements. Unlike the ISO11452 measurement, the IC stripline does not use a wiring harness but instead covers the IC under test.
- The evolving local injection horn antenna standard also extends IC testing to higher frequencies. Typically, the ICs under test are equipped with minimal external circuitry mounted on a small PCB, and the field strength deviation is less than 3dB across the surface of the IC. For measuring radiated immunity, a standard (IEC 62132-6) is under development that uses a horn antenna in the 1GHz to 18GHz frequency range. The IC is exposed to the antenna’s electrical field, and the magnetic field deflects circularly around the IC.
- IC-based scanning systems can provide precise and repeatable measurements. Several electric and magnetic field probes for IC-based measurement are already available. E-field and H-field magnetic probes can be used within a frequency range of 30MHz to 3GHz. H-field probes with a low-frequency range of 9kHz to 50MHz are available for specific applications.
For diagrams and more details about these emerging standards and trends, see the article “Automotive IC-Level EMC Testing—Trends and Forthcoming Standards.”