Bulk Curent Injection (IEC 62132-2)
Although susceptibility is not as critical as emission, the demand for precise characterization of device behavior to radio frequency parasitic injection has increased recently. The method presented here is based on current injection through cables to the interface of the integrated circuit. The mechanism for current generation is based on weak inductive coil coupling. The current injected to the device is measured by a second coil.
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| Inductive coils Widely used in embedded electronics Very similar to EM wave in Automotive (DC-150MHz) |
This method is issued from automotive susceptibility tests, called "Bulk current injection", operating from DC to 150MHz.
BCI in CAN Bus (IEC 62132-2)
An example of BCI set up in the case of a CAN (Control Area Network) bus, widely used in automotive applications, is described in this slide. The parasitic current is injected by a coil which may alter the CAN driver information, and induce a fault inside the micro-controller. This method is limited to 400 MHz, due to the cut-off frequency of the injection coil.
| Inductive coupling to the network Parasitic current injected on the chip Limited to 1GHz |
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BCI measurement example
An example of BCI measurement is presented in this slide, with 2 configuration set ups. One includes a typical circuit (lower curve) which exhibits a susceptibility weakness from 200 to 800 MHz. The second one (upper curve) shows an improved behavior, meaning a lower sensitivity to injected parasitic sinusoidal wave. For example, a 20dBµA RF current is sufficient to induces a failure for configuration 1 at 350MHz. In configuration 2, the required amplitude to induce failure is close to the maximum current (55dB). This spectacular improvement is done by appropriate filtering, protection, careful PC, package and IC floorplan routing.
Direct Power Injection "DPI" (IEC 62132-3)
An important method to measure susceptibility of integrated circuits is the direct power injection, based on capacitor coupling. The interference wave form, such as burst or continuous sinus wave, is created using the signal generator. This RFI wave is amplified and superimposed on functional signals, via a coupling capacitance.
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| Quite simple to use Very simple to modelize at low frequency Several set-up problems Limited 1 GHz |
DPI setup example
This slides illustrates the setup of the direct power injection method involving a software control of the injected power, a feedback through the oscilloscope which features envelope detection. The signal generator creates a sinusoidal wave with programmable amplitude and frequency. A small amplitude is generated first. While the signal is kept within a predefined envelope, the chip is considered as safe, and the amplitude is increased. When the signal goes out the envelope, an error message is sent to the control software, which stops the incremental power injection. A new frequency can be investigated, until the whole frequency range is analyzed.
Workbench Faraday Cage from Philips (WBFC) IEC 62132-5
A method called Workbench Faraday Cage has been proposed by Philips and standardized under reference IEC 62132-5. This method is also used in emission measurements. It consists of placing the whole test board in the chamber and injecting the RF signal through the shielded box to the DUT. This limit is limited to 1GHz.
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| Common mode methodology Frequency range 150kHz - 1 GHz Emulates real case equipment |
What is available above 1GHz?
The GTEM cell is a vary promising candidate for susceptibility analysis above 1GHz. Already in use for emission measurements, the GTEM cell is currently being proposed as an international standard for susceptibility too. Power around 10-100Watts should be injected leading to very strong electromagnetic fields inside the chamber (1000V/m) at the test location.
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| Most methods limited to 1GHz The GTEM cell could be used as a RF source Its frequency limit is 18GHz (24GHz chamber now exist) Research undergoing Not standard available yet |
Summary
This slide summarizes the measurement methods used for susceptibility.
| EMC for ICs > Measurement Methods > Measurement of Susceptibility |   |