A Methodology to Characterize Substrate Noise Currents Injected by Digital IP Cores

Because of the growing complexity and the reduced turn-around time of modern designs, IP based strategies are becoming more and more popular. Usually, IPs are characterized as stand alone units, neglecting their mutual interaction. Unfortunately, this oversimplification is not always realistic. As a result, the overall operation of the circuit may be considerably affected. In fact, with the shrinking of the devices, the proximity of high frequencies noise sources and sensitive devices causes the substrate to carry spurious signals. In particular, in mixed designs, the presence of slow analog signals and fast switching digital waveforms may lead to unwanted interaction that might corrupt the circuit operation. To overcome this issue, heavy over-designs are often adopted, thus giving up part of the potential of the new technologies. Due to these complications, substrate modeling has become an issue among the RF and mixed-signal designer community.