THE FREQUENCY BEHAVIOUR OF THE INTRINSIC IMMUNITY OF THE ON-CHIP TRANSISTOR CIRCUIT

Abstract

To extract the immunity model in an easy way and to complete the immunity simulation in a short time, it is preferred to consider only the disturbance propagation network in an integrated circuit system. However, through theoretical analyses, simulations and measurements, this paper shows that the on-chip transistor circuit has a nonuniform frequency response on its immunity against arrival disturbances. Including the nonuniform frequency response qualitatively improves the match between the simulation and measurement results. The conclusion is that both the disturbance propagation network and on-chip transistor circuit should be considered in the immunity simulation. The evaluation of the electrical performance in the design phase of an electronic system can only be conducted with simulation. Simulating the radio frequency (RF) immunity of integrated circuits (ICs) is interesting in the design phase of the ICs and printed circuit boards. IEC has established a standard for immunity modelling of ICs (1). The frequency of the RF interference (RFI) signal is labeled with fRFI. The RF immunity of ICs is characterized with immunity curves in fRFI range from below 1MHz to near or above 1GHz. The immunity curve shows, for each fRFI, the maximal RFI power (PRFI T) that the IC can tolerate. Normally, a measured RF immunity has the frequency behaviour that PRFI T varies strongly with fRFI. The main task of the RF immunity modeling is to simulate that frequency behaviour. When a RFI signal is applied to an IC, the signal goes through the disturbance propagation network (DPN) and arrives at the on-chip transistor circuit (OCTC). Previous researches (2{7) in immunity modeling of modern ICs have focused on constructing the model of DPN and use the frequency behaviour of DPN to reproduce the frequency behaviour of the RF immunity. However, besides DPN, the response of OCTC to the arrived RFI may vary with fRFI. The relationship between the maximal tolerable RFI voltage which has arrived at OCTC and fRFI is called the intrinsic immunity of OCTC. The motivation of this paper is to check whether the intrinsic immunity of OCTC is, in fRFI range from 1MHz to 1GHz, a constant or not. If the intrinsic immunity is a constant, then modeling the DPN is su-cient to simulate the RF immunity of the IC. Otherwise, the frequency behaviour of the intrinsic immunity of OCTC should be included in simulating the RF immunity of the IC. The latter will complicate the immunity modeling to a greater degree, because simulating a modern IC, no matter the whole chip or a functional module, at transistor level normally requires huge resources. The \Frequency Behaviour of the Immunity section analyses the signal relations in the immunity test flxture, and explains the concepts of immunity and intrinsic immunity. The \simulation section illustrates two approaches of the immunity simulation. One approach considers the intrinsic immunity of OCTC while the other does not. The \Discussion section compares the simulation results with the measurement results. The difierence in the results of the two approaches brings out the conclusion on the importance of the intrinsic immunity.