Measurements of Dynamic Current in Switching CMOS Buffer

As the speed and complexity of digital systems increase, the performance of the power system becomes more important. Due to switching in digital circuits, the power system will also contain high frequency current components. This high frequency currents introduces noise in the system and the result is reduced noise margins. For CMOS circuits the trend is towards lower voltages and the noise in the system becomes more critical. For a designer, the goal is to design the power system in such a way that the noise from the switching circuits is reduced to a minimum. To meet this goal, the designer need to know the behavior of the IC during switching; i.e. the current transients in power pins. There are two main problems: (1) the power system must supply the IC with the current needed. (2) the current transient in one IC should not influence the power to another IC. This paper focus on the current in ICs, and presents a method for measuring the transient current in power pins in digital circuits.