Analog Dialogue Volume 50 Number 2

The challenge of designing robust electronic circuitry often results in a design with a multitude of discrete protection components with associated cost, design time, and space additions. This article discusses fault protected switch architecture, along with the performance benefits and other advantages it offers vs. traditional discrete protection solutions. A new novel switch architecture and proprietary high voltage process that provides industry-leading fault protection along with the performance required for precision signal chains is discussed. ADI’s new portfolio of fault protected switches and multiplexers (ADG52xxF and ADG54xxF) uses this technology. Analog input protection for high performance signal chains is often a pain point for system designers. There is typically a significant trade-off between analog performance (such as leakage and on resistance) and the level of protection that can be offered by discrete components. Replacing the discrete protection components with overvoltage protected switches and multiplexers can offer significant benefits in terms of analog performance, robustness, and solution size. The overvoltage protected component sits between sensitive downstream circuitry and the input that is exposed to external stresses. An example of this would be the sensor input terminal in a process control signal chain. This article details the issues caused by overvoltage events, discusses traditional discrete protection solutions and the associated drawbacks, presents the solution offered by overvoltage protected analog switches including features and system benefits, and finally introduces the industry-leading portfolio of ADI fault protected analog switches. Overvoltage Issues—Back to Basics When the input signal applied to a switch exceeds the power supplies (VDD or VSS) by more than a diode drop, the ESD protection diodes within the IC become forward-biased and current flows from the input signal to the supplies, as shown in Figure 1. This current could damage the part and may trigger a latch-up event if the current is not limited. Internal ESD Protection of Switch