[FAQ] Which Device Do I Choose If I Need Powered-Off Protection?

System isolation is critical for power sequencing, managing bus contentions, and turning off sub-circuits to save power. Signal switches are one way to provide isolation in both analog and digital signaling applications such as I2C, LAN, MIPI, SPI, UART, JTAG, etc. Signal switches can ensure that a high impedance (Hi-Z) path is maintained between the input and output (I/O) signal paths and system power rails. However, there are cases where power sequencing, hot plug / hot insertion, and fault / overvoltage events can cause the switch isolation to fail.

During these events, voltages on the switch I/O path can exceed the supply voltage rail (VDD) which forward-biases the internal electrostatic discharge (ESD) protection diode that exists between the I/O pins and VDD. When the internal ESD diode is forward-biased, the voltage on the I/O path can back power the switch supply pin and damage components on the power rail. Additionally, the forward biased diode can provide a path to back-power the signal switch itself, unintentionally turning on the I/O path. Designers must know the voltage limits of the signal switch I/O pins relative to the switch power supply (VDD) especially when the switch is powered off (VDD = 0 V). Devices with powered-off protection features protect their systems in cases where the signal switch is powered-off and a voltage is present on the I/O path and eliminate the need for power sequencing.

The following table outlines various popular devices without powered off protection and alternative replacements that have this feature. This list is not exhaustive so make sure to check our product selection table to see which devices TI offers with this feature.