Embedded electronics, the Internet of Things (IoT), and machine-to-machine (M2M) connections have become widespread in diverse areas, so it is important to protect interface connections from overvoltage conditions and transient events that can cause damage (Figure 1):
Figure 1: Protect interface connections from overvoltage conditions and transient events. (Source: Bourns)
Several devices can be useful to protect power, signal, and communication interfaces from damage involving destructive transient voltages. Two common types of protection circuits may employ (1) clamp-circuit devices or (2) crowbar-circuit devices:
When choosing protection devices for power and signal connections an engineer must consider the fit of the application with the various options of clamps, crowbars, silicon, and ceramic devices (Table 1). Let’s examine these options in more detail.
Table 1: The decision to use clamps or crowbars also depends on the device materials.
Clamps will conduct enough current to maintain the voltage across it at a safe, specified value when the transient is above the conduction voltage. It receives a rating according to the power it can dissipate for a specific time. The protection device needs a rating for the power to dissipate during the transient event. The voltage across the load rises only slightly above the rated clamp voltage during the maximum surge voltage. An example is the Bourns ChipGuard© MLA μVaristor Series ESD Clamp Protectors which are developed especially to protect sensitive automotive electronics from the threat of ESD up to IEC 61000-4-2 Level 4.
A crowbar device trigger occurs at a voltage above the protection voltage. The device protects by applying a low impedance across the protected load when an overvoltage condition triggers it. The device stays in the low impedance state until the current decreases below the holding current and the device returns to the high impedance state. In the low impedance state the device conducts the current that the external circuit limits. In this way, the voltage flowing across the protected device stays low. Ultimately, the crowbar protection device acts as the low impedance device on the low voltage side of a voltage divider, keeping the high voltage in the external circuit and protecting the sensitive load on the low voltage side.
Protecting interface connections from overvoltage conditions and transient events is more important than ever with the proliferation of embedded electronics. Bourns clamp and crowbar protection devices are effective at protecting circuit interfaces within silicon and ceramic electronic components. For more information, visit the Bourns site at Mouser.com.
Bourns is a leading manufacturer and supplier of automotive sensors, circuit protection solutions, magnetic products, microelectronic modules, trimming and precision potentiometers, panel controls, encoders, and resistive products. Headquartered in Riverside, CA, Bourns serves a broad range of markets, including telecommunications, computer, industrial, instrumentation, automotive, consumer, non-critical life support medical, audio, and various other market segments. Bourns products are manufactured according to ISO-9000 standards under Six Sigma quality programs. Bourns automotive products are manufactured in accordance with the TS16949 standard.
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