SMF45A

TVS (Transient Voltage Suppression) diodes are specialized diodes used to prevent damage to system components caused by high overvoltage transients. SMF45A is a unique dual-technology TVS which combines ESD protection diode clamping with a uni-directional gas tube designed to clamp and absorb the high voltage transients. It is designed for use as a rugged protection device in commercial and industrial applications.

Application Field of SMF45A

SMF45A TVS devices provide protection of data lines from exceeding the maximum voltage level set by the communication protocol, as well as provide ESD protection. Such applications range from I/O protection on communication boards to serial bus devices including Ethernet, S-ATA/P-ATA/USB ports, CAN bus ports, as well as various type of portable and PDA devices. In addition, it is designed for use as a DC-DC power supply line protection, which requires low stand-off voltage and fast response time, as well as protection against auxiliary power overvoltages and EFT.

Working Principle of SMF45A

SMF45A TVS consists of two elements: an ESD diode clamping element and a uni-directional gas tube breakdown element. The ESD diode monitors the voltage and instantly responds to the fast transients or ESD. The gas tube features unique characteristics and remains non-conductive until a certain high voltage threshold is reached. Above the threshold, the gas tube\'s voltage-current characteristic is V-shaped and much like a zener diode. The dual-technology design, therefore, provides ESD transient protection combined with higher overvoltage protection in one single device.

The ESD diode is typically on the order of 2pF and has a built-in voltage breakdown of 5V. As the voltage exceeds 5V, the ESD diode begins to conduct and limits the voltage to 5V or less, thus providing ESD protection. The gas tube element provides a much higher breakdown voltage, with a typical value of 30V. Above this voltage, the current begins to conduct in the gas tube with a V-shaped current-voltage characteristic. The low capacitance of the device (typically 20pF) ensures fast response time so that the device can protect equipment from high-voltage transient spikes and phantoms.

Conclusion

SMF45A is a dual-technology TVS which combines ESD diode clamping and uni-directional gas tube breakdown elements for robust protection of data lines from overvoltage conditions and ESD. The device is suitable for use in applications from I/O protection to DC-DC power supply line protection, and can quickly react to fast transients or ESD in order to protect the system components from damages.