TVSsuojat

TVS-suojat, or TVS diodes, are protective semiconductors used to guard electronic circuits against transient voltage spikes. They act as high-speed surge clamps that shunt excess current away from sensitive components, preventing damage during events such as inductive switching, power line transients, or electrostatic discharge.

TVS-suojat are available in unidirectional and bidirectional configurations. Unidirectional types resemble a Zener diode that conducts heavily in reverse once a breakdown voltage is reached, providing protection primarily for DC rails. Bidirectional types conduct in both polarities and are common on AC lines or data interfaces where signals swing around ground.

Key electrical specifications include the stand-off voltage (VWM), the breakdown voltage (VBR), the clamping voltage (VC) under a given peak pulse current (Ipp), and the junction capacitance. Selection also considers the peak pulse current rating, the operating temperature range, and the physical package. In signal paths, parasitic capacitance and leakage can affect circuit performance, so layout and routing are important.

Applications include protection of power rails, USB, HDMI, CAN bus, Ethernet interfaces, automotive electronics, and other sensitive devices. They are used in conjunction with or as alternatives to external fuses or polyfuses, often placed close to the protected ICs. Standards such as IEC 61000-4-5 for surge and IEC 61000-4-2 for ESD guide testing and qualification.

TVS-suojat are manufactured by many semiconductor vendors, including Littelfuse, STMicroelectronics, ON Semiconductor, Bourns, and Vishay. Selection requires balancing protection level, speed, and circuit impact to ensure reliable operation without unintended clamping during normal transients or high-frequency signals.