An Introduction to Transient Voltage Suppression Diodes
Overview: This article reviews the critical role of transient voltage suppression diodes in mitigating electrostatic discharge and transient overvoltage risks in electronic systems, enhancing electronic component safety.
The physical phenomenon known as electrostatic discharge (ESD) is also defined as the abrupt transfer of static electric charge between objects when they come into contact. It can cause electronic component destruction because of its high discharge current, which can reach several amperes in nanoseconds.
These ESDs are more risky for electronic components like microcircuits, diodes, and transistors. Smaller production dimensions and comparatively less chip protection have enhanced the sensitivity of today's electronic gadgets to ESD. The degree to which the electrical component is at risk depends on the density of the ESD current.
The heat generated and dielectric breakdown are two reasons that result in the failure of the system. In an ESD environment, the charged body produces a powerful electric field that rapidly collapses, which may allow noise to enter the system.
The magnetic field likewise experiences a sharp rise due to the discharged current. The rate of fluctuation of these magnetic and electric fields adds noise to the system.
Another phenomenon that seriously stresses and damages circuit components is transient voltages. Most of the time, transient overvoltages have strong damping and short periods.
Overvoltages with higher rates of rise but lesser amplitudes can still be dangerous. Transient voltage suppressors were added to the microelectronics systems to guard against transient overvoltages, and ESD overstress.
What are transient voltage suppression diodes?
These devices, known as transient voltage suppression (TVS) diodes, guard delicate semiconductor components against transient overvoltages and ESD damage.
However, because of their ultra-fast response time and lower clamping voltage, TVS diodes are frequently used when higher voltage protection levels are needed.
Working Principles of TVS Diode
Similar to metal oxide transistors, TVS diodes function as high-resistance open circuits with no current flow under normal circumstances, having no impact on the component. However, an extremely, very low leakage current is predicted.
When there is an event of transient voltage, the TVS diode acts as a short circuit to protect the electronic components, enabling current to pass through it and allowing the clamping voltage to pass through the connected electronic component.
The clamping voltage is lower than the breakdown voltage. It keeps the electrical components safe until the transient voltage decreases, after which the TVS diode acts as an open circuit.
Types of TVS diodes
There are two varieties of TVS diodes:
- Unidirectional TVS diode
- Bidirectional TVS diode
With their asymmetrical I-V characteristics, unidirectional TVS diodes are more frequently used to safeguard signal lines that are above or below the reference. Bidirectional TVS diodes have symmetrical I-V characteristics and contain two TVS diodes. The symbols of these diodes are shown in Fig. 1.
Fig. 1 Symbol of transient voltage suppression diode. Source: Rakesh Kumar, Ph.D.
Applications
TVS devices are perfect for safeguarding I/O interfaces and other susceptible circuits in telecom, computers, phones, hard drives, and industrial and consumer electrical applications. Their use is more prevalent in applications with moderate power delivery.
Key Parameters Affecting the Efficiency of TVS Diode
A few critical parameters that are addressed here are essential in understanding the TVS diode's operation.
Reverse Stand-off Voltage
It is the normal operating voltage of a diode, which depends on the component's working voltage and has a high impedance with no current flow. For a TVS diode to function effectively, the stand-off voltage must be larger than the standard working voltage.
Breakdown Voltage
It is the point at which the resistance drops and the TVS diode starts to conduct electricity until the transient condition lasts, also referred to as the reverse breakdown voltage.
Peak Pulse Current
It is the highest transient current that the diode can withstand for a brief amount of time, lasting for a few seconds without suffering damage.
Clamping Voltage
The TVS diode prevents damage to the components by clamping the transient voltage across the component connected in parallel to it to an ideal level in the event of a surge. This voltage is dependent on the highest input voltage that is permitted.
Response Time
It is the amount of time that the TVS diode needs to go from an open circuit to a short circuit to safeguard the components that are connected to it. The response time should be minimal for a TVS diode to be effective.
Capacitance
The diode's capacitance is a factor to consider in the case of high-speed applications that demand low capacitance.
IEC 61600-4-2 Standard
This standard provides a degree of protection the device can offer against ESD. The degree of protection increases with an increased IEC rating.
Transient Voltage Suppression Diode to Consider
This is the SMCJ series transient voltage suppression diode, as shown in Fig. 2, that Littelfuse made to protect electrical circuits from surges caused by lightning, electrostatic discharge, inductive switching loads, and other events.
Fig. 2: SMCJ28CA Transient Voltage Suppression Diode by Littelfuse. Source: oemsecrets
It has an excellent capacity to clamp transient voltage and a very fast response time (usually less than 1.0 ps). One significant advantage is that its surface-mounted applications can be employed to maximize board space. It includes built-in strain relief, which provides mechanical protection against stress.
It can handle very high power, with a peak pulse power capability of around 1500 W at a waveform of 10/1000 μs. TVS devices are useful for protecting diverse interfaces in telecommunications, computing, industrial, and consumer electronics applications.
To conclude, TVS diodes are expensive when compared to metal oxide varistors but have longer lifespans and can be effectively deployed in the protection of electronic circuits from transient overvoltages and ESD. Understanding the working principles of TVS diodes, including clamping voltage and response time, is crucial for effective transient voltage protection.
Summarizing the Key Points
- Transient voltage suppression diodes protect electronic circuits from surges like lightning and electrostatic discharge, offering fast response times and high power handling capabilities
- These diodes play a significant role in safeguarding against transient overvoltages by acting as short circuits, preventing the overvoltage from damaging electronic components
- Understanding key parameters like reverse stand-off voltage and peak pulse current is essential for maximizing the performance of TVS diodes in diverse electronic systems
Reference
Georgios Fotis, “Electromagnetic Fields Radiated by Electrostatic Discharges: A Review of the Available Approaches,” Electronics 12, no. 12 (June 7, 2023): 2577, https://doi.org/10.3390/electronics12122577.
Yu-Shu Shen and Ming-Dou Ker, “The Impact of Holding Voltage of Transient Voltage Suppressor (TVS) on Signal Integrity of Microelectronics System With CMOS ICs Under System-Level ESD and EFT/Burst Tests,” I.E.E.E. Transactions on Electron Devices/IEEE Transactions on Electron Devices 68, no. 5 (May 1, 2021): 2152–59, https://doi.org/10.1109/ted.2021.3063208.
“How to Select a TVS Diode for IO-Link Devices,” Analog Devices, November 18, 2022, https://www.analog.com/en/resources/technical-articles/how-to-select-a-tvs-diode-for-maxims-iolink-devices.html.
Oemsecrets, “SMCJ28CA - Compare Distributor Prices & Inventory | oemsecrets.com,” oemsecrets.com, n.d., https://www.oemsecrets.com/compare/SMCJ28CA.