What is it?
Transient voltage suppressor diodes, also known as TVS diodes, are semiconductor surge protection devices used to protect electronic equipment from voltage transients. They are constructed in such a way that they allow normal operation of circuits but provide a low-impedance path to divert excess current caused by transients away from sensitive circuitry. TVS diodes have a specific breakdown voltage above which they start conducting heavily. Once the transient voltage exceeds this breakdown level, the diode clamps the voltage by turning on and shunting the excess current to ground.
Working of Transient Voltage Suppressor Diodes
Internally, a TVS diode consists of a pn junction and specially optimized semiconductor materials. During normal operation, the diode behaves like a regular rectifier diode, blocking current flow until its breakdown voltage is reached. However, unlike normal diodes which break down destructively, TVS diodes are designed to safely and rapidly turn on once voltage transients exceed their rated level. This avalanche breakdown technique enables the diode to conduct large spike currents while maintaining a regulated maximum clamping voltage.
When a transient overvoltage event occurs in a circuit protected by a Transient Voltage Suppressor Diode, the excess voltage immediately starts forward biasing the junction. This causes the diode junction to avalanche multiply, dramatically lowering its resistance. As a result, instead of letting the spike voltage rise indefinitely and damage other components, the TVS diode clamps the voltage to a safe limit by bypassing the excess current to ground. The wide semiconductor junction acts like a switch, protecting sensitive downstream circuitry within nanoseconds of the transient onset.
Selection of Transient Voltage Suppressor Diodes
There are several parameters to consider when selecting the appropriate TVS diode for a given application:
Breakdown Voltage – This is the maximum repetitive working voltage or the voltage at which the diode safely begins conducting heavy currents under surge conditions. It should be selected based on the maximum expected operating voltage range.
Peak Pulse Current – Specifies the maximum non-destructive current the device can conduct during a transient event. It depends on surge pulse parameters like amplitude, waveshape, duration etc. Choosing a higher rating provides adequate safety margins.
Response Time – Indicates how quickly the TVS diode will react under a transient. Speeds under 5 nanoseconds are common for fast-switching applications like data lines. Slower 50-100 nanosecond devices may be used for power circuits.
Clamping Voltage – This is the regulated maximum voltage that will be allowed across the protected circuit during and after the transient. Lower clamping voltages ensure better equipment protection.
Packaging – Available package types include lead, surface mount, etc. with through-hole or radial-leaded packages being easiest to work with.
Operating Temperature Range – Devices usually operate from -55°C to +150°C depending on intended environment. Industrial versions have wider temperature ratings.
Common Applications of Transient Voltage Suppressor Diodes
Given their fast switching and voltage regulating capabilities, TVS diodes are widely used for protecting electronic equipment from overvoltage transients arising from various sources:
Power supplies – To absorb switching spikes and surges from the AC power line that can damage ICs and sensitive components downstream.
Communication ports – Used to suppress transient induced noises and surges coupled onto data and signal lines in computer, networking and telecom interfaces.
Motors and relays – Protect solid state switches, drives and controllers from high-frequency noise generated by relay contacts or motor brushes.
Lightning and electrostatic discharge protection – TVS arrays provide primary protection at equipment entry points against high voltage discharges and inductive-coupled surges.
Automotive systems – Surge protective devices are essential for suppressing load dump, battery jump-start and inductive load switching transients encountered in vehicles.
Industrial equipment – Robust TVS types safeguard factory floor devices from unpredictable externally-coupled fast transients.
Transient voltage suppressor diodes serve as a critical first line of defense against unspecified transient overvoltages that can severely damage or destroy vulnerable electronic components if left unprotected. Their ultrafast response and precise clamping abilities make them suitable for shielding sensitive circuits across a wide range of application areas prone to voltage surges and ESD events. Proper selection and installation of TVS diodes is essential for achieving robust and reliable equipment performance.
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it.