In electronic equipment, power fluctuations, switching operations, and external transient disturbances can all generate short-duration overvoltages. If a transient voltage exceeds a component's voltage withstand threshold, it can cause immediate damage to the device.
The MOV (Metal Oxide Varistor) is a widely used transient overvoltage protection device in the industry. The 07D220K is a compact varistor designed for low-voltage circuit applications; it suppresses transient voltages and absorbs surge energy, protecting downstream circuitry from overvoltage stress.
I. 07D220K Core Specifications
The 07D220K is a radial-leaded metal oxide varistor (MOV) with a 7mm diameter.
Operating Principle: It maintains high impedance under normal conditions; when a transient overvoltage occurs, the MOV's impedance drops rapidly, shunting the surge current and clamping the line voltage to a safe range.
07D220K Key Parameters:
- Varistor Voltage (V₁ₘₐ): 22V
- Max. AC Operating Voltage: 14V AC
- Max. DC Operating Voltage: 18V DC
- Max. Clamping Voltage: 43V
- Max. Surge Current (8/20μs): 250A
- Max. Energy: 2.4J
- Typical Capacitance: 1150pF
- Operating Temperature: -40°C ~ +125°C
II. 07D220K Operating Principle
When the circuit operates at its normal voltage, the 07D220K remains in a high-impedance state, having virtually no impact on circuit operation.
When a transient overvoltage occurs, the MOV rapidly conducts to shunt the surge current, thereby limiting the peak voltage on the line.
Note: The 07D220K has a varistor voltage of 22V (at 1mA test current) and a maximum clamping voltage of 43V. Circuit design should not rely solely on the 22V varistor voltage rating; evaluation must also consider the circuit's normal operating voltage and the voltage withstand capabilities of sensitive downstream components.
III. 07D220K Application Scenarios
The 07D220K features a compact 7mm package, making it suitable for low-voltage circuits where PCB space is limited yet transient protection is required. Typical scenarios include:
- Low-voltage DC power supply circuits
- Compact power adapters
- Industrial and consumer electronics control boards
- Relay and switch circuits
- Inductive loads such as solenoid valves (suppressing reverse voltage spikes during coil de-energization)
- Transient overvoltage protection for ICs and semiconductor devices
👉 07D220K Datasheet: https://en.semiware.com/varistors/07d220k/
IV. Considerations for Varistor Selection and Circuit Design
4.1 Verify the circuit's normal operating voltage first
- The 07D220K has a maximum AC operating voltage of 14V AC and a maximum DC operating voltage of 18V DC.
- If the circuit's steady-state operating voltage approaches or exceeds these values, the MOV will experience increased continuous leakage current and accelerated aging; it is unsuitable for such use, and a varistor with a higher operating voltage rating should be selected.
4.2 Do not focus solely on varistor voltage; clamping voltage is equally critical
- Many engineers focus primarily on varistor voltage during selection, yet clamping voltage represents the actual voltage experienced by downstream components during a surge event.
- The 07D220K has a maximum clamping voltage of 43V; ensure during design that this value is lower than the withstand voltage rating of the protected components.
4.3 Evaluate surge current and energy capacity based on actual surge conditions
- Voltage compatibility alone does not guarantee suitability; surge energy and peak current are equally important.
- The 07D220K can withstand an 8/20μs surge current of 250A and a maximum energy of 2.4J. If your application involves higher surge energy, you must select an MOV with a larger disc diameter and higher energy specifications.
4.4 Consider the impact of parasitic capacitance
- MOVs possess inherent parasitic capacitance; the 07D220K has a typical capacitance of approximately 1150pF.
- Standard power supply and control circuits are generally unaffected; however, if placed on high-speed signal lines, parasitic capacitance can cause signal attenuation and phase shift, requiring specific evaluation.
Contact Us
SEMIWARE provides samples, datasheets, and relevant technical support for the 07D220K. If you are evaluating the 07D220K for your circuit project, please contact the SEMIWARE technical team to obtain samples and technical assistance.
