05D221K is a common varistor, which belongs to voltage-sensitive electronic components. The code in its name has a specific meaning:

  • "05" indicates that the diameter of the component is 5mm
  • "D" represents the disc shape
  • "221" indicates that the nominal voltage is 220V
  • "K" indicates that the voltage tolerance is ±10%

The varistor is mainly sintered by zinc oxide (ZnO) and other metal oxides, and has excellent nonlinear volt-ampere characteristics. When the voltage at both ends is lower than the threshold, it presents a high resistance state, and when the voltage exceeds the threshold, it quickly changes to a low resistance state.

Main Techanical Parameters

  • Varistor voltage (V@₁mA): 220V
  • Maximum continuous operating voltage (VAC/VDC): 140V AC / 180V DC
  • Limiting voltage (Vc): Typically 360V at 1mA test current
  • Maximum peak current (8/20μs): Approximately 400A
  • Energy absorption capacity: Approximately 8.8J
  • Response time: Nanosecond level (<25ns)
  • Capacitance value: 110pF

Working Principle

The core of 05D221K varistor is the nonlinear relationship between voltage and current. Under normal operating voltage, its resistance value is extremely high (up to megohm level) and leakage current is extremely small (usually <20μA). When the voltage exceeds the threshold (220V), the internal grain boundary barrier is broken down, the resistance drops sharply, and a conduction channel is formed, which dissipates the overvoltage energy in the form of heat, thereby protecting the back-end circuit.

Applications

  • Surge protection of consumer equipment
  • Surge protection of communication,measuring and controller instrument
  • Surge protection in electronic home appliances,gas and petroleum appliances
  • Relay and electromagnetic valve surge absorbtion
  • Transistor,Diode, IC,Thyristor or Triac semiconductor protection

Test and Verification

1.Static Test

  • Use a multimeter to measure insulation resistance at room temperature (should be >1MΩ)
  • Leakage current test (should be <50μA when 75% Vn is applied)

2.Dynamic Test

  • 8/20μs surge test
  • Multiple impact tests (at least 10 times)

3.Aging Test

  • 1000 hours test at 85°C/85%RH environment
  • Temperature cycle test (-40°C~+85°C)

Compared With Other Devices

1.Compared with TVS diode:

  • Advantages: Stronger current capacity, lower cost
  • Disadvantages: Slightly slower response, aging problem

2.Compared with gas discharge tube:

  • Advantages: Faster response, no continuous current problem
  • Disadvantages: Weak current resistance

3.Combination

  • Two-level protection with TVS
  • Combined with PTC resistor to achieve dual protection of overcurrent and overvoltage

Summary

As a basic circuit protection component, varistors play an important role in various electronic devices. Correct selection and use of varistors can significantly improve the reliability and anti-interference ability of electronic products and reduce the failure rate caused by voltage transients.

Product Line

For datasheet and more details of 05D221K, please visit the website:

https://semiware.com/en/product-general-mov/05d221k

About Semiware
Semiware has a comprehensive product lineup of circuit protection device products. The company leverages its technology in the semiconductor field and application background in end products to serve customers in the electronics, automotive and industrial markets. For more information, please visit semiware official website: https://semiware.com/en/

Welcome to contact us for more details as follows:
Email: cassie@semiware.com;
Tel: +86-18930674110;
Whatsapp: 008618123742225