How to Use TVS-Diode SMBJ28CA: Examples, Pinouts, and Specs

The SMBJ28CA is a bidirectional Transient Voltage Suppressor (TVS) diode manufactured by Diodes Incorporated. It is designed to protect sensitive electronic components from voltage spikes, electrostatic discharge (ESD), and other transient events. With a standoff voltage of 28V and a robust clamping capability, the SMBJ28CA is ideal for safeguarding power supply circuits, data lines, and other critical electronic systems.

• Protection of power supply circuits from voltage transients
• Safeguarding data and signal lines in communication systems
• ESD protection in industrial and consumer electronics
• Automotive electronics and control systems

The SMBJ28CA is a two-terminal device with no polarity marking, as it is bidirectional. The pin configuration is as follows:

1. Placement in Circuit:

   • Connect the SMBJ28CA across the component or circuit you want to protect.
   • For power supply protection, place the diode between the power line and ground.
   • For data line protection, connect the diode between the signal line and ground.

2. Polarity:

   • The SMBJ28CA is bidirectional, so it does not have a specific polarity. This makes it suitable for AC signals or bidirectional data lines.

3. Voltage Selection:

   • Ensure the reverse standoff voltage (28V) is higher than the normal operating voltage of the circuit.
   • The breakdown voltage (31.1V to 34.4V) should be within the acceptable range for transient suppression.

4. PCB Layout Considerations:

   • Minimize the trace length between the diode and the protected component to reduce inductance.
   • Use wide traces to handle high transient currents.

• Power Dissipation: Ensure the diode can handle the peak power dissipation (600W) during transient events.
• Thermal Management: If the diode is expected to handle frequent transients, consider thermal management techniques to prevent overheating.
• ESD Protection: For ESD-sensitive applications, place the diode as close as possible to the input/output connector.

To protect an Arduino UNO's 5V power supply from voltage spikes, you can connect the SMBJ28CA as follows:

1. Connect one terminal of the SMBJ28CA to the 5V line.
2. Connect the other terminal to the ground (GND) line.

Here is an example Arduino sketch to demonstrate a simple circuit with transient protection:

// Example: Simple LED Blink with TVS Diode Protection
// This sketch demonstrates a basic LED blink circuit.
// The SMBJ28CA is used to protect the Arduino's 5V line from voltage spikes.

const int ledPin = 13; // Pin connected to the onboard LED

void setup() {
  pinMode(ledPin, OUTPUT); // Set the LED pin as an output
}

void loop() {
  digitalWrite(ledPin, HIGH); // Turn the LED on
  delay(1000);                // Wait for 1 second
  digitalWrite(ledPin, LOW);  // Turn the LED off
  delay(1000);                // Wait for 1 second
}

Note: The SMBJ28CA is not directly involved in the code but protects the Arduino's power supply from transients.

1. Can the SMBJ28CA be used for AC circuits?
   Yes, the SMBJ28CA is bidirectional and can protect AC circuits or bidirectional signal lines.

2. What happens if the diode is exposed to continuous overvoltage?
   Continuous overvoltage beyond the standoff voltage may cause the diode to conduct continuously, leading to overheating and potential failure.

3. How do I select the right TVS diode for my application?
   Consider the following parameters: reverse standoff voltage, breakdown voltage, clamping voltage, peak pulse current, and power dissipation. Ensure these values align with your circuit's requirements.

4. Can I use the SMBJ28CA for automotive applications?
   Yes, the SMBJ28CA is suitable for automotive applications, provided the voltage and power ratings match the system requirements.

By following this documentation, you can effectively integrate the SMBJ28CA into your designs and protect your circuits from harmful transients.