24. TVS Diode for 3.3V GPIO ESD Protection

Mary is designing a control board where several 3.3V MCU GPIO pins are connected to external connectors for field wiring. 

These exposed pins are vulnerable to ESD strikes during cable assembly, field installation, and maintenance. 

To protect the MCU GPIO from ESD damage, she needs to place a bidirectional TVS diode on each exposed signal line. 

Key requirements: 

• GPIO operates at 3.3V logic level 

• TVS standoff voltage: 5V to 6.5V (well above 3.3V to avoid interfering with GPIO) 

• Clamping voltage: ≤20V (brief ESD clamp pulses within MCU transient survival range) 

• Capacitance: ≤50pF (to avoid slowing down signal edges) 

• SMD package: SOD-323 

The company's approved vendor list (AVL) specifies Littelfuse for circuit protection components, so the part must be selected from Littelfuse on DigiKey. 

Help her select a suitable bidirectional TVS diode from Littelfuse on DigiKey. 

Make sure it has the correct standoff voltage, low clamping voltage, acceptable capacitance, and works reliably in industrial temperatures.