SZ1SMA48CAT3G Littelfuse

The SZ1SMA48CAT3G from Littelfuse is a high-performance, bidirectional Transient Voltage Suppression (TVS) diode in the compact DO-214AC (SMA) surface-mount package. Designed to protect sensitive electronic circuits from voltage transients, Electrostatic Discharge (ESD), and electrical fast transients (EFT), it features a working voltage of 48V and a low clamping voltage of 77.4V. With a robust peak pulse power dissipation of 400W (8/20µs) and compliance with the stringent AEC-Q101 automotive qualification, this device is engineered for reliability in demanding environments. Its bidirectional polarity simplifies PCB layout by eliminating orientation concerns for AC or bipolar signal lines, making it an ideal solution for safeguarding data lines, power rails, and I/O ports in automotive, industrial, and communication systems.

Key Features

• High Power Handling: Offers 400W peak pulse power (8/20µs) and 5.2A peak pulse current for robust surge protection against transient events.
• Low Clamping Ratio: Features a precise clamping voltage of 77.4V, providing effective voltage limiting to protect downstream components.
• Bidirectional Protection: Single-channel, bidirectional design simplifies circuit implementation for AC lines or bipolar signals without regard for polarity.
• Automotive Grade Reliability: Qualified to AEC-Q101 standards, ensuring performance and durability for automotive and other high-reliability applications.
• High ESD Immunity: Rated for 16kV contact and air-gap discharge per IEC 61000-4-2, offering superior protection against electrostatic discharge.

Technical Specifications

• Part Number: SZ1SMA48CAT3G
• Working Voltage (Vrwm): 48 V
• Breakdown Voltage (Vbr): 53.3 V (Min)
• Clamping Voltage (Vc): 77.4 V at Ipp
• Peak Pulse Current (Ipp): 5.2 A (8/20µs)
• Peak Pulse Power (Pppm): 400 W (8/20µs)
• Leakage Current (Ir): 2.5 µA (Max) at Vrwm
• Capacitance (Cd): 135 pF (Typ)
• ESD Rating (IEC 61000-4-2): Contact/Air: 16 kV
• Operating Temperature Range: -65°C to +150°C
• Qualification: AEC-Q101

Pin Configuration and Functions

• No pin definition: This is a two-terminal passive device. The DO-214AC (SMA) package has an anode/cathode marking on the body, but for this bidirectional TVS diode, the terminals are functionally identical and interchangeable.

Typical Applications

• Automotive ECU Power Bus Protection: Safeguarding 12V/24V automotive power supply lines from load-dump and transients.
• Industrial Communication Ports (RS-485, CAN): Protecting data lines in harsh industrial environments from ESD and electrical noise.
• DC Power Input/Output Clamping: Providing secondary protection on 48V DC power rails in telecom and networking equipment.
• Consumer Electronics I/O Port Protection: Securing USB, HDMI, or other high-speed data interfaces against ESD events.

Equivalent / Alternative Parts

• SMAJ48CA (Littelfuse / Other Brands): Similar SMA package, bidirectional, 48V working voltage, and comparable power rating for direct replacement.
• 1.5SMC48CA (Littelfuse): Higher-power alternative in DO-214AB (SMC) package with similar electrical characteristics for more demanding surge requirements.

Advantages

• Superior Power-to-Size Ratio: The 400W surge capability in the compact SMA package offers excellent protection density for space-constrained PCB designs.
• Wide Temperature Robustness: An operating range of -65°C to +150°C exceeds commercial-grade parts, supporting applications in extreme environmental conditions.
• Design Simplification: The bidirectional characteristic eliminates the need for two unidirectional diodes in series, reducing part count and board area.

Limitations

• Moderate Capacitance: With a typical capacitance of 135pF, it may not be suitable for protecting very high-speed data lines (e.g., USB 3.0+, HDMI 2.0+) where signal integrity is critical.
• Fixed Voltage Protection: As a discrete device, it is optimized for a specific voltage rail (48V), requiring different part numbers for other voltage levels.
• Power Dissipation Limit: The 1.5W steady-state power dissipation rating is for thermal management; it is not designed for continuous overvoltage conditions.

Package Information

DO-214AC (SMA) package (approximately 4.3 x 2.6mm), 2 terminals, surface mount. The package is designed for automated assembly and provides a robust form factor for handling surge energy.

Manufacturer Information

Littelfuse is a globally recognized leader in circuit protection, power control, and sensing technologies. The company provides highly reliable and innovative solutions for the automotive, industrial, and electronics markets. This product is part of their portfolio of AEC-Q101 qualified components, meeting the rigorous quality and reliability standards required for automotive applications.

Design-in Tips

• Minimize Inductive Loops: Place the TVS diode as close as possible to the connector or protected line, using short and wide traces to reduce parasitic inductance and maximize clamping performance.
• Thermal Management Consideration: Ensure adequate copper pour or thermal relief on the PCB pads to help dissipate heat generated during a surge event, especially for repetitive pulses.
• Verify System Voltage Margins: Confirm that the 77.4V maximum clamping voltage is safely below the breakdown voltage of the protected IC, allowing sufficient design margin.

Lifecycle Status & PCN/PDN Notes

Lifecycle status information is not provided in the input parameters. No Product Change Notification (PCN) or Product Discontinuation Notice (PDN) information is available for this specific part number at this time. For the most current status, please consult the manufacturer's official product page or contact Littelfuse directly.