CG300 Equivalent / Substitute – SMD 300V GDT for Telecom and Signal Line Protection | YINT

YINT Electronics — Gas Discharge Tube (GDT)

Target Keywords: CG300 equivalent, CG300 substitute, CG300 replacement, CG300 alternative, Littelfuse CG300 cross reference, SMD GDT 300V, SMD1812-301

SEMrush Data: "gas discharge tube" — 2,400/mo US · KD 29%

1. Introduction

The Littelfuse CG300 is a 300V SMD gas discharge tube used in telecom, signal line, and data interface protection. It provides primary surge protection with capacitance under 0.5pF to preserve signal integrity at high data rates. When a voltage transient exceeds 300V, the gas inside the GDT ionizes and switches from a high-impedance off-state (gigaohms) to a low-impedance arc (ohms), shunting the surge current to ground. After the surge passes, the GDT extinguishes and returns to standby.

GDTs are the preferred choice for primary surge protection in outdoor telecom and industrial equipment because they handle high surge currents with near-zero leakage in standby. Unlike TVS diodes that clamp voltage, GDTs crowbar the line to a low voltage during conduction, which reduces stress on downstream secondary protection stages. The SMD1812-301 follows this same design principle, protecting downstream TVS diodes and interface ICs from lightning-induced overvoltage per ITU-T K.12 and IEC 61000-4-5.

YINT SMD1812-301 is a direct CG300 equivalent. It delivers identical 300V DC breakdown, 2kA impulse discharge current (8/20µs), and 0.5pF capacitance in the same SMD 1812 package. Engineers searching for a CG300 replacement or CG300 substitute can pick YINT SMD1812-301 as a drop-in without PCB layout or circuit changes. YINT manufactures this GDT with 100% electrical testing on every device for consistent impulse spark-over voltage and DC breakdown across all production lots.

2. Product Overview

The SMD 1812 GDT family uses a compact ceramic surface-mount package rated for 2kA impulse current. These gas-filled devices protect sensitive transceivers, line drivers, and interface ICs from lightning surges, AC power cross events, and inductive switching transients. The 1812 footprint — 4.5mm x 3.2mm — balances surge capability with board space and is the dominant package for telecom and industrial interface protection worldwide.

The SMD1812-301 sits at the 300V breakdown point, suitable for protecting telecom subscriber lines, RS-485/RS-232 interfaces, Ethernet PoE ports, CATV amplifiers, and security camera video feeds. Its 0.5pF capacitance introduces negligible loading on high-frequency signals up to 1 Gbps and beyond. The device is bidirectional and symmetric, so orientation during PCB assembly does not matter. After a surge, the DC holdover voltage of 150V ensures the GDT extinguishes reliably when the line voltage drops below this threshold.

YINT produces the full SMD1812 GDT series from 90V to 800V. This complete voltage range lets design teams source all SMD GDT needs from one manufacturing partner, simplifying qualification and supply chain management. The SMD1812-301 uses a hermetic ceramic gap construction with stable DC breakdown performance over the full -40°C to +85°C operating range. YINT's 19+ years of circuit protection manufacturing experience means each device benefits from mature, proven production processes that deliver reliable long-term field performance.

In a typical multi-stage protection circuit, the SMD1812-301 serves as the primary (first) stage that handles the bulk of the surge energy. A secondary TVS diode or transient suppressor downstream then absorbs the residual let-through voltage for sensitive IC protection. This staged approach is standard in telecom central office equipment, base stations, and industrial I/O modules where reliability and uptime are critical.

3. Key Features

• DC Breakdown: 300V — Protects 300V-rated telecom and signal lines
• Impulse Discharge: 2kA — 8/20µs waveform, 10 hits per ITU-T K.12
• Capacitance: 0.5pF — Minimal signal loading for high-speed data up to 1 Gbps
• Impulse Spark-over: 300V — 1kV/µs response for fast transient turn-on
• SMD 1812 Package — Industry-standard 4.5mm x 3.2mm footprint
• Bidirectional Protection — Symmetrical breakover, no polarity concerns
• Hermetic Ceramic Seal — Stable performance in humid outdoor environments
• Low Leakage — Near-zero standby current in off-state
• DC Holdover: ≥150V — Reliable arc extinction after surge event
• RoHS Compliant — Lead-free and halogen-free per EU directive
• Tape & Reel Packaging — 2,500 pcs/reel for automated pick-and-place

4. Specifications

5. Cross Reference

The SMD1812-301 is a universal replacement for industry-standard 300V SMD GDTs. Each part listed below shares the same 300V DC breakdown, 2kA impulse discharge current, and SMD 1812 package footprint. Engineers searching for a CG300 equivalent can confidently specify YINT SMD1812-301 as a direct drop-in substitute across all major brands without any design changes or re-qualification.

6. Comparison with Similar Models

Engineers evaluating a CG300 replacement often compare nearby voltage variants and competing GDT models to select the correct part for their application. The table below highlights key electrical differences for proper part selection.

The SMD1812-301 matches the Littelfuse CG300 and Bourns 2036-30-B on every key parameter. The CG350 (350V) suits higher-voltage lines where additional margin is required — for example, when protecting 300V-rated lines with a higher safety tolerance. The SMD1812-471 (470V) serves 400V+ protection needs for industrial power interfaces and higher-voltage communication buses. For standard 300V telecom and signal line applications, the YINT SMD1812-301 delivers identical protection levels with competitive pricing, shorter lead times, and reliable long-term availability.

7. Applications

• Telecom subscriber line protection per ITU-T K.12 and K.21 recommendations
• Ethernet interface and PoE port primary surge protection
• RS-485, RS-232, and RS-422 serial data interface protection
• CATV and broadband amplifier RF port surge clamping
• CCTV camera video signal and power line protection
• Security alarm and access control communication lines
• Industrial automation sensor and actuator signal lines
• Building management system (BMS) RS-485 bus protection
• Data acquisition and SCADA telemetry I/O port protection
• Medical equipment isolated communication port protection
• Smart meter and energy management communication interfaces
• Outdoor LED lighting data and control signal protection
• Base station and small cell backhaul interface protection

8. Why Choose YINT

• 19+ years of manufacturing expertise in circuit protection components since 2006
• 40+ patents and ISO-certified production with 100% electrical testing on every GDT
• Global sales network serving North America, Europe, Asia, and Latin America
• Full SMD1812 GDT series from 90V to 800V for one-stop SMD GDT sourcing
• Direct CG300 replacement — identical 300V breakdown, 2kA rating, and 1812 footprint
• Engineering team available for cross-reference verification and application support
• Free samples for qualification testing and design validation upon request
• Direct manufacturer pricing with volume discount options and short lead times
• Consistent quality across production lots with 100% surge current testing
• Customer-first approach with responsive technical and commercial support

9. Ordering Information

10. FAQ

Q1: Is YINT SMD1812-301 a direct replacement for Littelfuse CG300?
A: Yes. The SMD1812-301 has identical 300V DC breakdown, 2kA impulse discharge, 0.5pF capacitance, and SMD 1812 package. It drops in without PCB changes.

Q2: What is the difference between CG300 and CG350?
A: CG350 has 350V DC breakdown, while CG300 is 300V. Choose CG300 for standard 300V telecom lines and CG350 for applications needing a higher breakdown margin.

Q3: Can SMD1812-301 replace Bourns 2036-30-B?
A: Yes. Both parts share 300V breakdown, 2kA discharge, and SMD 1812 footprint. YINT SMD1812-301 is a fully compatible drop-in substitute.

Q4: What is the capacitance of SMD1812-301 and why does it matter?
A: 0.5pF at 1MHz. Low capacitance prevents signal distortion and attenuation on high-speed data lines operating at 100 Mbps to 1 Gbps or higher.

Q5: What surge standards does SMD1812-301 comply with?
A: It meets ITU-T K.12 and IEC 61000-4-5 for 2kA 8/20µs impulse waveforms on telecom and signal line ports.

Q6: How should I use the SMD1812-301 in a multi-stage protection design?
A: Place it as the primary stage between the line and ground. Use a TVS diode or transient suppressor as the secondary stage downstream. A resistor or PTC between stages limits the let-through current.

Q7: Does YINT provide free samples for testing?
A: Yes. Contact YINT with your project details for sample requests and cross-reference qualification support.

11. Conclusion

YINT SMD1812-301 is a reliable CG300 equivalent with identical 300V DC breakdown, 2kA surge rating, and low 0.5pF capacitance. It protects telecom, signal, and data lines with direct drop-in compatibility for Littelfuse CG300, Bourns 2036-30-B, and EPCOS B88089X.

Contact YINT Electronics at global@yint.com.cn for datasheets, samples, or pricing. Our engineering team is ready to assist with cross-references and application support.