The **ALTG-823-R** is a specific model of an **SMD (Surface Mount Device) Gas Discharge Tube (GDT)**, typically manufactured by companies like **Littelfuse** (as part of their GDT series). These components are critical for circuit protection against high-voltage transients. --- ### 1. General Overview A Gas Discharge Tube acts as a high-speed switch that turns into a low-impedance path when a high-voltage surge (like lightning or static discharge) is detected. This diverts the excess energy away from sensitive downstream electronics. ### 2. Technical Specifications Below are the typical electronic characteristics for the ALTG-823-R: | Parameter | Specification | | :--- | :--- | | **DC Sparkover Voltage** | 800V ± 20% | | **Impulse Sparkover Voltage** | < 1300V (at 1kV/µs) | | **Insulation Resistance** | > 1 GΩ | | **Capacitance** | < 1.0 pF | | **Impulse Discharge Current** | 2kA (8/20µs waveform) | | **Package Type** | SMD (Surface Mount) | | **Termination** | Square Lead / Square Terminal | --- ### 3. Key Electronic Features * **Low Capacitance:** Because it has a capacitance of less than 1pF, it is ideal for high-speed data transmission lines (like Ethernet or RF) as it does not distort the signal. * **High Insulation Resistance:** Under normal operating conditions, it acts as an open circuit with extremely high resistance, ensuring zero leakage current. * **Ruggedness:** Designed to handle multiple hits of high-current surges without failing, provided they stay within the rated 2kA limit. * **Fast Response:** It transitions from a non-conductive state to a conductive state in nanoseconds once the "sparkover" voltage is reached. --- ### 4. Circuit Application In a typical circuit, the ALTG-823-R is placed in parallel with the load it is protecting. ```mermaid graph LR A[Input/Surge Source] --> B{ALTG-823-R} B -- Ground Path --> G[Earth Ground] B --> C[Protected IC/Circuit] ``` ### 5. Common Uses 1. **Telecommunications:** Protection for ADSL/VDSL/Ethernet ports. 2. **Power Supplies:** Input surge protection for AC/DC converters. 3. **Industrial:** Protection for RS-485 or CAN bus interfaces in harsh environments. ---