ELT302X ELT305X Series Photocoupler Datasheet - 4-Pin DIP Package - 400V/600V Peak Voltage - Random-Phase Triac Driver - English Technical Document

1. Product Overview

The ELT302X and ELT305X series are 4-pin Dual In-line Package (DIP) random-phase triac driver photocouplers. These devices are designed to provide electrical isolation and drive capability for controlling AC loads using triacs. They consist of a Gallium Arsenide (GaAs) infrared light-emitting diode (LED) optically coupled to a monolithic silicon random-phase phototriac. The primary function is to interface low-voltage electronic control circuits (like microcontrollers) with high-voltage AC power triacs, enabling safe control of resistive and inductive loads operating from 115VAC to 240VAC mains.

The key differentiator within the series is the peak blocking voltage: the ELT302X series is rated for 400V, while the ELT305X series is rated for 600V. This allows designers to select the appropriate device based on their line voltage and required safety margin. The devices feature a high isolation voltage of 5000 Vrms between the input and output, which is critical for user safety and system reliability. They are compliant with various international safety standards including UL, cUL, VDE, and are designed to be halogen-free and RoHS compliant.

1.1 Core Features and Advantages

• High Voltage Isolation: 5000 Vrms isolation ensures safe separation between control and power circuits.
• Dual Voltage Ratings: 400V (ELT302X) and 600V (ELT305X) peak blocking voltage options.
• Random-Phase Triggering: The phototriac can be turned on at any point in the AC voltage cycle, providing flexibility for various control schemes.
• Compact DIP Package: The standard 4-pin DIP is a widely used, through-hole package that is easy to prototype and manufacture.
• International Safety Approvals: Certified by UL (E214129), cUL, VDE (40028391), SEMKO, NEMKO, DEMKO, FIMKO, and CQC.
• Environmental Compliance: Halogen-free (Br < 900ppm, Cl < 900ppm, Br+Cl < 1500ppm), RoHS compliant, and compliant with EU REACH regulations.

1.2 Target Applications

These photocouplers are suited for a wide range of AC switching and control applications, including:

• Solenoid and valve controls in appliances and industrial equipment.
• Static AC power switches and solid-state relays.
• Interfacing microprocessors or logic circuits to 115/240VAC peripherals.
• Incandescent lamp dimmers and lighting ballasts.
• Temperature controls in heaters and ovens.
• Motor controls for fans, pumps, and small appliances.

2. Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operating the device continuously at these limits is not recommended.

• Input (LED Side): Maximum forward current (I_F) is 60 mA. Maximum reverse voltage (V_R) is 6 V. Power dissipation (P_D) is 100 mW at 25°C, derating by 3.8 mW/°C above 85°C.
• Output (Triac Side): Off-state terminal voltage (V_DRM) is 400V for ELT302X and 600V for ELT305X. Peak repetitive surge current (I_TSM) is 1 A. Power dissipation (P_C) is 300 mW at 25°C, derating by 7.4 mW/°C above 85°C.
• Total Device: Total power dissipation (P_TOT) must not exceed 330 mW. Isolation voltage (V_ISO) is 5000 Vrms for 1 minute. Operating temperature range (T_OPR) is -55°C to +100°C. Storage temperature (T_STG) is -55°C to +125°C. Soldering temperature (T_SOL) is 260°C for 10 seconds.

2.2 Electro-Optical Characteristics

These parameters define the device's performance under normal operating conditions at 25°C.

Input Characteristics (LED):

• Forward Voltage (V_F): Typically 1.18V, maximum 1.5V at I_F = 10 mA.
• Reverse Leakage Current (I_R): Maximum 10 µA at V_R = 6V.

Output Characteristics (Phototriac):

• Peak Blocking Current (I_DRM): Maximum 100 nA at the rated V_DRM with I_F = 0 mA.
• Peak On-state Voltage (V_TM): Maximum 2.5V at I_TM = 100 mA peak and the rated LED trigger current.
• Critical Rate of Rise of Off-State Voltage (dv/dt): Minimum 100 V/µs for ELT302X at rated V_DRM. For ELT305X, it is 1000 V/µs at V_PEAK = 400V. This parameter indicates the device's immunity to false triggering from rapidly rising voltage transients.

Transfer Characteristics (Coupling):

• LED Trigger Current (I_FT): This is the minimum LED current required to reliably turn on the output triac with a 3V main terminal voltage. It is graded into three levels: 15 mA max (ELT3021/3051), 10 mA max (ELT3022/3052), and 5 mA max (ELT3023/3053). Selecting a lower I_FT grade reduces the drive current required from the control circuit.
• Holding Current (I_H): Typically 250 µA. This is the minimum current that must continue to flow through the triac to keep it in the on-state after it has been triggered.

3. Performance and Application Analysis

3.1 dv/dt Performance and Measurement

The datasheet provides a detailed test circuit and methodology for measuring the static dv/dt capability. A high-voltage pulse is applied to the output through an RC network. The resistance (R_TEST) is varied to change the voltage rise time (τ = R*C). The dv/dt value at which the device begins to trigger unintentionally (without LED current) is recorded. The formula dv/dt = 0.632 * V_PEAK / τ_RC is used for calculation. A higher dv/dt rating, like the 1000 V/µs of the ELT305X, is advantageous in noisy electrical environments or when driving highly inductive loads, as it provides greater immunity against false triggering caused by voltage spikes.

3.2 Design Considerations and Application Guidelines

When designing with these photocouplers, several factors must be considered:

• LED Drive Circuit: The control circuit must provide sufficient current to exceed the I_FT of the selected device grade. A current-limiting resistor is essential. The LED can be driven directly from a microcontroller GPIO pin for lower I_FT grades (e.g., 5mA), but a transistor driver may be needed for higher grades or faster switching.
• Snubber Circuits: When switching inductive loads (motors, solenoids), a snubber network (typically an RC circuit) across the main triac (not the photocoupler output) is highly recommended. This suppresses voltage spikes and reduces dv/dt stress on both the main triac and the photocoupler, improving reliability and reducing EMI.
• Heat Dissipation: Ensure the total power dissipation (LED side + Triac side) does not exceed 330 mW, considering derating with temperature. Adequate PCB copper area or airflow may be necessary in high ambient temperatures.
• Gate Resistor for Main Triac: The output of the photocoupler is connected to the gate of a higher-power triac. A gate resistor (typically 100-1000 Ω) is usually placed in series to limit peak gate current, damp oscillations, and improve noise immunity.

4. Mechanical and Packaging Information

4.1 Package Dimensions and Types

The devices are offered in three primary lead form options within the 4-pin DIP outline:

• Standard DIP: Through-hole package with 0.1 inch (2.54 mm) row spacing and standard lead length.
• Option M (Wide Bend): Through-hole package with leads bent to a 0.4 inch (10.16 mm) row spacing, suitable for wider PCB traces or specific layout requirements.
• Option S1 (Surface Mount): A low-profile surface-mount lead form. This option is typically supplied on tape and reel for automated assembly. The datasheet includes a recommended PCB pad layout for this SMD type.

Detailed dimensional drawings for all three types are provided, including body size, lead spacing, and standoff height.

4.2 Polarity and Pin Configuration

The pinout is standard for a 4-pin DIP photocoupler:

1. Pin 1: Anode of the input LED.
2. Pin 2: Cathode of the input LED.
3. Pin 3: Main Terminal 1 (MT1) of the output phototriac.
4. Pin 4: Main Terminal 2 (MT2) of the output phototriac.

A dot or notch on the package typically identifies Pin 1. Correct polarity is crucial for the LED side to function. The output triac is bidirectional, so polarity is less critical, but standard practice is to connect MT2 to the AC line side and MT1 to the gate resistor leading to the main triac's gate.

5. Ordering and Manufacturing Information

5.1 Part Numbering System

The part number follows the format: ELT30[2 or 5]X Y (Z) - V

• 30[2/5]: 302 for 400V rating, 305 for 600V rating.
• X: Part number/IFT grade (1, 2, or 3 corresponding to max I_FT of 15mA, 10mA, 5mA).
• Y: Lead form option: None (Standard DIP), M (Wide bend), S1 (Surface mount).
• (Z): Tape and Reel option for S1: TU or TD (reel orientation). Omitted for tube packaging.
• -V: Optional suffix denoting VDE safety approval.

Example: ELT3053S1(TU)-V is a 600V rated device, with 5mA max I_FT, in surface-mount lead form, on TU orientation tape and reel, with VDE approval.

5.2 Packaging Specifications

Standard DIP and Option M parts are packaged in tubes containing 100 units. The Option S1 surface-mount parts are available on tape and reel, with 1500 units per reel. Detailed tape dimensions (width, pocket spacing, etc.) are provided for compatibility with automated pick-and-place equipment.

5.3 Device Marking

Devices are marked on the top of the package. The marking includes: \"EL\" (manufacturer code), the device number (e.g., T3053), a 1-digit year code (Y), a 2-digit week code (WW), and the letter \"V\" if it is the VDE-approved version.

6. Comparison and Selection Guide

The main selection criteria between ELT302X and ELT305X is the required blocking voltage. For 120VAC applications, a 400V device often provides sufficient margin (peak line voltage ~170V). For 230VAC applications (peak ~325V) or in environments with significant voltage surges, the 600V rating of the ELT305X series offers a much safer margin and is generally recommended.

Within each series, the choice of I_FT grade (1, 2, or 3) is a trade-off between drive circuit simplicity and cost. Grade 3 (5mA) is the most sensitive and easiest to drive directly from logic, but may be slightly more expensive. Grade 1 (15mA) requires more drive current but might be chosen for its potentially higher noise immunity or lower cost.

Compared to zero-crossing photocouplers, these random-phase devices offer the advantage of being able to trigger at any point in the AC cycle. This is essential for applications like phase-angle dimming of incandescent lamps or soft-start of motors, where controlling the power delivered each half-cycle is required. The trade-off is that random-phase switching can generate more electromagnetic interference (EMI) than zero-crossing switching.