EL2514-G Photocoupler Datasheet - 4-Pin DIP Package - Isolation 5000Vrms - CTR 50-200% - English Technical Document

1. Product Overview

The EL2514-G series represents a family of high-performance, 4-pin Dual In-line Package (DIP) phototransistor photocouplers. These devices are designed to provide reliable electrical isolation and signal transmission between two circuits. The core component is an infrared emitting diode optically coupled to a silicon phototransistor detector. A key design feature of the EL2514-G is its optimization for relatively high switching speeds, achievable even with load resistors in the kilohm range. This makes it suitable for applications requiring both isolation and moderate bandwidth.

The series is characterized by its compliance with stringent environmental and safety standards. It is manufactured as a halogen-free product, adhering to specific limits for bromine (Br) and chlorine (Cl) content. Furthermore, it carries approvals from major international safety agencies including UL, cUL, VDE, SEMKO, NEMKO, DEMKO, FIMKO, and CQC, ensuring its suitability for global markets and regulated applications.

2. Technical Parameters Deep Dive

2.1 Absolute Maximum Ratings

The device is designed to operate reliably within specified limits. Exceeding these Absolute Maximum Ratings may cause permanent damage. Key ratings include: a continuous forward current (I_F) of 50 mA for the input LED, a peak forward current (I_FP) of 0.5 A for a 1µs pulse, and a reverse voltage (V_R) of 6 V. On the output side, the collector current (I_C) is rated at 20 mA, with a collector-emitter voltage (V_CEO) of 40 V. The total power dissipation (P_TOT) for the device is 200 mW. A critical safety parameter is the isolation voltage (V_ISO) of 5000 V_rms, tested for 1 minute under specific humidity conditions (40-60% RH) with input and output pins shorted separately. The operating temperature range is extensive, from -55°C to +110°C.

2.2 Electro-Optical Characteristics

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

2.2.1 Input Characteristics (LED Side)

• Forward Voltage (V_F): Typically 1.2 V, with a maximum of 1.4 V when driven at I_F = 20 mA. This is crucial for designing the driving circuit's voltage supply.
• Reverse Current (I_R): Maximum of 10 µA at V_R = 4V, indicating good diode characteristics.
• Input Capacitance (C_in): Ranges from a typical 30 pF to a maximum of 250 pF. This capacitance can affect high-frequency driving capability.

2.2.2 Output Characteristics (Phototransistor Side)

• Collector-Emitter Dark Current (I_CEO): Maximum of 100 nA at V_CE = 10V with the LED off. This low leakage current is essential for achieving a good \"off\" state.
• Collector-Emitter Breakdown Voltage (BV_CEO): Minimum of 40 V, measured at I_C = 0.1 mA.
• Emitter-Collector Breakdown Voltage (BV_ECO): Minimum of 0.45 V, which is relatively low and indicates the asymmetry of the phototransistor.

2.2.3 Transfer Characteristics

• Current Transfer Ratio (CTR): This is a core performance metric, defined as (I_C / I_F) * 100%. For the EL2514-G, CTR ranges from 50% to 200% under the standard test condition of I_F = 5 mA and V_CE = 5V. This wide range necessitates proper circuit design to accommodate unit-to-unit variation.
• Collector-Emitter Saturation Voltage (V_CE(sat)): Maximum of 0.35 V at I_F = 5 mA and I_C = 0.4 mA. A low saturation voltage is desirable for achieving a strong logic-low output level.
• Isolation Resistance (R_IO): Minimum of 5 x 10¹⁰ Ω at 500 V_DC, ensuring excellent DC isolation.
• Floating Capacitance (C_IO): Typically 0.6 pF, with a maximum of 1.0 pF. This low capacitance contributes to high common-mode transient immunity.
• Switching Times: Both turn-on time (t_on) and turn-off time (t_off) have a maximum specification of 25 µs under the test conditions of V_CC = 5V, I_F = 5 mA, and R_L = 5 kΩ. This defines the device's speed for digital signal transmission.

3. Performance Curve Analysis

The datasheet references typical electro-optical characteristic curves. While the specific graphs are not detailed in the provided text, such curves typically illustrate the relationship between key parameters. Designers should expect to see curves depicting:

• CTR vs. Forward Current (I_F): Shows how the current transfer ratio changes with different LED drive currents.
• CTR vs. Ambient Temperature (T_A): Illustrates the temperature dependence of the CTR, which typically decreases as temperature increases.
• Collector Current (I_C) vs. Collector-Emitter Voltage (V_CE): Family of curves for different LED currents, showing the output characteristics of the phototransistor.
• Switching Waveforms: A test circuit and associated waveforms are provided (Figure 7) to define the conditions for measuring t_on and t_off. This typically involves a pulse generator driving the LED and an oscilloscope monitoring the phototransistor output across the load resistor.

Analyzing these curves is essential for optimizing circuit performance across the intended operating temperature and current ranges.

4. Mechanical and Package Information

4.1 Package Options and Dimensions

The EL2514-G is offered in several 4-pin DIP package variants to suit different assembly processes:

• Standard DIP: The classic through-hole package.
• Option M: Features a \"wide lead bend\" providing a 0.4-inch (approx. 10.16mm) lead spacing, which may be useful for specific PCB layouts or creepage requirements.
• Option S1: A surface-mount (SMD) lead form with a low profile. It is offered with two tape-and-reel options (TU, TD), packing 1500 units per reel.
• Option S2: Another surface-mount lead form, also low profile, with tape-and-reel options packing 2000 units per reel.

Detailed dimensioned drawings are provided for each package type, including critical measurements such as body size, lead length, lead spacing, and standoff height. The creepage distance between the input and output sides is specified to be greater than 7.62 mm, contributing to the high isolation rating.

4.2 Pin Configuration and Polarity

The device uses a standard 4-pin DIP pinout:

1. Anode (of the input LED)
2. Cathode (of the input LED)
3. Emitter (of the output phototransistor)
4. Collector (of the output phototransistor)

Proper orientation is critical. The device marking includes the code \"EL2514GYWWV\", where EL stands for the manufacturer, 2514 is the device number, G denotes halogen-free, Y is a one-digit year code, WW is a two-digit week code, and V indicates optional VDE approval.

4.3 Recommended PCB Pad Layout

For the surface-mount options (S1 and S2), the datasheet provides suggested pad layouts. These are reference designs intended to ensure reliable soldering and mechanical stability. The documentation explicitly notes that these dimensions should be modified based on individual manufacturing processes and requirements, such as solder paste volume and thermal relief considerations.

5. Soldering and Assembly Guidelines

The device is rated for a soldering temperature (T_SOL) of 260°C for a maximum of 10 seconds. This is consistent with typical lead-free reflow soldering profiles. For wave soldering of through-hole packages, standard industry practices should be followed, taking care not to exceed the maximum package body temperature. The storage temperature range is -55°C to +125°C. It is recommended to store devices in moisture-sensitive packaging if intended for SMD assembly and to follow appropriate baking procedures if the moisture exposure level is exceeded.

6. Packaging and Ordering Information

The ordering code follows the pattern: EL2514X(Y)-VG.

• X: Lead form option (S1, S2, M, or none for Standard DIP).
• Y: Tape and reel option (TU, TD, or none for tube packaging).
• V: Denotes VDE safety approval (optional).
• G: Indicates Halogen-free construction.

Packing quantities vary: 100 units per tube for through-hole options, and 1500 or 2000 units per reel for the SMD tape-and-reel options. Detailed tape and reel specifications, including pocket dimensions (A0, B0), tape width (W), pitch (P0), and reel hub diameter, are provided for automated pick-and-place machine programming.

7. Application Suggestions

7.1 Typical Application Scenarios

The EL2514-G is well-suited for applications requiring galvanic isolation, noise immunity, or level shifting. Specific applications mentioned include:

• Programmable Logic Controllers (PLCs): For isolating digital I/O modules from the central processing unit and field devices.
• System Appliances & Measuring Instruments: Isolating sensor signals or communication lines in industrial equipment.
• Electronic Electricity Meters: Providing isolation in metering circuits for safety and noise rejection.
• Telecommunication Equipment: Signal isolation in data lines or power supply feedback loops.
• Power Supplies: Commonly used in feedback loops of switch-mode power supplies (SMPS) to isolate the secondary-side feedback signal from the primary-side controller, enhancing safety and stability.

7.2 Design Considerations

• CTR Variation: Design the receiving circuit (e.g., comparator thresholds, pull-up resistor values) to work reliably across the full 50-200% CTR range.
• Speed vs. Load: The switching speed is specified with a 5 kΩ load. Using a smaller load resistor will generally improve switching speed but reduce output swing and increase power consumption. A larger resistor slows the response, particularly the turn-off time, due to the phototransistor's storage time.
• LED Current Limiting: Always use a series resistor to limit the forward current (I_F) to the recommended operating range (5-7 mA typical) or below the absolute maximum. This ensures long-term reliability and stable CTR.
• Noise Immunity: While photocouplers provide excellent common-mode rejection, ensure proper PCB layout by keeping the input and output traces separated and using bypass capacitors near the device pins to suppress high-frequency noise.

8. Technical Comparison and Positioning

The EL2514-G differentiates itself in the market through a combination of key attributes. Its high isolation voltage (5000 Vrms) and long creepage distance make it a strong candidate for applications with stringent safety requirements. The halogen-free construction addresses environmental regulations and customer preferences for \"green\" electronics. The broad approval portfolio (UL, VDE, etc.) reduces qualification barriers for end products targeting global markets. While its switching speed (25 µs) is suitable for many digital isolation and power supply feedback applications, it is not positioned as an ultra-high-speed coupler for data communication; those applications would require devices with nanosecond-range switching times. Therefore, the EL2514-G is best viewed as a robust, general-purpose photocoupler optimized for reliability, safety compliance, and moderate performance.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What does the CTR range of 50-200% mean for my circuit design?
A: It means the output current can be as low as half the input current or as high as double it. Your circuit must function correctly at both extremes. For a digital interface, this affects the choice of pull-up resistor and the input threshold of the following gate or microcontroller.

Q: Can I drive the LED with a voltage source directly?
A: No. An LED is a current-driven device. You must always use a current-limiting resistor in series with the LED to set the desired I_F and prevent damage from overcurrent, even if your supply voltage matches the typical V_F.

Q: The isolation voltage is 5000 Vrms. Does this mean I can apply 5000V between the input and output continuously?
A: No. This is a withstand voltage tested for one minute under controlled conditions. The continuous working voltage in an application should be significantly lower, as defined by relevant safety standards for the end equipment.

Q: What is the difference between Options S1 and S2?
A: The primary difference is in the package footprint and tape dimensions. S2 is slightly larger in body width (B0 dimension) and uses a wider tape (24mm vs. 16mm for S1), allowing more units per reel (2000 vs. 1500). The choice depends on your PCB space constraints and assembly line feeder compatibility.

10. Practical Design Case

Scenario: Isolating a Digital Signal from a Microcontroller to a High-Voltage Section.
A microcontroller (3.3V logic) needs to send an ON/OFF signal to a circuit operating at a different and noisy high-voltage potential. An EL2514-G can be used for isolation.

Design Steps:

1. Input Side: Connect the microcontroller GPIO pin to the photocoupler's anode via a current-limiting resistor (R_limit). Calculate R_limit = (V_{CC_MCU} - V_F) / I_F. For V_{CC_MCU}=3.3V, V_F~1.2V, and targeting I_F=5mA, R_limit = (3.3-1.2)/0.005 = 420Ω. Use a standard 470Ω resistor. Connect the cathode to ground.
2. Output Side: Connect the collector to a pull-up resistor (R_L) on the isolated high-voltage supply (e.g., 12V). The emitter connects to the isolated ground. The value of R_L affects speed and current. Using the datasheet test condition of 5kΩ provides the specified switching time. The signal from the collector node can then drive a MOSFET gate or another logic input on the isolated side.
3. Layout: Physically separate the input and output sections on the PCB. Maintain the >7.62mm creepage distance as per the package capability. Place a small bypass capacitor (e.g., 0.1µF) between the supply and ground on both sides of the coupler, close to the device pins.

This setup prevents ground loops, blocks noise, and protects the microcontroller from voltage transients on the high-voltage side.

11. Operating Principle

A photocoupler, or optocoupler, is a device that transfers an electrical signal between two isolated circuits using light. In the EL2514-G, an electrical current applied to the input pins (1 and 2) causes the infrared Light Emitting Diode (LED) to emit photons. These photons travel across a transparent insulating gap (typically made of mold compound) and strike the base region of the silicon phototransistor on the output side (pins 3 and 4). The incoming light generates electron-hole pairs in the base, effectively acting as a base current. This photogenerated base current is then amplified by the transistor's gain, resulting in a collector current (I_C) that is proportional to the input LED current (I_F). The ratio I_C/I_F is the Current Transfer Ratio (CTR). The key aspect is that the only connection between the input and output is the beam of light, providing the galvanic isolation.

12. Technology Trends

The photocoupler market continues to evolve. Trends influencing devices like the EL2514-G include:

• Increased Integration: Combining multiple channels of isolation or integrating additional functions like gate drivers or error amplifiers into a single package.
• Higher Speed: Development of couplers using faster detectors like photodiodes with integrated amplifiers to support digital communication protocols (USB, CAN, RS-485) at Mbps data rates.
• Enhanced Reliability and Lifetime: Focus on improving the long-term stability of CTR, which can degrade over time due to LED aging, especially at high temperatures and currents.
• Stricter Environmental Compliance: Beyond RoHS and halogen-free, there is growing attention to substances like PFAS and broader sustainability metrics in the supply chain.
• Alternative Isolation Technologies: While photocouplers remain dominant for many applications, technologies like capacitive isolation (using SiO₂ barriers) and magnetic isolation (using transformers) compete in areas requiring very high speed, low power consumption, or high integration density. Photocouplers maintain advantages in simplicity, high common-mode transient immunity (CMTI), and well-established safety certifications.

The EL2514-G, with its focus on safety certifications, environmental compliance, and robust performance, addresses the enduring needs of industrial, power, and appliance markets where these trends are critically important.