EL260L Logic Gate Photocoupler Datasheet - 8-Pin DIP Package - 3.3V/5V Supply - 10Mbit/s Speed - English Technical Document

1. Product Overview

The EL260L is a high-speed logic gate photocoupler designed for digital signal isolation. It integrates an infrared emitting diode optically coupled to a high-speed integrated photo-detector with a strobable logic gate output. Packaged in an 8-pin Dual In-line Package (DIP), it is engineered to provide reliable electrical isolation and signal integrity in demanding applications.

Core Advantages: The device's primary strengths include its high-speed data transmission capability of up to 10 Mbit/s, robust common-mode transient immunity (CMTI) of 10 kV/μs minimum, and dual supply voltage compatibility (3.3V and 5V). It guarantees performance across a wide operating temperature range from -40°C to +85°C. The logic gate output can drive up to 10 standard loads (Fan-out 10).

Target Market: This component is targeted at applications requiring high-speed digital isolation, ground loop elimination, and noise immunity in industrial automation, power supply systems, computer peripherals, and communication interfaces.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The Absolute Maximum Ratings define the stress limits beyond which permanent damage to the device may occur. Key parameters include a maximum forward current (I_F) of 50 mA for the input LED, a reverse voltage (V_R) of 5 V, and supply/output voltages (V_CC, V_O) of 7.0 V. The total power dissipation for the input side is 45 mW, while the output side can handle 85 mW. The isolation voltage (V_ISO) between input and output is rated at 5000 V_rms for one minute. Operating and storage temperature ranges are -40°C to +85°C and -55°C to +125°C, respectively. The device can withstand a soldering temperature of 260°C for 10 seconds.

2.2 Electrical Characteristics

These specifications detail the device's performance under normal operating conditions (T_A = -40°C to 85°C).

Input Characteristics: The forward voltage (V_F) typically measures 1.4V at I_F=10mA, with a maximum of 1.8V. The input capacitance (C_IN) is typically 60 pF.

Output Characteristics: Supply current varies with state: I_CCH (high level) is typically 7 mA (max 10 mA), and I_CCL (low level) is typically 9 mA (max 13 mA) at V_CC=3.3V. The enable input has an internal pull-up resistor, requiring no external component. The low-level enable voltage (V_EL) is guaranteed to be below 0.8V.

Transfer Characteristics: Critical for logic operation, the low-level output voltage (V_OL) is typically 0.35V (max 0.6V) when sinking 13 mA. The input threshold current (I_FT) to trigger a logic low output is typically 2.5 mA (max 5 mA).

2.3 Switching Characteristics

Measured at V_CC=3.3V, I_F=7.5mA, with a load of R_L=350Ω and C_L=15pF.

Propagation Delays: The propagation delay time to output low (t_PHL) is typically 40 ns (max 75 ns), and to output high (t_PLH) is typically 45 ns (max 75 ns). Pulse width distortion, the absolute difference between t_PHL and t_PLH, is typically 5 ns (max 35 ns), crucial for timing-sensitive applications.

Transition Times: Output rise time (t_r) is typically 40 ns, while fall time (t_f) is typically 10 ns, indicating faster turn-off.

Enable Times: The enable propagation delay to output low (t_EHL) is typically 10 ns, and to output high (t_ELH) is typically 25 ns.

Common-Mode Transient Immunity (CMTI): A key isolation metric. The device guarantees a minimum of 10,000 V/μs for both logic high (CM_H) and logic low (CM_L) states, ensuring reliable operation in noisy environments with fast voltage transients across the isolation barrier.

3. Pin Configuration and Schematic

The 8-pin DIP configuration is as follows: Pin 1 (NC), Pin 2 (Anode), Pin 3 (Cathode), Pin 4 (NC), Pin 5 (GND), Pin 6 (V_OUT), Pin 7 (V_E - Enable), Pin 8 (V_CC). A critical design requirement is the placement of a 0.1μF (or larger) bypass capacitor with good high-frequency characteristics between pins 8 (V_CC) and 5 (GND), located as close as possible to the package to ensure stable operation and minimize noise.

4. Truth Table and Logic Function

The device functions as a strobable logic gate. The truth table (using positive logic) defines its operation:

• Input (I_F) High, Enable (V_E) High: Output (V_O) = Low
• Input Low, Enable High: Output = High
• Input High, Enable Low: Output = High
• Input Low, Enable Low: Output = High
• Input High, Enable NC (No Connection): Output = Low
• Input Low, Enable NC: Output = High

The enable pin provides a third-state control, allowing the output to be forced high regardless of the input signal when the enable is low.

5. Mechanical and Packaging Information

The device is offered in a standard 8-pin DIP package. The datasheet indicates availability in both wide-lead spacing and Surface-Mount Device (SMD) options, though the primary focus here is the through-hole DIP variant. Detailed dimensional drawings would typically be included in a full datasheet to guide PCB layout and footprint design.

6. Soldering and Assembly Guidelines

The Absolute Maximum Ratings specify a soldering temperature (T_SOL) of 260°C for 10 seconds. This is a critical parameter for wave or reflow soldering processes. Standard IPC guidelines for through-hole component soldering should be followed. Proper ESD handling procedures are recommended during assembly due to the sensitive semiconductor components inside.

7. Application Suggestions

7.1 Typical Application Scenarios

• Ground Loop Elimination & Logic Level Translation: Isolating digital signals between circuits with different ground potentials, such as translating signals between LSTTL and TTL/CMOS logic families.
• Data Transmission & Multiplexing: High-speed serial data isolation in communication lines and data bus isolation.
• Switching Power Supplies: Providing feedback isolation in flyback or other isolated converter topologies.
• Pulse Transformer Replacement: Offering a solid-state, potentially more compact and reliable alternative to traditional pulse transformers for signal isolation.
• Computer Peripheral & Industrial Interface: Isolating digital I/O lines in noisy industrial environments or for interfacing with motors and actuators.

7.2 Design Considerations

• Bypass Capacitor: The 0.1μF capacitor across V_CC and GND is mandatory for stable high-speed operation and must be placed close to the pins.
• Current Limiting Resistor: An external resistor is required in series with the input LED (Anode) to set the forward current (I_F) according to the application needs (e.g., 7.5mA for specified switching times).
• Load Resistor: The output characteristics are specified with a 350Ω pull-up resistor to V_CC. This value must be used or adjusted carefully based on the required output current and speed.
• Enable Pin: The internal pull-up on the enable pin simplifies design. Driving it low forces the output high; leaving it unconnected (NC) defaults to a high state, allowing normal operation controlled solely by the input.
• PCB Layout: Maintain good isolation clearance and creepage distances on the PCB between the input and output sides as per safety standards, even though the component itself provides the primary isolation barrier.

8. Technical Comparison and Differentiation

The EL260L differentiates itself in the photocoupler market through its combination of high speed (10 Mbit/s) and exceptionally high CMTI (10 kV/μs). Many standard photocouplers operate at lower speeds (e.g., 1 Mbit/s) or have lower CMTI ratings. The dual 3.3V/5V supply compatibility offers design flexibility in modern mixed-voltage systems. The integrated logic gate with enable function and guaranteed performance over a wide temperature range makes it a robust choice for industrial applications compared to basic transistor-output optocouplers.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the enable (V_E) pin?
A: The enable pin provides a third-state control. When driven low, it overrides the input signal and forces the output to a logic high state. This can be used for bus contention management or to disable the output.

Q: Why is the 0.1μF bypass capacitor so critical?
A: At high switching speeds (10 Mbit/s), sudden current demands can cause voltage spikes on the supply rail. The local bypass capacitor provides a immediate charge reservoir, stabilizing V_CC and preventing malfunctions or noise generation.

Q: How do I select the value for the input current limiting resistor?
A: Use Ohm's Law: R_LIMIT = (Supply Voltage - V_F) / I_F. For example, with a 5V supply, V_F~1.4V, and desired I_F=10mA: R = (5 - 1.4) / 0.01 = 360Ω. Choose a standard value like 360Ω or 390Ω. For optimal speed, use I_F=7.5mA as per the switching specs.

Q: Can I use this with a 5V supply for the output side?
A: Yes, the datasheet specifies dual supply voltage compatibility (3.3V and 5V). The electrical characteristics tables often list conditions at V_CC=3.3V, but the device is designed to operate with 5V as well. Always check all parameters at your intended supply voltage.

10. Practical Design and Usage Case

Scenario: Isolated RS-485/RS-422 Transceiver Interface. In an industrial sensor node, a microcontroller communicates with an RS-485 transceiver over UART. To protect the sensitive microcontroller from ground shifts and high-voltage transients on the long RS-485 bus, the EL260L can be used to isolate the UART TX and RX lines. The microcontroller side (input) operates at 3.3V, while the transceiver side (output) can operate at 5V. The high 10 Mbit/s speed easily handles standard serial baud rates (e.g., 115200 baud, 1 Mbaud). The 10 kV/μs CMTI ensures the isolation remains effective even during severe electrical noise events on the bus. The enable pin could be tied to a microcontroller GPIO to disable the communication path if needed.

11. Operating Principle

The EL260L operates on the principle of optical coupling. An electrical current applied to the input side (pins 2 & 3) causes an infrared Light Emitting Diode (LED) to emit light. This light traverses a transparent isolation barrier within the package. On the output side, a high-speed integrated photodetector converts the received light back into an electrical current. This current is processed by an internal amplifier and logic gate circuit to produce a clean, buffered digital output signal (on pin 6) that mirrors the state of the input but is electrically isolated from it. The isolation barrier, typically made of mold compound or similar material, provides the high voltage isolation (5000 V_rms) between the two sides.

12. Industry Trends and Context

The demand for high-speed digital isolators is driven by several trends: the proliferation of industrial IoT and automation requiring robust communication in noisy environments; the adoption of higher switching frequencies in power electronics necessitating faster feedback isolation; and the move towards higher system-level integration and reliability. Components like the EL260L represent a mature and cost-effective technology for galvanic isolation. The industry also sees growth in alternative isolation technologies like capacitive and magnetic (giant magnetoresistance) isolators, which can offer even higher speeds, lower power consumption, and greater integration density. However, photocouplers remain highly popular due to their simplicity, proven reliability, high CMTI, and ease of use in a wide range of applications. The focus for advanced photocouplers continues to be on increasing speed, improving power efficiency, reducing package size, and enhancing reliability metrics like long-term insulation resistance.