EL220X Series Logic Gate Photocoupler Datasheet - 8-Pin DIP Package - High Speed 5Mbd - Low Input Current 1.6mA - Isolation Voltage 5000Vrms - English Technical Document

1. Product Overview

The EL220X series represents a family of high-performance, high-speed logic gate photocouplers (opto-isolators) designed for digital signal isolation. The core function is to provide galvanic isolation between input and output circuits while transmitting logic-level signals with high fidelity and speed. The device integrates an infrared emitting diode optically coupled to a high-speed integrated photodetector with a logic gate output stage. It is offered in a standard 8-pin Dual In-line Package (DIP) and is also available in Surface-Mount Device (SMD) variants.

The primary advantage of this series lies in its combination of high speed and low input current requirements. It is engineered to replace pulse transformers and other isolation methods in demanding digital interfaces, offering superior noise immunity, simpler design integration, and reliable performance across a wide temperature range.

1.1 Core Advantages and Target Market

The EL220X photocoupler is distinguished by several key features that define its application space:

• High-Speed Data Transmission: A typical signal rate of 5 Megabaud (Mbd) enables its use in fast digital communication links, microprocessor system interfaces, and computer peripheral interfaces where timing is critical.
• Excellent Noise Immunity: A minimum Common Mode Transient Immunity (CMTI) of 1kV/μs ensures reliable operation in electrically noisy environments, such as industrial controls and motor drives, by rejecting fast voltage transients between the input and output grounds.
• Low Input Drive Requirement: An input threshold current of 1.6mA (max) allows direct interfacing with low-power logic families like LSTTL and CMOS, simplifying driver circuit design and reducing system power consumption.
• Robust Isolation: A high isolation voltage of 5000 V_rms between input and output provides a strong safety barrier and protection for sensitive circuitry, crucial for medical equipment, industrial automation, and power supply feedback loops.
• Wide Operating Range: Guaranteed performance from -40°C to +85°C and a supply voltage (V_CC) range of 4.5V to 20V make it suitable for automotive, industrial, and extended commercial temperature applications.

The target markets include industrial automation, programmable logic controllers (PLCs), data acquisition systems, isolated bus drivers, medical instrumentation requiring patient isolation, telecommunications equipment, and any application requiring ground loop elimination or high-voltage isolation for digital signals.

2. Technical Parameter Deep-Dive

The electrical and transfer characteristics of the EL220X series are specified under conditions of T_A = -40°C to 85°C, V_CC = 4.5V to 20V, and specific input/enable conditions, ensuring reliable operation across the entire stated range.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage may occur. They are not for continuous operation.

• Input Forward Current (I_F): 50 mA (max). This limits the peak current through the internal LED.
• Input Reverse Voltage (V_R): 5 V (max). The LED should not be subjected to reverse bias exceeding this value.
• Output Current (I_O): 25 mA (max). The maximum continuous current the output transistor can sink or source.
• Supply/Output Voltage (V_CC, V_O): 20 V (max). The maximum voltage applied to the output side supply pin or the output pin itself.
• Isolation Voltage (V_ISO): 5000 V_rms. This is the hi-pot test voltage for one minute, defining the basic insulation capability between input and output.
• Total Power Dissipation (P_T): 210 mW. The maximum power the entire package can dissipate at 25°C ambient.

2.2 Electrical Characteristics: Input & Output

Input Characteristics:

• Forward Voltage (V_F): Typically 1.4V, with a maximum of 1.8V at I_F=10mA. This parameter is essential for designing the current-limiting resistor for the input LED.
• Temperature Coefficient of V_F: Approximately -1.8 mV/°C. The LED forward voltage decreases as temperature increases, a common characteristic of diodes.
• Input Capacitance (C_IN): Typically 60 pF. This affects the high-frequency response and drive requirements of the input circuit.

Output & Supply Characteristics:

• Supply Currents (I_CCH, I_CCL): The current drawn by the output-side IC. I_CCH (output high) is typically 2.3-3mA, and I_CCL (output low) is typically 3.7-4.5mA, depending on V_CC. These values are critical for system power budget calculations.
• Output Logic Levels:
  • High-Level Output Voltage (V_OH): Minimum of 2.4V when sinking -2.6mA (I_OH). This guarantees compatibility with TTL and CMOS logic high input thresholds.
  • Low-Level Output Voltage (V_OL): Maximum of 0.5V when sourcing 6.4mA (I_OL) at V_CC=4.5V. This ensures a solid logic low state.
• Enable Characteristics (EL2200 only): The three-state enable function has specific voltage (V_EH min 2.0V, V_EL max 0.8V) and current (I_EH, I_EL) requirements for proper control of the high-impedance output state.

2.3 Transfer Characteristics

These parameters define the signal transfer behavior from input to output.

• Input Threshold Current (I_FT): Maximum of 1.6mA. This is the guaranteed current needed at the input LED to force the output to a valid logic low state under specified conditions. It directly relates to the device's sensitivity.
• Input Current Hysteresis (I_HYS): Typically 0.03mA. This built-in hysteresis provides differential mode noise immunity, preventing output chatter when the input signal is near the switching threshold.
• Output Leakage Currents (I_OHH, I_OZL, I_OZH): These are the small currents that flow in the output high state or high-impedance state when the output is off. They are typically in the microamp range but must be considered in high-impedance bus applications.
• Short-Circuit Output Current (I_OSL, I_OSH): The current the output can deliver into a short circuit, typically 25-40mA. This indicates the output stage's robustness but is not a condition for continuous operation.

2.4 Switching Characteristics

These parameters define the timing performance, crucial for high-speed data transmission.

• Propagation Delays (t_PLH, t_PHL): The time from the input LED crossing its threshold to the output crossing its logic threshold. Typical values are 100ns (low-to-high) and 105ns (high-to-low), with maximums of 300ns. These delays limit the maximum usable data rate.
• Rise/Fall Times (t_r, t_f): The output signal edge speeds. Typical t_r is 45ns and t_f is 10ns. Faster edges improve signal integrity but may increase EMI.
• Enable/Disable Times (EL2200 only): Parameters like t_PZH, t_PZL, t_PHZ, t_PLZ define how quickly the output enters or leaves the high-impedance state when the enable pin is toggled. These are critical for bus-sharing applications.
• Common Mode Transient Immunity (CM_H, CM_L): Minimum of 1000 V/μs. This quantifies the device's ability to maintain correct output logic states during fast voltage transients between the input and output grounds. The test is performed with |V_CM|=50V.

3. Device Variants and Truth Tables

The EL220X series includes specific variants with different output configurations.

3.1 EL2200 (Three-State Output)

The EL2200 features a three-state (tri-state) output. This allows multiple devices to be connected to a common data bus without contention. The output can be in a logic High, logic Low, or a high-impedance (Z) state. The high-impedance state is controlled by an active-low Enable (E) pin.

Truth Table for EL2200:

When Enable is high, the output is disabled (high-Z) regardless of the input. When Enable is low, the output actively follows the input state (non-inverting).

3.2 EL2201/EL2202 (Standard Output)

The EL2201 and EL2202 have a standard, always-active output with no enable pin. The output directly follows the input state. The difference between EL2201 and EL2202 is typically in-channel-to-channel matching or other parametric selections not detailed in this excerpt.

Truth Table for EL2201/02:

The transfer function is non-inverting.

4. Application Suggestions and Design Considerations

4.1 Typical Application Circuits

1. Microprocessor System Interface / Isolated Bus Driver: The EL2200 is ideal for this. Multiple EL2200s can have their outputs connected to a microprocessor data bus. Each device's Enable pin is controlled by an address decoder. Only the selected device drives the bus, while others remain in high-Z state, preventing bus contention.

2. Ground Loop Elimination in Data Transmission: When sending digital signals (e.g., RS-232, RS-485 control signals) between systems with different ground potentials, the EL220X breaks the galvanic connection, preventing ground loop currents that cause noise and errors. Its high CMTI handles the ground shift.

3. Pulse Transformer Replacement: In switch-mode power supply feedback loops or gate drive circuits, the EL220X can replace small pulse transformers. It offers advantages like simpler design (no concern for transformer saturation, simpler driver), better stability over temperature, and potentially lower cost.

4.2 Critical Design Considerations

• Input Current Limiting Resistor (R_LIM): This is the most critical external component. It must be calculated based on the forward voltage (V_F) of the LED, the drive voltage (V_DRIVE), and the desired forward current (I_F). I_F must be greater than I_FT (1.6mA max) for a guaranteed low output but should not exceed the Absolute Maximum Rating.
  Formula: R_LIM = (V_DRIVE - V_F) / I_F
  Example: For V_DRIVE=5V, V_F=1.4V, and I_F=5mA, R_LIM = (5 - 1.4) / 0.005 = 720Ω. Use a standard 680Ω or 750Ω resistor.
• Power Supply Decoupling: A bypass capacitor (typically 0.1µF ceramic) should be placed as close as possible between the V_CC and GND pins on the output side to minimize noise and ensure stable switching.
• Output Loading: Ensure the connected load does not require more sink/source current (I_OL/I_OH) than specified. For heavy loads, an external buffer may be needed. The sum of I_CC and the load current must be considered for the output side power supply.
• Enable Pin Handling (EL2200): The Enable pin must not be left floating. It should be tied to V_CC (via a resistor if necessary) to disable the output, or actively driven by control logic.
• PCB Layout for High CMTI: To maintain the high CMTI rating, maximize the creepage and clearance distance on the PCB between the input and output sections. Avoid running input and output traces parallel or close to each other. Use a slot or barrier in the PCB if necessary.

5. Mechanical, Packaging, and Assembly

5.1 Package Information

The device is housed in a standard 8-pin DIP package. The exact body dimensions, lead spacing, and seating plane should be obtained from the detailed mechanical drawing (not fully provided in this excerpt). Key points include:

• Standard DIP pin spacing: 2.54mm (0.1") between pins in a row, and 7.62mm (0.3") between rows.
• The package is available in both through-hole and SMD styles.
• Polarity is indicated by a notch or dot at the end of the package corresponding to pin 1.

5.2 Soldering and Handling

• Soldering Temperature: The absolute maximum soldering temperature is 260°C. This refers to the peak temperature experienced by the package body during reflow or wave soldering processes.
• ESD Precautions: Photocouplers contain sensitive semiconductor junctions. Standard ESD (Electrostatic Discharge) handling procedures should be followed during assembly and handling.
• Storage Conditions: The storage temperature range is -55°C to +125°C. Devices should be stored in a dry, anti-static environment.

6. Technical Comparison and FAQs

6.1 Differentiation from Other Photocouplers

The EL220X series differentiates itself in the photocoupler market through its specific combination of attributes:

• vs. Standard Transistor-Output Optocouplers (e.g., 4N25): The EL220X is significantly faster (5Mbd vs. ~100kbd), has a defined logic output stage (vs. an analog transistor), and features much higher CMTI. It is designed for digital signals, not analog isolation.
• vs. Other High-Speed Logic Gate Optocouplers: Its competitive advantages include the very low 1.6mA input threshold current, which reduces driver burden, and the availability of a three-state version (EL2200) for bus applications, which is not common in all families.
• vs. Digital Isolators (Silicon-based): Digital isolators use capacitive or magnetic coupling and can achieve much higher speeds (e.g., 100Mbps+). However, optocouplers like the EL220X offer superior isolation voltage (5000Vrms vs. typically 2500-5000V_RMS for many digital isolators) and have a long-proven reliability record in high-noise, high-voltage environments. The choice depends on the required speed, isolation strength, and cost targets.

6.2 Frequently Asked Questions (Based on Parameters)

Q: What is the maximum data rate I can achieve with this device?
A: The typical signal rate is 5 Megabaud. The maximum practical data rate is limited by the propagation delays and rise/fall times. For a non-return-to-zero (NRZ) signal, a conservative estimate for the maximum frequency is 1/(2 * t_PLH). Using the typical t_PLH of 100ns, this suggests a maximum frequency around 5 MHz, which aligns with the 5 Mbd rating. For reliable operation, design with the maximum specified delays (300ns).

Q: How do I use the three-state function of the EL2200?
A> Connect the Enable (E) pin to your system's control logic. Drive it high (>\u20092.0V) to place the output in a high-impedance state, effectively disconnecting it from the bus or line. Drive it low (<\u20090.8V) to enable the output, allowing it to actively drive High or Low based on the input LED state. Never leave the pin unconnected.

Q: The datasheet mentions "hysteresis." What does this mean for my design?
A: Input current hysteresis means the current required to turn the output ON (I_FT) is slightly higher than the current at which it turns OFF. This creates a noise margin. If your input signal has slow edges or noise superimposed on it, the hysteresis prevents the output from oscillating or chattering as the input passes through the switching threshold, ensuring a clean digital transition.

Q: Can I use this device to isolate analog signals?
A: No, the EL220X is specifically a logic gate photocoupler. Its output is a digital logic level (High/Low/Z), not a linear representation of the input LED current. For analog signal isolation, a linear optocoupler (with a phototransistor or photodiode output operating in its linear region) or an isolation amplifier should be used.

7. Operational Principle and Trends

7.1 Basic Operating Principle

The operation is based on optoelectronic conversion. An electrical current applied to the input side causes an Infrared Emitting Diode (IRED) to emit light. This light traverses an optically transparent isolation barrier within the package. On the output side, a silicon photodetector (typically a photodiode integrated with a signal conditioning IC) converts the received light back into an electrical current. This photocurrent is processed by a high-speed comparator or logic circuit with hysteresis to produce a clean, noise-immune digital output signal that replicates the input logic state. The key is that the signal is transmitted by light, providing the galvanic isolation between the two electrical circuits.

7.2 Industry Trends

Photocoupler technology continues to evolve. Trends relevant to devices like the EL220X include:

• Higher Speed: Demand for faster data isolation in industrial Ethernet, servo drives, and renewable energy systems pushes for photocouplers with rates beyond 10 Mbd and even into the 25-50 Mbd range.
• Lower Power Consumption: Reducing I_F and I_CC is a constant goal to meet the needs of portable and energy-efficient equipment.
• Enhanced Integration: Combining multiple isolated channels in a single package (dual, quad) or integrating additional functions like fail-safe outputs or I2C isolation is becoming more common.
• Package Miniaturization: The move towards smaller, surface-mount packages like SOIC-8 and even smaller footprints to save board space in compact designs.
• Improved Reliability and Longevity: Focus on extending the operational lifetime, especially the LED's longevity, under high-temperature and continuous operation conditions.

The EL220X series, with its balanced set of speed, low input current, and robust isolation, occupies a well-established position in this evolving landscape, serving applications where its specific performance envelope is optimal.