ELD3H7 ELQ3H7 Optocoupler Datasheet - 8-pin/16-pin SSOP Package - Isolation Voltage 3750Vrms - Current Transfer Ratio 50-600% - Technical Documentation

1. Product Overview

ELD3H7 and ELQ3H7 are phototransistor-based optocouplers designed for electrical signal isolation. They consist of an infrared light-emitting diode optically coupled to a silicon phototransistor, all housed in a compact surface-mount package. Their primary function is to transfer electrical signals between two circuits while maintaining high electrical isolation to prevent the propagation of noise, ground loops, and voltage spikes.

The ELD3H7 integrates 2 independent isolation channels within an 8-pin SSOP (Shrink Small Outline Package). The ELQ3H7 integrates 4 independent channels within a 16-pin SSOP. Both models feature an ultra-thin profile of 2.0 mm, making them ideal for space-constrained applications. The devices use halogen-free, green molding compound and comply with lead-free and RoHS directives.

2. Key Features and Core Advantages

• High Isolation Voltage:Rated value is 3750 V_rms(for 1 minute), ensuring reliable protection and safety in high-voltage environments.
• Wide current transfer ratio:At I_F= 5mA, V_CEUnder 5V conditions, the range from 50% to 600% provides design flexibility for different signal amplification requirements.
• Compact Form Factor:The SSOP package with a profile height of 2.0 mm is an ideal choice for high-density PCB designs.
• Comprehensive Safety Certifications:Obtained UL (E214129), VDE (40028116), SEMKO, NEMKO, DEMKO, FIMKO, and CQC certifications, facilitating use in regulated equipment worldwide.
• Fast Switching Characteristics:Under specified test conditions, typical rise time (t_r) is 5 µs, and the fall time (t_f) is 3 µs, suitable for digital signal transmission.

3. Target Market and Applications

These optocouplers are specifically designed for applications requiring reliable signal isolation and noise immunity.

• DC-DC converter:Provides feedback loop isolation in switching power supplies.
• Programmable Logic Controllers and Industrial Automation:Isolate digital I/O signals between the controller and field devices.
• Telecommunications Equipment:Isolate signal lines in modems, interfaces, and network hardware.
• General Circuit Isolation:Transmitting signals between circuits with different ground potentials or impedance levels.

4. In-depth Technical Parameter Analysis

4.1 Absolute Maximum Ratings

These are the stress limits that must not be exceeded under any conditions to prevent permanent damage to the device.

• Input (LED side):Forward current (I_F) 60 mA; Peak forward current (I_FP) 1 A (continuous 1 µs pulse); reverse voltage (V_R) 6 V; power dissipation (P_D) 70 mW.
• Output (transistor side):Collector current (I_C) 50 mA; Collector-emitter voltage (V_CEO) 80 V; Emitter-collector voltage (V_ECO)7 V; Power Consumption (P_C)150 mW.
• Overall Device:Total Power Consumption (P_TOT) 200 mW; Isolation Voltage (V_ISO)3750 V_rms.
• Temperature:Operating range -55°C to +110°C; storage range -55°C to +125°C; soldering temperature 260°C (for 10 seconds).

4.2 Electrical and Optical Characteristics

Typical performance parameters measured at 25°C.

4.2.1 Input (Infrared LED) Characteristics

• Forward Voltage (V_F):Typical value 1.2V, at I_FMaximum 1.4V at =20mA. This parameter is crucial for designing LED drive circuits.
• Reverse current (I_R):At V_RMaximum 10 µA at =4V, indicating the diode has good reverse blocking characteristics.
• Input capacitance (C_in):Typical value 30 pF, affecting high-frequency switching performance.

4.2.2 Output (Phototransistor) Characteristics

• Dark current (I_CEO):At V_CE=20V, I_F=0mA max 100 nA. This is the leakage current when the LED is off, affecting signal integrity in the off state.
• Breakdown voltage: BV_CEO≥ 80V, BV_ECO≥ 7V, defines the maximum allowable voltage across the transistor.
• Collector-emitter saturation voltage (V_CE(sat)):Typical value 0.1V, at I_F=10mA, I_C=1mA maximum 0.2V. For logic level output, lower V_CE(sat)It is ideal.

4.2.3 Transfer Characteristics

• Current Transfer Ratio:Defined as (I_C/ I_F) * 100%. At I_F=5mA, V_CEUnder the condition of =5V, the specified range is from 50% to 600%. This broad grading allows for selection based on the required gain.
• Isolation resistor (R_IO):Minimum of 5×10 at 500V DC¹⁰Ω, ensuring excellent DC isolation.
• Isolation capacitance (C_IO):Typical 0.3 pF, maximum 1.0 pF. Low capacitance minimizes capacitive coupling of high-frequency noise across the isolation barrier.
• Switching time:Under test conditions (V_r=2V, I_f=2mA, R_CE=100Ω), rise time (t_C) typical value 5 µs, fall time (t_L) typical value 3 µs. These values determine the maximum usable data rate.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Outline Drawing

The device is offered in an SSOP package. The ELD3H7 (2-channel) uses an 8-pin SSOP, while the ELQ3H7 (4-channel) uses a 16-pin SSOP. Both share a common low-profile height of 2.0 mm. The datasheet provides a detailed dimension drawing, including all key dimensions (body size, lead pitch, standoff height), for PCB pad design.

5.2 Pin Configuration and Polarity

For ELD3H7 (8-pin):

• Pins 1, 3: Anodes for Channel 1 and Channel 2 LEDs, respectively.
• Pin 2, 4: Cathodes for Channel 1 and Channel 2 LEDs, respectively.
• Pin 5, 7: Emitters for Channel 1 and Channel 2 phototransistors, respectively.
• Pin 6, 8: Collectors for Channel 1 and Channel 2 phototransistors, respectively.

For ELQ3H7 (16-pin):

• Pins 1, 3, 5, 7: Anode of LED for Channels 1 to 4.
• Pin 2, 4, 6, 8: Cathodes for LEDs of channels 1 to 4.
• Pin 9, 11, 13, 15: Emitters for phototransistors of channels 1 to 4.
• Pin 10, 12, 14, 16: Collectors for phototransistors of channels 1 to 4.

5.3 Recommended PCB Pad Layout

The datasheet contains recommended land pattern designs for the 8-pin and 16-pin SSOP packages. Following these recommendations ensures reliable solder joint formation during reflow soldering and provides adequate mechanical stability.

5.4 Device Marking

The device is marked on the top side. The marking includes:

• "EL": Manufacturer identifier.
• "D3H7" or "Q3H7": Model numbers for 2-channel or 4-channel devices.
• "Y": A single-digit year code.
• "WW": A two-digit week code.
• "V": Alama ya hiari, inayoonyesha uthibitisho wa VDE.

6. Soldering and Assembly Guide

These devices are suitable for surface mount assembly using reflow soldering technology.

• Reflow soldering:The maximum allowable soldering temperature measured at the package body is 260°C for a duration not exceeding 10 seconds. The standard lead-free reflow profile (IPC/JEDEC J-STD-020) applies.
• Operation:Standard ESD (Electrostatic Discharge) precautions should be followed as the device contains static-sensitive semiconductors.
• Cleaning:Follow standard PCB cleaning procedures compatible with green epoxy molding compounds.
• Storage:Store in a dry environment with a temperature between -55°C and +125°C. It is recommended to use within 12 months after the date code for optimal solderability.

7. Packaging and Ordering Information

7.1 Model Naming Rules

Part numbers follow the format:EL[D3H7/Q3H7](Z)-V

• EL:Series prefix.
• D3H7 / Q3H7:Indicates a 2-channel or 4-channel device.
• (Z):Tape and reel packaging option. "TA" indicates tape and reel packaging; absence of this marking indicates tube packaging.
• V:Optional suffix, indicating VDE certification.

7.2 Packaging Specifications

• ELD3H7 (Tube):80 pieces per tube.
• ELD3H7 (Reel):1000 per reel.
• ELQ3H7 (Tube):40 per tube.
• ELQ3H7 (Tape & Reel):1000 per reel.

Reel specifications, including carrier tape width, pocket size, and reel diameter, are detailed for easy automatic placement machine setup.

8. Application Design Considerations

8.1 Typical Application Circuit

The most common application is digital signal isolation. A current-limiting resistor must be connected in series with the LED anode to set the required forward current (I_F). The formula for calculating its resistance is: R_limit= (V_{CC_input}- V_F) / I_F. On the output side, a pull-up resistor (R_L) is connected between the collector and the output side power supply voltage (V_{CC_output}) between, used to define the output logic level and limit the phototransistor collector current.

8.2 Design Essentials and Best Practices

• Current Transfer Ratio Selection:Select the appropriate Current Transfer Ratio (CTR) grade based on your drive current and required output current. A higher CTR allows for lower I_F, thereby reducing input power consumption.
• Speed vs. Current Trade-off:Switching speed (t_r, t_f) typically increases with I_Fincreasing and R_Ldecreasing, but this increases power consumption. Test circuit (I_Fpulse, V_CE=2V, I_C=2mA, R_L=100Ω) provides a reference for expected performance.
• Noise Immunity:High isolation resistance (R_IO) and low isolation capacitance (C_IO) are key to suppressing common-mode noise. Ensure proper PCB layout to avoid creepage and clearance issues that could affect the rated isolation voltage.
• Thermal considerations:Must not exceed the total power dissipation of the device (P_TOT= 200 mW). Total power dissipation is the sum of the input LED power (I_F*V_F) and the output transistor power (I_C*V_CE) sum.

9. Technical Comparison and Differentiation

Compared to standard DIP-4 or DIP-6 optocouplers, the ELD3H7/ELQ3H7 series offers significant advantages:

• Size Reduction:For 2-channel devices, the SSOP package occupies less than 25% of the board area of a standard DIP-8 package, achieving miniaturization.
• Multi-Channel Integration:2-channel and 4-channel options are provided in a single package, reducing component count and board space in multi-isolation applications.
• Profile Height:A height of 2.0 mm is crucial for ultra-thin designs.
• Performance:Despite its compact size, it maintains high isolation voltage and a wide current transfer ratio range, which is a key distinction from many miniaturized alternatives.

10. Frequently Asked Questions

10.1 What is the maximum data rate achievable with these optocouplers?

Based on typical rise/fall times of 5 µs and 3 µs, the maximum practical data rate for a clean digital signal is approximately 1/(t_r+t_f) ≈ 125 kHz. For reliable operation, a conservative design target of 50-100 kHz is recommended.

10.2 How do I select the correct Current Transfer Ratio grade for my application?

Idan ƙirarku tana buƙatar tabbatar da mafi ƙarancin ƙarfin lantarki na fitarwa (I_C) a ƙarƙashin takamaiman ƙarfin lantarki na shigarwa (I_F), lissafta mafi ƙarancin rabon watsa ƙarfin lantarki da ake buƙata: CTR_{min_req}= (I_C/ I_F) * 100%. Select a device whose minimum guaranteed current transfer ratio (e.g., 50%) meets or exceeds this value. Using a higher CTR rating provides greater design margin.

10.3 Can these devices be used to isolate analog signals?

Although primarily designed for digital isolation, they can also be used for low-frequency, low-precision analog applications (e.g., feedback in isolated power supplies). However, the current transfer ratio has a strong temperature dependence and a nonlinear relationship with I_F, making them unsuitable for precision analog signal transmission without extensive calibration or compensation circuitry. Dedicated linear optocouplers are more suitable for analog isolation.

10.4 What is the purpose of the isolation voltage rating, and how is it tested?

3750 V_rmsThe rated value (for 1 minute) is a safety specification indicating the dielectric strength of the insulation between the input and output sides. During testing, all pins on the LED side are shorted together, and all pins on the transistor side are also shorted together. A high AC voltage is applied between these two groups. This rating ensures protection against high-voltage transients that may occur in industrial or mains-connected equipment.

11. Practical Design Example

Scene:Isolate the 3.3V digital signal of the microcontroller to a 5V system.

• Input side: V_{CC_input}= 3.3V. Target I_F= 5 mA, to achieve good speed and current transfer ratio. Assuming V_F≈ 1.2V, then R_limit= (3.3V - 1.2V) / 0.005A = 420Ω. Use a standard 430Ω resistor.
• Output side: V_{CC_output}= 5V. Select R_LTo limit I_Cand set the logic level. For I_F=5mA, the current transfer ratio is 100%, so I_C≈ 5mA. When the transistor is on (saturated), V_CE≈ 0.1V, so the output is low (about 0.1V). When off, the output is pulled high to 5V. When on, R_LThe power consumption on it is (5V - 0.1V) * 5mA ≈ 24.5 mW, which is completely within the rated range. A standard 1 kΩ resistor will give I_C≈ (5V - 0.1V)/1kΩ = 4.9mA, which is also acceptable.
• Layout:Place the device close to the isolation barrier on the PCB. Maintain the recommended creepage and clearance distances between input and output copper traces (refer to safety standards such as IEC 60950-1), especially for high isolation voltage ratings.

12. Working Principle

An optocoupler works by converting an electrical signal into light, transmitting it across an electrically isolated gap, and then converting the light back into an electrical signal. In the ELD3H7/ELQ3H7:

1. Current (I_F) flows through the infrared LED, causing it to emit photons.
2. These photons pass through the transparent insulating medium (molding compound) and strike the base region of the silicon phototransistor.
3. The photon energy generates electron-hole pairs in the base region, effectively creating a base current that turns the transistor on.
4. The transistor conducts collector current (I_C), the current is proportional to the received light intensity, and therefore also to the input I_Fis proportional. The proportionality constant is the current transfer ratio.

The key point is that the only connection between input and output is optical, thereby providing electrical isolation.

13. Industry Trends and Development

The development trend of optocoupler technology is driven by the demand for higher speed, smaller size, lower power consumption, and integration of more functions. While traditional phototransistor couplers like ELD3H7/ELQ3H7 excel in cost-effectiveness, robustness, and high isolation voltage, new technologies are continuously emerging:

• High-Speed Digital Couplers:Utilizing CMOS technology and integrated LEDs to achieve data rates of tens or hundreds of Mbps, far exceeding those of phototransistor-based devices.
• Integrated Isolation Function:Devices that combine isolation with functions such as isolated gate drivers, isolated ADCs, or isolated power supplies.
• Enhanced Safety and Reliability:Ongoing development focuses on improving the durability and surge immunity of isolation materials, as well as achieving higher working voltage ratings in smaller packages to meet evolving international safety standards.

Phototransistor couplers remain a fundamental and widely used solution for cost-sensitive, general-purpose isolation applications where moderate speed and high reliability are crucial.