SIR204C 3mm Infrared LED Datasheet - 3.0mm Diameter - 1.3V Forward Voltage - 875nm Wavelength - 150mW Power Dissipation - English Technical Document

1. Product Overview

The SIR204C is a high-intensity infrared emitting diode housed in a 3mm (T-1) water-clear transparent plastic package. It is designed for applications requiring reliable infrared emission with good spectral matching to silicon-based photodetectors. The device utilizes a GaAlAs chip to produce light at a peak wavelength of 875nm, making it ideal for various sensing and transmission systems.

1.1 Core Advantages and Target Market

This LED offers several key advantages including high reliability, low forward voltage, and a compact form factor with standard 2.54mm lead spacing. It is spectrally matched with common phototransistors, photodiodes, and infrared receiver modules. The product is compliant with RoHS, EU REACH, and halogen-free standards (Br < 900ppm, Cl < 900ppm, Br+Cl < 1500ppm). Its primary target markets include consumer electronics, industrial automation, and safety equipment requiring infrared signaling or sensing.

2. In-Depth Technical Parameter Analysis

The following sections provide a detailed breakdown of the device's electrical, optical, and thermal specifications.

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation under these conditions is not guaranteed.

• Continuous Forward Current (I_F): 100 mA
• Peak Forward Current (I_FP): 1.0 A (Pulse Width ≤ 100μs, Duty Cycle ≤ 1%)
• Reverse Voltage (V_R): 5 V
• Operating Temperature (T_opr): -40°C to +85°C
• Storage Temperature (T_stg): -40°C to +100°C
• Soldering Temperature (T_sol): 260°C (for ≤ 5 seconds)
• Power Dissipation (P_d): 150 mW (at or below 25°C ambient temperature)

2.2 Electro-Optical Characteristics

These parameters are measured at an ambient temperature (T_a) of 25°C and define the typical performance of the device.

• Radiant Intensity (I_e): 4.0 mW/sr (Min) to 6.4 mW/sr (Typ) at I_F=20mA. Under pulsed conditions (I_F=100mA, 1% duty), it can reach 30 mW/sr, and up to 300 mW/sr at I_F=1A.
• Peak Wavelength (λ_p): 875 nm (Typical) at I_F=20mA.
• Spectral Bandwidth (Δλ): 80 nm (Typical) at I_F=20mA.
• Forward Voltage (V_F): 1.3V (Typ) to 1.6V (Max) at I_F=20mA. This increases under higher current pulsed operation.
• Reverse Current (I_R): Maximum of 10 μA at V_R=5V.
• View Angle (2θ_1/2): 30 degrees (Typical) at I_F=20mA.

Note: Measurement uncertainties are ±0.1V for V_F, ±10% for I_e, and ±1.0nm for λ_p.

3. Performance Curve Analysis

The datasheet includes several characteristic curves that illustrate device behavior under varying conditions.

3.1 Forward Current vs. Ambient Temperature

This curve shows the relationship between the maximum allowable continuous forward current and the ambient operating temperature. As temperature increases, the maximum permissible current decreases linearly to prevent exceeding the power dissipation limit and ensure long-term reliability.

3.2 Spectral Distribution

The spectral output graph confirms the peak emission at 875nm with a typical bandwidth of 80nm. This wide bandwidth ensures good compatibility with silicon detectors, which have broad spectral sensitivity in the near-infrared region.

3.3 Peak Emission Wavelength vs. Ambient Temperature

The peak wavelength exhibits a slight shift with temperature, a common characteristic of semiconductor LEDs. Designers must account for this shift in wavelength-critical applications, especially over the full operating temperature range of -40°C to +85°C.

3.4 Forward Current vs. Forward Voltage

This IV curve demonstrates the exponential relationship between current and voltage. The typical forward voltage is low (1.3V at 20mA), contributing to energy-efficient operation. The curve is essential for designing appropriate current-limiting circuitry.

3.5 Radiant Intensity vs. Forward Current

The radiant intensity increases with forward current but exhibits a sub-linear relationship at higher currents due to thermal and efficiency effects. The graph helps determine the optimal drive current for a required output intensity.

3.6 Relative Radiant Intensity vs. Angular Displacement

This polar plot defines the spatial emission pattern, characterized by a 30-degree half-angle. The intensity is highest at 0° (on-axis) and decreases according to a cosine-like function, which is important for optical system design to ensure proper alignment and signal strength.

4. Mechanical and Packaging Information

4.1 Package Dimensions

The SIR204C uses a standard T-1 (3mm) round package. Key dimensions include a body diameter of 3.0mm, a typical lead spacing of 2.54mm, and an overall length. All dimensional tolerances are ±0.25mm unless otherwise specified. The lens is water-clear, allowing the full infrared spectrum to pass through without significant absorption.

4.2 Polarity Identification

The LED has a flat side on the rim of the plastic lens, which typically indicates the cathode (negative) lead. The longer lead is usually the anode (positive). Correct polarity must be observed during circuit assembly to prevent reverse bias damage.

5. Soldering and Assembly Guidelines

Hand soldering or wave soldering can be used. The absolute maximum soldering temperature is 260°C, and the soldering time must not exceed 5 seconds. It is recommended to keep the LED body at least 1.5mm above the PCB surface during wave soldering to minimize thermal stress on the epoxy package. The device should be stored in a dry, anti-static environment at temperatures between -40°C and +100°C.

6. Packaging and Ordering Information

6.1 Packing Quantity Specification

The LEDs are typically packed in bags and boxes: 200-1000 pieces per bag, 5 bags per box, and 10 boxes per carton.

6.2 Label Form Specification

Product labels include key identifiers: Customer's Production Number (CPN), Production Number (P/N), Packing Quantity (QTY), Ranks (CAT), Peak Wavelength (HUE), Reference (REF), and Lot Number (LOT No).

7. Application Suggestions

7.1 Typical Application Scenarios

• Free Air Transmission Systems: Remote controls, short-range data links.
• Optoelectronic Switches: Object detection, position sensing, slot sensors.
• Smoke Detectors: Used in obscuration-type smoke detection chambers.
• General Infrared Systems: Night vision illuminators, security systems.
• Floppy Disk Drives: Historical use for track-zero detection.

7.2 Design Considerations

• Current Limiting: Always use a series resistor or constant current driver to limit I_F to the desired value, typically between 20mA and 100mA for continuous operation.
• Heat Management: While the power dissipation is low, ensure adequate PCB copper area or heatsinking if operating near maximum ratings or at high ambient temperatures.
• Optical Design: Consider the 30-degree viewing angle when designing lenses, reflectors, or apertures to collect or collimate the emitted light effectively.
• Reverse Voltage Protection: The low reverse voltage rating (5V) makes the device susceptible to damage from static discharge or incorrect polarity. Consider adding a parallel protection diode in circuits where reverse voltage transients are possible.

8. Technical Comparison and Differentiation

The SIR204C differentiates itself through its combination of a standard 3mm package, relatively high radiant intensity (up to 6.4 mW/sr at 20mA), and low forward voltage. Compared to some older infrared LEDs, it offers better reliability and compliance with modern environmental regulations (RoHS, Halogen-Free). Its spectral match to silicon detectors is a key advantage over LEDs with different peak wavelengths, maximizing system sensitivity.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between continuous and peak forward current?

The continuous forward current (100mA) is the maximum DC current that can be applied indefinitely without risk of damage. The peak forward current (1A) is a much higher current that can only be applied for very short pulses (≤100μs) at a very low duty cycle (≤1%). This allows for brief, high-intensity bursts of light for long-range sensing or synchronization purposes.

9.2 How does ambient temperature affect performance?

As shown in the characteristic curves, increasing temperature reduces the maximum allowable continuous current and can cause a slight shift in the peak wavelength. Radiant intensity may also decrease at higher temperatures. Designs intended for operation at the extremes of the -40°C to +85°C range should derate operating currents accordingly.

9.3 Is a heatsink required?

For most applications operating at or below 50mA continuous current, a dedicated heatsink is not necessary if the PCB provides some copper area for heat spreading. For operation at 100mA continuous current, especially in elevated ambient temperatures, careful thermal design is recommended to keep the junction temperature within safe limits.

10. Practical Design and Usage Case

Case: Object Proximity Sensor
In a typical optoelectronic switch, the SIR204C is paired with a phototransistor. The LED is driven with a 20-50mA current, often modulated at a specific frequency (e.g., 38kHz) to reject ambient light interference. The emitted infrared light reflects off a nearby object and is detected by the phototransistor. The 30-degree viewing angle of the LED provides a good balance between detection range and field of view. The low forward voltage allows the sensor to be powered efficiently from a 3.3V or 5V logic supply with a simple current-limiting resistor. Designers must ensure mechanical alignment of the LED and detector and may use a barrier to prevent direct optical crosstalk.

11. Principle of Operation

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction diode. When forward biased, electrons from the n-region and holes from the p-region are injected into the active region. When these charge carriers recombine, energy is released in the form of photons. The wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material (Gallium Aluminum Arsenide - GaAlAs in this case), which is engineered to produce photons in the near-infrared spectrum around 875nm. This wavelength is invisible to the human eye but is efficiently detected by silicon-based sensors.

12. Industry Trends and Developments

The trend in infrared LEDs continues toward higher efficiency (more radiant output per electrical watt), higher power densities for longer-range applications like LiDAR and surveillance, and smaller package sizes for integration into compact consumer devices. There is also a focus on improving modulation speed for high-speed data communication (e.g., IrDA, Li-Fi). Multi-wavelength and dual-emitter packages are becoming more common for advanced sensing applications. Environmental compliance (RoHS, REACH, Halogen-Free) is now a standard requirement across the industry. The SIR204C represents a reliable, mature technology well-suited for cost-sensitive, high-volume applications requiring proven performance.