SIR234 3mm Infrared LED Datasheet - 3.0mm Diameter - 1.6V Forward Voltage - 875nm Wavelength - 150mW Power Dissipation - English Technical Document

1. Product Overview

The SIR234 is a high-intensity infrared emitting diode housed in a 3mm (T-1) blue transparent plastic package. It is designed for applications requiring reliable infrared emission with good spectral matching to silicon photodetectors, phototransistors, and infrared receiver modules. The device features a low forward voltage and is constructed using lead-free, RoHS-compliant, halogen-free materials, also complying with EU REACH regulations.

1.1 Core Advantages

• High reliability and long operational life.
• Compact form factor with standard 2.54mm lead spacing for easy PCB integration.
• Low forward voltage, contributing to energy-efficient operation.
• Excellent spectral match with common silicon-based photodetectors, optimizing signal reception.
• Environmentally friendly construction (Pb-Free, Halogen-Free, RoHS, REACH compliant).

1.2 Target Market & Applications

This infrared LED is suitable for a variety of optoelectronic systems. Primary applications include free-air transmission systems for remote controls, optoelectronic switches for object detection and counting, smoke detectors, various infrared-based sensing systems, and integration into legacy storage devices like floppy disk drives.

2. Technical Parameters Deep Dive

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 +85°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

Measured at an ambient temperature (T_a) of 25°C, these parameters define the device's performance under normal operating conditions.

• Radiant Intensity (E_e):
  • At I_F = 20mA: Typical 9.3 mW/sr (Minimum 5.6 mW/sr).
  • At I_F = 100mA (pulsed): Typical 35 mW/sr.
  • At I_F = 1A (pulsed): Typical 350 mW/sr.
• 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):
  • At I_F = 20mA: 1.3V (Min), 1.6V (Typ).
  • At I_F = 100mA (pulsed): 1.4V (Typ), 1.8V (Max).
  • At I_F = 1A (pulsed): 2.6V (Typ), 4.0V (Max).
• Reverse Current (I_R): ≤ 10 μA at V_R = 5V.
• View Angle (2θ_1/2): 30 degrees (typical).

3. Binning System Explanation

The SIR234 is available in different performance grades or \"bins\" based on its radiant intensity. This allows designers to select a device that meets specific output requirements for their application.

Measurement Condition: I_F = 20mA, T_a = 25°C.

4. Performance Curve Analysis

4.1 Forward Current vs. Ambient Temperature

The derating curve shows how the maximum allowable continuous forward current decreases as the ambient temperature increases above 25°C to prevent exceeding the power dissipation limit.

4.2 Spectral Distribution

The spectral output graph confirms the peak emission at 875nm with a typical bandwidth of 80nm, ensuring compatibility with silicon photodetectors which have peak sensitivity in the near-infrared region.

4.3 Forward Current vs. Forward Voltage (I-V Curve)

This curve illustrates the non-linear relationship between current and voltage. The low typical V_F of 1.6V at 20mA indicates efficient operation, but the voltage increases significantly under high pulsed currents (e.g., 1A).

4.4 Relative Radiant Intensity vs. Angular Displacement

This plot defines the spatial emission pattern, showing the 30-degree half-angle where the intensity drops to 50% of its peak value. This is crucial for designing optical coupling and alignment.

4.5 Temperature Dependence of Wavelength and Intensity

Curves demonstrate that the peak wavelength shifts slightly, and the radiant intensity typically decreases as the junction temperature rises, important for thermal management in precision applications.

5. Mechanical & Package Information

5.1 Package Dimensions

The SIR234 uses a standard T-1 (3mm diameter) round package. Key dimensions include a body diameter of 3.0mm, a typical lead spacing of 2.54mm (0.1 inches), and an overall length. All dimensional tolerances are ±0.25mm unless otherwise specified. The cathode is typically identified by a flat spot on the package rim and/or a shorter lead.

6. Soldering & Assembly Guidelines

• Hand Soldering: Use a temperature-controlled iron. Limit soldering time per lead to a maximum of 3 seconds at a temperature not exceeding 350°C.
• Wave/Reflow Soldering: The device can withstand a peak soldering temperature of 260°C for a maximum of 5 seconds, as per the absolute maximum ratings.
• Cleaning: Use appropriate solvents that are compatible with the blue transparent plastic epoxy.
• Storage Conditions: Store in a dry, anti-static environment within the specified temperature range of -40°C to +85°C. Avoid exposure to excessive moisture.

7. Packaging & Ordering Information

7.1 Packing Specification

Units are typically packaged in bags: 200 to 1000 pieces per bag. Five bags are packed into one box, and ten boxes are packed into one master carton.

7.2 Label Information

The product label includes key identifiers: Customer Part Number (CPN), Manufacturer Part Number (P/N), Packing Quantity (QTY), Performance Rank (CAT), Peak Wavelength (HUE), and Lot Number (LOT No).

8. Application Design Suggestions

8.1 Typical Application Circuits

For continuous operation, a simple series current-limiting resistor is required. The resistor value is calculated as R = (V_supply - V_F) / I_F. For pulsed operation to achieve higher peak intensity, ensure the driver circuit can provide the necessary current pulse within the specified width and duty cycle limits (≤100μs, ≤1%).

8.2 Design Considerations

• Current Driving: Never exceed the absolute maximum continuous or pulsed current ratings. Use a stable current source or a well-calculated series resistor for reliable operation.
• Heat Sinking: While the package is small, for continuous operation at high currents or in elevated ambient temperatures, consider PCB layout techniques (thermal relief pads, copper pours) to aid heat dissipation and maintain performance.
• Optical Design: The 30-degree viewing angle and 875nm wavelength should be matched with the field of view and spectral sensitivity of the receiving sensor (photodiode, phototransistor, or IR receiver IC) for optimal signal-to-noise ratio.
• Reverse Polarity Protection A reverse voltage exceeding 5V can damage the LED. Incorporate protection if the supply polarity could be reversed.

9. Technical Comparison & Differentiation

The SIR234 differentiates itself through its combination of a standard 3mm package, relatively high radiant intensity (up to 24 mW/sr in the P bin), and a low forward voltage. Compared to some older or generic IR LEDs, its guaranteed specifications for pulsed operation (1A peak) and explicit compliance with modern environmental standards (RoHS, Halogen-Free, REACH) make it suitable for contemporary design requirements.

10. Frequently Asked Questions (FAQs)

10.1 What is the purpose of the blue transparent package?

The blue plastic acts as a short-wavelength pass filter, blocking visible light from outside (which could cause noise in the detector) while allowing the 875nm infrared light from the chip to pass through efficiently. It also provides mechanical and environmental protection.

10.2 Can I drive this LED directly from a 5V microcontroller pin?

No. A microcontroller GPIO pin typically cannot source 20mA continuously without risk, and it certainly cannot provide 100mA or 1A pulses. You must use an external driver circuit, such as a transistor (BJT or MOSFET) controlled by the MCU pin, to switch the higher current required by the LED.

10.3 How do I select the correct bin (L, M, N, P)?

Choose based on the required radiant intensity for your application's link budget (distance, detector sensitivity). For longer distances or lower-sensitivity detectors, a higher bin (N or P) is preferable. For short-range applications, a lower bin (L or M) may be sufficient and cost-effective.

10.4 Why is the forward voltage higher at 1A pulse compared to 20mA?

This is due to the internal series resistance of the semiconductor chip and bond wires. As current increases, the voltage drop across this resistance (V = I * R) increases significantly, leading to a higher total forward voltage.

11. Practical Use Case Example

Scenario: Object Detection in a Vending Machine. An SIR234 LED and a matching phototransistor are placed on opposite sides of a product chute. The LED is driven with a 20mA continuous current (Bin M selected for consistent output). When no object is present, the phototransistor receives the IR beam and conducts. When a product falls through the chute, it interrupts the beam, causing the phototransistor's output to change state. This signal is fed to the machine's controller to confirm product dispensing. The 30-degree beam ensures reliable detection even with slight mechanical misalignment over time.

12. Principle of Operation

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction diode. When forward biased (positive voltage applied to the anode relative to the cathode), electrons from the n-region and holes from the p-region are injected into the junction region. When these charge carriers recombine, they release energy. In this specific device, made from Gallium Aluminum Arsenide (GaAlAs), this energy is released primarily as photons of infrared light with a peak wavelength of 875 nanometers, which is invisible to the human eye but detectable by silicon-based sensors.

13. Industry Trends

The trend in infrared emitters for sensing continues toward higher efficiency, lower power consumption, and increased integration. This includes devices with built-in drivers, modulated output for noise immunity, and surface-mount packages (SMD) for automated assembly. While through-hole components like the 3mm T-1 package remain vital for prototyping, repairs, and certain industrial applications, new designs increasingly favor SMD variants for their smaller footprint and suitability for high-volume manufacturing. The emphasis on environmental compliance (RoHS, halogen-free) is now a standard requirement across the electronics industry.