3mm Infrared LED HIR234C Datasheet - T-1 Package - Peak Wavelength 850nm - Forward Voltage 1.65V - English Technical Document

1. Product Overview

The HIR234C is a high-intensity infrared emitting diode housed in a standard 3mm (T-1) water-clear plastic package. It is designed to emit light at a peak wavelength of 850nm, making it spectrally compatible with common silicon phototransistors, photodiodes, and infrared receiver modules. This device is engineered for applications requiring reliable and efficient infrared transmission.

1.1 Core Advantages

• High Radiant Intensity: Delivers strong optical output, suitable for long-range or low-sensitivity receiver systems.
• High Reliability: Built for consistent performance and long operational life.
• Low Forward Voltage: Typically 1.65V at 20mA, contributing to lower power consumption in designs.
• Environmental Compliance: The product adheres to RoHS, EU REACH, and halogen-free standards (Br < 900ppm, Cl < 900ppm, Br+Cl < 1500ppm).
• Standard Package: The familiar T-1 (3mm) form factor with 2.54mm lead spacing ensures easy integration into existing designs and PCB layouts.

1.2 Target Applications

This infrared LED is suitable for a variety of systems requiring non-visible light communication or sensing.

• Infrared remote control units, especially those with higher power requirements.
• Free-space optical data transmission links.
• Smoke detection systems.
• General-purpose infrared applied systems, including proximity sensors and object counters.

2. Technical Parameter Analysis

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
• Power Dissipation (P_d): 150 mW (at or below 25°C ambient)
• Soldering Temperature (T_sol): 260°C for ≤ 5 seconds

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):
  • 7.8 mW/sr (Min) / 15 mW/sr (Typ) at I_F = 20mA (DC).
  • 50 mW/sr (Typ) at I_F = 100mA (pulsed).
  • 300 mW/sr (Typ) at I_F = 1A (pulsed).
• Peak Wavelength (λ_p): 850 nm (Typical) at I_F = 20mA.
• Spectral Bandwidth (Δλ): 45 nm (Typical) at I_F = 20mA.
• Forward Voltage (V_F):
  • 1.45V (Min) / 1.65V (Typ) / 1.65V (Max) at I_F = 20mA.
  • 1.80V (Typ) / 2.40V (Max) at I_F = 100mA (pulsed).
  • 4.10V (Typ) / 5.25V (Max) at I_F = 1A (pulsed).
• Reverse Current (I_R): 10 μA (Max) at V_R = 5V.
• Viewing Angle (2θ_1/2): 30 degrees (Typical) at I_F = 20mA.

Measurement Tolerances: Forward Voltage ±0.1V, Radiant Intensity ±10%, Peak Wavelength ±1.0nm.

3. Performance Curve Analysis

The datasheet provides several characteristic curves that are crucial for understanding device behavior under different operating conditions.

3.1 Thermal and Current Dependencies

Forward Current vs. Ambient Temperature (Fig.1): This curve shows the derating of the maximum allowable forward current as ambient temperature increases. To ensure reliability and stay within the power dissipation limit, the drive current must be reduced at higher temperatures.

Peak Emission Wavelength vs. Ambient Temperature (Fig.3): The peak wavelength of an LED has a temperature coefficient, typically shifting slightly with temperature. This curve quantifies that shift for the HIR234C, which is important for applications where precise spectral matching is critical.

Forward Current vs. Forward Voltage (Fig.4): This is the fundamental I-V curve of the diode. It shows the exponential relationship between current and voltage. The curve helps in designing the current-limiting circuitry and understanding the voltage drop across the LED under different drive conditions.

3.2 Optical Output Characteristics

Spectral Distribution (Fig.2): This graph plots the relative radiant intensity against wavelength. It visually confirms the 850nm peak and the approximately 45nm spectral bandwidth, showing the range of wavelengths emitted.

Radiant Intensity vs. Forward Current (Fig.5): This curve demonstrates the relationship between optical output power (in mW/sr) and the electrical input current. It is generally linear in the mid-range but may saturate at very high currents due to thermal and efficiency effects.

Relative Radiant Intensity vs. Angular Displacement (Fig.6): This polar plot defines the radiation pattern of the LED. It shows how the intensity drops off as you move away from the central axis (0°), ultimately defining the 30-degree viewing angle where intensity falls to half its peak value.

Radiant Intensity vs. Ambient Temperature (Fig.7): Optical output decreases as junction temperature rises. This curve quantifies the typical reduction in radiant intensity as the ambient (and consequently junction) temperature increases, which is vital for designing systems that operate over a wide temperature range.

Relative Forward Voltage vs. Ambient Temperature (Fig.8): The forward voltage of a diode has a negative temperature coefficient. This curve shows how V_F typically decreases as temperature increases, which can be a factor in constant-voltage drive schemes or for using the LED as a temperature sensor.

4. Mechanical and Packaging Information

4.1 Device Selection and Construction

• Chip Material: GaAlAs (Gallium Aluminum Arsenide).
• Lens/Color: Water-clear plastic.

4.2 Package Dimensions (T-1, 3mm)

The device conforms to the standard T-1 (3mm) round LED package dimensions. Key mechanical notes from the datasheet include:

• All dimensions are in millimeters (mm).
• Standard dimensional tolerances are ±0.25mm unless otherwise specified.
• The drawing typically shows the body diameter (3.0mm), lead spacing (2.54mm), and overall dimensions including the lens shape and lead length/diameter.

Polarity Identification: The cathode is typically identified by a flat spot on the plastic lens rim and/or a shorter lead. Always refer to the package drawing for definitive identification.

5. Soldering and 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 Soldering: Can be used, but preheating and exposure time should be controlled to minimize thermal stress on the plastic package.
• 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. This is compatible with standard lead-free (Pb-free) reflow profiles (e.g., IPC/JEDEC J-STD-020).
• General Precautions:
  • Avoid applying mechanical stress to the leads or lens during handling.
  • Do not exceed the specified storage temperature range.
  • Use proper ESD (Electrostatic Discharge) precautions during handling and assembly.

6. Packaging and Ordering Information

6.1 Packing Specification

• Standard packing: 200 to 1000 pieces per bag.
• 5 bags are packed into 1 box.
• 10 boxes are packed into 1 carton.

6.2 Label Information

The product label includes key identifiers for traceability and verification:

• CPN: Customer's Part Number
• P/N: Production Number (HIR234C)
• QTY: Quantity in the package
• CAT: Ranks/Categories (e.g., brightness bin)
• HUE: Peak Wavelength information
• REF: Reference
• LOT No: Manufacturing Lot Number for traceability

7. Application Design Considerations

7.1 Driving the LED

Constant Current Drive: LEDs are current-driven devices. For stable and predictable optical output, use a constant current source or a current-limiting resistor in series with a voltage source. The resistor value can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Always use the maximum V_F from the datasheet for a conservative design.

Pulsed Operation: For applications requiring very high instantaneous intensity (like long-range remote controls), the LED can be driven with short, high-current pulses (up to 1A) as specified. This must be done with strict adherence to the pulse width (≤100μs) and duty cycle (≤1%) limits to prevent overheating.

7.2 Optical Design

Lens Selection: The water-clear lens emits a 30-degree beam. For narrower or differently shaped beams, secondary optics (plastic lenses, reflectors) can be used.

Receiver Matching: The 850nm peak wavelength is optimally detected by silicon-based sensors. Ensure the selected phototransistor, photodiode, or IR receiver module has peak sensitivity in the 800-900nm range.

Ambient Light Immunity: In environments with strong ambient light (especially sunlight containing IR), consider modulating the LED drive signal at a specific frequency and using a receiver tuned to that frequency to reject background noise.

8. Technical Comparison and Positioning

The HIR234C positions itself as a general-purpose, high-reliability infrared emitter in the ubiquitous 3mm package.

• vs. Standard 5mm IR LEDs: The 3mm package offers a smaller footprint, which can be advantageous in miniaturized designs, while still providing substantial radiant intensity.
• vs. SMD IR LEDs: The through-hole T-1 package is often preferred for prototyping, hand assembly, or applications where higher mechanical robustness or easier heat sinking via leads is desired compared to surface-mount devices.
• Key Differentiator: Its combination of high pulsed radiant intensity (300 mW/sr) and standard package makes it suitable for applications needing strong bursts of IR light from a commonly available form factor.

9. Frequently Asked Questions (FAQ)

Q1: What is the difference between radiant intensity (mW/sr) and power output (mW)?
A1: Radiant intensity measures optical power per solid angle (steradian). It indicates how concentrated the beam is. Total radiant flux (mW) would require integrating intensity over the entire emission pattern. For a 30-degree LED, the total power is significantly lower than the peak intensity value.

Q2: Can I drive this LED continuously at 100mA?
A2: The Absolute Maximum Rating for continuous forward current is 100mA. However, continuous operation at this maximum current will generate significant heat, raising the junction temperature. For reliable long-term operation, it is advisable to operate at a lower current (e.g., 20-50mA) or implement adequate heat sinking, especially in high ambient temperatures.

Q3: Why is the forward voltage so much higher at 1A pulsed (5.25V max) compared to 20mA DC (1.65V max)?
A3: This is due to the series resistance within the LED chip and package. At very high currents, the voltage drop across this internal resistance becomes significant, leading to a higher total V_F. This is a common characteristic of all LEDs.

Q4: Is an 850nm LED visible?
A4: 850nm is in the near-infrared (NIR) spectrum. It is generally invisible to the human eye. However, some people may perceive a very faint deep red glow from high-power 850nm LEDs, as the emission spectrum has a small "tail" extending into the visible red region. For completely covert operation, 940nm LEDs are typically used.

10. Design and Usage Case Study

Case: Long-Range Infrared Remote Control Transmitter

Objective: Design a remote control that must operate reliably at a distance of 15 meters in a typical living room environment.

Design Choices:

1. LED Selection: The HIR234C is chosen for its high pulsed radiant intensity (300 mW/sr typ at 1A).
2. Drive Circuit: A simple transistor switch is used to pulse the LED from a 3V battery supply. A series resistor is calculated to limit the pulse current to approximately 800mA (safely below the 1A max), accounting for battery voltage drop and LED V_F at high current.
3. Signal Modulation: The drive pulses are encoded with a 38kHz carrier frequency, a common standard for IR remotes.
4. Optics: A simple plastic collimating lens is placed in front of the LED to narrow the beam from 30 degrees to about 10 degrees, concentrating more of the emitted energy towards the distant receiver.

Result: The combination of high-intensity pulsed drive and beam collimation ensures a strong, detectable signal reaches the IR receiver module at the target distance, even in the presence of moderate ambient IR noise.

11. Operating Principle

An Infrared Light Emitting Diode (IR LED) is a semiconductor p-n junction diode. When a forward voltage is applied, electrons from the n-region and holes from the p-region are injected into the junction region. When these charge carriers recombine, energy is released. In the case of the HIR234C's GaAlAs material, this energy corresponds to photons with a wavelength centered around 850 nanometers, which is in the infrared portion of the electromagnetic spectrum. The specific wavelength is determined by the bandgap energy of the semiconductor material. The water-clear epoxy package acts as a lens, shaping the emitted light into the specified viewing angle.

12. Technology Trends

Infrared LED technology continues to evolve alongside visible LED technology. General trends relevant to devices like the HIR234C include:

• Increased Efficiency: Ongoing material and epitaxial growth improvements lead to higher wall-plug efficiency (more light output per electrical watt input), reducing power consumption and heat generation.
• Higher Speed Modulation: Development of LEDs capable of faster switching is driven by applications in optical data communications (IrDA, Li-Fi) and advanced sensing like time-of-flight (ToF).
• Miniaturization: While through-hole packages remain popular, there is a strong market shift towards surface-mount device (SMD) packages (e.g., 0805, 0603, chip-scale) for automated assembly and space-constrained designs.
• Multi-Wavelength and VCSELs: For specialized sensing (e.g., gas analysis, biometrics), multi-wavelength IR sources are emerging. Vertical-Cavity Surface-Emitting Lasers (VCSELs) are also gaining traction in high-performance 3D sensing and structured light applications due to their precise beam characteristics.

The HIR234C represents a mature, reliable, and cost-effective solution within this evolving landscape, perfectly suited for its target applications in consumer electronics and industrial sensing.