IR Emitter LED LTE-306 Datasheet - Side-Looking Package - Peak Wavelength 940nm - Forward Voltage 1.6V - Viewing Angle 30 deg - English Technical Document

1. Product Overview

The LTE-306 is a miniature, side-looking infrared (IR) emitter designed for use in optoelectronic sensing and detection systems. Its core function is to emit infrared light at a peak wavelength of 940 nanometers (nm). This device is engineered to be mechanically and spectrally matched with corresponding phototransistors from the LTR-306 series, ensuring optimal performance in receiver-emitter pairs for applications like object detection, position sensing, and data transmission. The primary advantage of this component is its low-cost construction within a compact plastic package, combined with the availability of pre-selected bins for consistent radiant intensity output.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The device's operational limits are defined under an ambient temperature (T_A) of 25°C. Key ratings include a continuous forward current (I_F) of 50 mA and a peak forward current of 1 A for pulsed operation (300 pulses per second, 10 µs pulse width). The maximum power dissipation is 75 mW. The reverse voltage rating is 5 V, indicating the LED should not be subjected to reverse bias exceeding this value. The operating temperature range is from -40°C to +85°C, and the storage range is from -55°C to +100°C. Lead soldering temperature is specified at 260°C for 5 seconds when measured 1.6mm from the package body.

2.2 Electrical & Optical Characteristics

All characteristics are measured at T_A=25°C. The primary optical parameters are Aperture Radiant Incidence (E_e) and Radiant Intensity (I_E), both tested at a forward current of 20 mA. These parameters are grouped into bins (A through H), providing a range of minimum and typical/maximum values for selection based on application needs. For example, Bin A offers E_e from 0.088 to 0.168 mW/cm² and I_E from 0.662 to 1.263 mW/sr, while Bin H offers higher output. The peak emission wavelength (λ_Peak) is typically 940 nm with a spectral half-width (Δλ) of 50 nm. The forward voltage (V_F) is 1.6V typical at 20 mA. The reverse current (I_R) is 100 µA maximum at a reverse voltage of 5V. The viewing angle (2θ_1/2) is 30 degrees.

3. Binning System Explanation

The product utilizes a radiant intensity binning system. Devices are tested and sorted into groups (Bins A to H) based on their measured Radiant Intensity (I_E) and Aperture Radiant Incidence (E_e) at a standard 20 mA drive current. This allows designers to select components with guaranteed minimum light output levels, ensuring consistency in system performance, particularly important in applications where detection threshold or signal strength is critical. The bins provide a graduated scale of output power.

4. Performance Curve Analysis

The datasheet references several typical characteristic curves. Figure 1 shows the Spectral Distribution, illustrating the light output centered around 940 nm. Figure 2 depicts the relationship between Forward Current and Ambient Temperature, important for understanding derating. Figure 3 is the Forward Current vs. Forward Voltage (I-V) curve, showing the diode's turn-on characteristics. Figure 4 shows how Relative Radiant Intensity varies with Ambient Temperature, indicating a decrease in output as temperature rises. Figure 5 plots Relative Radiant Intensity against Forward Current, showing the non-linear relationship between drive current and light output. Figure 6 is the Radiation Diagram, a polar plot visualizing the 30-degree viewing angle and spatial distribution of the emitted infrared light.

5. Mechanical & Package Information

The device uses a miniature plastic side-looking package. The dimensions are provided in a drawing (referenced but not fully detailed in the text). Key notes specify that all dimensions are in millimeters, with a general tolerance of ±0.25mm unless stated otherwise. Lead spacing is measured at the point where leads exit the package. The side-looking orientation means the primary emission direction is perpendicular to the axis of the leads, which is a key differentiator from top-emitting LEDs.

6. Soldering & Assembly Guidelines

The primary guideline provided is for lead soldering: the temperature at a point 1.6mm (0.063 inches) from the package body must not exceed 260°C for a duration of 5 seconds. This is critical to prevent damage to the internal semiconductor die and the plastic package. For modern assembly, this implies careful control of wave soldering parameters or the use of selective soldering techniques. Hand soldering should be performed quickly with a temperature-controlled iron.

7. Application Recommendations

7.1 Typical Application Scenarios

The LTE-306 is ideal for applications requiring non-visible light emission for sensing. Common uses include object detection and counting (e.g., in vending machines, printers), position sensing (e.g., paper edge detection), slot sensors, and proximity switches. Its spectral matching to the LTR-306 phototransistor makes it perfect for constructing compact opto-interrupters or reflective object sensors.

7.2 Design Considerations

Designers must consider several factors: First, always use a current-limiting resistor in series with the LED when driving from a voltage source to prevent exceeding the maximum continuous forward current (50 mA). Second, select the appropriate intensity bin (A-H) based on the required sensing distance and the sensitivity of the paired detector. Third, account for the 30-degree viewing angle when aligning the emitter and detector in a system; misalignment will reduce signal strength. Fourth, consider the effects of ambient temperature on radiant output (as shown in Figure 4), especially in harsh environments. Fifth, ensure the reverse voltage across the LED never exceeds 5V, potentially requiring protection circuitry in some circuit configurations.

8. Technical Comparison

The key differentiating advantages of this component are its side-looking package and pre-binned intensity. Compared to standard top-emitting IR LEDs, the side-looking form factor allows for more flexible PCB layout and can enable slimmer product designs. The availability of multiple intensity bins provides a level of performance grading not always available in low-cost IR emitters, giving designers the ability to fine-tune system performance and potentially reduce costs by not over-specifying. The explicit mechanical and spectral matching to a specific phototransistor series simplifies the design of reliable optical pairs.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the binning system?

A: The binning (A-H) guarantees a minimum level of radiant intensity. This ensures consistency in production. You can choose a lower bin for less demanding/short-range applications or a higher bin for longer range or more reliable detection.

Q: Can I drive this LED with a 3.3V supply?

A: Yes, but you must use a series resistor. With a typical V_F of 1.6V at 20mA, the resistor value would be (3.3V - 1.6V) / 0.02A = 85 Ohms. Always calculate the resistor based on your desired current and actual supply voltage.

Q: Why is the viewing angle important?

A: The 30-degree viewing angle defines the cone within which most of the light is emitted. In a paired sensor system, both the emitter and detector have viewing angles. Their overlap defines the effective sensing zone. A narrower angle can allow for more precise detection.

Q: How does temperature affect performance?

A: As ambient temperature increases, the radiant intensity typically decreases (see Figure 4). The forward voltage also decreases slightly for a given current. In critical applications, temperature compensation in the driving or receiving circuit may be necessary.

10. Practical Use Case

Case: Designing a Paper Presence Sensor in a Printer. An LTE-306 IR emitter is paired with an LTR-306 phototransistor across the paper path to form a transmissive sensor. When paper is absent, light from the emitter reaches the detector. When paper is present, it blocks the light. The side-looking package allows both components to be mounted flat on the main PCB, with their optical axes aligned across the gap. The designer selects Bin D emitters to ensure sufficient signal strength reaches the detector after potential contamination (dust) over the product's lifetime. A microcontroller monitors the phototransistor's output to determine paper presence.

11. Operational Principle

An infrared emitter LED is a semiconductor diode. When forward biased (positive voltage applied to the anode relative to the cathode), electrons and holes recombine in the active region of the semiconductor material (typically based on gallium arsenide). This recombination process releases energy in the form of photons (light particles). The specific material composition and structure of the semiconductor determine the wavelength of the emitted light. For the LTE-306, this results in photons primarily in the infrared spectrum around 940 nm, which is invisible to the human eye but detectable by silicon photodetectors.

12. Technology Trends

The trend in such discrete optoelectronic components is towards further miniaturization, higher efficiency (more light output per unit of electrical input power), and increased integration. While discrete emitter-detector pairs remain common, there is a move towards integrated modules that include the LED, photodetector, and sometimes signal conditioning circuitry in a single package. This simplifies design and improves reliability. Additionally, there is ongoing development to achieve more precise and stable wavelength emission and tighter viewing angle control for specialized sensing applications. The demand for low-power components for battery-operated IoT devices also drives efficiency improvements.