LTE-C9901 Infrared Emitter Datasheet - 940nm Wavelength - 5mm Package - 1.4V Forward Voltage - 100mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTE-C9901 is a discrete infrared emitter component designed for surface-mount applications. It is part of a broad range of infrared solutions intended for applications requiring reliable, high-performance infrared emission. The device operates at a peak wavelength of 940nm, which is ideal for minimizing visible light interference and is commonly used in consumer electronics and industrial sensing.

The core advantages of this component include its compatibility with automated placement equipment and infrared reflow soldering processes, making it suitable for high-volume manufacturing. Its top-view design with a water-clear lens provides a wide radiation pattern. The product is compliant with RoHS and green product standards, ensuring environmental responsibility.

The target market for this infrared emitter includes manufacturers of remote control units for consumer electronics (TVs, audio systems, air conditioners), infrared wireless data transmission systems, security alarms, and various PCB-mounted infrared sensor applications where non-visible light communication or sensing is required.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Optical Characteristics

The key optical parameter is the Radiant Intensity (I_E), which is specified with a typical value of 8.0 mW/sr at a forward current (I_F) of 20mA, with a minimum of 5.0 and a maximum of 10.0 mW/sr. A tolerance of ±15% applies to the test measurement of I_E. The peak emission wavelength (λ_Peak) is 940nm, placing it in the near-infrared spectrum. The spectral line half-width (Δλ) is 50nm, defining the bandwidth of the emitted light. The viewing angle (2θ_1/2) is 65 degrees, where θ_1/2 is the off-axis angle at which the radiant intensity drops to half of its axial value. This wide angle is suitable for applications requiring broad coverage.

2.2 Electrical Characteristics

The forward voltage (V_F) is typically 1.4V at I_F = 20mA. The reverse current (I_R) is specified with a maximum of 10 μA when a reverse voltage (V_R) of 5V is applied. These parameters are crucial for circuit design, particularly for calculating series resistor values and ensuring proper biasing.

2.3 Absolute Maximum Ratings and Thermal Management

The device has a maximum power dissipation of 100 mW. The DC forward current must not exceed 60 mA. For pulsed operation, a peak forward current of 600 mA is allowed under specific conditions (300 pulses per second, 10 μs pulse width). The maximum reverse voltage is 5V. The operating temperature range is from -40°C to +85°C, and the storage temperature range is from -55°C to +100°C. Exceeding these ratings may cause permanent damage. The device can withstand infrared reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds, which is standard for lead-free (Pb-free) assembly processes.

3. Performance Curve Analysis

The datasheet provides several typical characteristic curves that are essential for design engineers. The Forward Current vs. Forward Voltage (I-V) curve shows the exponential relationship, critical for determining the operating point and thermal effects. The Relative Radiant Intensity vs. Forward Current curve demonstrates how light output increases with current, helping to optimize drive current for desired output. The Relative Radiant Intensity vs. Ambient Temperature curve shows the output's temperature dependence, which is vital for applications operating in varying environmental conditions. The Radiation Diagram graphically represents the spatial distribution of the emitted infrared light, confirming the 65-degree viewing angle. Finally, the Spectral Distribution curve illustrates the concentration of emitted power around the 940nm peak wavelength.

4. Mechanical and Package Information

4.1 Outline Dimensions

The component is housed in a standard EIA package. All critical dimensions, including body size, lead spacing, and overall height, are provided in the outline drawing. Tolerances are typically ±0.1mm unless otherwise specified. The package is designed for top-view emission.

4.2 Solder Pad Layout and Polarity

Recommended solder pad dimensions are provided to ensure a reliable solder joint and proper alignment during reflow. The anode and cathode are clearly identified in the footprint diagram. Adhering to these pad dimensions is crucial for preventing tombstoning and ensuring good thermal and electrical connection.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Profile

A detailed suggestion for an IR reflow profile suitable for Pb-free processes is included. Key parameters include a pre-heat zone (150-200°C), a pre-heat time (max 120 seconds), a peak temperature (max 260°C), and a time above liquidus (max 10 seconds). The profile is based on JEDEC standards to ensure component reliability. It is emphasized that the actual profile must be characterized for the specific PCB design, solder paste, and oven used.

5.2 Manual Soldering and Cleaning

If manual soldering is necessary, a soldering iron temperature should not exceed 300°C, and contact time should be limited to 3 seconds per pad. For cleaning, only alcohol-based solvents like isopropyl alcohol are recommended.

5.3 Storage and Handling Precautions

For unopened, moisture-proof packaging with desiccant, the device should be stored at ≤30°C and ≤90% Relative Humidity (RH) and used within one year. Once the original packaging is opened, the storage conditions should be ≤30°C and ≤60% RH. Components exposed to ambient conditions for more than one week should be baked at approximately 60°C for at least 20 hours before soldering to remove absorbed moisture and prevent \"popcorning\" during reflow.

6. Packaging and Ordering Information

The device is supplied in 8mm carrier tape on 7-inch diameter reels, compatible with automatic pick-and-place machines. Each reel contains 3000 pieces. The packaging follows ANSI/EIA 481-1-A-1994 specifications. Empty component pockets are sealed with a top cover tape. The maximum allowable number of consecutive missing parts in the tape is two.

7. Application Notes and Design Considerations

7.1 Typical Application Circuits

An infrared emitter is a current-operated device. To ensure uniform intensity when driving multiple LEDs in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED (Circuit A), rather than sharing a single resistor for multiple LEDs (Circuit B). This compensates for slight variations in the forward voltage (V_F) of individual emitters. The series resistor value (R_S) can be calculated using the formula: R_S = (V_CC - V_F) / I_F, where V_CC is the supply voltage, V_F is the forward voltage of the LED at the desired current I_F.

7.2 Application Scope and Limitations

This component is intended for ordinary electronic equipment such as office equipment, communication devices, and household appliances. It is not designed or qualified for applications where high reliability is critical to life or safety (e.g., aviation, medical life-support, transportation safety systems) without prior consultation and specific qualification.

8. Technical Comparison and Differentiation

Compared to standard visible LEDs, the 940nm wavelength is invisible to the human eye, making it ideal for discreet operation. The 65-degree viewing angle offers a good balance between beam concentration and coverage area. The SMD package and compatibility with reflow soldering provide a significant advantage over through-hole infrared LEDs in modern, automated assembly lines, reducing manufacturing cost and board space.

9. Frequently Asked Questions (FAQ)

Q: What is the purpose of the 940nm wavelength?

A: 940nm is in the near-infrared spectrum. It is largely invisible to the human eye, reducing light pollution in the application. It is also well-matched with the sensitivity of silicon photodiodes and phototransistors commonly used as receivers.

Q: Can I drive this LED directly from a microcontroller pin?

A: No. A microcontroller pin typically cannot source or sink enough current (60mA max DC for this LED) and lacks voltage headroom. You must use a driver circuit, such as a transistor switch, with a series current-limiting resistor as described in the application notes.

Q: Why is baking necessary if the package has been opened for over a week?

A> Plastic SMD packages can absorb moisture from the air. During the high-temperature reflow soldering process, this trapped moisture can vaporize rapidly, causing internal delamination, cracking, or \"popcorning,\" which destroys the component. Baking removes this absorbed moisture.

10. Practical Design and Usage Examples

Example 1: Simple Remote Control Transmitter. The LTE-C9901 can be used as the transmitting element in an IR remote. A microcontroller generates a modulated signal (e.g., 38kHz carrier) which switches a transistor driving the LED. The series resistor is calculated based on the battery voltage (e.g., 3V) and the desired pulse current (e.g., 50mA), using the typical V_F of 1.4V.

Example 2: Proximity Sensor. Paired with a phototransistor, the emitter can create a reflective object sensor. The emitter shines IR light, and an object in close proximity reflects some light back to the phototransistor. The change in the phototransistor's output indicates the presence of the object. The 65-degree viewing angle of the emitter helps cover a reasonable detection area.

11. Operating Principle

An infrared emitter is a semiconductor diode. When a forward voltage is applied, electrons and holes recombine in the active region (made of materials like GaAs or AlGaAs), releasing energy in the form of photons. The specific material composition (in this case, resulting in a 940nm peak) determines the wavelength (color) of the emitted light. The radiant intensity is directly proportional to the forward current over the normal operating range.

12. Industry Trends

The trend in infrared components is towards higher efficiency (more radiant output per unit of electrical input), smaller package sizes for denser PCB layouts, and increased integration. This includes devices with built-in drivers, modulated output, or combined emitter-sensor pairs in a single package. There is also a continuous drive for improved reliability and performance over wider temperature ranges to meet the demands of automotive and industrial applications. The move to Pb-free and RoHS-compliant manufacturing, as seen with this component, is a universal standard in the electronics industry.