UVC LED LTPL-G35UV275PR Datasheet - 3.5x3.5x1.2mm - 6.2V Typ - 37mW Radiant Flux - 275nm Peak Wavelength

1. Product Overview

The LTPL-G35UV product series represents a significant advancement in solid-state ultraviolet light sources. This product is engineered specifically for sterilization and medical applications, offering a high-performance alternative to conventional UV technologies such as mercury lamps. By leveraging Light Emitting Diode (LED) technology, it combines exceptional energy efficiency with the reliability and long operational lifetime inherent to semiconductor devices. This provides designers with greater freedom to create innovative solutions for disinfection, water purification, and surface sterilization systems.

The core advantage lies in its ability to deliver effective UVC radiation (in the 270-280nm range) with lower operating and maintenance costs. The device is designed to be compatible with integrated circuit (IC) drive systems and adheres to environmental standards, being RoHS compliant and lead-free. Its primary target markets include medical equipment manufacturers, water and air purification system integrators, and developers of consumer or industrial sterilization devices.

1.1 Core Advantages and Target Market

The transition from traditional UV sources to UVC LEDs offers several distinct benefits. Firstly, the instant-on capability and lack of warm-up time improve system responsiveness. Secondly, the compact form factor enables integration into smaller and more portable devices. The directional nature of LED emission allows for more efficient optical design, focusing energy where it is needed most. Furthermore, the absence of mercury addresses environmental and safety concerns associated with disposal and breakage.

The target application is primarily germicidal irradiation, where UVC light at around 275nm is highly effective at disrupting the DNA and RNA of microorganisms, including bacteria, viruses, and molds, rendering them inactive. This makes the LED suitable for applications such as surface disinfection in healthcare settings, water treatment in point-of-use systems, and air purification in HVAC units.

2. Technical Parameter Deep-Dive Analysis

2.1 Absolute Maximum Ratings

The device is specified for operation under stringent conditions. The absolute maximum ratings define the limits beyond which permanent damage may occur. Key parameters include a maximum power dissipation (P_O) of 2.1W and a maximum continuous forward current (I_F) of 300mA. The operating temperature range (T_opr) is specified from -40°C to +80°C, indicating suitability for both harsh industrial and controlled medical environments. The storage temperature range (T_stg) extends to -40°C to +100°C. A critical parameter is the maximum junction temperature (T_j) of 115°C. Exceeding this temperature will accelerate degradation and significantly reduce the device's lifetime. The datasheet explicitly warns against operating the LED under reverse bias conditions for extended periods, as this can lead to immediate failure.

2.2 Electro-Optical Characteristics

These characteristics are measured at a standard test condition of 25°C ambient temperature (T_a) and provide the expected performance under normal operation.

• Forward Voltage (V_F): At a drive current of 250mA, the typical forward voltage is 6.2V, with a maximum of 7.0V and a minimum of 5.0V. The measurement tolerance is ±0.1V. This parameter is crucial for designing the LED driver circuit, as it determines the required supply voltage and power dissipation.
• Radiant Flux (Φ_e): This is the total optical power output in the UVC spectrum. At 250mA, the typical radiant flux is 37.0mW (min 29.0mW). When driven at the maximum rated current of 300mA, the typical output increases to 43.0mW. The measurement tolerance is ±10%. Radiant flux is the key metric for determining the germicidal efficacy of the LED in a given application.
• Peak Wavelength (λ_P): The LED emits UVC light with a peak wavelength between 270nm and 280nm, centered around 275nm. This wavelength is within the optimal range for germicidal effectiveness. The measurement tolerance is ±3nm.
• Thermal Resistance (R_{th j-s}): The typical thermal resistance from the semiconductor junction to the solder point is 12.3 K/W. This value, measured on a specific aluminum MCPCB, is vital for thermal management design. A lower thermal resistance allows heat to be conducted away from the junction more efficiently, helping to maintain a lower T_j and ensure long-term reliability.
• Viewing Angle (2θ_1/2): The typical viewing angle is 120 degrees. This wide emission pattern is beneficial for applications requiring broad-area coverage but may necessitate reflectors or lenses for focused applications.
• Electrostatic Discharge (ESD): The device meets a minimum ESD withstand voltage of 2000V according to the JESD22-A114-B standard (Human Body Model). Proper ESD handling procedures must be followed during assembly and installation.

3. Bin Code System Explanation

To ensure consistent performance, LEDs are sorted into bins based on key parameters measured during production. The bin code is marked on the packaging.

3.1 Forward Voltage (V_F) Binning

LEDs are categorized into four voltage bins (V1 to V4) when driven at 250mA:

• V1: 5.0V – 5.5V
• V2: 5.5V – 6.0V
• V3: 6.0V – 6.5V
• V4: 6.5V – 7.0V

Tolerance within each bin is ±0.1V. This binning allows designers to select LEDs with tighter voltage matching for applications driven in series, ensuring more uniform current distribution.

3.2 Radiant Flux (Φ_e) Binning

Output power is sorted into four flux bins (X1 to X4) at 250mA:

• X1: 29.0mW – 34.0mW
• X2: 34.0mW – 39.0mW
• X3: 39.0mW – 44.0mW
• X4: 44.0mW and above

Tolerance is ±10%. Selecting a higher flux bin provides greater optical output, which can translate to shorter disinfection times or allow the use of fewer LEDs in an array.

3.3 Peak Wavelength (λ_P) Binning

For this product, all devices fall within a single wavelength bin, W1, covering 270nm to 280nm with a tolerance of ±3nm. This ensures consistent germicidal performance across all units, as microbial inactivation rates are highly wavelength-dependent.

4. Performance Curve Analysis

The provided graphs offer insight into the LED's behavior under varying conditions.

4.1 Relative Spectral Distribution

This curve shows the intensity of light emitted across the ultraviolet spectrum. It confirms the narrow emission band centered at 275nm, which is ideal for maximizing germicidal effect while minimizing emission at less effective or potentially harmful wavelengths.

4.2 Relative Radiant Flux vs. Forward Current

This graph illustrates the sub-linear relationship between drive current and optical output. While increasing current boosts output, the efficiency (radiant flux per unit of electrical power) typically decreases at higher currents due to increased thermal effects and droop. This highlights the importance of optimizing the drive current for the desired balance of output, efficiency, and lifetime.

4.3 Forward Voltage vs. Forward Current & Junction Temperature

The forward voltage has a negative temperature coefficient, meaning it decreases as the junction temperature rises. This characteristic must be considered in constant-current driver designs, as a lower V_F at high temperature could slightly reduce the electrical power dissipation.

4.4 Relative Radiant Flux vs. Junction Temperature

This is one of the most critical curves. UVC LED output is highly sensitive to junction temperature. The graph shows a significant decrease in radiant flux as T_j increases. Effective thermal management to keep the junction as cool as possible is paramount to maintaining high output and achieving the rated lifetime.

4.5 Forward Current Derating Curve

This curve defines the maximum allowable forward current as a function of the ambient temperature. As ambient temperature rises, the maximum permissible current must be reduced to prevent the junction temperature from exceeding its 115°C limit. This graph is essential for designing systems that operate reliably across their specified temperature range.

5. Mechanical and Package Information

5.1 Outline Dimensions

The LED package has a compact footprint of approximately 3.5mm x 3.5mm, with a height of about 1.2mm. All dimensions have a tolerance of ±0.2mm unless otherwise noted. The mechanical drawing specifies the exact location of the LED chip, solder pads, and any optical lens structure.

5.2 Recommended PCB Attachment Pad

A detailed land pattern design is provided for the surface-mount pads. Adhering to this recommended footprint is critical for achieving reliable solder joints, proper thermal conduction to the PCB, and correct alignment. The specification tolerance for the pad dimensions is ±0.1mm. The design typically includes thermal vias under the thermal pad to transfer heat into the PCB's ground plane or a dedicated heatsink layer.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed lead-free reflow profile is specified to prevent damage during the Surface Mount Technology (SMT) assembly process. Key parameters include:

• Preheat: 150-200°C for 60-120 seconds.
• Time above liquidus (217°C): 60-150 seconds.
• Peak temperature: Recommended 245°C, maximum 260°C.
• Time within 5°C of peak: 10-30 seconds.
• Maximum ramp-up rate: 3°C/second.
• Maximum ramp-down rate: 6°C/second.

The temperatures refer to the top of the package. A rapid cooldown process is not recommended. The LED can withstand a maximum of three reflow cycles.

6.2 Hand Soldering and Cleaning

If hand soldering is necessary, the iron tip temperature should not exceed 300°C, and contact time should be limited to a maximum of 2 seconds per pad, performed only once. For cleaning, only alcohol-based solvents like isopropyl alcohol should be used. Unspecified chemical cleaners may damage the silicone lens or package material.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied on embossed carrier tape and reels for automated pick-and-place assembly. The tape dimensions (pocket size, pitch) and reel dimensions (hub diameter, flange diameter) conform to EIA-481-1-B standards. A 7-inch reel can hold a maximum of 500 pieces. Minimum packing quantities for remainder lots are 100 pieces. The tape is sealed with a cover tape to protect the components.

8. Application Suggestions and Design Considerations

8.1 Thermal Management

This is the single most critical design factor. The high sensitivity of output to junction temperature necessitates an effective heatsinking strategy. Use a Metal Core PCB (MCPCB) or a standard FR4 PCB with an extensive copper pour and thermal vias connected to an external heatsink. The goal is to minimize the thermal resistance from the LED junction to the ambient environment (R_{th j-a}). Always refer to the forward current derating curve when designing for high ambient temperatures.

8.2 Electrical Drive

A constant current driver is mandatory for stable operation. The driver should be selected to provide the desired current (e.g., 250mA or 300mA) while accommodating the forward voltage range of the selected bin. Consider implementing pulse-width modulation (PWM) for dimming or duty-cycled operation, which can help manage thermal load. Ensure the driver is protected against reverse polarity and voltage transients.

8.3 Optical and Material Considerations

UVC radiation at 275nm is highly energetic and can degrade many common materials, including certain plastics, epoxies, and adhesives. Ensure all materials in the optical path and near the LED (lenses, reflectors, gaskets, wire insulation) are rated for prolonged UVC exposure. Quartz glass is typically used for protective windows. Avoid direct exposure of skin and eyes to the UVC output.

9. Reliability and Lifetime

The datasheet outlines a comprehensive reliability test plan, including Room Temperature Operating Life (RTOL), High/Low Temperature Storage Life (HTSL/LTSL), damp heat testing, and thermal shock. These tests simulate years of operation under various stress conditions. The criteria for failure are defined as a forward voltage shift exceeding 10% or a radiant flux drop below 50% of the initial value. Proper thermal design and electrical operation within the specified limits are essential to achieving the projected lifetime in the field.

10. Technical Comparison and Differentiation

Compared to traditional low-pressure mercury lamps (which emit at 254nm), this UVC LED offers several advantages: instant on/off, compact size, directional emission, robustness (no fragile glass, no mercury), and the potential for wavelength tuning. Compared to other UVC LEDs, the key differentiators of this specific part are its combination of 275nm wavelength, 37mW typical output at 250mA, and the 3.5x3.5mm package format. The wide 120-degree viewing angle may be an advantage or disadvantage depending on the optical design requirements of the application.

11. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between radiant flux (mW) and germicidal effectiveness?
A: Radiant flux is the total UVC optical power. Germicidal effectiveness depends on this power, the emission spectrum (peak wavelength), the distance to the target, exposure time, and the specific microorganism's susceptibility. The 275nm wavelength is very effective against a broad range of pathogens.

Q: Can I drive this LED with a constant voltage source?
A: No. LEDs are current-driven devices. A constant voltage source will not regulate the current, leading to thermal runaway and rapid failure. Always use a constant current driver.

Q: How do I calculate the required heatsink?
A: You need to determine the total thermal resistance path. Start with the junction-to-solder resistance (R_{th j-s} = 12.3 K/W). Add the thermal resistance of your thermal interface material, PCB, and external heatsink. Using the formula T_j = T_a + (P_diss * R_{th j-a}), ensure T_j remains below 115°C at your maximum ambient temperature and drive power (P_diss ≈ I_F * V_F).

Q: Why is the output so sensitive to temperature?
A> This is a fundamental characteristic of semiconductor light sources, particularly in the ultraviolet range. Increased temperature increases non-radiative recombination within the semiconductor material, reducing the internal quantum efficiency and thus the light output.

12. Practical Design and Usage Case

Case: Designing a Portable Surface Sterilizer Wand.
A designer wants to create a handheld wand for disinfecting surfaces like countertops, keyboards, and phones. They select the LTPL-G35UV275PR LED for its compact size and 275nm output. They plan to use an array of 4 LEDs to increase coverage area. Each LED will be driven at 250mA (typical V_F=6.2V, P_diss=1.55W). The total system power is ~6.2W. A lightweight aluminum heatsink with fins is integrated into the wand's body to dissipate the ~6W of heat. A constant-current driver powered by a rechargeable lithium-ion battery is designed. A safety interlock ensures the LEDs only activate when the wand is held at the correct distance from a surface. The optical design uses the native 120-degree beam to create a broad sterilization spot. The designer selects LEDs from the X2 flux bin (34-39mW) for consistent performance and uses PWM to control exposure time (e.g., 10-second cycles).

13. Principle Introduction

UVC LEDs are based on semiconductor materials, typically aluminum gallium nitride (AlGaN). When a forward voltage is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons. The wavelength of these photons is determined by the bandgap energy of the semiconductor material. By carefully controlling the aluminum content in the AlGaN layers, the bandgap can be engineered to emit light in the UVC range (200-280nm). The 275nm emission is achieved through precise epitaxial growth processes. The generated UVC photons are highly energetic and can break molecular bonds, most critically in the DNA/RNA of microorganisms, preventing them from replicating.

14. Development Trends

The field of UVC LEDs is rapidly evolving. Key trends include:

• Increased Wall-Plug Efficiency (WPE): Ongoing research aims to improve the electrical-to-optical power conversion efficiency, which directly reduces heat generation and system power requirements.
• Higher Output Power: Development of LEDs with higher radiant flux from a single emitter or smaller package, enabling more compact and powerful disinfection systems.
• Longer Lifetime (L70/B50): Improvements in materials, packaging, and thermal management are extending the operational lifetime, making LEDs more competitive with traditional lamps for high-duty-cycle applications.
• Cost Reduction: As manufacturing volumes increase and processes mature, the cost per milliwatt of UVC output is steadily decreasing, broadening the range of feasible applications.
• Wavelength Optimization: Research continues into the optimal wavelength for specific pathogens and applications, potentially leading to tailored LEDs for healthcare, water, and air purification.

The transition to solid-state UVC sources is a clear long-term trend driven by their inherent advantages in form factor, safety, and controllability.