LTL17KCGM4J Green LED Datasheet - T-1 Package - 518nm Wavelength - 3.2V Voltage - 108mW Power - English Technical Document

1. Product Overview

The LTL17KCGM4J is a high-efficiency, through-hole LED lamp designed for status indication and illumination in a wide range of electronic applications. It features a popular T-1 (3mm) diameter package with a white diffused lens, providing a wide viewing angle and uniform light distribution. The device utilizes InGaN technology to produce a green light with a typical dominant wavelength of 518nm.

1.1 Core Advantages

• Low Power Consumption & High Efficiency: Delivers high luminous intensity with minimal power draw.
• Environmental Compliance: Lead-free and fully compliant with RoHS directives.
• Standard Package: The T-1 form factor ensures compatibility with existing PCB layouts and manufacturing processes.
• Diffused Lens: The white diffused lens offers a wide, uniform viewing angle of 40 degrees, ideal for indicator applications.

1.2 Target Markets

This LED is suitable for diverse applications across multiple industries, including:

• Communication Equipment
• Computer Peripherals
• Consumer Electronics
• Home Appliances
• Industrial Controls and Instrumentation

2. In-Depth 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.

• Power Dissipation (Pd): 108 mW. This is the maximum power the LED can dissipate as heat.
• DC Forward Current (IF): 30 mA continuous. The device should be driven at or below this current for reliable operation.
• Peak Forward Current: 100 mA, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Reverse Voltage (VR): 5 V. Exceeding this voltage in reverse bias can cause immediate failure.
• Operating Temperature Range: -30°C to +85°C. The LED is guaranteed to function within this ambient temperature range.
• Storage Temperature Range: -40°C to +100°C.
• Lead Soldering Temperature: 260°C for a maximum of 5 seconds at a distance of 2.0mm from the LED body.

2.2 Electrical & Optical Characteristics

These parameters are measured at an ambient temperature (TA) of 25°C and define the typical performance of the device.

• Luminous Intensity (Iv): Ranges from 680 mcd (min) to 3200 mcd (max) at a forward current (IF) of 20 mA. The typical value is 1500 mcd. Note that a ±15% testing tolerance applies to these values.
• Forward Voltage (VF): Typically 3.2V, with a range from 2.9V to 3.6V at IF=20mA. This parameter is crucial for designing the current-limiting resistor in the drive circuit.
• Viewing Angle (2θ1/2): 40 degrees. This is the full angle at which the luminous intensity drops to half of its axial (on-axis) value.
• Dominant Wavelength (λd): The primary color perceived by the human eye. For this product, it is binned from 514nm to 527nm, with a typical target of 518nm.
• Peak Emission Wavelength (λP): Approximately 515nm, which is the wavelength at the highest point in the LED's emission spectrum.
• Spectral Line Half-Width (Δλ): 35 nm. This indicates the spectral purity; a smaller value means a more monochromatic light.
• Reverse Current (IR): 10 μA maximum when a reverse voltage of 5V is applied. The LED is not designed for reverse operation.

3. Binning System Specification

To ensure color and brightness consistency in production, LEDs are sorted into bins. The LTL17KCGM4J uses a two-dimensional binning system.

3.1 Luminous Intensity Binning

Bins are defined by minimum and maximum luminous intensity values at 20mA. Tolerance for each bin limit is ±15%.

• NP Bin: 680 mcd (Min) to 1150 mcd (Max)
• QR Bin: 1150 mcd (Min) to 1900 mcd (Max)
• ST Bin: 1900 mcd (Min) to 3200 mcd (Max)

3.2 Dominant Wavelength Binning

Bins are defined by specific wavelength ranges at 20mA. Tolerance for each bin limit is ±1nm.

• G07: 514.0 nm to 516.0 nm
• G08: 516.0 nm to 518.0 nm
• G09: 518.0 nm to 520.0 nm
• G10: 520.0 nm to 523.0 nm
• G11: 523.0 nm to 527.0 nm

4. Performance Curve Analysis

While specific graphs are not detailed in the provided text, typical curves for such a device would include:

4.1 Relative Luminous Intensity vs. Forward Current

This curve shows how light output increases with forward current. It is generally linear at lower currents but may saturate at higher currents due to thermal effects and efficiency droop.

4.2 Forward Voltage vs. Forward Current

This IV characteristic curve is exponential in nature. The specified forward voltage (e.g., 3.2V typ.) is a single point on this curve at 20mA.

4.3 Relative Luminous Intensity vs. Ambient Temperature

LED light output decreases as the junction temperature rises. This curve is essential for applications operating in high-temperature environments.

4.4 Spectral Distribution

A graph showing the relative power emitted across different wavelengths, peaking around 515nm with a characteristic width (35 nm FWHM).

5. Mechanical & Packaging Information

5.1 Outline Dimensions

The LED conforms to the standard T-1 (3mm) round through-hole package. Key dimensional notes include:

• All dimensions are in millimeters (inches).
• Tolerance is ±0.25mm (.010") unless otherwise specified.
• Maximum resin protrusion under the flange is 1.0mm (.04").
• Lead spacing is measured where the leads exit the package body.

5.2 Polarity Identification

Typically, the longer lead denotes the anode (positive), and the shorter lead denotes the cathode (negative). The cathode may also be indicated by a flat spot on the LED lens flange.

6. Soldering & Assembly Guidelines

6.1 Storage Conditions

For optimal shelf life, store LEDs in an environment not exceeding 30°C and 70% relative humidity. If removed from the original moisture-barrier bag, use within three months. For longer storage, use a sealed container with desiccant or a nitrogen ambient.

6.2 Lead Forming

• Bend leads at a point at least 3mm from the base of the LED lens.
• Do not use the LED body as a fulcrum.
• Perform forming at room temperature and before the soldering process.
• Use minimum clinch force during PCB assembly to avoid mechanical stress.

6.3 Soldering Process

Critical Rule: Maintain a minimum distance of 2mm from the base of the epoxy lens to the solder point. Never immerse the lens in solder.

• Hand Soldering (Iron): Maximum temperature 350°C for no more than 3 seconds per lead.
• Wave Soldering:
  • Pre-heat: Maximum 100°C for up to 60 seconds.
  • Solder Wave: Maximum 260°C for up to 5 seconds.
• Important: IR reflow soldering is NOT suitable for this through-hole LED product. Excessive heat or time will damage the epoxy lens or the semiconductor die.

6.4 Cleaning

If necessary, clean only with alcohol-based solvents such as isopropyl alcohol (IPA).

7. Packaging & Ordering Information

7.1 Packaging Specification

The product is available in multiple packaging configurations:

• Unit Pack: 1000, 500, 200, or 100 pieces per moisture-barrier packing bag.
• Inner Carton: Contains 10 packing bags (e.g., 10,000 pieces if using 1000pc bags).
• Outer Carton (Shipping Lot): Contains 8 inner cartons (e.g., 80,000 pieces). The final pack in a lot may not be full.

8. Application Design Recommendations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness and prevent damage:

• Always use a current-limiting resistor in series with each LED. The resistor value (R) can be calculated using Ohm's Law: R = (Vsupply - VF) / IF, where VF is the LED forward voltage and IF is the desired forward current (e.g., 20mA).
• Avoid connecting multiple LEDs directly in parallel without individual resistors. Small variations in the forward voltage (VF) characteristic between LEDs can cause significant current imbalance, leading to uneven brightness and potential over-current in one device (as illustrated in the datasheet's Circuit B). The recommended method is to use a series resistor for each LED branch (Circuit A).

8.2 Thermal Management

Although power dissipation is low (108mW max), proper design is necessary for reliability:

• Observe the DC forward current derating of 0.45 mA/°C above 30°C ambient temperature. This means the maximum allowable continuous current decreases as ambient temperature increases.
• Ensure adequate spacing between LEDs and other heat-generating components on the PCB.

8.3 Electrostatic Discharge (ESD) Protection

The LED is susceptible to damage from electrostatic discharge. Implement the following in the handling and assembly area:

• Use conductive wrist straps or anti-static gloves.
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• Ensure all equipment, workstations, and storage racks are properly grounded.
• Use ionizers to neutralize static charge that may accumulate on the plastic lens.
• Maintain ESD training and certification for all personnel.

9. Technical Comparison & Differentiation

The LTL17KCGM4J offers specific advantages within the through-hole LED market:

• Wavelength Consistency: The tight binning system for dominant wavelength (±1nm per bin) ensures superior color consistency in applications requiring multiple LEDs, compared to parts with looser tolerances.
• High Intensity Options: The availability of the high-brightness ST bin (up to 3200 mcd) makes it suitable for applications requiring high visibility or where light may be attenuated by filters or diffusers.
• Robust Packaging: The standard T-1 package with a diffused lens provides a proven, reliable mechanical form factor with good viewing characteristics.

10. Frequently Asked Questions (FAQs)

10.1 What resistor value should I use with a 5V supply?

Using the typical forward voltage (VF=3.2V) and a target current of 20mA (0.02A): R = (5V - 3.2V) / 0.02A = 90 Ohms. A standard 91 Ohm or 100 Ohm resistor would be appropriate. Always calculate based on the maximum VF from the datasheet (3.6V) to ensure the current does not exceed the limit under worst-case conditions.

10.2 Can I drive this LED at 30mA continuously?

Yes, 30mA is the absolute maximum continuous DC current rating at 25°C. However, for long-term reliability and to account for temperature rise, it is often advisable to operate at a lower current, such as 20mA. If operating at 30mA, ensure the ambient temperature is well below 85°C and consider the derating factor.

10.3 Why is a series resistor necessary if my power supply is constant current?

If you are using a dedicated, properly set constant current driver, a series resistor is not required and may even be detrimental. The resistor is essential when using a constant voltage source (like a battery or voltage regulator) to limit the current to a safe value.

10.4 How do I interpret the luminous intensity bin code on the bag?

The bin code (e.g., ST, QR, NP) printed on the packaging bag corresponds to the luminous intensity range of the LEDs inside. This allows designers to select the appropriate brightness grade for their application and ensures consistency within a production run.

11. Practical Design Case Study

Scenario: Designing a status indicator panel for an industrial control unit. The panel requires 10 green indicator LEDs to show "system active" status. The unit is powered by a 12V rail, and the operating environment can reach 50°C.

Design Steps:

1. Current Selection: Due to the elevated ambient temperature (50°C), derate the maximum current. Derating from 30°C: (50°C - 30°C) * 0.45 mA/°C = 9 mA derating. Max current at 50°C ≈ 30mA - 9mA = 21mA. Choosing 18mA provides a good safety margin while maintaining brightness.
2. Resistor Calculation: Use max VF (3.6V) for reliability. R = (12V - 3.6V) / 0.018A ≈ 467 Ohms. Use the nearest standard value, 470 Ohms.
3. Circuit Topology: Place each LED with its own 470Ω resistor in series, and connect all 10 of these LED-resistor pairs in parallel to the 12V supply. This ensures equal current through each LED despite VF variations.
4. Bin Selection: For uniform appearance, specify a single luminous intensity bin (e.g., QR) and a single dominant wavelength bin (e.g., G08 for 518nm) from the supplier.
5. Layout: Follow the 2mm minimum solder distance rule on the PCB layout. Provide slight spacing between LEDs to prevent localized heating.

12. Operating Principle

The LTL17KCGM4J is a semiconductor light source based on an Indium Gallium Nitride (InGaN) chip. When a forward voltage is applied across the anode and cathode, electrons and holes are injected into the active region of the semiconductor. These charge carriers recombine, releasing energy in the form of photons (light). The specific composition of the InGaN material determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, green at approximately 518nm. The epoxy package serves to protect the chip, act as a lens to shape the light output, and includes a diffusing material to widen the viewing angle.

13. Technology Trends

While through-hole LEDs remain vital for prototyping, repair, and certain legacy or high-reliability applications, the broader industry trend has shifted significantly towards surface-mount device (SMD) packages like 0603, 0805, and 2835. SMD LEDs offer advantages in automated assembly, board space savings, and often better thermal performance. However, through-hole LEDs like the T-1 package continue to be relevant due to their ease of manual handling, robustness in high-vibration environments, and excellent suitability for breadboarding and educational purposes. The technology within the chip itself continues to evolve, with ongoing research focused on improving efficiency (lumens per watt), color rendering, and longevity.