LTL87HTBK Blue LED Datasheet - 5mm Round Lens - 4.0V Forward Voltage - 120mW Power Dissipation - English Technical Document

1. Product Overview

The LTL87HTBK is a blue light-emitting diode (LED) utilizing an Indium Gallium Nitride (InGaN) semiconductor material. It is packaged in a standard 5mm round through-hole format with a water-clear lens, designed for general-purpose indicator and illumination applications. Its primary features include low power consumption, a wide viewing angle, and the inherent long life and reliability of solid-state lighting technology.

1.1 Core Advantages

• Low Power Consumption: Operates efficiently at typical drive currents, making it suitable for battery-powered devices.
• Wide Viewing Angle (120°): Provides a broad, uniform light distribution, ideal for panel indicators and status lights.
• Solid-State Reliability: Offers a long operational lifespan with no filaments or glass envelopes to break, ensuring durability in various environments.

1.2 Target Applications

This LED is intended for use in ordinary electronic equipment. Typical applications include status indicators on consumer electronics, backlighting for small displays, panel illumination, and decorative lighting. It is not designed for applications requiring exceptional reliability where failure could jeopardize safety (e.g., aviation, medical life-support).

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation (Pd): 120 mW maximum. This is the total power (Vf * If) the package can dissipate as heat.
• Forward Current (DC): 30 mA continuous maximum.
• Peak Forward Current: 100 mA maximum, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• Operating Temperature (Ta): -25°C to +80°C ambient temperature range.
• Storage Temperature (Tstg): -30°C to +100°C.
• Lead Soldering Temperature: 260°C for 5 seconds maximum, measured 1.6mm from the LED body.

2.2 Electrical & Optical Characteristics

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

• Luminous Intensity (Iv): Ranges from a minimum of 65 mcd to a typical 180 mcd and a maximum of 520 mcd at a forward current (If) of 20 mA. A ±15% tolerance applies to the guaranteed intensity.
• Forward Voltage (Vf): Typically 4.0V, with a maximum of 4.0V at If=20mA. The minimum is 3.5V.
• Viewing Angle (2θ1/2): 120 degrees. This is the full angle where luminous intensity drops to half its axial value.
• Peak Wavelength (λp): 468 nm. This is the wavelength at the highest point in the emission spectrum.
• Dominant Wavelength (λd): 470 nm. This is the single wavelength perceived by the human eye that defines the color.
• Spectral Half-Width (Δλ): 25 nm. This indicates the spectral purity; a smaller value means a more monochromatic light.
• Reverse Current (Ir): 100 μA maximum at a reverse voltage (Vr) of 5V. The device is not designed for reverse operation.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted (binned) based on key optical parameters. The LTL87HTBK uses two primary binning criteria.

3.1 Luminous Intensity Binning

LEDs are classified into bins based on their measured luminous intensity at 20mA. Each bin has a minimum and maximum value, with a ±15% tolerance on the bin limits. The bin code (e.g., D, E, F...L) is marked on the packing bag.

• Example: Bin 'G' has an intensity range of 140 to 180 mcd.

3.2 Dominant Wavelength Binning

LEDs are also binned by their dominant wavelength to control color consistency. The tolerance for each bin limit is ±1 nm.

• Example: Bin 'B08' has a dominant wavelength range of 465.0 to 470.0 nm.

4. Performance Curve Analysis

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

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the exponential relationship between current and voltage. The forward voltage has a negative temperature coefficient, meaning it decreases slightly as the junction temperature increases.

4.2 Luminous Intensity vs. Forward Current

This curve is generally linear at lower currents but may saturate at higher currents due to thermal effects and efficiency droop.

4.3 Luminous Intensity vs. Ambient Temperature

The light output of an LED decreases as the junction temperature rises. This derating curve is critical for designing applications that operate over a wide temperature range.

4.4 Spectral Distribution

A graph showing relative intensity versus wavelength, centered around 468 nm with a typical half-width of 25 nm, defining the blue color point.

5. Mechanical & Package Information

5.1 Package Dimensions

The device is a standard 5mm round LED. Key dimensional notes include:

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

5.2 Polarity Identification

The longer lead is the anode (positive), and the shorter lead is the cathode (negative). Additionally, the cathode side often has a flat spot on the LED lens's plastic flange.

6. Soldering & Assembly Guidelines

6.1 Lead Forming

• Bend leads at a point at least 3mm from the base of the LED lens.
• Do not use the lead frame base as a fulcrum.
• Perform lead forming at room temperature and before the soldering process.

6.2 Soldering Parameters

Maintain a minimum 2mm clearance from the lens base to the solder point. Avoid immersing the lens in solder.

• Hand Soldering (Iron): Maximum temperature 300°C for a maximum of 3 seconds (one time only).
• Wave Soldering: Pre-heat to a maximum of 100°C for up to 60 seconds. Solder wave at a maximum of 260°C for up to 10 seconds.

Warning: Excessive temperature or time can deform the lens or cause catastrophic failure.

6.3 Storage Conditions

• Recommended storage ambient: ≤30°C and ≤70% relative humidity.
• LEDs removed from original packaging should be used within three months.
• For extended storage outside original packaging, use a sealed container with desiccant or a nitrogen ambient.

7. Packaging & Ordering Information

7.1 Packaging Specification

• Basic Unit: 1000, 500, or 250 pieces per anti-static packing bag.
• Inner Carton: 10 packing bags per carton (total 10,000 pcs).
• Outer Carton: 8 inner cartons per box (total 80,000 pcs). The last pack in a shipping lot may not be full.

8. Application Design Recommendations

8.1 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness when connecting multiple LEDs in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED. Driving multiple LEDs in parallel directly from a voltage source (without individual resistors) can lead to significant brightness mismatch due to natural variations in the forward voltage (Vf) of each device.

8.2 Electrostatic Discharge (ESD) Protection

This LED is susceptible to damage from electrostatic discharge. Precautions must be taken during handling and assembly:

• Use grounded wrist straps or anti-static gloves.
• Ensure all equipment, workstations, and storage racks are properly grounded.
• Use an ionizer to neutralize static charge that may accumulate on the plastic lens.

8.3 Thermal Management

While this is a low-power device, operating at or near the maximum DC current (30mA) will generate heat. Ensure adequate ventilation in the application to keep the LED's junction temperature within the specified operating range, as excessive heat reduces light output and lifespan.

9. Technical Comparison & Differentiation

The LTL87HTBK, as a standard 5mm blue InGaN LED, is differentiated by its specific combination of luminous intensity bins and dominant wavelength bins. Compared to older technology blue LEDs (e.g., using silicon carbide), InGaN LEDs offer significantly higher efficiency and brighter, more saturated blue light. Its key advantage lies in the well-defined binning system, allowing designers to select parts for consistent color and brightness in their applications.

10. Frequently Asked Questions (FAQs)

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

Using Ohm's Law: R = (Vsupply - Vf_led) / If. For a typical Vf of 4.0V at 20mA: R = (5V - 4.0V) / 0.020A = 50 ohms. The nearest standard value is 51 ohms. Always calculate power dissipation in the resistor: P = I²R = (0.02)² * 51 = 0.0204W, so a standard 1/4W resistor is sufficient.

10.2 Can I drive this LED with a 3.3V supply?

Possibly, but not reliably. The minimum forward voltage is 3.5V, and the typical is 4.0V. A 3.3V supply may not turn the LED on, or it may produce very dim and inconsistent light. A boost converter or a higher supply voltage is recommended.

10.3 Why is there a ±15% tolerance on the luminous intensity?

This tolerance accounts for measurement system variations and minor production variances. The binning system provides a more precise range for selection. The actual intensity of a device in bin 'G' (140-180 mcd) will be within that range, plus the measurement tolerance.

11. Practical Design Case Study

11.1 Multi-LED Status Indicator Panel

Scenario: Designing a control panel with 10 blue status indicators, all requiring uniform brightness, powered from a 12V rail.

Design Solution:

1. Circuit Topology: Use 10 identical drive circuits in parallel, each consisting of the LED and its own series resistor. Avoid a single resistor driving all LEDs in parallel.
2. Resistor Calculation: Target If = 20mA. Vf (typical) = 4.0V. R = (12V - 4.0V) / 0.020A = 400 ohms. Use a standard 390 or 430 ohm resistor. Power: P = (0.02)² * 400 = 0.16W, so a 1/4W resistor is adequate.
3. Binning: Specify LEDs from the same luminous intensity bin (e.g., all from bin 'G') and the same dominant wavelength bin (e.g., all from bin 'B08') to ensure visual consistency.
4. Layout: Maintain the 3mm lead bend distance and 2mm solder clearance. Provide some space between LEDs for heat dissipation.

12. Operating Principle

The LTL87HTBK is a semiconductor p-n junction diode based on Indium Gallium Nitride (InGaN). When a forward voltage exceeding the diode's turn-on voltage (approximately 3.5V) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region (the junction). When electrons recombine with holes in this active region, energy is released in the form of photons (light). The specific composition of the InGaN alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, blue at around 470 nm.

13. Technology Trends

Blue InGaN LEDs, pioneered in the early 1990s, were a foundational breakthrough in solid-state lighting. They enabled the creation of white LEDs (by combining blue light with yellow phosphors) and full-color displays. Current trends in this technology focus on increasing efficiency (lumens per watt), improving color rendering index (CRI) for white light applications, and developing miniaturized and high-density packages. While 5mm through-hole LEDs remain popular for indicators, surface-mount device (SMD) packages are now dominant for illumination due to their better thermal performance and suitability for automated assembly.