LTL307JGT Green LED Lamp Datasheet - T-1 3/4 Package - 2.4V Forward Voltage - 75mW Power Dissipation - English Technical Document

1. Product Overview

This document details the technical specifications for a high-intensity green LED lamp designed for through-hole mounting. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce green light. It is housed in a popular T-1 3/4 diameter package, which is a standard size widely used in electronic assemblies. The primary design goal is to provide a reliable, rugged light source with a narrow viewing angle, resulting in higher perceived brightness when viewed on-axis. This makes it suitable for a variety of general-purpose indicator and illumination applications where a distinct, focused green signal is required.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device must not be operated beyond these limits to prevent permanent damage. Key ratings include a maximum power dissipation of 75 mW at an ambient temperature (T_A) of 25°C. The continuous forward current is rated at 30 mA. For pulsed operation, a peak forward current of 60 mA is permissible under specific conditions: a 1/10 duty cycle and a pulse width of 0.1 ms. The device can withstand a reverse voltage of up to 5 V. The operating and storage temperature ranges are from -40°C to +100°C. For soldering, the leads can tolerate 260°C for 5 seconds when measured 1.6mm from the body.

2.2 Electrical & Optical Characteristics

These parameters are measured at T_A=25°C and define the typical performance of the LED. The luminous intensity (I_V) has a typical value of 310 mcd at a forward current (I_F) of 20 mA, with a minimum specified value of 140 mcd. The viewing angle (2θ_1/2), defined as the full angle where intensity drops to half its axial value, is 40 degrees. The peak emission wavelength (λ_P) is 574 nm, and the dominant wavelength (λ_d), which defines the perceived color, is 572 nm. The spectral line half-width (Δλ) is 11 nm. The forward voltage (V_F) typically measures 2.4 V at I_F=20mA, with a maximum of 2.4 V. Reverse current (I_R) is a maximum of 100 µA at V_R=5V, and the junction capacitance (C) is typically 40 pF.

3. Performance Curve Analysis

The datasheet references typical characteristic curves which are essential for design. These curves, though not displayed in the provided text, would typically illustrate the relationship between forward current and forward voltage (I-V curve), the variation of luminous intensity with forward current, the temperature dependence of forward voltage and luminous intensity, and the spectral power distribution. Analyzing these curves allows designers to predict performance under non-standard conditions, such as different drive currents or ambient temperatures, ensuring stable operation across the intended application environment.

4. Mechanical & Packaging Information

The LED uses a standard T-1 3/4 (approximately 5mm) diameter round package. Key dimensional notes specify that all dimensions are in millimeters, with a general tolerance of ±0.25mm unless stated otherwise. The maximum protrusion of resin under the flange is 1.0mm. Lead spacing is measured at the point where the leads emerge from the package body. The lens is transparent, and the source color is green from the AlInGaP chip.

5. Soldering & Assembly Guidelines

Proper handling is critical for reliability. For lead forming, bends must be made at least 3mm from the base of the epoxy bulb, and the base should not be used as a fulcrum. Forming must be done at room temperature before soldering. When mounting, avoid creating residual mechanical stress from clinching the leads. For soldering, maintain a minimum 2mm clearance between the solder point and the resin body. Do not immerse the resin into solder. Recommended conditions are: soldering iron temperature maximum 300°C for 3 seconds max (one time only), or wave soldering with pre-heat to 100°C max for 60 seconds max, followed by a solder wave at 260°C max for 10 seconds max. The housing material is sensitive to temperature; exceeding these limits can cause melting.

6. Application Suggestions

6.1 Typical Application Scenarios

This LED is intended for ordinary electronic equipment such as office equipment, communication devices, and household appliances. Its high intensity and narrow viewing angle make it suitable for status indicators, panel lights, and backlighting where a bright, focused green point is needed.

6.2 Drive Circuit Design

LEDs are current-operated devices. A current-limiting mechanism is mandatory in the driving circuit. The simplest method is to use a series resistor. The resistor value must be chosen considering the power supply voltage variation to prevent the forward current from exceeding 40% over the desired value. The datasheet recommends a circuit where each LED has its own current-limiting resistor (Circuit A). Using a single resistor for multiple LEDs in parallel (Circuit B) is discouraged due to the natural variation in forward voltage (V_f) between individual LEDs, which leads to uneven current sharing and thus uneven brightness.

6.3 Design Considerations

Consider thermal management; the maximum power dissipation derates linearly above 50°C ambient at 0.4 mA/°C. Electrostatic discharge (ESD) protection is crucial; handlers should use grounded wrist straps, and all equipment must be properly grounded. For storage before use, keep at 30°C or less and 70% RH or less, with a recommended use-within period of 3 months. For longer storage (up to one year), a sealed container with a nitrogen atmosphere and desiccant is advised.

7. Reliability & Testing

The device undergoes several reliability tests per industry standards. Endurance testing includes a 1000-hour operational life test at room temperature with pulsed current. Environmental tests include temperature cycling between -55°C and +105°C, solder resistance at 260°C, and solderability tests. These tests ensure the device can withstand the rigors of manufacturing and long-term operation.

8. Cautions & Limitations

This product is not designed for safety-critical applications where failure could jeopardize life or health (e.g., aviation, automotive primary controls, medical life-support). For such applications, consultation with the manufacturer is required prior to design-in. The specifications and product appearance are subject to change for quality improvement without notice. Users must avoid rapid temperature transitions in high humidity to prevent condensation on or inside the device. Cleaning should be done with alcohol-based solvents like isopropyl alcohol.

9. Technical Principle Introduction

This LED is based on AlInGaP semiconductor material. When a forward voltage is applied across the p-n junction, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, green at around 572 nm. The transparent epoxy lens serves to protect the semiconductor die, shape the radiation pattern to a 40-degree viewing angle, and enhance light extraction from the chip.

10. Common Questions Based on Technical Parameters

Q: What resistor value should I use with a 5V supply for 20mA drive current?

A: Using the typical V_f of 2.4V, the voltage across the resistor is (5V - 2.4V) = 2.6V. Using Ohm's Law (R = V/I), R = 2.6V / 0.02A = 130 Ω. A standard 130 Ω or 120 Ω resistor would be suitable, considering the power rating (P = I²R = 0.0004 * 130 = 0.052W, so a 1/8W or 1/10W resistor is sufficient).

Q: Can I drive this LED at 30mA continuously?

A: Yes, 30mA is the maximum continuous forward current rating at 25°C. However, ensure the ambient temperature is considered, as the permissible current derates above 50°C.

Q: Why is a narrow viewing angle an advantage?

A: A narrow viewing angle (40°) concentrates the luminous flux into a smaller solid angle. This results in higher axial luminous intensity (candelas) when viewed head-on, making the LED appear brighter for indicator applications where the viewer is typically aligned with the LED axis.

11. Practical Usage Case

Scenario: Designing a multi-indicator status panel. A control unit requires three independent status LEDs: Power (green), Warning (yellow), and Fault (red). For the green "Power On" indicator, this LTL307JGT LED is selected. The design uses a 5V logic supply. A 130 Ω series resistor is chosen for each LED to set the current to approximately 20mA. Each LED-resistor pair is driven directly by a microcontroller output pin. The narrow 40-degree viewing angle ensures the indicators are clearly visible to an operator directly in front of the panel, even in moderately lit environments. The through-hole package allows for secure mounting on the PCB and easy visual inspection during assembly.