Low Current Diffused LED Lamps LTL1CHJxDNN Series - Through Hole - 60/45 Degree Viewing Angle - 2mA Operation - 1.8-2.4V - 75mW - Red/Amber/Yellow/Green - English Datasheet

1. Product Overview

This document details a series of tinted, diffused LED lamps engineered specifically for operation at low direct current (DC) levels. The primary design objective is to provide consistent and reliable visual indication in circuits where power consumption is a critical constraint. These components are characterized by their compatibility with common logic families and a selection of package styles and colors to suit diverse application requirements.

The core advantage of this product family lies in its optimization for low-current drive, typically at 2mA. This ensures that the LEDs can be driven directly from the output stages of TTL or CMOS logic circuits without requiring additional current-boosting components, simplifying circuit design and reducing component count. The diffused lens provides a wide, uniform viewing angle, making the emitted light easily visible from various perspectives, which is essential for status indicators.

The target markets for these LEDs are broad, encompassing any electronic system requiring low-power status indication. This includes, but is not limited to, portable battery-operated devices, telecommunications equipment, computer peripherals like keyboards, and general-purpose low-power DC circuits where efficiency and longevity are paramount.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. For all color variants in this series, the continuous power dissipation is rated at 75mW at an ambient temperature (T_A) of 25°C. The maximum continuous forward current is 30mA. A derating factor of 0.4 mA/°C applies linearly from 70°C, meaning the allowable continuous current decreases as temperature rises above this point to prevent thermal overstress.

The peak forward current, for pulsed operation at a 1/10 duty cycle and 0.1ms pulse width, is higher: 90mA for the red spectrum LEDs (Hyper Red, Super Red, Red) and 60mA for the yellow/orange/green spectrum LEDs. The maximum reverse voltage is 5V at a leakage current of 100µA. The operating and storage temperature range is specified from -40°C to +100°C, indicating robust performance across a wide environmental range. Lead soldering temperature is rated at 260°C for 5 seconds when measured 1.6mm from the LED body.

2.2 Electrical & Optical Characteristics

The performance is detailed across three main series, distinguished by their luminous intensity and viewing angle: the LTL1CHJxDNN (F Series), LTL2F7JxDNN (H Series), and LTL2R3JxDNN (H Series with higher intensity). All testing is performed at T_A=25°C and I_F=2mA.

Luminous Intensity (I_v): This is the primary measure of perceived brightness. For the F and standard H series (LTL1CHJx/LTL2F7Jx), the typical luminous intensity ranges from 5.0 to 7.2 mcd depending on the color. The LTL2R3Jx series offers higher typical intensity, ranging from 7.2 to 10.6 mcd. All parts have a minimum intensity of 3.0 or 3.8 mcd, ensuring a baseline brightness level.

Viewing Angle (2θ_1/2): The LTL1CHJx and LTL2F7Jx series feature a wide 60-degree viewing angle (where intensity is half the on-axis value). The LTL2R3Jx series has a narrower 45-degree viewing angle, which typically correlates with a higher axial intensity for a given drive current, as observed in the data.

Wavelength Parameters: Key spectral characteristics are defined:

• Peak Wavelength (λ_P): The wavelength at which the optical power output is maximum. It ranges from 650nm (Hyper Red) down to 575nm (Green).
• Dominant Wavelength (λ_d): Derived from the CIE chromaticity diagram, this represents the single wavelength that best defines the perceived color of the LED. It is generally slightly shorter than the peak wavelength for these devices.
• Spectral Half-Width (Δλ): The width of the emission spectrum at half its maximum power. It is approximately 20nm for red LEDs and narrows to 15-17nm for yellow, amber, and green LEDs, indicating a more monochromatic output in the latter colors.

Forward Voltage (V_F): Critical for circuit design, the forward voltage at 2mA is very consistent across all colors and series, with a typical value of 2.4V and a maximum of 2.4V (2.3V max for Super Red). The minimum is 1.8V. This low V_F at low current is a key feature enabling compatibility with low-voltage logic.

Other Parameters: Reverse current (I_R) is guaranteed to be 100µA or less at 5V reverse bias. Junction capacitance (C) is typically 40pF when measured at 0V bias and 1MHz frequency.

3. Binning System Explanation

The datasheet indicates the use of a luminous intensity binning system. Note 2 states "Luminous intensity rank classified products support two ranks," and Note 4 specifies that "Iv classification code is marked on each packing bag." This implies that LEDs are sorted (binned) based on their measured luminous intensity at the test condition. Customers receive products within a specific intensity range (e.g., a minimum and typical value), ensuring consistency in brightness within a production lot. The exact bin codes and their corresponding intensity ranges are not detailed in this excerpt but would be critical for high-volume procurement to maintain application uniformity.

While not explicitly stated as a formal binning system for wavelength, the listing of multiple color options (Hyper Red, Super Red, Red, etc.) with specific dominant and peak wavelengths effectively serves as a color binning system. Designers select the part number corresponding to their desired color point.

4. Performance Curve Analysis

Although specific graphical curves are referenced (Fig.1 for peak emission measurement, Fig.5 for viewing angle definition) but not provided in the text, their implications can be discussed based on standard LED behavior and the parameters given.

I-V (Current-Voltage) Curve: The specified V_F of 1.8-2.4V at 2mA indicates the operating point on the LED's I-V curve. This curve is exponential. At currents significantly below 2mA, V_F would be lower; driving the LED at its maximum continuous current of 30mA would result in a higher V_F, likely exceeding 2.4V, which must be considered in the driving circuit's voltage headroom.

Temperature Characteristics: The derating factor of 0.4 mA/°C above 70°C is a direct indicator of thermal performance. It highlights that the maximum allowable current decreases as the junction temperature increases. This is crucial for design reliability, especially in enclosed spaces or high ambient temperatures. The forward voltage (V_F) of AlInGaP LEDs typically has a negative temperature coefficient, meaning it decreases slightly as temperature rises.

Spectral Distribution: Referenced by the peak wavelength (λ_P) and spectral half-width (Δλ), the emission spectrum is relatively narrow, which is characteristic of AlInGaP material. The spectrum shifts slightly with temperature (typically towards longer wavelengths as temperature increases) and may vary slightly with drive current.

5. Mechanical & Packaging Information

The LEDs are offered in through-hole packages. The datasheet provides dimensional drawings for three series: LTL1CHx, LTL2F7x, and LTL2R3x. Key dimensional notes include:

• All dimensions are in millimeters, with tolerances of ±0.25mm unless specified otherwise.
• A maximum protrusion of resin under the flange of 1.0mm is allowed.
• Lead spacing is measured at the point where leads emerge from the package body, which is critical for PCB hole spacing.

The physical differentiation between series likely relates to lens size and shape, which directly influences the viewing angle and light output pattern. The LTL2R3x series' 45-degree viewing angle, compared to the 60-degree of the others, is a result of its specific mechanical lens design.

6. Soldering & Assembly Guidelines

The primary soldering specification provided is for the leads: they can withstand a temperature of 260°C for 5 seconds when measured 1.6mm (0.063") from the LED body. This is a standard wave or hand soldering parameter. It is crucial to adhere to this time-distance specification to prevent excessive heat from traveling up the leads and damaging the internal LED die or the epoxy lens material. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. The storage temperature range is -55°C to +100°C.

7. Packaging & Ordering Information

The part numbering system follows a structured format: LTL [Series Code] [Color Code] xDNN.

• Series Code: 1CHJ, 2F7J, or 2R3J. This defines the package style, viewing angle, and intensity group.
• Color Code: The letter following 'J' indicates the color and technology:
  • D: Hyper Red (AlInGaP)
  • R: Super Red (AlInGaP)
  • E: Red (AlInGaP)
  • F: Amber / Yellow Orange (AlInGaP)
  • Y: Yellow / Amber Yellow (AlInGaP)
  • S: Yellow (AlInGaP)
  • G: Green (AlInGaP)
• The 'xDNN' suffix likely indicates packaging options (e.g., bulk, tape-and-reel).

The luminous intensity bin code is marked on the packing bag, as per the notes. Specific packaging quantities (e.g., per bag, per reel) are not stated in this excerpt.

8. Application Recommendations

8.1 Typical Application Circuits

The most straightforward application is direct connection to a logic gate output. A simple series current-limiting resistor is required. The resistor value (R_s) can be calculated using Ohm's Law: R_s = (V_CC - V_F) / I_F. For example, with a 5V TTL supply (V_CC=5V), a V_F of 2.4V, and a desired I_F of 2mA: R_s = (5 - 2.4) / 0.002 = 1300 Ohms. A standard 1.2kΩ or 1.5kΩ resistor would be suitable. For microcontroller GPIO pins (often 3.3V), the resistor value would be smaller: e.g., (3.3 - 2.4) / 0.002 = 450Ω.

8.2 Design Considerations

Current Limiting: Always use a series resistor. Even though these LEDs are rated for low current, connecting them directly to a voltage source without current limit will destroy them almost instantly due to excessive current.

Viewing Angle Selection: Choose the 60-degree series (LTL1CHJx/LTL2F7Jx) for indicators that need to be seen from a wide range of angles (e.g., panel lights). Choose the 45-degree series (LTL2R3Jx) when a more focused, brighter-on-axis beam is desired, or when the indicator will be viewed more directly.

Color Selection: Consider the application environment. Green and yellow often offer the highest luminous efficacy for the human eye under typical lighting conditions. Red is traditional for "power on" or "standby" indicators. Amber can be useful for "warning" or "attention" states.

Thermal Management: While power dissipation is low, in high-density layouts or high ambient temperatures, ensure the maximum current is derated according to the 0.4 mA/°C factor above 70°C ambient.

9. Technical Comparison & Differentiation

The key differentiator of this product family is its characterization and guaranteed performance at a very low drive current of 2mA. Many standard LEDs are specified at 20mA. This low-current optimization offers several advantages:

1. Direct Logic Drive: Eliminates the need for transistor buffers when driving from microcontroller pins or logic ICs, saving cost and board space.
2. Ultra-Low Power Consumption: At 2mA and ~2.4V, power consumption is below 5mW per LED, which is critical for battery-powered and energy-harvesting applications.
3. Reduced Heat Generation: Lower operating current minimizes junction temperature rise, enhancing long-term reliability and lumen maintenance.

Compared to older technologies like GaAsP LEDs, the use of AlInGaP material provides higher efficiency, better temperature stability, and more saturated colors (purer reds, yellows). The availability of multiple viewing angles (45° and 60°) within the same electrical specification family provides design flexibility not always available in low-current LED lines.

10. Frequently Asked Questions (FAQs)

Q: Can I drive this LED at 20mA for more brightness?
A: While the absolute maximum continuous current is 30mA, the optical characteristics (luminous intensity, wavelength) are only specified at 2mA. Driving at 20mA will produce more light, but the exact intensity and color may vary from the datasheet values, and V_F will be higher. Ensure the power dissipation (I_F * V_F) does not exceed 75mW after derating for temperature.

Q: What is the difference between Hyper Red, Super Red, and Red?
A: The difference is in their spectral characteristics. Hyper Red (650nm peak) emits light at a longer wavelength, appearing deeper/darker red. Super Red (639nm) and standard Red (632nm) have progressively shorter wavelengths, appearing brighter red to the human eye for a given radiant power due to higher eye sensitivity in that region. The choice depends on the desired color point.

Q: How do I interpret the luminous intensity bin code on the bag?
A: The datasheet notes its existence but does not define the codes. For production, you must obtain the binning specification document from the manufacturer to understand the exact intensity range associated with each code (e.g., Code A: 3.0-4.5 mcd, Code B: 4.5-6.0 mcd). This ensures consistency in your application.

Q: Is a reverse protection diode necessary?
A: The LED can withstand a reverse voltage of 5V. If there is any possibility of a reverse voltage greater than 5V being applied across the LED (e.g., in an inductive circuit or if connected incorrectly), an external reverse polarity protection diode in parallel with the LED (cathode-to-cathode) is recommended.

11. Practical Design & Usage Examples

Example 1: Multi-Channel Status Indicator for a Router: A network router has status LEDs for Power, Internet, Wi-Fi, and Ethernet. Using the LTL2F7JGDNN (Green) for power and internet, and LTL2F7JEDNN (Red) for activity blinking, all driven directly from the main processor's GPIO pins (3.3V) with 470Ω series resistors. The 60-degree viewing angle ensures visibility from across a room. The low 2mA current per LED minimizes the total load on the processor's power rail.

Example 2: Low-Battery Warning in a Portable Device: In a handheld meter, an LTL1CHJFDNN (Amber) LED is connected to a comparator circuit monitoring the battery voltage. When voltage drops below a threshold, the comparator output goes high, lighting the LED. The low current draw (2mA) adds minimal burden to the already depleted battery, extending usable warning time.

Example 3: Backlighting for a Membrane Switch Panel: The LTL2R3Jx series with its 45-degree viewing angle and higher intensity is suitable for edge-lighting a small, translucent membrane key. The narrower beam can be directed more effectively into the light guide, providing even illumination with lower optical loss compared to a wider-angle LED.

12. Operating Principle

These LEDs are based on Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material. When a forward voltage exceeding the material's bandgap voltage (approximately 1.8-2.4V) is applied, electrons and holes are injected into the active region of the semiconductor junction. Their recombination releases energy in the form of photons (light). The specific color of the light is determined by the bandgap energy of the AlInGaP alloy, which is controlled during the crystal growth process by adjusting the ratios of Aluminum, Indium, Gallium, and Phosphorus. A diffused epoxy lens encapsulates the semiconductor die. This lens contains scattering particles that randomize the direction of the emitted light, transforming the inherently directional emission from the tiny die into a wide, uniform viewing angle suitable for indicator applications.

13. Technology Trends

The development of low-current, high-efficiency LEDs like these is driven by several enduring trends in electronics:

• Miniaturization & Integration: As devices shrink, the space and power available for indicators decrease. LEDs that perform well at sub-5mA currents are essential.
• Internet of Things (IoT) & Energy Harvesting: For battery-less or coin-cell-powered IoT sensors, every microamp matters. Optimizing indicator LEDs for minimal current draw directly extends device operational life.
• Material Advancements: Ongoing improvements in AlInGaP and InGaN (for blue/green/white) epitaxial growth and chip design continue to push the boundaries of efficiency (more light output per mA of current) and reliability.
• Standardization: There is a trend towards tighter binning and more detailed characterization at multiple current levels, giving designers greater predictability in their optical designs.

While surface-mount device (SMD) packages dominate new designs, through-hole LEDs like these remain relevant for prototyping, hobbyist use, repair, and applications requiring higher mechanical robustness or easier manual assembly.