LTS-3861JE LED Display Datasheet - 0.3-inch Digit Height - AlInGaP Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-3861JE is a high-performance, single-digit, seven-segment display module designed for applications requiring clear numeric readouts. Its core component is an Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material, which is responsible for its characteristic bright red emission. The device features a light gray face with white segment markings, providing excellent contrast for enhanced readability. With a digit height of 0.3 inches (7.62 mm), it offers a compact yet easily legible display solution suitable for a wide range of electronic equipment.

1.1 Core Advantages and Target Market

The display is engineered for reliability and efficiency. Key advantages include low power consumption, high brightness output, and a wide viewing angle, ensuring consistent performance from various perspectives. It utilizes solid-state LED technology, which offers superior longevity and shock resistance compared to older display technologies like incandescent or vacuum fluorescent displays. The device is categorized for luminous intensity, allowing for consistent brightness matching in multi-digit applications. Its primary target markets include industrial control panels, test and measurement equipment, consumer appliances, and instrumentation where clear, reliable numeric indication is required.

2. Technical Parameter Deep Dive

The performance of the LTS-3861JE is defined by a set of electrical and optical parameters measured under standard conditions (Ta=25°C). Understanding these parameters is crucial for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single illuminated segment.
• Peak Forward Current per Segment: 90 mA. This is the maximum allowable pulsed current, typically specified under conditions like a 1/10 duty cycle and 0.1 ms pulse width, used for multiplexing or brief overdrive.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at a rate of 0.28 mA/°C as ambient temperature increases above 25°C.
• Reverse Voltage per Segment: 5 V. Exceeding this voltage in reverse bias can damage the LED junction.
• Operating & Storage Temperature Range: -35°C to +105°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the component.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters under normal operating conditions.

• Average Luminous Intensity (I_V): Ranges from 320 μcd (min) to 800 μcd (typ) at a forward current (I_F) of 1 mA. This measures the perceived brightness by the human eye.
• Peak Emission Wavelength (λ_p): Typically 632 nm at I_F=20mA. This is the wavelength at which the optical power output is greatest.
• Dominant Wavelength (λ_d): Typically 624 nm at I_F=20mA. This is the single wavelength perceived by the human eye, defining the color.
• Spectral Line Half-Width (Δλ): Typically 20 nm. This indicates the spectral purity or bandwidth of the emitted light.
• Forward Voltage per Segment (V_F): Typically 2.6 V (max 2.6V) at I_F=20mA. This is the voltage drop across the LED when conducting.
• Reverse Current per Segment (I_R): Maximum 100 μA at a reverse voltage (V_R) of 5V.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1. This specifies the maximum allowable brightness variation between different segments of the same device at I_F=1mA, ensuring uniform appearance.

3. Binning System Explanation

The LTS-3861JE employs a categorization system for luminous intensity. This means devices are tested and sorted into specific bins based on their measured light output at a standard test current (typically 1mA or 20mA). This allows designers to select displays with consistent brightness levels, which is critical for multi-digit displays where uneven illumination would be visually distracting. While the specific bin codes are not detailed in this datasheet, the practice ensures that all segments within a display and across multiple displays in a system have closely matched performance.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. These graphs are essential for understanding device behavior beyond the single-point data in the tables.

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

This curve shows the relationship between the current flowing through the LED and the voltage across it. It is non-linear, exhibiting a threshold voltage (around 2V for AlInGaP red) below which very little current flows. Above this threshold, the current increases rapidly with a small increase in voltage. This characteristic necessitates the use of a current-limiting resistor or constant-current driver in series with the LED to prevent thermal runaway and destruction.

4.2 Luminous Intensity vs. Forward Current

This graph illustrates how the light output (in millicandelas or microcandelas) varies with the drive current. Generally, luminous intensity increases with current, but the relationship may not be perfectly linear, especially at higher currents where efficiency can drop due to heating effects.

4.3 Temperature Dependence

While not explicitly graphed here, the derating of continuous forward current (0.28 mA/°C) indicates a strong temperature dependence. LED forward voltage typically decreases with increasing temperature, while luminous efficiency also decreases. Proper thermal management in the application is vital to maintain performance and longevity.

5. Mechanical & Package Information

5.1 Package Dimensions

The LTS-3861JE comes in a standard 10-pin single-digit package. All critical dimensions such as overall height, width, digit window size, and pin spacing are provided in a detailed drawing. Tolerances for these dimensions are typically ±0.25 mm (0.01 inch) unless otherwise specified. This information is crucial for PCB footprint design and ensuring proper fit within the end product's enclosure.

5.2 Pin Connection and Polarity

The device has a common anode configuration. This means the anodes (positive terminals) of all LED segments are connected internally to common pins (Pin 1 and Pin 6). The cathodes (negative terminals) for each segment (A, B, C, D, E, F, G, and Decimal Point DP) are brought out to individual pins (Pins 2, 3, 4, 5, 7, 8, 9, 10). To illuminate a segment, the common anode pin(s) must be connected to a voltage source higher than the LED's forward voltage, and the corresponding cathode pin must be connected to ground (or a lower voltage) through a current-limiting resistor.

5.3 Internal Circuit Diagram

The datasheet includes an internal circuit diagram which visually confirms the common anode architecture. It shows the interconnection of the ten pins to the anodes and cathodes of the seven main segments (A-G) and the decimal point (DP). This diagram is an invaluable reference for troubleshooting and understanding the electrical layout.

6. Soldering & Assembly Guidelines

The absolute maximum rating for soldering is clearly stated: a peak temperature of 260°C for a maximum duration of 3 seconds, measured at a point 1.6mm below the package body. This is compatible with standard lead-free reflow soldering profiles. It is critical to adhere to these limits to prevent damage to the internal LED chips, wire bonds, or the plastic package material. Prolonged exposure to high temperature can cause yellowing of the lens, delamination, or increased forward voltage. Recommended storage conditions are within the specified temperature range of -35°C to +105°C in a dry environment to prevent moisture absorption.

7. Application Suggestions

7.1 Typical Application Circuits

The most common drive method for a common anode display like the LTS-3861JE is multiplexing, especially when multiple digits are used. A microcontroller sequentially activates the common anode of each digit while outputting the segment pattern for that digit on the cathode lines. This reduces the number of required I/O pins significantly. Each cathode line must have a series current-limiting resistor. The resistor value is calculated using the formula: R = (V_supply - V_F) / I_F, where V_F is the forward voltage of the LED (e.g., 2.6V) and I_F is the desired forward current (e.g., 10-20 mA).

7.2 Design Considerations

• Current Limiting: Always use a current-limiting resistor or constant-current driver. Connecting the LED directly to a voltage source will cause excessive current flow and immediate failure.
• Heat Dissipation: While power dissipation is low per segment, in multiplexed applications with high peak currents, ensure the average power and temperature derating are respected.
• Viewing Angle: The wide viewing angle is beneficial but consider the primary viewing direction during mechanical design to maximize contrast and readability.
• ESD Protection: AlInGaP LEDs can be sensitive to electrostatic discharge (ESD). Implement standard ESD handling precautions during assembly.

8. Technical Comparison

Compared to older red LED technologies like Gallium Arsenide Phosphide (GaAsP), AlInGaP offers significantly higher luminous efficiency, resulting in brighter displays at the same current, or similar brightness at lower power. It also provides better color purity (a more saturated red) and stability over temperature and time. Compared to side-glow or dot matrix displays, the seven-segment format is optimized for numeric and limited alphanumeric character display with minimal driver complexity.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the two common anode pins (Pin 1 and Pin 6)?
A: They are internally connected. Having two pins helps distribute the total anode current (which can be the sum of currents for multiple lit segments) and improves mechanical stability on the PCB.

Q: Can I drive this display with a 3.3V microcontroller without a level shifter?
A: Possibly, but you must check the forward voltage. With a typical V_F of 2.6V, the voltage drop across a current-limiting resistor would only be 0.7V (3.3V - 2.6V). For a 10mA current, this requires a very small resistor (70 ohms). Small variations in V_F or supply voltage can cause large changes in current. A 5V supply is more typical and provides better headroom for stable current control.

Q: What does \"categorized for luminous intensity\" mean for my design?
A: It means you can order devices from the same intensity bin to ensure uniform brightness across all digits in your product. If uniformity is not critical, you may receive displays from a wider range of bins.

10. Practical Use Case

Case: Designing a Digital Multimeter Display: A designer is creating a 3.5-digit multimeter. They would use four LTS-3861JE displays (three full digits and one for the \"half\" digit, typically showing only segments '1' and possibly others). The microcontroller would multiplex the displays. The high brightness and contrast ensure readability in various lighting conditions. The low power consumption is aligned with the goal of maximizing battery life in a portable instrument. The categorization for luminous intensity is critical here to prevent one digit from appearing noticeably dimmer or brighter than the others, which would degrade the professional appearance and readability of the instrument.

11. Operating Principle

The LTS-3861JE is based on the principle of electroluminescence in a semiconductor p-n junction. The active material is AlInGaP. When a forward voltage exceeding the junction's built-in potential is applied, electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. In a direct bandgap semiconductor like AlInGaP, this recombination releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, red at approximately 624-632 nm. The non-transparent GaAs substrate helps reflect light upward, improving overall light extraction efficiency from the top of the device.

12. Technology Trends

AlInGaP technology represents a mature and highly efficient solution for red, orange, and yellow LEDs. Current trends in display technology for such indicators include a continued push for higher efficiency (more lumens per watt) to enable lower power systems. There is also ongoing development in packaging to allow for even smaller form factors or different viewing characteristics. While not directly applicable to this segmented display, the broader LED industry is seeing integration of driver electronics directly with the LED die (e.g., in COB - Chip-on-Board or integrated IC-LED packages), which simplifies system design. For seven-segment displays, the core AlInGaP technology remains the dominant choice for high-brightness red applications due to its proven reliability and performance.