LTS-2807SKG-P LED Display Datasheet - 0.2-inch Digit Height - AlInGaP Green - 2.4V Forward Voltage - English Technical Document

1. Product Overview

The LTS-2807SKG-P is a compact, high-performance single-digit numeric display designed for modern surface-mount applications. It features a 0.2-inch (5.08 mm) digit height, making it suitable for devices where space is at a premium but readability is essential. The display utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce a bright green light. This material system is grown on a non-transparent GaAs substrate, which contributes to high contrast by minimizing internal light scattering and reflection. The device has a distinctive appearance with a gray face and white segments, enhancing character definition. It is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives, aligning with global environmental standards for electronic components.

1.1 Key Features and Advantages

• Compact Size with High Readability: The 0.2-inch digit height provides a clear numeric readout in a minimal footprint, ideal for consumer electronics, instrumentation, and control panels.
• Superior Optical Performance: The AlInGaP chip technology delivers high brightness and excellent contrast. The continuous, uniform segments ensure a consistent and pleasing character appearance without gaps or dim spots.
• Energy Efficiency: Designed for low power requirement, it is suitable for battery-powered or energy-conscious applications.
• Wide Viewing Angle: The display offers a broad viewing angle, ensuring the numeric readout remains visible from various perspectives, which is critical for user interfaces.
• High Reliability: As a solid-state device, it offers long operational life, resistance to shock and vibration, and consistent performance over time compared to mechanical displays.
• Quality Assurance: Devices are categorized (binned) based on luminous intensity, allowing designers to select parts with consistent brightness levels for uniform panel appearance.

1.2 Device Configuration

The LTS-2807SKG-P is configured as a common anode display. This means the anodes of all the LED segments are connected together internally to common pins (Pin 3 and Pin 8). Individual segments (A, B, C, D, E, F, G, and the decimal point DP) are controlled by applying a ground (low) signal to their respective cathode pins. The specific part number denotes an AlInGaP Green Common Anode display with a right-hand decimal point. This configuration is common and simplifies driving circuitry, as a constant voltage can be applied to the common anode while multiplexing the cathode signals to illuminate different segments.

2. Technical Parameters and Characteristics

This section provides a detailed, objective analysis of the device's electrical and optical specifications, which are fundamental for circuit design and system integration.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or near these limits is not recommended for normal use.

• Power Dissipation per Segment: 70 mW maximum. Exceeding this can lead to overheating and accelerated degradation of the LED chip.
• Peak Forward Current per Segment: 60 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This rating is for brief, high-current pulses, not for continuous operation.
• 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. For example, at 85°C, the maximum allowable continuous current would be approximately 25 mA - (0.28 mA/°C * 60°C) = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can withstand these extreme temperatures during non-operational storage and within its specified operating environment.
• Soldering Temperature: The leads can be subjected to iron soldering at 260°C for a maximum of 3 seconds, measured 1/16 inch (approx. 1.6 mm) below the seating plane of the package.

2.2 Electrical and Optical Characteristics

These are the typical operating parameters measured at an ambient temperature (Ta) of 25°C. Designers should use these values as a guide for normal operating conditions.

• Average Luminous Intensity (I_V): This is the key measure of brightness.
  • Typical value is 700 µcd (microcandelas) at a forward current (I_F) of 1 mA.
  • At 10 mA, the typical intensity rises significantly to 8400 µcd. The relationship between current and light output is generally linear within the operating range.
  • A tolerance of ±15% applies, meaning actual intensity can vary between parts.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λ_p): 574 nm (typical). This is the wavelength at which the emitted light power is maximum.
  • Spectral Line Half-Width (Δλ): 15 nm (typical). This indicates the spectral purity; a narrower width means a more monochromatic (pure) green color.
  • Dominant Wavelength (λ_d): 571 nm (typical, with a tolerance of ±1 nm). This is the wavelength perceived by the human eye and is crucial for color specification.
• Forward Voltage per Chip (V_F): 2.4 V typical (2.0 V min, tolerance ±0.1V) at I_F=20 mA. This parameter is vital for selecting the appropriate current-limiting resistor or constant-current driver. The voltage drop is relatively consistent across segments due to the use of identical LED chips.
• Reverse Current (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This test is for characterization only; the device is not designed to operate under reverse bias.
• Luminous Intensity Matching Ratio: Maximum 2:1 between any two segments within the same digit when driven at 1 mA. This ensures visual uniformity.
• Cross Talk: Specified as ≤ 2.5%. This refers to unwanted illumination of a segment when an adjacent segment is driven, caused by internal optical or electrical leakage.

2.3 Performance Curve Analysis

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

• I-V (Current-Voltage) Curve: Shows the exponential relationship between forward voltage and current. The knee voltage is around 2.0-2.4V, after which current increases rapidly with small voltage increments.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): A generally linear relationship, confirming that light output is directly proportional to drive current within the safe operating area.
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises. AlInGaP LEDs typically have good high-temperature performance compared to other technologies, but output still declines with heat.
• Spectral Distribution: A bell-shaped curve centered around 574 nm (peak) with a width defined by the 15 nm half-width, confirming the green color emission.

3. Mechanical and Package Information

3.1 Package Dimensions

The device is a surface-mount package. Key dimensional notes include:

• All dimensions are in millimeters with a general tolerance of ±0.25 mm unless otherwise specified.
• Critical quality checks include limits on foreign material within segments (≤10 mils), surface ink contamination (≥20 mils acceptable), bubbles in segments (≤10 mils), and package bending (≤1% of reflector length).
• Due to the small size of the package, the part number marked on the device is abbreviated to "2807SKG-P"; the "LTS" prefix is omitted.

3.2 Pin Configuration and Circuit Diagram

The display has a 10-pin configuration. The internal circuit diagram shows a common anode structure. The pinout is as follows:

• Pin 1: Cathode for segment E
• Pin 2: Cathode for segment D
• Pin 3: Common Anode (CA)
• Pin 4: Cathode for segment C
• Pin 5: Cathode for Decimal Point (DP)
• Pin 6: Cathode for segment B
• Pin 7: Cathode for segment A
• Pin 8: Common Anode (CA)
• Pin 9: Cathode for segment F
• Pin 10: Cathode for segment G

Pin 3 and Pin 8 are internally connected. This dual-anode design helps in current distribution and thermal management. Proper polarity identification is crucial during PCB layout and assembly to prevent damage.

3.3 Recommended Soldering Pattern (Footprint)

A recommended land pattern (footprint) for PCB design is provided. Adhering to this pattern ensures proper solder joint formation, mechanical stability, and alignment during the reflow soldering process. The pattern typically includes pad sizes and spacing that account for solder paste volume and thermal relief.

4. Assembly, Handling, and Reliability

4.1 SMT Soldering Instructions

The device is designed for reflow soldering. Critical parameters must be controlled to prevent thermal damage.

• Reflow Profile: A maximum of two reflow cycles is permitted. A cooling period to normal ambient temperature is required between cycles.
  • Pre-heat: 120–150°C for a maximum of 120 seconds.
  • Peak Temperature: 260°C maximum.
  • Time above liquidus: 5 seconds maximum at peak temperature.
• Hand Soldering: If necessary, a soldering iron can be used once only, with a tip temperature not exceeding 300°C and contact time limited to 3 seconds maximum.

4.2 Moisture Sensitivity and Storage

Like most SMD components with plastic packages, this display is sensitive to moisture absorption, which can cause "popcorning" (package cracking) during reflow.

• Storage: Unopened moisture-proof bags should be stored at ≤30°C and ≤60% Relative Humidity.
• Baking: If the bag is opened or parts are exposed to humid environments beyond specified limits, they must be baked before reflow to drive out moisture.
  • Parts on reel: Bake at 60°C for ≥48 hours.
  • Loose parts (in bulk): Bake at 100°C for ≥4 hours or 125°C for ≥2 hours.
• Important: Baking should be performed only once to avoid additional thermal stress on the package.

4.3 Packing Specification

The device is supplied on tape-and-reel for automated assembly.

• Reel Dimensions: Provided for compatibility with standard pick-and-place equipment (e.g., 13-inch or 22-inch reels).
• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions conform to EIA-481-D standards. Key specifications include a 10-sprocket-hole pitch cumulative tolerance of ±0.20 mm and camber within 1 mm over 250 mm.
• Packing Quantities: A standard 13-inch reel contains 1000 pieces. A 22-inch reel holds 56.5 meters of tape. The minimum order quantity for remainder reels is 250 pieces.
• Leader/Trailer Tape: Includes a minimum 400mm leader and 40mm trailer sections to facilitate machine loading.

5. Application Guidelines and Design Considerations

5.1 Application Scope and Warnings

The display is intended for ordinary electronic equipment in office, communication, and household applications. It is not designed or qualified for safety-critical systems (e.g., aviation, medical life-support, transportation control) where failure could jeopardize life or health. For such applications, consultation with the manufacturer is mandatory.

5.2 Driving Circuit Design

Proper design is essential for reliability and performance.

• Current Limiting: Always use a series resistor or a constant-current driver to limit the forward current to the recommended continuous value (e.g., 10-20 mA for typical brightness). Exceeding the maximum ratings leads to severe light output degradation and premature failure.
• Thermal Management: The forward current must be derated as ambient temperature increases, as specified in the Absolute Maximum Ratings. Ensure adequate PCB copper area or other heatsinking if operating in high-temperature environments.
• Reverse Voltage Protection: The driving circuit should incorporate protection (e.g., a diode in series or parallel) to prevent the application of reverse voltage across the LED segments, which can damage them.
• Multiplexing: For multi-digit applications, this common-anode display is well-suited for multiplexed driving. The refresh rate must be high enough (typically >60 Hz) to avoid visible flicker.

5.3 Typical Application Scenarios

• Consumer Electronics: Digital clocks, microwave oven displays, audio equipment readouts.
• Instrumentation: Panel meters, test equipment, handheld measurement devices.
• Industrial Controls: Process control indicators, timer displays, counter readouts.
• Automotive Aftermarket: Non-critical interior displays (e.g., for audio systems).

6. Technical Comparison and Differentiation

Compared to other single-digit displays, the LTS-2807SKG-P offers specific advantages:

• vs. Older Red GaAsP/GaP Displays: The AlInGaP technology provides significantly higher luminous efficiency (more light output per mA), better high-temperature performance, and a more saturated green color.
• vs. Blue/White InGaN Displays: The green AlInGaP LED typically has a lower forward voltage (~2.4V vs. ~3.2V+ for InGaN), potentially simplifying power supply design in low-voltage systems.
• vs. Larger Digit Displays: The 0.2-inch size offers a balance between readability and board space savings, fitting between smaller 0.15-inch and larger 0.3-inch or 0.5-inch digits.
• vs. Non-binned Displays: The categorization for luminous intensity is a key differentiator for applications requiring uniform panel brightness, reducing the need for manual calibration or current adjustment per digit.

7. Frequently Asked Questions (FAQs)

Q1: What is the purpose of the two common anode pins (3 and 8)?
A1: They are internally connected. Having two pins helps distribute the total anode current, reduces current density in a single pin/PCB trace, and can improve thermal dissipation from the package.

Q2: Can I drive this display directly from a 5V microcontroller pin?
A2: No. You must use a current-limiting resistor. For a 5V supply and a typical V_F of 2.4V, if you want 10 mA through a segment, the resistor value would be R = (5V - 2.4V) / 0.01A = 260 Ohms. A 270 Ohm resistor is a standard value close to this calculation.

Q3: Why is there a limit on the number of reflow cycles?
A3: Multiple reflow cycles subject the plastic package and internal wire bonds to repeated thermal stress, which can lead to delamination, cracking, or bond failure, compromising reliability.

Q4: What does "categorized for luminous intensity" mean in practice?
A4: The manufacturer tests and sorts the displays into different brightness bins (e.g., a high-brightness bin and a standard bin). When you order, you can specify a bin code to ensure all displays in your batch have very similar brightness, avoiding noticeable variations in your product's display.

8. Design-in Case Study

Scenario: Designing a compact digital timer for a kitchen appliance.
Requirements: Clear 1-digit readout (0-9), low power consumption, reliable operation in up to 60°C ambient temperature, and compatibility with automated assembly.
Solution: The LTS-2807SKG-P is an ideal fit.

1. Circuit Design: A microcontroller with sufficient I/O pins drives the display in a static (non-multiplexed) configuration for simplicity. A current-limiting resistor is placed on the common anode line. The forward current is set to 8 mA (derated from 25 mA considering the 60°C ambient, using the 0.28 mA/°C derating factor). This provides adequate brightness while ensuring long-term reliability.
2. PCB Layout: The recommended soldering pattern is used. Thermal relief connections are added to the anode pads to facilitate soldering while maintaining a good thermal path to a ground plane for heat dissipation.
3. Assembly: Components are placed using a pick-and-place machine from the provided tape-and-reel. A standard lead-free reflow profile with a peak temperature of 245°C is used, well within the specified 260°C limit.
4. Result: The final product features a bright, uniform, and reliable numeric display that meets all size, performance, and manufacturability requirements.

9. Technology and Market Trends

AlInGaP Technology: This material system, introduced in the 1990s, revolutionized high-brightness red, orange, and yellow LEDs and later efficient green LEDs. It remains the dominant technology for high-performance green LEDs in the 560-590 nm range due to its superior efficiency and thermal stability compared to older technologies.

Market Direction: The trend for SMD indicator and display components continues towards:

• Miniaturization: Even smaller packages with maintained or improved brightness.
• Higher Efficiency: More lumens per watt, reducing power consumption and thermal load.
• Enhanced Reliability: Improved package materials and manufacturing processes for longer lifetime in demanding environments.
• Integration: Combining the LED display with driver ICs or microcontrollers in multi-chip modules (MCMs) or system-in-package (SiP) solutions to simplify end-product design.

The LTS-2807SKG-P represents a mature and well-optimized product within this evolving landscape, offering a proven balance of size, performance, and cost for a wide range of applications.