LTS-2807CKD-P LED Display Datasheet - 0.2 Inch Digit Height - Hyper Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-2807CKD-P is a surface-mount device (SMD) designed as a single-digit numeric display. Its core function is to provide clear, reliable numeric indication in a compact, modern package suitable for automated assembly processes. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) epitaxial layers grown on a GaAs substrate to produce its characteristic hyper red emission. This material technology is chosen for its efficiency and stability in producing high-brightness red light. The visual design features a gray faceplate with white segment markings, a combination engineered to maximize contrast and readability under various lighting conditions, making it suitable for consumer electronics, instrumentation panels, and industrial control interfaces where space is at a premium and legibility is critical.

1.1 Key Features and Advantages

The product is defined by several key performance and reliability features that differentiate it in the market for small-format displays.

• Compact Form Factor: A digit height of 0.2 inches (5.08 mm) allows for integration into densely packed PCBs without sacrificing numeric size.
• Optical Performance: The display offers high brightness and excellent contrast, facilitated by the AlInGaP chips and the gray-on-white design. A wide viewing angle ensures visibility from various positions.
• Segment Uniformity: The segments are designed for continuous and uniform illumination, preventing hot spots or dim areas that can impair character appearance.
• Energy Efficiency: It has a low power requirement, contributing to lower overall system power consumption.
• Quality and Reliability: The device features solid-state reliability and is categorized for luminous intensity, meaning units are binned for consistent brightness. It is also constructed as a lead-free package in compliance with RoHS environmental directives.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the device's operational limits and performance characteristics under defined conditions.

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 per Segment: 70 mW maximum. Exceeding this can lead to overheating and catastrophic failure.
• Peak Forward Current per Segment: 60 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is for brief, high-intensity flashes.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly by 0.28 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum continuous current would be approximately 25 mA - (0.28 mA/°C * 60°C) = 8.2 mA.
• Temperature Ranges: Operating and storage temperature range is -35°C to +105°C.
• Soldering Tolerance: The device can withstand iron soldering at 260°C for 3 seconds, with the iron tip positioned at least 1/16 inch below the seating plane.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at Ta=25°C, representing expected behavior under normal operating conditions.

• Luminous Intensity (Iv): The light output is current-dependent. At a forward current (I_F) of 1 mA, the intensity ranges from 201 to 650 µcd (microcandelas). At 10 mA, the typical value rises to 8250 µcd. A tolerance of ±15% applies to these measurements.
• Wavelength Characteristics: The device emits in the hyper red spectrum. The peak emission wavelength (λ_p) is 650 nm. The dominant wavelength (λ_d) is 639 nm with a tolerance of ±1 nm. The spectral line half-width (Δλ) is 20 nm, indicating the spread of the emitted light's wavelength.
• Forward Voltage (V_F): Typically 2.6V at I_F=20 mA, with a tolerance of ±0.1V. The minimum specified is 2.05V.
• Reverse Current (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This parameter is for test purposes only; the device is not designed for continuous reverse bias operation.
• Luminous Intensity Matching Ratio: A ratio of 2:1 maximum for segments within a similar light area at I_F=1 mA. This specifies the maximum allowable brightness variation between segments.
• Cross Talk: Specified as ≤ 2.5%, referring to unwanted illumination of a non-selected segment when an adjacent segment is driven.

3. Binning and Grading System

The datasheet indicates the product is \"categorized for luminous intensity,\" which implies a binning process.

• Luminous Intensity Binning: Devices are tested and sorted into bins based on their measured light output at a standard test current (e.g., 1 mA or 10 mA). This ensures designers receive LEDs with consistent brightness levels for uniform display appearance.
• Wavelength Binning: While not explicitly stated as binned, the tight tolerance on dominant wavelength (±1 nm) indicates tight process control, resulting in very consistent color output across all units.
• Forward Voltage Sorting: The specified V_F tolerance of ±0.1V suggests parts are likely screened to meet this electrical parameter, contributing to consistent driver circuit behavior.

4. Performance Curve Analysis

While the provided PDF excerpt references typical curves but does not display them, standard analysis for such a device would include:

• I-V (Current-Voltage) Curve: Would show the exponential relationship between forward voltage and current, with the knee voltage around 2.0-2.2V for AlInGaP red LEDs.
• Luminous Intensity vs. Forward Current (I_v-I_F): Expected to be nearly linear at lower currents, potentially showing saturation effects at higher currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: Would demonstrate the decrease in light output as junction temperature rises, a critical factor for design reliability.
• Spectral Distribution: A plot showing intensity versus wavelength, centered at 650 nm (peak) with a 20 nm half-width, confirming the hyper red color point.

5. Mechanical and Package Information

5.1 Package Dimensions

The device has a defined SMD footprint. Key dimensional notes include: all dimensions are in millimeters with a general tolerance of ±0.25 mm unless specified otherwise. Specific quality controls are noted, such as limits on foreign material, ink contamination, bubbles within the segment area, and plastic pin burrs. Due to the small size of the package, the part marking is abbreviated to \"2807CKD-P\" (the \"LTS\" prefix is omitted).

5.2 Internal Circuit and Pinout

The device has a common anode configuration. The internal circuit diagram shows ten pins corresponding to the following connections: Two pins are dedicated as common anodes (pins 3 and 8). The remaining pins are individual cathodes for segments A, B, C, D, E, F, G, and the decimal point (DP). Pin 1 is listed as \"No Connection.\" This configuration requires a current-sourcing driver to the common anode pins and current-sinking to the individual cathode pins to illuminate segments.

6. Soldering and Assembly Guidelines

6.1 SMT Soldering Instructions

The device is designed for reflow soldering processes. A critical restriction is that the number of reflow process cycles must be less than two. If a second reflow is necessary (e.g., for double-sided assembly), the board must be cooled to normal temperature between the first and second process.

• Reflow Profile (Max 2 cycles): Pre-heat to 120-150°C for a maximum of 120 seconds. The peak temperature must not exceed 260°C.
• Hand Soldering (Max 1 cycle): If using a soldering iron, the tip temperature must not exceed 300°C, and contact time must be limited to 3 seconds maximum.

6.2 Recommended Soldering Pattern

A land pattern (footprint) is provided for PCB design. Adhering to this pattern is essential for reliable solder joint formation, proper alignment, and thermal management during reflow.

6.3 Moisture Sensitivity and Storage

The components are shipped in moisture-proof packaging. They must be stored at ≤30°C and ≤60% Relative Humidity (RH). Once the sealed bag is opened, the components begin to absorb moisture from the environment. If they are not used immediately and are not stored in a dry cabinet (<10% RH is typical), they must be baked before reflow soldering to prevent \"popcorning\" or delamination damage caused by rapid vapor expansion.

• Baking Conditions: If components are on reel: 60°C for ≥48 hours. If components are in bulk: 100°C for ≥4 hours or 125°C for ≥2 hours. Baking should only be performed once.

7. Packaging and Ordering Information

7.1 Packing Specifications

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

• Reel Dimensions: Provided for both the component carrier tape and the overall reel (e.g., 13-inch and 22-inch reel options are indicated).
• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions conform to EIA-481-D standards. The tape thickness is 0.30 ±0.05 mm.
• Packing Quantities: A standard 13\" reel contains 1000 pieces. A 22\" reel contains tape length for 56.5 meters. The minimum order quantity for remainder reels is 250 pieces.
• Leader and Trailer Tape: The reel includes a leader (minimum 400mm) and trailer (minimum 40mm) for machine feeding.

8. Application Notes and Design Considerations

8.1 Intended Use and Limitations

The display is designed for ordinary electronic equipment in office, communications, and household applications. It is not rated for safety-critical or high-reliability applications where failure could jeopardize life or health (e.g., aviation, medical systems) without prior consultation and potential qualification.

8.2 Critical Design Rules

• Drive Circuit Protection: The driving circuit must include protection against reverse voltages and voltage transients, as these can instantly damage the LED junctions.
• Current Limiting: Always use a series current-limiting resistor or a constant-current driver. Never connect the LED directly to a voltage source. Calculate the resistor value based on the supply voltage (V_supply), the LED forward voltage (V_F ~2.6V), and the desired forward current (I_F). Formula: R = (V_supply - V_F) / I_F.
• Thermal Management: Observe the power dissipation and current derating rules. Operating at currents or ambient temperatures above the recommended limits will accelerate light output degradation (lumen depreciation) and can cause premature failure. Ensure adequate PCB copper area or thermal vias if operating near maximum ratings.
• Multiplexing: For multi-digit displays using multiplexing, ensure the peak current in the pulsed mode does not exceed the 60 mA absolute maximum rating, and calculate the average current to stay within the continuous current rating.

9. Technical Comparison and Differentiation

Compared to older technologies like GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP technology in the LTS-2807CKD-P offers significantly higher luminous efficiency, resulting in greater brightness for the same input current. It also typically provides better wavelength stability over temperature and lifetime. Compared to some white-segment displays that use a color filter over a blue/white LED, the monochromatic AlInGaP chip offers pure color saturation and potentially higher efficiency for the target red color. Its SMD package provides better mechanical robustness and suitability for high-volume automated manufacturing compared to through-hole LED displays.

10. Frequently Asked Questions (FAQ)

10.1 Based on Technical Parameters

Q: What resistor value should I use with a 5V supply?
A: For a typical forward voltage of 2.6V and a desired current of 10 mA, the calculation is: R = (5V - 2.6V) / 0.01A = 240 Ohms. Use the nearest standard value (e.g., 240Ω or 220Ω). Always verify actual current in circuit.

Q: Can I drive it with 20 mA continuously?
A: Yes, 20 mA is below the 25 mA maximum at 25°C. However, you must check the ambient temperature. If the operating environment is above 25°C, you must derate the current. At 70°C, the max current would be 25 mA - (0.28 mA/°C * 45°C) ≈ 12.4 mA.

Q: Why is the reverse current rating important if I shouldn't operate it in reverse?
A: It's a quality and leakage indicator. A high reverse current can signal a defective junction. The rating also informs the level of protection needed; any reverse bias event exceeding 5V or causing current over 100 µA is damaging.

Q: What does \"2:1 luminous intensity matching ratio\" mean for my design?
A: It means the dimmest segment in a digit can be no less than half as bright as the brightest segment under the same test conditions. This ensures visual uniformity. For critical applications, you may select from a tighter bin.

11. Practical Application Example

Scenario: Designing a single-digit temperature readout for a consumer appliance.
The LTS-2807CKD-P is an ideal choice. The microcontroller (MCU) port pins can sink current (connect to the segment cathodes). A single PNP transistor or a dedicated driver IC can source current to the common anode pin. The MCU firmware implements a 7-segment decoder and a multiplexing timer if multiple digits are used. The gray face/white segment provides excellent contrast against the appliance's bezel. The low power consumption aligns with energy efficiency goals. The designer must ensure the PCB layout includes the recommended solder pad pattern, place a current-limiting resistor in series with each cathode (or use a constant-current driver IC), and follow the reflow profile guidelines during manufacturing. The components must be stored in a dry environment after the reel is opened until the assembly date.

12. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor P-N junction. When a forward voltage exceeding the junction's built-in potential (roughly 2.0-2.2V for AlInGaP) is applied, electrons from the N-type material and holes from the P-type material are injected across the junction. They recombine in the active region (the AlInGaP quantum well layers). A portion of this recombination energy is released as photons (light). The specific composition of the Aluminum, Indium, Gallium, and Phosphide in the epitaxial layers determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, hyper red at ~650 nm. The common anode configuration internally connects the anodes of all LED segments, simplifying the drive circuitry by requiring only one current source node per digit.

13. Technology Trends

The use of AlInGaP for red and amber LEDs represents a mature and highly optimized technology. Current trends in display LEDs focus on several areas: 1) Increased Efficiency: Ongoing research aims to reduce efficiency droop at high currents and improve light extraction from the chip package. 2) Miniaturization: While 0.2-inch is standard, there is demand for smaller digit heights in ultra-compact devices. 3) Integration: Trends include combining the LED display with driver ICs and controllers in multi-chip modules or system-in-package (SiP) solutions to simplify end-product design. 4) Enhanced Reliability: Improvements in packaging materials and die attach techniques continue to push operational lifetime and tolerance to higher temperature reflow profiles required for lead-free soldering.