LTS-2806SKG-P LED Display Datasheet - 0.28 Inch Digit Height - AlInGaP Green - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-2806SKG-P is a single-digit, surface-mount device (SMD) LED display designed for applications requiring clear numeric indication in a compact form factor. It features a 0.28-inch (7.0 mm) digit height, making it suitable for integration into various electronic devices where space is at a premium. The display utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting segments, which provides a distinct green color output. The package is characterized by a gray face and white segments, enhancing contrast and readability. This device is categorized for luminous intensity and is compliant with lead-free and RoHS (Restriction of Hazardous Substances) directives, making it suitable for modern electronic manufacturing.

1.1 Key Features

• Digit Size: 0.28 inch (7.0 mm) character height.
• Technology: Utilizes AlInGaP LED chips on a non-transparent GaAs substrate for green emission.
• Uniformity: Continuous and uniform segment illumination.
• Power Efficiency: Low power requirement for energy-sensitive applications.
• Optical Performance: Excellent character appearance, high brightness, and high contrast ratio.
• Viewing Angle: Wide viewing angle for visibility from various positions.
• Reliability: Solid-state construction ensures long operational life.
• Quality Control: Devices are categorized (binned) based on luminous intensity.
• Environmental Compliance: Lead-free package compliant with RoHS standards.

1.2 Device Identification

The part number LTS-2806SKG-P identifies this specific model. It is a common anode configuration AlInGaP green LED display.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed analysis of the electrical and optical specifications that define the performance boundaries and operating conditions of the LTS-2806SKG-P display.

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 and should be avoided in reliable design.

• Power Dissipation per Segment: 70 mW. This is the maximum power that can be safely dissipated by a single LED segment without causing thermal damage.
• Peak Forward Current per Segment: 60 mA. This current is permissible only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width) to prevent overheating.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating decreases linearly above 25°C at a derating factor of 0.28 mA/°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - (0.28 mA/°C * (85°C - 25°C)) = 25 mA - 16.8 mA = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can be stored and operated within this full range.
• Soldering Temperature: The package can withstand iron soldering at 260°C for 3 seconds, measured 1/16 inch (≈1.6 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured under specified test conditions (Ta=25°C). They are used for circuit design and performance expectation.

• Average Luminous Intensity (I_V): This is the primary measure of brightness.
  • Minimum: 201 µcd, Typical: 501 µcd at I_F = 2 mA.
  • Typical: 5210 µcd at I_F = 20 mA. This shows the non-linear relationship between current and light output; a 10x increase in current yields roughly a 10x increase in intensity in this range.
  • Measurement follows the CIE eye-response curve for accuracy.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λ_p): 574 nm (typical). This is the wavelength at which the emitted optical power is greatest.
  • Dominant Wavelength (λ_d): 571 nm (typical). This is the single wavelength perceived by the human eye, defining the color (green).
  • Spectral Line Half-Width (Δλ): 15 nm (typical). This indicates the spectral purity; a smaller value means a more monochromatic color.
• Forward Voltage per Chip (V_F): 2.6 V (typical), with a maximum of 2.6 V at I_F = 20 mA. Designers must ensure the driving circuit can provide this voltage.
• Reverse Current (I_R): 100 µA (maximum) at V_R = 5V. This parameter is for test purposes only; applying continuous reverse voltage is not recommended.
• Luminous Intensity Matching Ratio: 2:1 (maximum). This specifies the maximum allowable brightness variation between segments within a single device, ensuring visual uniformity.
• Cross Talk: ≤ 2.5%. This defines the maximum amount of unintended light emission from a non-activated segment when an adjacent segment is lit.

2.3 Binning System Explanation

The datasheet states the device is \"categorized for luminous intensity.\" This implies a binning process where manufactured units are sorted (binned) based on measured light output at a standard test current (likely 2 mA or 20 mA). Designers can select bins to ensure consistent brightness across multiple displays in a product. The specific bin codes or intensity ranges are not detailed in this document but would typically be available from the manufacturer for procurement.

3. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet, their typical implications are analyzed here based on standard LED behavior and the provided parameters.

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

The typical V_F of 2.05V to 2.6V at 20mA indicates the diode's turn-on characteristic. The curve would show an exponential rise in current after the turn-on voltage (~1.8-2.0V for AlInGaP), becoming more linear at higher currents. A constant current driver is recommended over a constant voltage driver to ensure stable light output and prevent thermal runaway.

3.2 Luminous Intensity vs. Forward Current (I-L Curve)

The data points (2mA -> 501 µcd, 20mA -> 5210 µcd) suggest a largely linear relationship between current and light output in this operating range. However, efficiency (light output per unit of electrical power) typically decreases at very high currents due to increased heat. The derating of continuous current with temperature directly relates to preserving this efficiency and device lifetime.

3.3 Spectral Distribution

With a dominant wavelength of 571 nm and a half-width of 15 nm, the emitted light is a relatively pure green. The peak at 574 nm is slightly higher, which is common. This spectral information is crucial for applications where color consistency or specific wavelength interaction is important.

4. Mechanical & Package Information

4.1 Package Dimensions

The device conforms to a standard 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 defined for the display face: foreign material on segments ≤ 10 mils, ink contamination ≤ 20 mils, bubbles in segments ≤ 10 mils, and bending of the reflector ≤ 1% of its length.
• The plastic pin's burr must not exceed 0.1 mm.

A detailed dimensioned drawing is provided in the original datasheet for PCB land pattern design.

4.2 Internal Circuit Diagram & Pin Connection

The display has a common anode configuration. This means the anodes (positive terminals) of all LED segments are connected internally to common pins (Pin 4 and Pin 9). Each segment cathode (negative terminal) has its own dedicated pin. To illuminate a segment, its corresponding cathode pin must be driven low (connected to ground or a current sink) while the common anode is held high (connected to the positive supply via a current-limiting resistor).

Pinout Definition:
1: No Connection (N/C)
2: Cathode D
3: Cathode E
4: Common Anode
5: Cathode C
6: Cathode DP (Decimal Point)
7: Cathode B
8: Cathode A
9: Common Anode
10: Cathode F
11: No Connection (N/C)
12: Cathode G

The dual common anode pins (4 & 9) are likely connected internally and provide flexibility in PCB routing and potentially better current distribution.

5. Soldering & Assembly Guidelines

5.1 SMT Soldering Instructions

The device is intended for reflow soldering processes. Critical instructions include:

• Maximum Reflow Cycles: The device can withstand a maximum of two reflow soldering processes. A complete cooling down to ambient temperature is required between the first and second cycle.
• Recommended Reflow Profile:
  • Pre-heat: 120–150°C.
  • Pre-heat time: Maximum 120 seconds.
  • Peak temperature: Maximum 260°C.
  • Time above liquidus: Maximum 5 seconds.
• Hand Soldering (Iron): If necessary, iron temperature should not exceed 300°C, and contact time should not exceed 3 seconds.

Adhering to these profiles prevents thermal damage to the LED chips, plastic housing, and internal wire bonds.

5.2 Recommended Soldering Pattern

A land pattern (footprint) recommendation is provided to ensure reliable solder joint formation and mechanical stability. This pattern considers the pad size, shape, and spacing relative to the device's terminals to achieve proper solder fillets and avoid bridging.

5.3 Moisture Sensitivity & Storage

The SMD displays are shipped in moisture-proof packaging (likely with a desiccant and humidity indicator card).

• Storage Conditions: Unopened bags should be stored at ≤ 30°C and ≤ 60% Relative Humidity (RH).
• Exposure: Once the sealed bag is opened, the devices begin to absorb moisture from the environment.
• Baking Requirement: If exposed to ambient conditions beyond the specified floor life (not stated, but typically 168 hours for a Level 3 device), the parts MUST be baked before reflow to drive out absorbed moisture. Failure to do so can cause \"popcorning\" or internal delamination during the high-temperature reflow process.
• Baking Parameters (only once):
  • For parts in reel: 60°C for ≥ 48 hours.
  • For parts in bulk: 100°C for ≥ 4 hours or 125°C for ≥ 2 hours.

6. Packaging & Ordering Information

6.1 Packing Specifications

The devices are supplied on tape-and-reel for automated pick-and-place assembly.

• Reel Type: Standard 13-inch (330 mm) diameter reel.
• Quantity per Reel: 1000 pieces.
• Packing Length: 38.5 meters of carrier tape per 22-inch reel (this seems to reference the tape length, possibly for a larger master reel).
• Minimum Order Quantity (MOQ): For remainder quantities, the minimum pack is 250 pieces.
• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions conform to EIA-481 standards. The tape has a camber limit of 1 mm over 250 mm and a thickness of 0.40 ± 0.05 mm.
• Leader & Trailer: The tape includes a leader (≥ 400 mm) and trailer (≥ 40 mm) for machine feeding, with a minimum 40 mm gap between the end of the components and the start of the trailer.

7. Application Suggestions & Design Considerations

7.1 Typical Application Scenarios

• Consumer Electronics: Digital readouts on appliances, audio equipment, power strips, or chargers.
• Instrumentation: Panel meters, test equipment displays, or control system interfaces.
• Industrial Controls: Status indicators, counter displays, or parameter readouts on machinery.
• Automotive Aftermarket: Displays for auxiliary gauges or custom electronic modules (consider extended temperature requirements).

7.2 Design Considerations

• Current Limiting: Always use a series current-limiting resistor for each common anode connection. The resistor value is calculated as R = (V_supply - V_F) / I_F. For a 5V supply and a target I_F of 10 mA with V_F ~2.4V: R = (5 - 2.4) / 0.01 = 260 Ω. Use the next standard value (270 Ω).
• Multiplexing: For multi-digit displays, a multiplexing scheme can be used where common anodes of different digits are driven sequentially at a high frequency, while the cathodes (segments) are driven with the pattern for the active digit. This significantly reduces the number of required I/O pins.
• Heat Management: Observe the current derating curve for elevated ambient temperatures. Ensure adequate PCB copper or ventilation if operating near the maximum temperature or current limits.
• ESD Protection: While not explicitly stated, standard ESD (Electrostatic Discharge) handling precautions should be observed during assembly.

8. Technical Comparison & Differentiation

Compared to other single-digit SMD displays, the LTS-2806SKG-P's key differentiators are:

• Material Technology: The use of AlInGaP chips offers higher efficiency and potentially better temperature stability for green emission compared to older technologies like GaP.
• Brightness: A typical intensity of over 5000 µcd at 20 mA is quite bright for a 0.28-inch display, suitable for well-lit environments.
• Contrast: The gray face/white segment design is optimized for high contrast, improving readability.
• Package: The lead-free, RoHS-compliant SMD package aligns with modern environmental regulations and automated assembly lines.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between peak wavelength and dominant wavelength?

Peak wavelength (λ_p=574 nm) is the physical peak of the light spectrum emitted. Dominant wavelength (λ_d=571 nm) is the single wavelength that would be perceived by the human eye as having the same color. They often differ slightly. Designers concerned with color matching should reference the dominant wavelength.

9.2 Can I drive this display with a 3.3V microcontroller pin directly?

No. The forward voltage (V_F) is typically 2.05-2.6V. While 3.3V is above this, you must include a current-limiting resistor. Furthermore, a microcontroller's GPIO pin typically cannot source or sink enough current (25 mA continuous max per segment) for direct drive. Use a transistor or dedicated LED driver IC.

9.3 Why are there two common anode pins?

Having two pins (4 and 9) internally connected to the common anode allows for more flexible PCB layout, can help distribute current more evenly across the display, and provides redundancy in case one solder joint is faulty.

9.4 How do I interpret the \"2:1\" luminous intensity matching ratio?

This means that within a single device, the brightest segment will be no more than twice as bright as the dimmest segment when driven under identical conditions (I_F=2mA). This ensures visual uniformity of the displayed number.

10. Practical Design & Usage Case Study

Scenario: Designing a simple digital temperature readout for a prototype device. The microcontroller has limited I/O pins.
Implementation: Use a 3-digit version of a similar display (or three LTS-2806SKG-P units). Connect all corresponding segment cathodes (A, B, C, D, E, F, G, DP) together across the three digits, using 8 microcontroller pins. Connect each digit's common anode to a separate microcontroller pin via a small NPN transistor (e.g., 2N3904) to handle the higher cumulative segment current. The microcontroller firmware rapidly cycles (multiplexes) through enabling each digit's anode transistor one at a time while outputting the segment pattern for that digit. A refresh rate of 100 Hz or higher prevents visible flicker. Current-limiting resistors are placed on the common anode lines (before the transistors). This approach controls 3 digits with only 8+3=11 I/O pins, instead of 8*3=24 pins for direct drive.

11. Principle Introduction

The LTS-2806SKG-P operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage is applied, electrons from the n-type AlInGaP layer recombine with holes from the p-type layer. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light—in this case, green (~571 nm). The non-transparent GaAs substrate helps reflect light outward, improving efficiency. Each segment of the digit is formed by one or more of these tiny LED chips wired in parallel or series within the package.

12. Development Trends

The evolution of SMD LED displays like the LTS-2806SKG-P follows broader trends in optoelectronics:

• Increased Efficiency: Ongoing material science research aims to improve lumens per watt (efficacy), reducing power consumption for the same brightness.
• Miniaturization: While 0.28-inch is standard, there is demand for smaller digit heights in ultra-compact devices, pushing packaging and chip technology limits.
• Enhanced Color Gamut & Options: Advances in phosphor and direct semiconductor materials (like InGaN for blue/green) may offer brighter and more saturated colors or new color options in similar form factors.
• Integration: Future devices may integrate the LED driver IC or logic (e.g., a BCD-to-7-segment decoder) directly into the display package, simplifying system design.
• Improved Thermal Performance: New package materials and designs to better dissipate heat, allowing for higher drive currents and brightness or improved longevity at high ambient temperatures.

These trends focus on providing higher performance, greater design flexibility, and increased reliability in increasingly demanding applications.