LTS-2306CKD-P LED Display Datasheet - 0.28-inch Digit Height - Hyper Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-2306CKD-P is a surface-mount device (SMD) designed as a single-digit numeric display. It utilizes advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology on a Gallium Arsenide (GaAs) substrate to produce a hyper red emission. The primary application is in electronic equipment where a compact, reliable, and bright numeric indicator is required, such as in instrumentation panels, consumer electronics, and communication devices.

1.1 Core Features and Advantages

The device offers several key advantages for design engineers:

• Compact Form Factor: Features a digit height of 0.28 inches (7.0 mm), making it suitable for space-constrained applications.
• High Optical Performance: Delivers high brightness and excellent contrast due to the AlInGaP chip technology, ensuring clear character visibility.
• Uniform Segment Illumination: The segments are designed for continuous and uniform light output, enhancing readability.
• Wide Viewing Angle: Provides consistent luminosity across a broad viewing range.
• Low Power Consumption: Operates efficiently with low current requirements.
• Enhanced Reliability: As a solid-state device, it offers long operational life and robustness against vibration.
• Environmental Compliance: The package is lead-free and compliant with RoHS directives.
• Binning for Consistency: Devices are categorized (binned) for luminous intensity, allowing for matched brightness in multi-digit displays.

1.2 Device Identification

The part number LTS-2306CKD-P specifies a common cathode configuration with AlInGaP Hyper Red LED chips.

2. Technical Parameters: In-Depth Objective Analysis

This section provides a detailed, objective breakdown of the device's operational limits and performance characteristics.

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.
• Peak Forward Current per Segment: 90 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is for short-duration testing, not continuous operation.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly above 25°C at a rate of 0.28 mA/°C. For example, at 85°C, the maximum allowable continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.28 mA/°C) = 8.2 mA.
• Temperature Range: Operating and storage temperature range is -35°C to +105°C.
• Soldering Temperature: Withstands iron soldering at 260°C for 3 seconds, measured 1/16 inch below the seating plane.

2.2 Electrical and Optical Characteristics

These are typical values measured under specified test conditions at an ambient temperature (Ta) of 25°C. They define the expected performance in normal operation.

• Luminous Intensity (Iv): Ranges from 201 µcd (min) to 650 µcd (typ) at a forward current (IF) of 1 mA. At 10 mA, the typical intensity is 8250 µcd. Intensity is measured using a filter that approximates the photopic (CIE) eye-response curve.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λp): 650 nm (typical).
  • Dominant Wavelength (λd): 639 nm (typical).
  • Spectral Line Half-Width (Δλ): 20 nm (typical). This indicates the spectral purity of the emitted red light.
• Forward Voltage per Chip (VF): Typically 2.6V, with a maximum of 2.6V at IF=20mA. The minimum is 2.05V. Circuit design must account for this range to ensure proper current regulation.
• Reverse Current (IR): Maximum of 100 µA at a reverse voltage (VR) of 5V. This parameter is for test purposes only; the device is not designed for continuous reverse bias operation.
• Luminous Intensity Matching Ratio: A maximum ratio of 2:1 between segments under similar lighting conditions at IF=1mA. This is important for ensuring uniform appearance.
• Cross Talk: Specified as ≤ 2.5%, referring to unwanted electrical or optical interference between segments.

3. Binning System Explanation

The datasheet indicates that devices are categorized for luminous intensity. This binning process groups LEDs based on their measured light output at a standard test current. Using binned parts ensures consistency in brightness across all digits in a multi-digit display, preventing some digits from appearing brighter or dimmer than others, which is critical for user interface quality.

4. Performance Curve Analysis

While specific graphical data is referenced in the PDF, typical curves for such devices would include:

• Current vs. Voltage (I-V) Curve: Shows the exponential relationship between forward current and forward voltage, crucial for designing the current-limiting circuitry.
• Luminous Intensity vs. Forward Current (Iv-IF): Demonstrates how light output increases with current, typically in a near-linear relationship within the operating range before efficiency drops at very high currents.
• Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as the junction temperature rises, highlighting the importance of thermal management.
• Spectral Distribution: A plot showing the relative power emitted across different wavelengths, centered around the dominant and peak wavelengths.

5. Mechanical and Package Information

5.1 Package Dimensions

The device conforms to a specific SMD footprint. Key dimensional notes include tolerances of ±0.25 mm unless specified otherwise, and quality controls on foreign material, ink contamination, bubbles in the segment, bending of the reflector, and plastic pin burrs.

5.2 Pin Connection and Polarity

The internal circuit diagram shows a common cathode configuration for the single digit. The pinout is as follows: Pins 4 and 9 are the common cathodes. The anodes for segments A, B, C, D, E, F, G, and DP (decimal point) are connected to specific pins (8, 7, 5, 2, 3, 10, 12, and 6 respectively). Pins 1 and 11 have no connection (NC). Correct polarity must be observed during assembly.

5.3 Recommended Soldering Pattern

A land pattern (footprint) is provided for PCB design to ensure reliable solder joint formation and proper alignment during the reflow process.

6. Soldering and Assembly Guidelines

6.1 SMT Soldering Instructions

The device is intended for surface-mount technology (SMT) assembly. Critical instructions include:

• Reflow Soldering (Maximum 2 cycles):
  • Pre-heat: 120–150°C.
  • Pre-heat Time: Maximum 120 seconds.
  • Peak Temperature: Maximum 260°C.
  • Time Above Liquidus: Maximum 5 seconds.
  • A cooling process to normal temperature is required between the first and second soldering cycle if rework is necessary.
• Hand Soldering (Iron): Maximum tip temperature of 300°C for a maximum of 3 seconds.

6.2 Moisture Sensitivity and Storage

The SMD package is moisture-sensitive. To prevent \"popcorning\" or delamination during reflow:

• Storage: Store unopened bags at ≤30°C and ≤60% Relative Humidity.
• Baking: If the bag is opened or parts are exposed to humid environments, baking is required before reflow:
  • Parts in reel: 60°C for ≥48 hours.
  • Parts in bulk: 100°C for ≥4 hours or 125°C for ≥2 hours.
  • Baking should be performed only once.

7. Packaging and Ordering Information

7.1 Packing Specifications

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

• Carrier Tape: Made of black conductive polystyrene alloy. Dimensions conform to EIA-481 standards. Camber is controlled within 1 mm over 250 mm length.
• Reel Specifications:
  • 22\" reel: Packing length of 38.5 meters.
  • 13\" reel: Contains 1000 pieces.
  • Minimum order quantity for remnants is 250 pieces.
• Leader and Trailer Tape: Included on the reel for machine feeding, with minimum lengths specified (40mm for leader/trailer, 400mm between components).

8. Application Suggestions and Design Considerations

8.1 Intended Use and Precautions

The display is designed for ordinary electronic equipment. For applications requiring exceptional reliability (e.g., aviation, medical, safety systems), consultation with the manufacturer is advised prior to design.

8.2 Critical Design Considerations

• Drive Current and Thermal Management: Do not exceed the absolute maximum ratings for current and power dissipation. Excess current or high operating temperature will cause severe light output degradation and premature failure. Use the derating curve for continuous current.
• Circuit Protection: The driving circuit must protect the LEDs from reverse voltages and transient voltage spikes during power-up or shutdown.
• Constant Current Drive: Highly recommended over constant voltage drive to ensure consistent luminous intensity and longevity, as the forward voltage (VF) has a range (2.05V to 2.6V). A constant voltage source could lead to large variations in current and brightness.
• Forward Voltage Range: The circuit must be designed to deliver the intended drive current across the entire VF range of the LEDs.
• Ambient Temperature Consideration: The safe operating current must be selected based on the maximum expected ambient temperature, applying the specified derating factor.

9. Technical Comparison and Differentiation

Compared to older technologies like standard GaAsP or GaP LEDs, the AlInGaP Hyper Red chip in the LTS-2306CKD-P offers significantly higher luminous efficiency, resulting in greater brightness for the same input current. The common cathode configuration may offer design simplicity in certain multiplexing circuits compared to common anode types, depending on the driver IC used. The 0.28-inch digit height positions it in a specific niche between smaller indicators and larger panel displays.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a 5V supply and a simple resistor?
A: Yes, but careful calculation is needed. Using a typical VF of 2.6V at 10mA, the series resistor would be (5V - 2.6V) / 0.01A = 240 Ω. However, you must ensure the resistor power rating is sufficient (0.024W in this case) and account for the VF range. A constant current driver is more reliable.

Q: Why is the maximum continuous current derated with temperature?
A: The derating is due to the increase in the LED junction temperature. Higher ambient temperatures reduce the ability of the package to dissipate heat, increasing the junction temperature. Exceeding the maximum junction temperature degrades the semiconductor material, drastically shortening lifespan and reducing light output.

Q: What does \"categorized for luminous intensity\" mean for my design?
A: It means you can order parts from a specific brightness \"bin.\" For a multi-digit display, specifying the same bin code for all units ensures uniform brightness across all digits, which is aesthetically and functionally important.

Q: How critical is the moisture baking requirement?
A: Very critical for SMD packages. Absorbed moisture can vaporize rapidly during the high-temperature reflow soldering process, causing internal pressure build-up and cracking (\"popcorning\"). This leads to immediate failure or latent reliability defects.

11. Practical Application Example

Scenario: Designing a digital thermometer readout. A microcontroller with multiplexed digital I/O pins can be used to drive a 4-digit display built with four LTS-2306CKD-P units. Given the common cathode configuration, the microcontroller would sink current through the common cathode pins (switching them to ground) and source current to the appropriate segment anode pins to form numbers. A driver IC with constant current outputs per segment is ideal to manage current and multiplexing timing, ensuring consistent brightness and simplifying software control. The design must include current-limiting resistors or a constant-current driver stage, and the PCB layout must follow the recommended soldering pattern for reliable assembly.

12. Operating Principle Introduction

Light emission in the AlInGaP LED is based on electroluminescence. When a forward voltage exceeding the chip's bandgap voltage is applied, electrons and holes are injected into the active region from the n-type and p-type semiconductor layers, respectively. These charge carriers recombine, releasing energy in the form of photons (light). The specific composition of the AlInGaP crystal lattice determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, hyper red. The GaAs substrate is used for crystal growth but is not transparent to the emitted light; the chip structure is designed to allow light extraction from the top surface.

13. Technology Trends

The use of AlInGaP material systems represents a mature and highly efficient technology for red, orange, and yellow LEDs. Ongoing development in the broader LED industry focuses on increasing efficiency (lumens per watt), improving color rendering and saturation, enhancing reliability at higher temperatures, and reducing costs. For indicator and display applications, trends include further miniaturization, higher integration (e.g., embedded drivers), and the development of flexible or conformable display substrates. While newer materials like perovskites are researched for future displays, AlInGaP remains the industry standard for high-performance red emitters in discrete packages.