LTS-2806CKR-P LED Display Datasheet - 0.28-inch Digit Height - Super Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-2806CKR-P is a surface-mount device (SMD) designed as a single-digit numeric display. Its core function is to provide clear, reliable numerical indication in a compact, modern package suitable for automated assembly processes. The defining characteristic of this component is its use of Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material for the light-emitting chips, which are grown on a Gallium Arsenide (GaAs) substrate. This material technology is specifically chosen for producing high-efficiency light in the red to amber-orange spectrum. The visual design features a gray-colored faceplate with white segment filters, a combination intended to enhance contrast and readability when the segments are illuminated.

1.1 Key Features and Target Applications

This display is engineered for integration into consumer and industrial electronic equipment where space, power efficiency, and reliability are key considerations. Its 0.28-inch (7.0 mm) digit height offers a balance between visibility and board space conservation. The continuous, uniform segment design ensures a consistent and professional character appearance. Key advantages include low power requirement, high brightness output, excellent contrast, and a wide viewing angle, making it suitable for a variety of readout applications. It is categorized for luminous intensity, allowing for brightness matching in multi-digit applications, and is supplied in a lead-free package compliant with RoHS directives. Typical applications include instrumentation panels, household appliances, communication equipment, office automation devices, and various control panels where a single numeric digit is required.

2. Technical Specifications and Objective Interpretation

The performance of the LTS-2806CKR-P is defined by a set of absolute maximum ratings and standard electrical/optical characteristics. Understanding these parameters is critical for reliable circuit design and long-term operation.

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. The maximum power dissipation per segment is 70 mW. The peak forward current per segment is rated at 90 mA, but this is only permissible under specific pulsed conditions: a 1/10 duty cycle with a 0.1 ms pulse width. The continuous forward current per segment is derated linearly from 25 mA at 25°C. The device is rated for an operating and storage temperature range of -35°C to +105°C. For hand soldering, the iron tip should be held 1/16 inch (approximately 1.6 mm) below the seating plane for a maximum of 3 seconds at 260°C.

2.2 Electrical and Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and represent typical performance. The average luminous intensity (Iv) is a primary metric. At a forward current (If) of 1 mA, the minimum intensity is 201 µcd, with a typical value of 650 µcd. At 10 mA, the typical intensity rises significantly to 8250 µcd. The forward voltage (Vf) per chip is typically 2.6V at a test current of 20 mA, with a maximum of 2.6V. The peak emission wavelength (λp) is typically 639 nm, and the dominant wavelength (λd) is 631 nm, both measured at 20 mA, placing the output firmly in the super red color region. The spectral line half-width (Δλ) is 20 nm. The reverse current (Ir) per segment is a maximum of 100 µA at a reverse voltage (Vr) of 5V. It is crucial to note that this reverse voltage condition is for test purposes only and the device must not be operated continuously under reverse bias. The luminous intensity matching ratio between segments is specified as 2:1 maximum when driven at 1 mA.

3. Binning and Performance Matching

The datasheet indicates that the LTS-2806CKR-P is \"categorized for luminous intensity.\" This refers to a binning process where manufactured units are sorted based on their measured light output at a standard test current. This allows designers to select displays from the same or adjacent intensity bins to ensure uniform brightness across all digits in a multi-digit display, avoiding noticeable variations in segment luminosity. While specific bin codes are not detailed in this excerpt, this feature is essential for applications requiring a consistent visual appearance.

4. Performance Curve Analysis

While the specific graphs are not reproduced in text, the datasheet references \"Typical Electrical / Optical Characteristics Curves.\" These curves are invaluable for design engineers. They typically include the relationship between forward current (If) and forward voltage (Vf), showing the diode's conduction behavior. More importantly, they include curves plotting luminous intensity (Iv) against forward current (If), which is non-linear. This curve helps designers select the optimal drive current to achieve the desired brightness while managing power consumption and heat. Another critical curve would depict the variation of luminous intensity with ambient temperature (Ta), showing how light output decreases as temperature rises. This is vital for designing systems that operate in elevated temperature environments, ensuring sufficient brightness margin is included.

5. Mechanical and Package Information

5.1 Package Dimensions and Tolerances

The LTS-2806CKR-P is provided in a surface-mount package. All critical dimensions are provided in millimeters. General tolerances are ±0.25 mm unless otherwise specified. The datasheet also includes specific visual and mechanical quality criteria: foreign material on a segment must be ≤10 mils, ink contamination on the surface ≤20 mils, bubbles within a segment ≤10 mils, bending of the reflector must be ≤1% of its length, and plastic pin burrs must not exceed 0.1 mm. These criteria ensure consistent physical quality and reliable placement during assembly.

5.2 Internal Circuit and Pin Configuration

The device has an internal circuit diagram showing a common anode configuration. This means the anodes of all LED segments are connected together internally. The display has 12 pins in total. The pin connection table is essential for PCB layout: Pin 4 and Pin 9 are both Common Anode connections. The cathodes for segments A, B, C, D, E, F, G, and DP (decimal point) are connected to pins 8, 7, 5, 2, 3, 10, 12, and 6 respectively. Pins 1 and 11 are marked as \"No Connection\" (N/C). This pinout must be followed precisely to ensure correct segment illumination.

6. Soldering, Assembly, and Handling Guidelines

6.1 SMT Soldering Instructions

The device is designed for reflow soldering processes. A critical instruction is that the number of reflow process cycles must be less than two. Furthermore, the device must be allowed to cool to normal ambient temperature between the first and second soldering process if a second pass is required. The recommended reflow profile includes a pre-heat stage at 120–150°C, with a pre-heat time of 120 seconds maximum. The peak temperature during reflow must not exceed 260°C. For manual soldering with an iron, the maximum tip temperature is 300°C, with a soldering time not exceeding 3 seconds per joint.

6.2 Recommended Soldering Pattern

A land pattern (footprint) recommendation is provided for PCB design. Adhering to this pattern is crucial for achieving reliable solder joints, proper alignment, and minimizing stress on the component during thermal cycling. The pattern defines the size, shape, and spacing of the copper pads on the PCB that correspond to the device's terminals.

6.3 Moisture Sensitivity and Storage

The SMD displays are shipped in moisture-proof packaging. They should be stored at 30°C or less and 60% relative humidity (RH) or less. Once the original sealed package is opened, the components begin to absorb moisture from the atmosphere. If the parts are not stored in a controlled dry environment (e.g., a dry cabinet) after opening, they must undergo a baking process before being subjected to reflow soldering to prevent \"popcorning\" or internal delamination caused by rapid vapor expansion. Baking conditions are specified: 60°C for ≥48 hours if still on the reel, or 100°C for ≥4 hours or 125°C for ≥2 hours if in bulk. Baking should only be performed once.

7. Packaging and Ordering Specifications

The device is supplied on tape and reel for automated pick-and-place assembly. The packing reel and carrier (tape) dimensions are provided, with the carrier material specified as black conductive polystyrene alloy. The carrier dimensions comply with EIA-481 standards. A standard 22-inch reel contains 38.5 meters of tape, which holds 1000 pieces of the component. A minimum packing quantity of 250 pieces is specified for remainder orders. The tape includes leader and trailer sections (minimum 400mm and 40mm respectively) to facilitate machine feeding.

8. Application Design Considerations and Cautions

The datasheet includes important application cautions. The display is intended for ordinary electronic equipment. For applications requiring exceptional reliability where failure could jeopardize life or health (aviation, medical systems, etc.), consultation with the manufacturer is required prior to use. Designers must adhere to the absolute maximum ratings. Exceeding the recommended driving current or operating temperature can lead to severe light output degradation or premature failure. The driving circuit should include protection against reverse voltages and transient voltage spikes during power-up or shutdown. Constant current driving is recommended over constant voltage driving to ensure consistent luminous intensity regardless of forward voltage (Vf) variations between individual LEDs or over temperature. The circuit design must account for the entire specified Vf range to ensure the intended drive current is always delivered. Proper heat sinking and board layout should be considered to maintain the junction temperature within safe limits, especially when operating at higher currents or in warm environments.

9. Technical Comparison and Differentiation

The LTS-2806CKR-P differentiates itself through its specific combination of attributes. The use of AlInGaP technology for the red chips typically offers higher efficiency and better performance at elevated temperatures compared to older technologies like standard GaAsP. The 0.28-inch digit height fills a niche between smaller, less visible displays and larger, more power-hungry ones. The common anode configuration is a key differentiator; many driver ICs are designed for common anode multiplexing, making this display compatible with a wide range of standard display drivers. Its categorization for luminous intensity is a significant advantage for multi-digit designs over non-binned parts, ensuring visual consistency.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 5V supply and a simple resistor?
A: Yes, but careful calculation is needed. Using a 5V supply with a typical Vf of 2.6V per segment leaves 2.4V to be dropped across the current-limiting resistor. For a desired current of 10 mA, the resistor value would be R = V/I = 2.4V / 0.01A = 240 Ω. However, you must use one resistor per segment cathode (or per common anode if multiplexing) and account for the maximum Vf of 2.6V in your calculation to ensure the current never exceeds the maximum rating.

Q: Why is constant current drive recommended?
A: LED brightness is primarily a function of current, not voltage. The forward voltage (Vf) has a negative temperature coefficient and can vary from unit to unit. A constant voltage source with a series resistor provides an approximate constant current, but it can vary with changes in Vf. A dedicated constant current driver provides a stable current regardless of these variations, ensuring consistent brightness and longer lifespan.

Q: What does \"1/10 duty cycle, 0.1ms pulse width\" mean for the peak current rating?
A: This rating allows a brief, high-current pulse to achieve extra brightness for multiplexing or strobe effects. You can pulse a segment with 90 mA, but the pulse itself must be no wider than 0.1 milliseconds, and the average current over time must respect the 1/10 duty cycle (i.e., the segment is only on for 10% of the time). The average current in this scenario would be 9 mA (90 mA * 0.1), which must also be within the continuous current derating limits for the device's temperature.

11. Design and Usage Case Study

Scenario: Designing a single-digit temperature readout for a thermostat. The LTS-2806CKR-P is an ideal candidate. The designer selects a drive current of 5 mA per segment to balance brightness and power consumption for a battery-powered device. A microcontroller with integrated segment display driver pins is chosen. Since the display is common anode, the microcontroller's driver is configured accordingly. The PCB layout strictly follows the recommended soldering pattern. The display is stored in a dry cabinet after the reel is opened. During assembly, a single reflow pass is used. The final product exhibits a clear, uniformly bright red number that is easily readable in typical indoor lighting conditions, with low overall power draw contributing to extended battery life.

12. Technology Principle Introduction

The core light-emitting principle is based on a semiconductor p-n junction. When a forward voltage is applied, electrons from the n-type material and holes from the p-type material are injected into the junction region. When an electron recombines with a hole, it falls to a lower energy state, releasing the energy difference as a photon (light). The specific wavelength (color) of this light is determined by the energy bandgap of the semiconductor material. The LTS-2806CKR-P uses AlInGaP (Aluminum Indium Gallium Phosphide), a compound semiconductor whose bandgap can be tuned by adjusting the ratios of its constituent elements to emit efficient light in the red to amber spectral region. The GaAs substrate provides the crystalline template for growing the AlInGaP epitaxial layers.

13. Industry Trends and Context

The trend in display components like the LTS-2806CKR-P is towards higher efficiency, smaller packages, and greater integration. While discrete segment displays remain vital for specific applications, there is a parallel trend towards integrated dot-matrix displays and OLEDs that offer more flexibility in showing characters and graphics. However, for simple, high-brightness, low-cost numeric indication, SMD segment displays using advanced semiconductor materials like AlInGaP and InGaN (for blue/green/white) continue to be widely used. Demands for lower power consumption, wider operating temperature ranges, and improved reliability drive material and packaging innovations. The move to lead-free and RoHS-compliant manufacturing, as seen with this component, is a standard industry requirement driven by environmental regulations.