LTS-4817CKS-P LED Display Datasheet - 0.39 Inch Digit Height - AlInGaP Yellow - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-4817CKS-P is a high-performance, surface-mount, single-digit LED display module. It is designed for applications requiring clear, bright numeric readouts in a compact form factor. The device utilizes advanced AlInGaP (Aluminium Indium Gallium Phosphide) LED chip technology grown on a GaAs substrate, which is known for its high efficiency and excellent color purity, particularly in the yellow spectrum. The display features a gray face with white segments, providing high contrast for optimal readability. It is configured as a common anode device, which is a standard configuration for simplifying drive circuitry in multi-digit applications, and includes a right-hand decimal point.

1.1 Key Features and Advantages

• Compact Size: Features a 0.39-inch (10.0 mm) digit height, making it suitable for space-constrained applications.
• Superior Optical Performance: Offers high brightness and high contrast ratio, ensuring excellent character appearance even in well-lit environments.
• Wide Viewing Angle: Provides consistent visibility from a broad range of angles.
• Low Power Consumption: Designed for energy-efficient operation, with a typical forward current of 20mA per segment.
• Uniform Segment Illumination: Continuous, uniform segments ensure a clean and professional-looking numeric display.
• High Reliability: Solid-state construction offers long operational life and robustness against shock and vibration.
• Quality Assurance: Devices are categorized for luminous intensity, ensuring consistent brightness levels across production batches.
• Environmental Compliance: The package is lead-free and compliant with RoHS (Restriction of Hazardous Substances) directives.

1.2 Target Applications and Market

This display is ideal for a wide range of electronic equipment requiring numeric indicators. Typical applications include industrial instrumentation (e.g., panel meters, timers, counters), consumer appliances (e.g., microwave ovens, washing machines, audio equipment), automotive dashboards (for auxiliary displays), medical devices, and test and measurement equipment. Its SMD (Surface Mount Device) package makes it perfectly suited for automated assembly processes, reducing manufacturing costs and improving reliability in high-volume production.

2. Technical Parameters and Objective Interpretation

This section provides a detailed, objective analysis of the device's electrical and optical specifications as defined in the datasheet.

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. This is the maximum power that can be safely dissipated as heat by a single LED segment.
• Peak Forward Current per Segment: 60 mA (at 1/10 duty cycle, 0.1ms pulse width). This rating is for pulsed operation only and should not be used for continuous DC driving.
• 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 * (85°C - 25°C)) = 8.2 mA.
• Operating & Storage Temperature Range: -35°C to +105°C. The device is rated for industrial temperature ranges.
• Soldering Temperature: Withstands 260°C for 3 seconds at 1/16 inch (approx. 1.6mm) below the seating plane, which is standard for lead-free reflow processes.

2.2 Electrical & Optical Characteristics (Typical at 25°C)

These parameters describe the device's performance under normal operating conditions.

• Luminous Intensity (I_V): The light output is current-dependent. At a low current of 1mA, the typical intensity is 650 µcd (microcandela). At the standard test current of 10mA, it rises significantly to 8450 µcd. Designers must select the drive current based on the required brightness and power budget.
• Forward Voltage (V_F): 2.6V typical at I_F=20mA. This parameter is crucial for designing the current-limiting circuitry. The minimum value is 2.05V, indicating some variation between individual LEDs.
• Peak/Dominant Wavelength (λ_p/λ_d): 588 nm (peak) and 587 nm (dominant). This confirms the emission is in the yellow region of the visible spectrum.
• Spectral Line Half-Width (Δλ): 15 nm. This narrow bandwidth is characteristic of AlInGaP technology and contributes to the pure color appearance.
• Reverse Current (I_R): 100 µA maximum at V_R=5V. This parameter is for test purposes only; applying a continuous reverse bias is not a normal operating condition.
• Luminous Intensity Matching Ratio: 2:1 maximum for segments within the same device. This means the dimmest segment will be at least half as bright as the brightest segment, ensuring uniform appearance.
• Cross Talk: ≤ 2.5%. This specifies the maximum amount of unintended light leakage from an adjacent, unlit segment, which is important for display clarity.

3. Binning System Explanation

The datasheet states that the devices are \"categorized for luminous intensity.\" This implies a binning process where LEDs are sorted after production based on measured light output (in µcd) at a specified test current (likely 10mA or 20mA). This ensures that customers receive parts with consistent brightness levels. While the specific bin codes are not detailed in this document, designers should consult the manufacturer for the available intensity bins to ensure consistency in their application, especially when using multiple displays side-by-side.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristics Curves.\" Although the specific graphs are not provided in the text, standard curves for such devices typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage and forward current. It is non-linear, with a sharp increase in current once the forward voltage exceeds the diode's threshold (around 2V for AlInGaP).
• Luminous Intensity vs. Forward Current: This curve is generally linear over a wide range. The intensity increases proportionally with current, up to the point of thermal saturation.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature rises. AlInGaP LEDs exhibit a negative temperature coefficient, meaning brightness drops with increasing temperature.
• Spectral Distribution: A graph showing the relative light output across wavelengths, centered around 587-588 nm with the specified 15 nm half-width.

Designers should use these curves to optimize drive conditions, understand thermal effects, and predict performance under different operating environments.

5. Mechanical and Package Information

5.1 Package Dimensions

The device is housed in a surface-mount package. Key dimensional notes from the datasheet include: all dimensions are in millimeters with a general tolerance of ±0.25 mm. Specific quality controls are in place for the display face: foreign material on a segment must be ≤10 mils, ink contamination on the surface ≤20 mils, bubbles in a segment ≤10 mils, and bending of the reflector ≤1% of its length. The plastic pin's burr is limited to a maximum of 0.14 mm. These specifications ensure consistent physical appearance and reliable mounting.

5.2 Pin Connection and Polarity

The internal circuit diagram and pin connection table show a common anode configuration for the 7-segment digit and the decimal point. The two common anode pins (pins 3 and 8) are internally connected. The cathodes for segments A through G and the decimal point (DP) are on separate pins (1, 2, 4, 5, 6, 7, 9, 10). Pin 5 is identified as the cathode for the right-hand decimal point. Correct polarity identification is critical for circuit design to avoid reverse biasing the LEDs.

5.3 Recommended Soldering Pad Pattern

A land pattern diagram is provided to guide PCB (Printed Circuit Board) design. Adhering to this recommended pattern, which includes appropriate pad size, spacing, and thermal relief features, is essential for achieving reliable solder joints during reflow soldering and for maintaining the mechanical integrity of the connection.

6. Soldering and Assembly Guidelines

6.1 SMT Soldering Instructions

The device is designed for reflow soldering. Critical instructions include:

• Reflow Profile: Maximum peak temperature of 260°C. A pre-heat stage of 120-150°C for a maximum of 120 seconds is recommended.
• Process Limit: The number of reflow process cycles must be less than two. A complete cooling to normal ambient temperature is required between the first and second soldering process if a second pass is necessary (e.g., for double-sided boards).
• Hand Soldering: If using a soldering iron, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds maximum.

Following these guidelines prevents thermal damage to the LED chips, the plastic package, and the internal wire bonds.

6.2 Moisture Sensitivity and Storage

The SMD displays are shipped in moisture-proof packaging. They must be stored at 30°C or less and 60% Relative Humidity (RH) or less. Once the sealed bag is opened, the components begin to absorb moisture from the atmosphere. If the parts are not used immediately and are not stored in a controlled dry environment (e.g., a dry cabinet), they must be baked before reflow soldering to prevent \"popcorning\" or delamination caused by rapid vapor expansion during the high-temperature reflow process. The datasheet provides specific baking conditions: 60°C for ≥48 hours for parts on reels, or 100°C for ≥4 hours / 125°C for ≥2 hours for parts in bulk. Baking should only be performed once.

7. Packaging and Ordering Information

7.1 Packing Specifications

The device is supplied on embossed carrier tape wound onto reels, suitable for automated pick-and-place machines.

• Reel Dimensions: Standard 13-inch and 22-inch reel sizes are indicated.
• Carrier Tape: Dimensions are provided and conform to EIA-481-C standards. The tape thickness is 0.40 ±0.05 mm.
• Packing Quantities: A 13-inch reel contains 800 pieces. A 22-inch reel contains tape length for 45.5 meters. The minimum packing quantity for remainder lots is 200 pieces.
• Leader and Trailer: The tape includes a leader (minimum 400mm) and trailer (minimum 40mm) to facilitate machine loading.

7.2 Part Number and Revision

The base part number is LTS-4817CKS-P. The \"-P\" suffix may indicate a specific variant or packaging type. The datasheet itself has a revision history (Revision A, effective 01/11/2020), and designers must always use the latest revision to ensure they have the most current specifications.

8. Application Notes and Design Considerations

8.1 Typical Application Circuit

For a common anode display like the LTS-4817CKS-P, the anodes (pins 3 & 8) are connected to a positive supply voltage (V_CC). Each cathode pin (for segments A-G and DP) is connected to a current-limiting resistor and then to the output of a driver IC (e.g., a decoder/driver or a microcontroller GPIO pin). The driver sinks current to ground to illuminate the segment. The value of the current-limiting resistor (R_LIMIT) is calculated using Ohm's Law: R_LIMIT = (V_CC - V_F) / I_F, where V_F is the forward voltage of the LED (use 2.6V typical) and I_F is the desired forward current (e.g., 10mA or 20mA).

8.2 Design Considerations

• Current Driving: Never connect the LED directly to a voltage source without a current-limiting mechanism (resistor or constant current driver) to prevent thermal runaway and destruction.
• Multiplexing: For multi-digit displays, a multiplexing technique is commonly used to control many segments with fewer driver pins. This involves rapidly cycling power to each digit's common anode. The LTS-4817CKS-P's peak current rating (60mA pulsed) allows for higher instantaneous currents during multiplexing to achieve the desired average brightness.
• Thermal Management: While the device itself has low power dissipation, the PCB layout should consider heat dissipation, especially if driving at higher currents or in high ambient temperatures. Adequate copper area around the pads can help.
• ESD Protection: LEDs are sensitive to electrostatic discharge (ESD). Standard ESD handling precautions should be observed during assembly.

9. Technical Comparison and Differentiation

The LTS-4817CKS-P differentiates itself through its use of AlInGaP technology for yellow emission. Compared to older technologies like GaAsP (Gallium Arsenide Phosphide), AlInGaP offers significantly higher luminous efficiency, resulting in brighter output for the same drive current, better temperature stability, and superior color purity (narrower spectral width). Its SMD package and 0.39-inch digit size position it well against other SMD numeric displays, offering a balance between readability and board space savings. The inclusion of intensity binning is a key quality differentiator for applications requiring uniform appearance.

10. Frequently Asked Questions (FAQs)

Q1: What is the difference between peak wavelength (λ_p) and dominant wavelength (λ_d)?
A1: Peak wavelength is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength is the single wavelength of monochromatic light that matches the perceived color of the LED's output. For a narrow-spectrum LED like this one, they are very close (587nm vs 588nm).

Q2: Can I drive this LED at 25mA continuously?
A2: Yes, but only if the ambient temperature (T_a) is at or below 25°C. At higher ambient temperatures, you must derate the current according to the specified 0.28 mA/°C derating factor to avoid exceeding the maximum junction temperature and degrading reliability.

Q3: Why is the reverse current test important if I shouldn't operate it in reverse?
A3: The I_R test is a quality control measure. A high reverse leakage current can indicate a defect in the LED chip's PN junction.

Q4: My assembly process requires two reflow passes. Is this allowed?
A4: Yes, but it is strictly limited to a maximum of two passes. You must ensure the board and components cool completely to room temperature between the first and second reflow cycle.

11. Practical Application Example

Scenario: Designing a simple digital timer display.
A designer is creating a countdown timer with a 2-digit display showing minutes and seconds. They would use two LTS-4817CKS-P devices. The common anodes of each digit would be connected to separate GPIO pins of a microcontroller configured as outputs. The 14 cathode pins (7 segments + DP for each digit) would be connected together across both digits (i.e., all 'A' segment cathodes connected, all 'B' segment cathodes connected, etc.) and each connected to a current-limiting resistor and then to a GPIO pin or an external driver IC capable of sinking the required current. The microcontroller would use time-division multiplexing: it would turn on the anode for the 'minutes' digit, set the cathode pattern for the desired minute number, wait a short time (e.g., 5ms), then turn off that anode, turn on the anode for the 'seconds' digit, set the cathode pattern for the seconds, wait, and repeat. This happens faster than the human eye can perceive, creating the illusion of both digits being lit continuously. The right-hand decimal point on each digit could be used as a blinking colon separator between minutes and seconds.

12. Technology Principle Introduction

The LTS-4817CKS-P is based on AlInGaP semiconductor material grown epitaxially on a Gallium Arsenide (GaAs) substrate. When a forward voltage is applied across the PN junction of this material, electrons and holes are injected into the active region where they recombine. This recombination process releases energy in the form of photons (light). The specific composition of the Aluminium, Indium, Gallium, and Phosphide atoms in the crystal lattice determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For this device, the composition is tuned to produce photons in the yellow wavelength range (~587-588 nm). The chip is then packaged with a molded plastic lens that shapes the light output and provides environmental protection.

13. Industry Trends and Developments

The trend in display technologies like the LTS-4817CKS-P is towards even higher efficiency, allowing for brighter displays at lower power consumption, which is critical for battery-powered devices. There is also a continuous push for miniaturization while maintaining or improving readability. Integration is another trend, with driver electronics sometimes being incorporated into the display module itself to simplify system design. Furthermore, advancements in materials and packaging are improving the thermal performance and long-term reliability of LEDs, allowing them to be used in more demanding environments. While full-color, dot-matrix, and OLED displays are expanding in high-end applications, single-digit, monochromatic LED displays like this one remain highly relevant due to their simplicity, robustness, low cost, and excellent readability in a wide range of lighting conditions.