LTS-2801AKS 0.28-inch Yellow LED Display Datasheet - Digit Height 7.0mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-2801AKS is a single-digit, seven-segment alphanumeric LED display module. It is designed to provide clear, high-contrast numeric and limited alphanumeric character representation in a compact form factor. The core technology utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material deposited on a Gallium Arsenide (GaAs) substrate, which is engineered to emit light in the yellow wavelength spectrum. This specific material choice offers advantages in efficiency and luminous intensity for the target color. The device features a gray-colored faceplate with white segment delineations, enhancing contrast and readability under various lighting conditions. Its primary design purpose is for integration into electronic equipment where space is constrained but clear numeric indication is required, such as in instrumentation panels, consumer electronics displays, and industrial control interfaces.

1.1 Key Features and Advantages

• Compact Digit Size: Features a 0.28-inch (7.0 mm) character height, making it suitable for applications with limited panel space.
• Optical Quality: Designed with continuous, uniform segments for consistent visual appearance across the digit.
• Power Efficiency: Engineered for low power requirement, contributing to energy-efficient system design.
• Superior Legibility: Offers excellent character appearance with high brightness and high contrast against the gray background.
• Wide Viewing Angle: Provides a broad viewing angle, ensuring readability from various perspectives.
• High Reliability: Benefits from solid-state construction, leading to long operational life and resistance to shock and vibration.
• Binning for Consistency: Devices are categorized (binned) for luminous intensity, allowing for matched brightness in multi-digit displays.
• Environmental Compliance: The package is lead-free, manufactured in accordance with the Restriction of Hazardous Substances (RoHS) directive.

1.2 Device Identification

The part number LTS-2801AKS specifically denotes a yellow-emitting AlInGaP LED display with a common anode electrical configuration and includes a right-hand decimal point. This naming convention allows for precise identification of the device's optical and electrical characteristics.

2. Mechanical and Package Information

The display is housed in a standard LED package designed for through-hole mounting on printed circuit boards (PCBs). Detailed dimensional drawings are provided in the datasheet, specifying the overall footprint, segment placement, and lead (pin) positions. Critical mechanical notes include tolerances of ±0.25mm on most dimensions, specifications regarding allowable cosmetic imperfections (such as foreign material or bubbles within the segment area), and pin positional tolerances. The manufacturer recommends a PCB hole diameter of 1.0 mm for optimal mechanical fit and solder joint reliability.

3. Electrical Configuration and Pinout

3.1 Internal Circuit Diagram

The device employs a common anode configuration. This means the anode terminals (positive side) of all LED segments and the decimal point are connected internally to common pins. Each individual segment (A through G) and the decimal point (D.P.) has its own dedicated cathode (negative) pin. This configuration is typical for multiplexed driving circuits, where the common anodes are selectively powered while the appropriate cathode pins are grounded to illuminate specific segments.

3.2 Pin Connection Table

The 10-pin device has the following pinout configuration: Pin 1: Cathode for segment E; Pin 2: Cathode for segment D; Pin 3: Common Anode; Pin 4: Cathode for segment C; Pin 5: Cathode for Decimal Point (D.P.); Pin 6: Cathode for segment B; Pin 7: Cathode for segment A; Pin 8: Common Anode (second connection); Pin 9: Cathode for segment G; Pin 10: Cathode for segment F. The dual common anode pins (3 and 8) are internally connected and provide design flexibility for current distribution.

4. Absolute Maximum Ratings and Characteristics

4.1 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. Key limits include: Maximum power dissipation per segment: 70 mW; Peak forward current per segment (under pulsed conditions: 1/10 duty cycle, 0.1ms pulse width): 60 mA; Continuous forward current per segment: 25 mA at 25°C, derating linearly above this temperature; Reverse voltage per segment: 5 V (Note: this is for test purposes only, continuous reverse bias operation is not supported); Operating and storage temperature range: -35°C to +105°C. The datasheet also specifies soldering conditions, limiting the temperature at the seating plane to a maximum of 260°C for 5 seconds during assembly.

4.2 Electrical and Optical Characteristics

These parameters are measured under typical conditions (Ta=25°C) and define the expected performance. Key specifications include: Average Luminous Intensity per Segment (Iv): 500 ucd (min), 1400 ucd (typ) at a forward current (If) of 1 mA; Peak Emission Wavelength (λp): 588 nm (typ) at If=20mA; Spectral Line Half-Width (Δλ): 15 nm (typ); Dominant Wavelength (λd): 587 nm (typ); Forward Voltage per Chip (Vf): 2.0 V (min), 2.60 V (typ) at If=20mA; Reverse Current per Segment (Ir): 100 µA (max) at Vr=5V; Luminous Intensity Matching Ratio: 2:1 (max) for segments within the same device. Important notes clarify that luminous intensity is measured with a CIE-standard eye-response filter and that the specified reverse voltage is solely for leakage current testing, not for functional operation.

5. Performance Curves and Graphical Data

The datasheet includes a section for typical performance curves. These graphs visually represent the relationship between key parameters, providing designers with a deeper understanding of device behavior beyond the tabulated minimum, typical, and maximum values. While the specific curves are not detailed in the provided text, typical plots for such a device would include: Forward Current (If) vs. Forward Voltage (Vf), showing the diode's IV characteristic; Relative Luminous Intensity vs. Forward Current (If), indicating how light output scales with drive current; Relative Luminous Intensity vs. Ambient Temperature (Ta), demonstrating the thermal dependence of brightness; and possibly a spectral distribution graph showing the intensity of emitted light across wavelengths, centered around the 588 nm peak.

6. Reliability Testing and Qualifications

The device undergoes a comprehensive suite of reliability tests based on established industry standards (MIL-STD, JIS). This ensures its robustness and longevity in the field. The test regimen includes: Operation Life (RTOL): 1000 hours of continuous operation at maximum rated current under room temperature conditions. Environmental Stress Tests: High Temperature High Humidity Storage (65°C, 90-95% RH for 500Hrs), High Temperature Storage (105°C for 1000Hrs), Low Temperature Storage (-35°C for 1000Hrs). Mechanical Stress Tests: Temperature Cycling (30 cycles between -35°C and 105°C) and Thermal Shock (30 cycles between -35°C and 105°C with rapid transitions). Process Validation Tests: Solder Resistance (260°C for 10 seconds) and Solderability (245°C for 5 seconds) to verify the integrity of the package leads during assembly.

7. Soldering and Assembly Guidelines

7.1 Automated Soldering Process

For wave or reflow soldering processes, the recommendation is to limit the temperature at a point 1/16 inch (approximately 1.6 mm) below the seating plane (where the package body meets the PCB) to a maximum of 260°C for a duration not exceeding 5 seconds. This profile helps prevent thermal damage to the internal LED chips and the epoxy package material.

7.2 Manual Soldering Process

When using a hand soldering iron, care must be taken to localize heat. The guideline is to apply the iron tip 1/16 inch below the seating plane for a maximum of 5 seconds, with the iron tip temperature controlled to 350°C ±30°C. Using a temperature-controlled iron and a skilled operator is crucial to avoid exceeding these limits.

8. Critical Application Cautions and Design Considerations

This section contains vital information for the design engineer to ensure safe and reliable operation of the display. Key cautions include: Intended Use: The display is designed for ordinary electronic equipment. Applications requiring exceptional reliability or where failure could jeopardize safety (aviation, medical, etc.) require prior consultation. Adherence to Ratings: Operation outside the Absolute Maximum Ratings voids responsibility for damage. Thermal and Current Management: Exceeding recommended drive currents or operating temperatures can cause severe light output degradation or premature failure. The safe operating current must be derated for high ambient temperatures. Drive Circuit Design: Constant current driving is strongly recommended for consistent brightness and longevity. The circuit must be designed to accommodate the full range of forward voltage (Vf) specified to ensure the target current is delivered. Furthermore, the circuit should incorporate protection against reverse voltages and voltage transients that may occur during power cycling. Reverse bias operation should be strictly avoided.

9. Application Notes and Design Insights

9.1 Typical Application Scenarios

The LTS-2801AKS is ideally suited for applications requiring a compact, single-digit numeric readout. Common uses include: panel meters for voltage, current, or temperature display; digital clocks and timers; appliance control panels (e.g., microwave ovens, washing machines); test and measurement equipment interfaces; and industrial controller status displays. Its yellow color offers good visibility and is often chosen for cautionary or status indicators.

9.2 Circuit Design Considerations

Designing with this display requires attention to several factors. Due to its common anode configuration, a suitable driver IC (like a 7-segment decoder/driver) or microcontroller GPIO pins configured as current sinks are needed. Current-limiting resistors must be calculated based on the supply voltage, the LED forward voltage (using the maximum Vf for worst-case design), and the desired forward current. For multiplexing multiple digits, the peak current per segment can be higher than the DC rating, but the average current must remain within the continuous forward current limit, considering the duty cycle. Heat dissipation should be considered if operating near maximum ratings or in high ambient temperatures.

9.3 Comparison and Selection Guidance

When selecting a display, compare key parameters: digit height (0.28\" is relatively small), color (yellow AlInGaP vs. red GaAsP or green/blue InGaN), brightness (luminous intensity bin), forward voltage (impacts driver design and power consumption), and viewing angle. The LTS-2801AKS's advantages lie in its efficient AlInGaP technology for yellow light, good brightness, and RoHS compliance. Designers should verify that its optical and electrical characteristics align with the specific requirements of brightness, color, power budget, and available drive voltage in their application.