LTS-2801AJD 0.28-inch Red LED Display Datasheet - Size 14.0x19.0x8.5mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-2801AJD is a single-digit, seven-segment alphanumeric LED display designed for applications requiring clear, low-power numeric indication. With a digit height of 0.28 inches (7.0 mm), it offers excellent readability in a compact form factor. The device utilizes high-efficiency Aluminium Indium Gallium Phosphide (AlInGaP) red LED chips, fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. This construction contributes to its high brightness and contrast. The display features a gray face with white segment markings, enhancing contrast and legibility under various lighting conditions.

Its core advantage lies in its optimized design for low-current operation. The segments are specifically tested and matched for excellent performance at currents as low as 1 mA per segment, making it ideal for battery-powered or energy-efficient devices. The device boasts a wide viewing angle and solid-state reliability, ensuring consistent performance over its operational life. It is categorized for luminous intensity and is offered in a lead-free package compliant with RoHS directives.

1.1 Key Features

• 0.28 inch (7.0 mm) digit height for clear visibility.
• Continuous, uniform segment appearance for a professional look.
• Very low power requirement, operable from 1 mA per segment.
• Excellent character appearance with high brightness and high contrast.
• Wide viewing angle for flexibility in mounting and viewing.
• Solid-state reliability with no moving parts.
• Luminous intensity is categorized (binned) for consistent performance.
• Lead-free package compliant with RoHS environmental standards.

1.2 Device Identification

The part number LTS-2801AJD specifies a device with AlInGaP high-efficiency red LEDs, configured in a common anode circuit, and includes a right-hand decimal point.

2. Technical Parameters Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation should always be maintained within these boundaries.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 100 mA maximum, under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width).
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This rating derates linearly at 0.33 mA/°C as ambient temperature (Ta) increases above 25°C.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Soldering Temperature: The unit can withstand 260°C for up to 5 seconds when soldered 1/16 inch (approx. 1.6 mm) below the seating plane.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (Ta) of 25°C.

• Average Luminous Intensity per Segment (I_V): 200 ucd (min), 600 ucd (typ) at a forward current (I_F) of 1 mA. This confirms its suitability for very low-current applications.
• Peak Emission Wavelength (λ_p): 650 nm (typ) at I_F=20 mA, indicating a bright red color.
• Spectral Line Half-Width (Δλ): 22 nm (typ) at I_F=20 mA.
• Dominant Wavelength (λ_d): 640 nm (typ) at I_F=20 mA.
• Forward Voltage per Chip (V_F): 2.10 V (min), 2.60 V (max) at I_F=20 mA. Designers must account for this voltage drop when calculating series resistors or designing driver circuits.
• Reverse Current per Segment (I_R): 100 µA (max) at a reverse voltage (V_R) of 5V. Important Note: This parameter is for test purposes only; the device is not intended for continuous operation under reverse bias.
• Luminous Intensity Matching Ratio: 2:1 (max) for segments within a similar lit area at I_F=1 mA, ensuring uniform brightness across the display.
• Cross Talk: Specification is less than 2.5%, minimizing unwanted illumination of adjacent segments.

3. Mechanical & Package Information

3.1 Package Dimensions

The overall package dimensions are 14.0 mm in width, 19.0 mm in height, and 8.5 mm in depth (excluding leads). Key dimensional tolerances are ±0.25 mm unless otherwise specified. Critical assembly notes include:

• Pin tip shift tolerance is ±0.40 mm.
• The recommended PCB hole diameter for the leads is 1.0 mm.
• Quality criteria limit foreign materials or bubbles within a segment to 10 mils (0.254 mm) and surface ink contamination to 20 mils (0.508 mm). Bending of the reflector must be less than 1% of its length.

3.2 Pin Configuration & Circuit Diagram

The display has a 10-pin single-row configuration. It is internally wired as a common anode device, meaning the anodes of all LED segments are connected together internally and brought out to two pins (3 and 8) for redundancy and lower current density. The internal circuit diagram clearly shows this common anode connection to each of the seven segments (A through G) and the decimal point (DP). Each segment cathode has its own dedicated pin.

Pin Connection Table:

1. Pin 1: Cathode for segment E
2. Pin 2: Cathode for segment D
3. Pin 3: Common Anode
4. Pin 4: Cathode for segment C
5. Pin 5: Cathode for Decimal Point (D.P.)
6. Pin 6: Cathode for segment B
7. Pin 7: Cathode for segment A
8. Pin 8: Common Anode
9. Pin 9: Cathode for segment G
10. Pin 10: Cathode for segment F

4. Performance Curve Analysis

The datasheet includes typical performance curves which are essential for detailed design analysis. While specific graph data points are not provided in the text, these curves typically illustrate the relationship between key parameters. Designers should refer to the original datasheet graphs for precise values.

• Forward Current vs. Forward Voltage (I-V Curve): This curve shows the non-linear relationship between the current flowing through an LED segment and the voltage across it. It is crucial for selecting the correct current-limiting resistor value to achieve the desired brightness without exceeding the maximum current rating.
• Luminous Intensity vs. Forward Current: This graph demonstrates how the light output (in ucd or mcd) increases with forward current. It typically shows a near-linear relationship in the normal operating range, allowing designers to tune brightness by adjusting current.
• Luminous Intensity vs. Ambient Temperature: LED light output generally decreases as the junction temperature rises. This curve helps designers understand the derating of brightness at higher operating temperatures, which is critical for applications in non-climate-controlled environments.
• Spectral Distribution: A graph showing the relative light intensity across different wavelengths, centered around the peak wavelength of 650 nm, confirming the red color output.

5. Soldering & Assembly Guidelines

5.1 Soldering Profile

Proper soldering is critical to prevent thermal damage to the LED chips and the plastic package.

• Automated Soldering (Wave/Reflow): The device can withstand a temperature of 260°C for 5 seconds at a point 1/16 inch (1.6 mm) below the seating plane (i.e., on the leads). The temperature of the display body itself should not exceed the maximum temperature rating during assembly.
• Manual Soldering: A soldering iron tip temperature of 350°C ±30°C is specified. The soldering time on each lead must not exceed 5 seconds, again measured 1/16 inch below the seating plane.

Adherence to these time and temperature limits is essential to avoid melting the plastic housing, damaging the internal wire bonds, or degrading the LED semiconductor material.

6. Application Suggestions & Design Considerations

6.1 Typical Application Scenarios

The LTS-2801AJD is suited for a wide range of electronic equipment requiring clear, low-power numeric readouts. Common applications include:

• Test and measurement equipment (multimeters, frequency counters).
• Consumer appliances (microwaves, ovens, coffee makers).
• Industrial control panels and instrumentation.
• Battery-powered devices like portable monitors or handheld tools.
• Embedded system prototypes and educational kits.

6.2 Critical Design Considerations

• Current Limiting: ALWAYS use a series current-limiting resistor for each segment or employ a constant-current driver circuit. The resistor value (R) can be calculated using Ohm's Law: R = (V_supply - V_F) / I_F, where V_F is the forward voltage of the LED (use max value for safety) and I_F is the desired forward current (e.g., 1-20 mA).
• Multiplexing: For multi-digit displays, a multiplexing technique is commonly used to control multiple digits with fewer I/O pins. Since this is a common anode display, digits are selected by applying a positive voltage to their common anode pin(s), while the segment patterns are applied to the cathode pins. Ensure the peak current during the multiplexing pulse does not exceed the absolute maximum rating.
• Heat Management: Although power dissipation is low, ensure adequate ventilation if multiple displays are used or if operating at higher currents near the maximum rating. The linear derating of continuous current above 25°C must be respected.
• Reverse Voltage Protection: The driving circuit should be designed to prevent the application of reverse voltage or voltage spikes exceeding 5V to the LED cathodes during power-up, shutdown, or in noisy electrical environments. A simple diode in parallel with the LED (cathode to anode) can provide protection, though it will affect the forward voltage.
• Viewing Angle: Mount the display considering its wide viewing angle to ensure optimal readability for the end-user.

7. Reliability Testing

The device undergoes a comprehensive suite of reliability tests based on military (MIL-STD), Japanese Industrial (JIS), and internal standards to ensure long-term performance and durability. Key tests include:

• Operating Life Test (RTOL): 1000 hours of continuous operation at maximum rated conditions to verify performance stability over time.
• Environmental Stress Tests: Including High Temperature/Humidity Storage (500 hrs at 65°C/90-95% RH), High Temperature Storage (1000 hrs at 105°C), and Low Temperature Storage (1000 hrs at -35°C).
• Thermal Stress Tests: Temperature Cycling (30 cycles between -35°C and 105°C) and Thermal Shock tests to validate robustness against thermal expansion and contraction.
• Solderability Tests: Solder Resistance (10 sec at 260°C) and Solderability (5 sec at 245°C) ensure the leads can withstand standard assembly processes.

8. Cautions & Important Notes

• This product is intended for general electronic equipment. Applications requiring exceptional reliability, especially where failure could risk life or health (aviation, medical, safety systems), require prior consultation and approval.
• The manufacturer is not responsible for damage resulting from operation outside the absolute maximum ratings or misuse of the product.
• Exceeding the recommended driving current or operating temperature can cause severe light output degradation or premature failure.
• Constant current driving is strongly recommended over constant voltage driving to ensure consistent luminous intensity and to protect the LEDs from current spikes.
• Circuit design must consider the performance of the entire system, including power supply stability and potential electrical noise.

9. Technical Comparison & Differentiation

The LTS-2801AJD differentiates itself in the market for single-digit displays through several key attributes:

• Ultra-Low Current Operation: Its characterization and matching at 1 mA per segment is a significant advantage for power-sensitive designs, where many comparable displays are only specified at 10-20 mA.
• AlInGaP Technology: Compared to older GaAsP or GaP red LEDs, AlInGaP offers higher efficiency, resulting in greater brightness for the same current or equivalent brightness at lower current, contributing to longer battery life.
• Intensity Binning: Categorization by luminous intensity allows designers to select displays with tightly matched brightness, which is critical for multi-digit applications where uniformity is visually important.
• Robust Reliability Suite: The extensive testing against military and industrial standards provides a high degree of confidence in the product's longevity and performance under stress.

10. Frequently Asked Questions (FAQ)

Q: Can I drive this display directly from a 5V microcontroller pin?
A: No. You must use a current-limiting resistor in series with each segment. For a 5V supply and a typical V_F of 2.4V at 10 mA, the resistor value would be R = (5V - 2.4V) / 0.01A = 260 Ohms. A 270 Ohm standard resistor would be suitable. The microcontroller pin acts as a current sink (for common anode) or source (for common cathode).

Q: What is the purpose of having two common anode pins (3 and 8)?
A> The two pins are internally connected. They serve two main purposes: 1) To reduce the current density through a single pin and PCB trace when all segments are lit (e.g., displaying the number '8'), and 2) To provide mechanical stability and redundancy during PCB mounting.

Q: How do I calculate the total power consumption of the display?
A> Power per segment = V_F * I_F. For example, at I_F=10 mA and V_F=2.4V, power per segment is 24 mW. If all 7 segments of the digit are on (displaying '8'), total power is 7 * 24 mW = 168 mW. This is well within the 70 mW per segment limit but must be considered for the power supply and the common anode driver.

Q: Is this display suitable for outdoor use?
A> The operating temperature range of -35°C to +85°C covers many outdoor conditions. However, the datasheet does not specify an Ingress Protection (IP) rating against dust and water. For outdoor use, the display would likely need to be behind a sealed window or within a protective enclosure to prevent moisture ingress and physical damage.

11. Operational Principle

A seven-segment display is a form of electronic display device composed of seven LED segments arranged in a figure-eight pattern. By selectively illuminating specific combinations of these segments (A through G), it can represent the numerals 0-9 and some letters (e.g., A, C, E, F, H, L, P). The LTS-2801AJD uses AlInGaP semiconductor material. When a forward voltage exceeding the diode's threshold (approx. 2.0V) is applied across an LED segment (i.e., a positive voltage on the common anode relative to the segment's cathode), electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light) at a wavelength characteristic of the material—in this case, red light at around 650 nm. The non-transparent GaAs substrate helps reflect more light out through the top of the chip, improving overall efficiency. The gray face and white markings absorb ambient light, reducing reflections and increasing contrast, making the lit red segments appear brighter and sharper.