LTS-2301AJE LED Display Datasheet - 0.28-inch Digit Height - AlInGaP Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTS-2301AJE is a compact, high-performance single-digit seven-segment display designed for applications requiring clear numeric readouts. Its primary function is to provide a highly legible, reliable, and energy-efficient means of displaying numerical information. The device is built using advanced AlInGaP (Aluminum Indium Gallium Phosphide) LED chip technology, which is renowned for its high efficiency and excellent color purity in the red spectrum. This makes it particularly suitable for instrumentation panels, consumer electronics, industrial controls, and any embedded system where a bright, unambiguous numeric indicator is needed.

The core advantages of this display include its excellent character appearance with continuous uniform segments, ensuring a clean and professional look. It offers high brightness and high contrast, which are critical for readability under various lighting conditions, including bright ambient light. The wide viewing angle ensures the displayed number remains visible from off-axis positions. Furthermore, its solid-state construction provides inherent reliability and long operational life compared to mechanical or other display technologies, with no moving parts to wear out.

2. Technical Parameters Deep Objective Interpretation

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The key parameter, Average Luminous Intensity (Iv), is specified with a typical value of 600 µcd at a forward current (IF) of 1mA. The minimum is 200 µcd and there is no maximum limit stated, indicating a focus on ensuring a baseline brightness. The luminous intensity matching ratio between segments is specified at a maximum of 2:1, which is important for ensuring uniform brightness across all segments of the digit, preventing some segments from appearing noticeably dimmer than others.

The color characteristics are defined by the Peak Emission Wavelength (λp) of 632 nm and the Dominant Wavelength (λd) of 624 nm, both measured at IF=20mA. This places the emitted light firmly in the red portion of the visible spectrum. The Spectral Line Half-Width (Δλ) of 20 nm indicates a relatively narrow spectral bandwidth, which contributes to the pure, saturated red color. It is important to note that luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the reported values correlate with human visual perception.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions for the device. The Absolute Maximum Ratings provide the boundaries for safe operation. The Power Dissipation per segment is 70 mW. The Continuous Forward Current per segment is 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum allowable continuous current decreases as the ambient temperature increases above 25°C to prevent overheating. For pulsed operation, a higher Peak Forward Current of 90 mA is allowed under specific conditions (1/10 duty cycle, 0.1ms pulse width). The maximum Reverse Voltage per segment is 5 V.

Under standard test conditions (TA=25°C), the typical Forward Voltage (VF) per segment is 2.6V at a current of 20mA, with a minimum of 2.05V. This voltage is crucial for designing the current-limiting circuitry. The Reverse Current (IR) is a maximum of 100 µA at the full reverse voltage of 5V, indicating good diode characteristics.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35°C to +85°C, and an identical Storage Temperature Range. This wide range makes it suitable for use in harsh environments, both indoors and outdoors. A critical assembly parameter is the maximum Solder Temperature of 260°C for a maximum duration of 3 seconds, measured at 1.6mm below the seating plane. This guideline is essential for preventing thermal damage during the reflow soldering process.

3. Binning System Explanation

The datasheet indicates that the device is \"Categorized for Luminous Intensity.\" This implies a binning or sorting process based on measured light output. Typically, LEDs are tested and grouped into bins according to specific parameters like luminous intensity, forward voltage, and sometimes wavelength. Being categorized means customers can select parts from consistent performance groups, which is vital for applications requiring multiple displays to have matched brightness levels. While the exact binning code structure is not detailed in this excerpt, the presence of this feature assures designers of a level of performance consistency across production batches.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves\" which are essential for in-depth design analysis. Although the specific curves are not provided in the text, such graphs typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This curve shows how light output increases with driving current. It is non-linear, and understanding this relationship is key to designing efficient drive circuits that achieve desired brightness without exceeding power limits.
• Forward Voltage vs. Forward Current: This confirms the diode behavior and helps in selecting appropriate series resistors or constant-current driver settings.
• Luminous Intensity vs. Ambient Temperature: This curve demonstrates how light output typically decreases as the junction temperature rises. This is critical for applications operating at high ambient temperatures.
• Spectral Distribution: A graph showing the relative intensity of light emitted across different wavelengths, centered around the peak wavelength of 632 nm.

These curves allow engineers to predict performance under conditions different from the standard test condition of 25°C.

5. Mechanical and Packaging Information

The device features a standard 10-pin single-digit seven-segment package. The Package Dimensions drawing (referenced but not detailed in text) would provide all critical mechanical outlines, including overall height, width, depth, segment window size, and pin spacing. Tolerances are noted as ±0.25 mm unless otherwise specified. The Pin Connection table is clearly provided: Pin 1 is Anode E, Pin 2 is Anode D, Pin 3 is Common Cathode, Pin 4 is Anode C, Pin 5 is Anode D.P. (decimal point), Pin 6 is Anode B, Pin 7 is Anode A, Pin 8 is the second Common Cathode, Pin 9 is Anode G, and Pin 10 is Anode F. The two common cathodes (pins 3 and 8) are internally connected, providing flexibility in PCB layout. The Internal Circuit Diagram shows a common cathode configuration, where all the cathodes of the LED segments are connected together to the common pins, and each segment anode is controlled independently.

6. Soldering and Assembly Guidelines

The key guideline provided is the solder temperature limit: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a standard specification for wave or reflow soldering processes. Designers must ensure their assembly profile stays within this limit to prevent damaging the LED chips or the plastic package. For hand soldering, a temperature-controlled iron should be used, and contact time should be minimized. No specific storage conditions beyond the temperature range are mentioned, but standard ESD (Electrostatic Discharge) precautions should be observed when handling the device.

7. Packaging and Ordering Information

The primary device part number is LTS-2301AJE. The description clarifies it is an AlInGaP Red, Common Cathode, Right-Hand Decimal type. While specific packaging details (e.g., tape and reel, tube quantities) are not in the provided excerpt, such information is typically found in a separate packaging specification or on the part's master datasheet. The model number itself may encode certain characteristics, but the naming rule is not explicitly detailed here.

8. Application Suggestions

Typical Application Scenarios: This display is ideal for any device requiring a single numeric digit. Common uses include digital multimeters, clock radios, kitchen appliances (microwaves, ovens), automotive dashboard indicators (e.g., gear position), industrial timer displays, test equipment, and consumer electronics where a simple numeric readout is sufficient.

Design Considerations:

1. Drive Circuitry: As a common cathode display, the cathodes are typically connected to ground. Each segment anode is driven high (through a current-limiting resistor or a constant-current driver) to illuminate it. The use of two common cathode pins helps distribute current and can aid in PCB routing.
2. Current Limiting: A series resistor must be used for each segment when driven by a voltage source to set the forward current. The resistor value is calculated as R = (Vcc - Vf) / If, where Vf is the forward voltage (typ. 2.6V at 20mA). For brightness control or multiplexing, constant current drivers are preferred.
3. Multiplexing: While this is a single-digit display, if multiple digits are used in a system, they can be multiplexed by rapidly switching the common cathode of each digit while driving the corresponding segment anodes. This greatly reduces the number of required I/O pins on a microcontroller.
4. Viewing Angle: The wide viewing angle allows for flexible placement in an enclosure, but the optimal legibility is typically achieved when viewed straight-on.

9. Technical Comparison

Compared to older technologies like incandescent or vacuum fluorescent displays (VFDs), this AlInGaP LED display offers significantly lower power consumption, longer lifespan, and higher shock/vibration resistance due to its solid-state nature. Compared to standard GaAsP or GaP red LEDs, AlInGaP technology provides higher luminous efficiency, resulting in greater brightness for the same drive current, and a more saturated, pure red color. The 0.28-inch digit height is a common size, offering a good balance between visibility and board space usage, being larger than 0.2-inch displays but more compact than 0.5-inch or larger digits.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of having two common cathode pins (3 and 8)?

A: They are internally connected. Having two pins helps distribute the total cathode current (which is the sum of currents from all lit segments) across two PCB traces and solder joints, improving reliability and reducing current density in any single connection. It also provides layout flexibility.

Q: Can I drive this display directly from a 5V microcontroller pin?

A: No, not directly. The typical forward voltage is 2.6V, and a microcontroller pin outputting 5V would cause excessive current to flow, potentially destroying the LED segment. You must use a current-limiting resistor in series with each segment. For a 5V supply and a target current of 20mA, the resistor value would be approximately (5V - 2.6V) / 0.02A = 120 ohms. A transistor or driver IC is often used if the microcontroller cannot source enough current.

Q: What does \"Luminous Intensity Matching Ratio of 2:1\" mean?

A: It means that the brightest segment will not be more than twice as bright as the dimmest segment when driven under the same conditions (IF=1mA). This ensures visual uniformity across the digit.

Q: How do I interpret the derating factor for continuous forward current?

A: The maximum continuous current of 25 mA is specified at 25°C ambient temperature. For every degree Celsius above 25°C, you must reduce the maximum current by 0.33 mA. For example, at 50°C, the derating is (50-25)*0.33 = 8.25 mA, so the maximum allowed continuous current becomes 25 - 8.25 = 16.75 mA per segment.

11. Practical Use Case

Case: Designing a Simple Digital Timer Display. A designer is creating a countdown timer for a laboratory device. They need a clear, single-digit display to show the remaining seconds from 9 to 0. The LTS-2301AJE is selected for its brightness and readability. The microcontroller has limited I/O pins. The solution is to connect the two common cathode pins to ground. The seven segment anodes (A-G) and the decimal point anode (DP) are connected to the microcontroller via eight individual I/O pins, each with a 120-ohm series resistor to the 5V rail (or to the microcontroller pin if it can source sufficient current). The software simply turns on the appropriate combination of segment anodes to form the desired number. The decimal point could be used as a \"blinking\" indicator when the timer reaches zero. The wide operating temperature range ensures reliability in a lab environment.

12. Principle Introduction

A seven-segment display is a form of electronic display device that uses seven individual LED segments arranged in a figure-eight pattern. By selectively illuminating specific combinations of these segments, it can represent the numerals 0-9 and some letters. Each segment is a separate LED. In a common cathode configuration like the LTS-2301AJE, the cathodes of all LEDs are connected together to a common terminal (or two, in this case). To light a segment, its corresponding anode pin is driven to a positive voltage relative to the common cathode, with appropriate current limiting. The AlInGaP material system used for the LED chips is a direct bandgap semiconductor that efficiently converts electrical energy into light in the red/orange/yellow spectrum, offering advantages in efficiency and brightness over older LED materials.

13. Development Trends

While traditional seven-segment LED displays remain widely used due to their simplicity and cost-effectiveness, display technology continues to evolve. Trends include the development of even higher efficiency LED materials, such as improved AlInGaP and the rise of GaN-based blue/green/white LEDs which enable full-color programmability. There is a move towards dot-matrix and graphic OLED/LCD displays that offer greater flexibility in showing alphanumeric characters and graphics. However, for applications where only simple, bright, highly reliable, and low-cost numeric readouts are required, single-digit seven-segment LEDs like the LTS-2301AJE continue to be an optimal and enduring solution. Their development focuses on increasing brightness per unit current (efficacy), improving color consistency, and enhancing reliability under wider environmental stresses.