LTS-2301AJD 0.28-inch Hyper Red LED Display Datasheet - Digit Height 7mm - Forward Voltage 2.6V - Power 70mW - English Technical Document

1. Product Overview

The LTS-2301AJD 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 visible, reliable numeric indicator. The core advantage of this device lies in its use of AlInGaP (Aluminum Indium Gallium Phosphide) hyper red LED chips, which offer superior brightness and efficiency compared to traditional materials. The device features a gray face with white segments, enhancing contrast and readability. It is categorized for luminous intensity, ensuring consistency in brightness across production batches. The target market includes industrial control panels, test and measurement equipment, consumer appliances, and any electronic device where a small, bright, and reliable numeric display is required.

2. In-Depth Technical Parameter Analysis

2.1 Optical Characteristics

The optical performance is central to this display's functionality. The key parameter is the Average Luminous Intensity (Iv), which ranges from a minimum of 200 µcd to a typical 600 µcd at a forward current (IF) of 1mA. This high brightness ensures visibility in various ambient lighting conditions. The light emitted is characterized by a Peak Emission Wavelength (λp) of 650 nm and a Dominant Wavelength (λd) of 639 nm, placing it firmly in the hyper red region of the spectrum. The Spectral Line Half-Width (Δλ) is 20 nm, indicating a relatively pure color emission. A Luminous Intensity Matching Ratio of 2:1 (max) ensures that the brightness difference between segments is minimal, providing a uniform appearance.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions for the display. The Absolute Maximum Ratings are critical for design reliability: the maximum continuous power dissipation per segment is 70 mW. The Continuous Forward Current per Segment is rated at 25 mA at 25°C, with a derating factor of 0.33 mA/°C above this temperature. A higher Peak Forward Current of 90 mA is allowed under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The Forward Voltage (VF) per segment is typically 2.6V at IF=20mA, with a maximum of 2.6V. The maximum Reverse Voltage (VR) is 5V, and the Reverse Current (IR) is 100 µA max at VR=5V.

2.3 Thermal Characteristics

Thermal management is implied through the derating specifications. The device has an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. The forward current derating from 25°C (0.33 mA/°C) is a direct indicator of its thermal performance; as ambient temperature increases, the maximum allowable continuous current decreases linearly to prevent overheating and ensure long-term reliability. The solder temperature rating (260°C max for 3 seconds at 1.6mm below the seating plane) is crucial for assembly processes.

3. Binning System Explanation

The datasheet indicates that the device is categorized for luminous intensity. This means the LEDs are sorted (binned) based on their measured light output at a standard test current (typically 1mA or 20mA). This binning process ensures that designers receive components with consistent brightness levels, which is vital for applications where multiple displays are used side-by-side to avoid noticeable differences in segment luminance. While the specific bin codes are not detailed in this document, the practice guarantees that the Iv parameter for a given order will fall within a predefined, narrower range than the full MIN to MAX specification.

4. Performance Curve Analysis

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

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with current, usually in a sub-linear fashion, highlighting the efficiency at different operating points.
• Forward Voltage vs. Forward Current: Demonstrates the diode's turn-on characteristics and helps in designing the current-limiting circuitry.
• Relative Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises, which is critical for high-temperature or high-current applications.
• Spectral Distribution: A plot of relative intensity versus wavelength, confirming the peak and dominant wavelengths and the shape of the emission spectrum.

These curves are essential for optimizing the drive conditions to achieve the desired brightness while maintaining efficiency and longevity.

5. Mechanical and Package Information

The device has a standard LED display package. The digit height is 0.28 inches (7.0 mm). The Package Dimensions drawing provides detailed mechanical outlines, though the exact millimeter values are not listed in the text. Tolerances are typically ±0.25 mm. The Pin Connection table is crucial for correct PCB layout. It is a 10-pin, common cathode device. The pinout is: 1(E), 2(D), 3(Common Cathode), 4(C), 5(DP), 6(B), 7(A), 8(Common Cathode), 9(G), 10(F). The two common cathode pins (3 and 8) are internally connected, providing design flexibility. The Internal Circuit Diagram confirms the common cathode architecture, where all segment anodes are independent, and the cathodes of all LEDs are tied together.

6. Soldering and Assembly Guidelines

The key assembly specification is the soldering temperature: a maximum of 260°C for a maximum of 3 seconds, measured at 1.6mm below the seating plane. This parameter is critical for wave soldering or reflow processes to prevent thermal damage to the LED chips or the plastic package. Designers must ensure their assembly profile stays within these limits. For storage, the specified range is -35°C to +85°C. It is advisable to store components in a dry, anti-static environment to prevent moisture absorption and electrostatic discharge damage before use.

7. Packaging and Ordering Information

The primary ordering code is LTS-2301AJD. The "LTS" prefix likely denotes the product family (LED display), "2301" may indicate the 0.28-inch size and hyper red type, and "AJD" could be a specific version or bin code. The datasheet does not specify bulk packaging details like reel size, tube quantity, or tray configuration. For volume production, contacting the supplier for specific packaging options (tape-and-reel, anti-static tubes) is necessary. The label on the packaging should clearly state the part number LTS-2301AJD.

8. Application Recommendations

8.1 Typical Application Scenarios

This display is ideal for:

• Digital Multimeters and Test Equipment: Where a single, bright digit is needed for a specific function or range indicator.
• Industrial Control Panels: For displaying setpoints, error codes, or status numbers on machinery.
• Consumer Appliances: Such as microwave ovens, coffee makers, or audio equipment for showing time, temperature, or track numbers.
• Medical Devices: For simple numeric readouts on monitors or handheld tools.
• Educational Kits: For demonstrating digital electronics and seven-segment decoding.

8.2 Design Considerations

• Current Limiting: Always use series current-limiting resistors for each segment anode. Calculate the resistor value based on the supply voltage (Vcc), the typical forward voltage (Vf ~2.6V), and the desired forward current (e.g., 10-20 mA for good brightness). Formula: R = (Vcc - Vf) / If.
• Multiplexing: For driving multiple digits, this common cathode display is well-suited for multiplexing. A microcontroller can sequentially enable one digit's cathode at a time while driving the segment anodes for that digit. This saves I/O pins and reduces power consumption.
• Viewing Angle: The wide viewing angle ensures readability from various positions, but consider the mounting orientation relative to the user.
• ESD Protection: While not explicitly stated, standard ESD precautions should be observed during handling and assembly.

9. Technical Comparison and Differentiation

The LTS-2301AJD differentiates itself primarily through its AlInGaP semiconductor material. Compared to older GaAsP or GaP LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. The hyper red color (639-650 nm) is often perceived as brighter by the human eye than standard red and is highly effective for alert indicators. The 0.28-inch digit height is a common size, offering a good balance between visibility and board space. Its common cathode configuration is standard and compatible with most driver ICs and microcontroller circuits. The categorization for luminous intensity is a key quality differentiator, ensuring visual consistency.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λp) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λd) is the single wavelength of monochromatic light that matches the perceived color of the emitted light. For LEDs, they are often close but not identical; λd is more relevant for color specification.

Q: Can I drive this display without current-limiting resistors?
A: No. LEDs are current-driven devices. Connecting them directly to a voltage source will cause excessive current to flow, potentially destroying the segment instantly. A series resistor is mandatory for safe operation.

Q: The two common cathode pins are connected internally. Do I need to connect both to the circuit?
A: No, you only need to connect one of them to ground (or your current sink) for the display to function. However, connecting both can provide a more robust electrical connection and better current distribution, which is good practice.

Q: How do I achieve different brightness levels?
A> Brightness is primarily controlled by the forward current (If). You can adjust the current-limiting resistor value. Alternatively, for dynamic control, you can use Pulse Width Modulation (PWM) on the cathode or anode drivers. Changing the duty cycle of the PWM signal effectively changes the average current and thus the perceived brightness.

Q: What does "categorized for luminous intensity" mean for my design?
A> It means the LEDs have been tested and sorted by their light output. When you order this part number, you can expect all units to have a similar brightness level, reducing the need for individual calibration or the risk of uneven displays in your product.

11. Practical Design and Usage Examples

Example 1: Microcontroller-Based Single Digit Display. A simple design uses a microcontroller (e.g., an Arduino) with 8 I/O pins. Seven pins are configured as outputs connected to the segment anodes (A-G) through 220Ω resistors (for a 5V supply: (5V-2.6V)/0.011A ≈ 220Ω). One pin is configured as an output connected to the common cathode, set to LOW to turn the digit on. The decimal point (DP) can be controlled by an eighth pin if needed. The microcontroller can display numbers 0-9 by setting the appropriate segment pins HIGH.

Example 2: Multiplexed Four-Digit Clock Display. Four LTS-2301AJD digits can be used to display hours and minutes (e.g., 12:45). This requires 7 segment lines (A-G) plus the decimal point line, and 4 digit control lines (each connected to one display's common cathode). A microcontroller uses a timer interrupt to refresh the display at a high frequency (e.g., 100Hz). In each interrupt cycle, it turns off all digit cathodes, sets the segment pattern for the next digit, and then turns on that digit's cathode. This happens so fast that the human eye perceives all digits as continuously lit.

12. Technical Principle Introduction

The LTS-2301AJD is based on light-emitting diode (LED) technology. An LED is a semiconductor p-n junction diode. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected into the junction region. When these charge carriers recombine, they release energy in the form of photons (light). The specific material used, AlInGaP, determines the bandgap energy of the semiconductor, which in turn dictates the wavelength (color) of the emitted light—in this case, hyper red. The seven-segment arrangement is a standardized pattern of seven rectangular LEDs (segments) that can be individually illuminated to form the numerals 0-9 and some letters. A common cathode configuration means the negative terminals (cathodes) of all LED segments are connected internally to one or more pins, simplifying circuit design where the microcontroller sinks current to ground.

13. Technology Trends and Developments

While discrete seven-segment displays like the LTS-2301AJD remain relevant for specific applications, broader trends in display technology are noteworthy. There is a general shift towards integrated display modules (LCD, OLED, TFT) that offer alphanumeric and graphical capabilities in similar or smaller form factors. However, LED segment displays retain advantages in extreme environments (wide temperature range, high brightness) and for simple, low-cost numeric readouts. The underlying LED technology continues to advance, with materials like InGaN (for blue/green/white) and improved AlInGaP offering ever-higher efficiencies and longer lifetimes. Furthermore, the drive towards miniaturization and lower power consumption in all electronics supports the continued use of efficient, direct-view LED indicators and displays where their specific benefits are required.