LTS-2301AJR 7-Segment LED Display Datasheet - 0.28-inch Digit Height - Super Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-2301AJR is a high-performance, single-digit, seven-segment alphanumeric display module. Its primary function is to provide clear, bright numeric and limited alphanumeric character representation in a wide range of electronic devices and equipment. The core application is in scenarios requiring a single-digit readout, such as panel meters, test equipment, industrial controls, consumer appliances, or as part of a multi-digit display array.

The device is engineered for excellent readability and reliability. It utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for its light-emitting segments. This material system is known for producing high-efficiency red and amber LEDs with superior performance compared to traditional GaAsP or GaP technologies. The display features a gray faceplate with white segment markings, which significantly enhances contrast and legibility when the segments are illuminated, especially under various ambient lighting conditions.

1.1 Core Advantages and Target Market

The LTS-2301AJR offers several key advantages that make it suitable for demanding applications:

• High Brightness & Contrast: The AlInGaP chips deliver high luminous intensity, while the gray face/white segment design maximizes contrast, ensuring clear visibility.
• Low Power Consumption: It operates efficiently at low forward currents, making it ideal for battery-powered or energy-conscious devices.
• Wide Viewing Angle: The design provides consistent brightness and color across a broad viewing angle, crucial for panels viewed from different positions.
• Solid-State Reliability: As an LED-based device, it offers long operational life, shock and vibration resistance, and instant-on capability without the drawbacks of filament-based or gas-discharge displays.
• Uniform Segments: The segments are designed for continuous, uniform illumination without dark spots, contributing to a professional appearance.

The target market includes industrial automation, instrumentation, medical equipment, consumer electronics (like scales or timers), automotive aftermarket displays, and any embedded system requiring a robust and clear numeric indicator.

2. Technical Parameter Deep-Dive

This section provides a detailed, objective analysis of the device's key technical parameters as defined in the datasheet.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. Key parameters are measured under standardized test conditions (typically at an ambient temperature of 25°C).

• Average Luminous Intensity (I_V): This is the measure of the perceived power of light emitted by a segment. The datasheet specifies a minimum of 200 µcd, a typical value of 480 µcd, and no stated maximum when driven at a forward current (I_F) of 1 mA. The typical value indicates the expected brightness under normal operating conditions. The intensity is measured using a sensor filtered to match the photopic (day-adapted) human eye response curve as defined by the CIE (Commission Internationale de l'Éclairage).
• Peak Emission Wavelength (λ_p): This is the wavelength at which the optical emission spectrum reaches its maximum power. For the LTS-2301AJR, the typical peak wavelength is 639 nanometers (nm), which falls within the deep red portion of the visible spectrum. This parameter defines the fundamental color of the light emitted.
• Dominant Wavelength (λ_d): At 631 nm (typical), this is the wavelength of monochromatic light that would produce a color sensation most closely matching the color of the LED's output. It is often more perceptually relevant than the peak wavelength.
• Spectral Line Half-Width (Δλ): This parameter, with a typical value of 20 nm, indicates the spectral purity or bandwidth of the emitted light. It is the width of the spectrum at half of its maximum intensity. A narrower half-width indicates a more monochromatic (pure color) light source.
• Luminous Intensity Matching Ratio (I_V-m): This ratio, specified as a maximum of 2:1, ensures consistency across the display. It means the brightness of the dimmest segment will be no less than half the brightness of the brightest segment when all are driven under identical conditions (I_F=1mA). This is critical for achieving uniform appearance.

2.2 Electrical Characteristics

The electrical parameters define the operating boundaries and conditions for the device.

• Forward Voltage per Segment (V_F): The voltage drop across an LED segment when current is flowing. The typical value is 2.6V at a forward current of 20 mA. The minimum is 2.0V. This parameter is essential for designing the current-limiting circuitry (usually a resistor in series with each segment or digit).
• Reverse Current per Segment (I_R): The maximum leakage current (100 µA) when a reverse voltage of 5V is applied. This indicates the diode's quality in blocking reverse current flow.
• Continuous Forward Current per Segment: The maximum DC current that can be continuously applied to a single segment is 25 mA at 25°C. This rating decreases linearly (derates) by 0.33 mA for every degree Celsius above 25°C to prevent thermal damage.
• Peak Forward Current per Segment: For pulsed operation (1/10 duty cycle, 0.1 ms pulse width), a segment can handle a peak current of up to 90 mA. This allows for multiplexing schemes or brief over-driving for increased perceived brightness.
• Power Dissipation per Segment: The maximum power that can be dissipated as heat by a single segment is 70 mW.

2.3 Thermal and Environmental Ratings

• Operating Temperature Range: The device is rated to function reliably in ambient temperatures from -35°C to +85°C.
• Storage Temperature Range: It can be stored without operation in temperatures from -35°C to +85°C.
• Solder Temperature: During assembly, the device can withstand a maximum soldering temperature of 260°C for a maximum duration of 3 seconds, measured 1.6mm below the seating plane of the package. This is critical for wave soldering or reflow processes.

3. Binning and Categorization System

The datasheet explicitly states that the device is \"Categorized for Luminous Intensity.\" This refers to a common practice in LED manufacturing known as \"binning.\"

Due to inherent variations in the semiconductor fabrication process, LEDs from the same production batch can have slight differences in key parameters like luminous intensity, forward voltage, and dominant wavelength. To ensure consistency for the end-user, manufacturers test and sort (bin) LEDs into groups where these parameters fall within tighter, predefined ranges.

For the LTS-2301AJR, the primary binning criterion is luminous intensity. While the datasheet provides a wide min/typ range (200-480 µcd), devices shipped for a specific order would typically be from a single bin or a combination of adjacent bins to meet the 2:1 matching ratio. Specific bin codes and their associated intensity ranges are usually defined in separate manufacturer documentation or can be specified during ordering. This system allows designers to select parts with the precise brightness level required for their application, ensuring visual consistency, especially when using multiple displays.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical datasheets for such devices include several key performance curves. Based on standard LED behavior, we can infer their importance:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph would show how the brightness (in µcd or as a relative percentage) increases with the forward current (I_F). It is typically non-linear, showing a region of rapid increase followed by a region of diminishing returns and eventual saturation or decline due to heating. This curve is vital for selecting the optimal drive current to achieve desired brightness without exceeding ratings.
• Forward Voltage vs. Forward Current: This curve shows the relationship between the applied voltage and the resulting current through the LED. It demonstrates the diode's exponential I-V characteristic. The typical V_F value (e.g., 2.6V @ 20mA) is a point on this curve.
• Relative Luminous Intensity vs. Ambient Temperature: This graph illustrates how the LED's light output decreases as the ambient (or junction) temperature increases. AlInGaP LEDs are generally more temperature-sensitive than some other types. Understanding this derating is crucial for applications operating in high-temperature environments to ensure sufficient brightness is maintained.
• Spectral Distribution: A plot of relative optical power versus wavelength, showing the peak at ~639 nm and the spectral width (Δλ) of ~20 nm at half maximum.

These curves allow engineers to model the device's behavior under non-standard conditions (different currents, temperatures) and design robust driving circuits.

5. Mechanical and Package Information

5.1 Physical Dimensions and Drawing

The device features a standard 10-pin, single-in-line (SIL) package. The package drawing provides critical dimensions for PCB (Printed Circuit Board) layout and mechanical integration:

• Digit Height: The defining feature is the 0.28-inch (7.0-millimeter) character height.
• Overall Package Dimensions: The drawing specifies the length, width, and height of the plastic body, the lead (pin) spacing, and the lead length and thickness.
• Tolerances: All linear dimensions have a standard tolerance of ±0.25 mm (±0.01 inch) unless a specific feature note states otherwise. This information is essential for ensuring the display fits correctly into a bezel or on a PCB.

5.2 Pin Connection and Polarity

The display has a common cathode configuration. This means the cathodes (negative terminals) of all LED segments are connected together internally and brought out to specific pins, while each segment's anode (positive terminal) has its own dedicated pin.

Pinout (10-pin):

1. Anode E

2. Anode D

3. Common Cathode

4. Anode C

5. Anode D.P. (Decimal Point)

6. Anode B

7. Anode A

8. Common Cathode (Note: Pins 3 and 8 are both common cathode, likely connected internally to handle current distribution)

9. Anode G

10. Anode F

The decimal point is specified as \"Rt. Hand Decimal,\" meaning it is positioned to the right of the digit when viewing the display from the front.

5.3 Internal Circuit Diagram

The internal diagram visually represents the electrical connections described above. It shows seven LED segments (A through G) and one decimal point (DP), each with its anode connected to a separate pin. All cathodes are tied together and connected to the two common cathode pins (3 and 8). This diagram is indispensable for understanding how to multiplex or directly drive the display.

6. Soldering and Assembly Guidelines

Proper handling during assembly is critical to long-term reliability.

• Reflow/Wave Soldering: Adhere strictly to the maximum temperature profile: 260°C peak temperature for no more than 3 seconds, measured at a point 1.6mm below the package body. Exceeding this can damage the internal wire bonds, the LED chips, or the plastic package.
• Cleaning: If cleaning is required after soldering, use methods and solvents compatible with the display's plastic material. Avoid ultrasonic cleaning unless explicitly approved, as it can cause mechanical stress.
• ESD (Electrostatic Discharge) Precautions: Although not explicitly stated, LEDs are semiconductor devices and can be sensitive to ESD. Standard ESD handling procedures (grounded workstations, wrist straps) are recommended during assembly.
• Storage Conditions: Store in the specified temperature range (-35°C to +85°C) in a low-humidity environment. Moisture-sensitive devices may require dry packing; consult the manufacturer for MSL (Moisture Sensitivity Level) rating if available.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

The common cathode configuration is typically driven in one of two ways:

1. Static Drive: Each segment anode is connected to a driver output (e.g., a microcontroller GPIO pin) through a current-limiting resistor. The common cathode(s) are connected to ground. To illuminate a segment, its corresponding anode pin is driven high (to a voltage above V_F). This method is simple but uses many I/O pins (8 for segments + DP).
2. Multiplexed Drive: For multi-digit displays or to save I/O pins, multiplexing is used. The anodes for the same segment across multiple digits are connected together. Each digit's common cathode is controlled separately. Digits are illuminated one at a time in rapid sequence (e.g., at 100Hz or faster). The persistence of vision makes all digits appear continuously lit. This requires segment drivers capable of handling the higher peak current needed during the brief on-time (up to the 90mA rating) and careful timing software.

Current-Limiting Resistor Calculation: For static drive at a desired forward current (I_F), use Ohm's Law: R = (V_supply - V_F) / I_F. For example, with a 5V supply, V_F = 2.6V, and I_F = 20mA: R = (5 - 2.6) / 0.02 = 120 Ω. A standard 120Ω or 150Ω resistor would be suitable. The resistor's power rating should be at least I_F² * R.

7.2 Design Considerations

• Viewing Angle and Bezel Design: Ensure the product's bezel or enclosure does not obstruct the wide viewing angle of the display.
• Brightness Control: Brightness can be controlled by adjusting the forward current (via PWM - Pulse Width Modulation) or by using the multiplexing duty cycle. PWM is preferred for smooth dimming.
• Heat Management: In high-brightness or high-temperature applications, ensure adequate ventilation. The derating of continuous current above 25°C must be respected.
• Electrical Noise: In electrically noisy environments (e.g., industrial controls), ensure clean power supplies and consider filtering on drive lines to prevent erratic display behavior.

8. Technical Comparison and Differentiation

Compared to older seven-segment technologies, the LTS-2301AJR's use of AlInGaP offers clear advantages:

• vs. Standard GaAsP/GaP Red LEDs: AlInGaP provides significantly higher luminous efficiency (more light output per mA of current), better temperature stability, and a more saturated, \"super red\" color. This translates to lower power consumption for the same brightness or much higher brightness at the same current.
• vs. LCDs: Unlike Liquid Crystal Displays, this LED display is self-illuminating, providing excellent visibility in low-light conditions without a backlight. It has a much wider operating temperature range, faster response time (instant on/off), and is not susceptible to image retention or slow response in cold temperatures.
• vs. VFDs (Vacuum Fluorescent Displays): While VFDs can be very bright and have a wide viewing angle, they require relatively high and complex driving voltages (anodes at +30-50V, filament supply). The LTS-2301AJR operates on simple, low-voltage DC, simplifying power supply design and improving safety.

Its primary trade-off is that it is a single-color (red) device, whereas some other technologies can offer multiple colors or full color capability.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display directly from a 3.3V microcontroller pin?

A: Possibly, but you must check the forward voltage. The typical V_F is 2.6V. A 3.3V supply leaves only 0.7V for the current-limiting resistor. At a desired I_F of 10mA, R = (3.3 - 2.6)/0.01 = 70 Ω. This is feasible, but brightness may be lower than at 5V/20mA. Ensure the microcontroller pin can source the required current.

Q: Why are there two common cathode pins (3 and 8)?

A> This is a common design practice to distribute the total cathode current. When all segments and the decimal point are lit, the total current flowing into the common cathode can be up to 8 * I_F. Having two pins reduces current density per pin, improves reliability, and helps with PCB trace routing for current handling.

Q: What does \"1/10 duty cycle, 0.1ms pulse width\" mean for the peak current rating?

A: This defines a safe pulsed operating mode. You can apply a 90mA current pulse to a segment, but the pulse must be no wider than 0.1 milliseconds, and the time between the start of one pulse and the start of the next must be at least 10 times the pulse width (i.e., 1 ms period). This allows the LED junction to cool between pulses, preventing thermal overload.

Q: How do I achieve uniform brightness if the luminous intensity matching ratio is 2:1?

A: The 2:1 ratio is a maximum specification. In practice, well-binned parts will have a much tighter match. For critical applications, you can specify a tighter bin or, in software/firmware, implement individual segment current calibration (e.g., using different PWM duty cycles per segment) to compensate for minor variations.

10. Operating Principle and Technology Trends

10.1 Fundamental Operating Principle

The LTS-2301AJR is based on the principle of electroluminescence in a semiconductor p-n junction. The active material is AlInGaP. When a forward voltage exceeding the diode's turn-on voltage (approximately 2.0V) is applied, electrons from the n-type region and holes from the p-type region 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 AlInGaP alloy determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light—in this case, red at ~639 nm. The transparent GaAs substrate allows more of this generated light to escape the chip, improving external quantum efficiency and brightness.

10.2 Technology Trends

The use of AlInGaP represents a mature but high-performance technology for red and amber LEDs. General trends in the display component industry that influence such products include:

• Increased Efficiency: Ongoing material science and chip design improvements continue to push the lumens-per-watt efficiency higher, allowing for brighter displays at lower power or reduced heat generation.
• Miniaturization: While 0.28-inch is a standard size, there is a trend towards smaller digit heights for portable devices and higher information density, as well as thinner package profiles.
• Integration: Some modern seven-segment modules integrate the driver IC (often an I2C or SPI controlled chip) directly onto the display PCB, simplifying the interface for the main system microcontroller to just a few wires.
• Color Options: While this is a red device, the underlying market demands a variety of colors. Blue and green InGaN-based LEDs are now highly efficient, and full RGB seven-segment displays are available for multi-color indication.
• Alternative Technologies: OLED (Organic LED) and micro-LED technologies are emerging for small displays, offering potential advantages in contrast, viewing angle, and flexibility. However, for many industrial and cost-sensitive applications requiring simple, robust, bright numeric readouts, traditional LED seven-segment displays like the LTS-2301AJR remain a highly reliable and optimal choice.