LTP-587JD 0.5-inch 16-Segment Alphanumeric LED Display Datasheet - Digit Height 12.7mm - Forward Voltage 2.6V - Hyper Red Color - English Technical Document

1. Product Overview

The LTP-587JD is a single-digit, 16-segment alphanumeric display designed for applications requiring clear, bright character readouts. Its primary function is to display alphanumeric characters (letters A-Z, numbers 0-9, and some symbols) with high visibility. The device is built using Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology, specifically engineered to produce a hyper red emission. This technology, combined with a black face and white segment design, targets applications where high contrast and excellent character appearance are critical, such as in instrumentation panels, industrial controls, test equipment, and consumer electronics displays.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for professional and industrial environments. Its high brightness and high contrast ratio ensure readability even under bright ambient lighting conditions. The wide viewing angle allows the display to be seen clearly from various positions. Furthermore, its solid-state construction provides inherent reliability, longevity, and resistance to shock and vibration compared to mechanical or vacuum-based displays. The low power requirement is a significant benefit for battery-operated or energy-efficient devices. The primary target market includes designers of embedded systems, control panels, medical devices, and any electronic equipment requiring a compact, reliable, and highly legible numeric or alphanumeric readout.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the electrical and optical characteristics specified in the datasheet. Understanding these parameters is crucial for proper circuit design and ensuring optimal display performance.

2.1 Photometric and Optical Characteristics

The luminous intensity (Iv) is a key performance metric. Under a standard test condition of a 1mA forward current (IF), the typical value is 700 µcd (microcandelas), with a minimum of 320 µcd. This categorization for luminous intensity indicates that devices are binned or sorted based on their measured output, allowing designers to select parts with consistent brightness levels for multi-digit displays. The dominant wavelength (λd) is 639 nm, and the peak emission wavelength (λp) is 650 nm, both measured at IF=20mA. This places the emission firmly in the hyper red region of the visible spectrum. The spectral line half-width (Δλ) of 20 nm indicates a relatively narrow emission band, characteristic of high-quality LED materials, resulting in a pure, saturated red color.

2.2 Electrical Parameters

The forward voltage (VF) per segment is specified with a typical value of 2.6V and a maximum of 2.6V at IF=20mA. The minimum value is 2.1V. This parameter is vital for designing the current-limiting circuitry. Designers must ensure the driving voltage source exceeds the maximum VF to achieve the desired current. The reverse current (IR) is a maximum of 100 µA at a reverse voltage (VR) of 5V, indicating the diode's leakage characteristics in the off-state. The luminous intensity matching ratio (IV-m) of 2:1 specifies the maximum allowable ratio between the brightest and dimmest segment within a single device, ensuring uniform appearance.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the stress limits beyond which permanent damage may occur. The continuous forward current per segment is 25 mA. A derating factor of 0.33 mA/°C applies linearly from 25°C, meaning the maximum allowable continuous current decreases as ambient temperature (Ta) increases. For example, at 85°C, the maximum current would be approximately 25 mA - (0.33 mA/°C * (85-25)°C) = 5.2 mA. The peak forward current is 90 mA but only under specific pulsed conditions (1/10 duty cycle, 0.1ms pulse width), which is useful for multiplexing schemes. The power dissipation per segment is 70 mW. The operating and storage temperature range is -35°C to +85°C, defining the environmental limits for reliable operation and non-operational storage.

3. Binning System Explanation

The datasheet explicitly states that the devices are "categorized for luminous intensity." This implies a binning or sorting process based on measured light output at the standard test condition (IF=1mA). Binning is a standard practice in LED manufacturing to group components with similar performance characteristics. For the LTP-587JD, this ensures that designers can procure displays with consistent brightness levels. When designing multi-digit displays, using LEDs from the same intensity bin prevents noticeable variations in brightness between digits, which is critical for aesthetic and functional uniformity. The datasheet does not specify detailed bin codes or thresholds, so for precise matching in critical applications, consultation with the component supplier for specific binning information is recommended.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical curves for such a device would be essential for design analysis. These usually include:

• Forward Current vs. Forward Voltage (I-V Curve): This non-linear relationship shows how voltage increases with current. It is crucial for determining the necessary supply voltage and for designing constant-current drivers to ensure stable brightness regardless of minor voltage fluctuations or temperature changes.
• Luminous Intensity vs. Forward Current: This curve shows that light output increases with current but may not be perfectly linear, especially at higher currents where efficiency can drop due to heating.
• Luminous Intensity vs. Ambient Temperature: This characteristic shows how light output decreases as the junction temperature of the LED increases. Understanding this derating is vital for applications operating at high ambient temperatures to ensure sufficient brightness is maintained.
• Spectral Distribution: A graph showing the relative intensity of light emitted across different wavelengths, centered around the 650 nm peak, confirming the color purity.

Designers should use these curves to model performance under their specific operating conditions, especially when driving the LEDs with pulsed or multiplexed currents, or in non-standard temperature environments.

5. Mechanical and Package Information

The LTP-587JD features a standard LED display package. The key mechanical specification is the digit height of 0.5 inches (12.7 mm). The package dimensions drawing (referenced on page 2 of the datasheet) provides the exact physical outline, lead spacing, and seating plane. This drawing is critical for PCB footprint design, ensuring the component fits correctly on the board. The notes specify that all dimensions are in millimeters, with standard tolerances of ±0.25 mm unless otherwise stated. Designers must adhere to these dimensions when creating the PCB land pattern to ensure proper soldering and mechanical stability.

5.1 Pin Connection and Polarity Identification

The device has an 18-pin configuration. It is a common anode type. This means the anodes of all LED segments are connected internally to a common pin (Pin 18). Each of the 16 segments (A, B, C, D, E, F, G, H, K, M, N, P, R, S, T, U) and the right-hand decimal point (D.P.) has its own individual cathode pin. To illuminate a specific segment, the common anode (Pin 18) must be connected to a positive voltage supply (through a current-limiting resistor or driver), and the corresponding cathode pin must be pulled to a lower voltage (typically ground). This configuration is common for multiplexed displays, where the common anode of each digit is driven sequentially.

6. Soldering and Assembly Guidelines

The absolute maximum ratings include a critical soldering parameter: the solder temperature must not exceed 260°C for a maximum of 3 seconds, measured at 1.6mm below the seating plane. This guideline is intended for wave soldering or hand soldering processes. For reflow soldering, a standard lead-free reflow profile with a peak temperature below 260°C and limited time above liquidus should be used. Prolonged exposure to high temperatures can damage the internal wire bonds, the LED chip, or the plastic package. It is also advisable to store the components in a dry environment to prevent moisture absorption, which can cause "popcorning" (package cracking) during reflow soldering.

7. Application Suggestions

7.1 Typical Application Scenarios

The LTP-587JD is ideal for any device requiring a single, highly visible alphanumeric readout. Common applications include: digital multimeters and oscilloscopes, blood pressure monitors and other medical readouts, industrial timer and counter displays, automotive diagnostic tool displays, and consumer audio equipment (e.g., tuner frequency display). Its ability to show letters expands its use beyond simple numeric counters.

7.2 Design Considerations and Circuit Implementation

When designing the drive circuit, the common anode configuration must be accounted for. For a static drive (all segments on continuously), a single current-limiting resistor can be placed on the common anode line, with each cathode connected to a microcontroller pin capable of sinking the required segment current. For multiplexing multiple digits, each digit's common anode is driven by a transistor, and the segment cathodes are connected in parallel across all digits. The microcontroller then cycles rapidly through each digit, turning on its anode and outputting the segment pattern for that digit. This reduces the number of required I/O pins significantly. Constant-current drivers are preferred over simple resistor limiting for better brightness uniformity and stability over temperature and voltage variations. Designers must also ensure the total current sourced or sunk by the microcontroller or driver IC does not exceed its ratings.

8. Technical Comparison and Differentiation

Compared to older technologies like incandescent or vacuum fluorescent displays (VFDs), the LTP-587JD offers superior advantages: lower power consumption, higher reliability (no filament to burn out), faster response time, and better shock/vibration resistance. Compared to standard red GaAsP LEDs, the AlInGaP technology used here provides significantly higher luminous efficiency (more light output per mA of current), better temperature stability, and a more saturated red color. Compared to multi-digit modules, a single-digit component like the LTP-587JD offers maximum design flexibility, allowing engineers to create custom display layouts and choose their own drive electronics.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the "luminous intensity matching ratio" of 2:1?

A: This ratio ensures visual uniformity within the single digit. It guarantees that no segment will be more than twice as bright as the dimmest segment when driven under identical conditions, preventing an uneven or patchy appearance of the character.

Q: Can I drive this display with a 3.3V microcontroller system?

A: Yes, but careful design is needed. The typical VF is 2.6V. With a 3.3V supply, there is only about 0.7V of headroom for the current-limiting resistor and the voltage drop across the driving transistor. A low-dropout constant-current driver or a carefully calculated resistor value is necessary to ensure proper current regulation. Using a higher voltage (e.g., 5V) provides more design margin.

Q: Why is the peak current (90mA) so much higher than the continuous current (25mA)?

A> The peak current rating is for very short pulses (0.1ms width). The LED junction does not have time to heat up significantly during such a brief pulse, allowing a higher current without exceeding thermal limits. This is exploited in multiplexing, where each digit is only powered for a fraction of the time.

10. Practical Design and Usage Case

Consider designing a simple digital counter with a single LTP-587JD display. A microcontroller would be programmed to increment a count. To display the number, the microcontroller's firmware would contain a look-up table that maps each digit (0-9) to the specific combination of segments (A, B, C, D, E, F, G) that need to be illuminated. For example, to display a "7," segments A, B, and C would be turned on. The microcontroller would set its I/O pin connected to the common anode (via a transistor) high. Then, it would set the I/O pins connected to the cathodes of segments A, B, and C to a low state (ground), while setting all other cathode pins high (open). A current-limiting resistor on the common anode line sets the current for all illuminated segments. This static drive method is simple but uses many I/O pins. For a more efficient design driving multiple digits, a multiplexing scheme would be implemented.

11. Operating Principle Introduction

The LTP-587JD operates on the fundamental principle of electroluminescence in a semiconductor p-n junction. The device is constructed using AlInGaP (Aluminium Indium Gallium Phosphide) epitaxial layers grown on a non-transparent GaAs substrate. When a forward voltage exceeding the diode's turn-on voltage (approximately 2.1V) is applied across a segment (anode positive relative to cathode), electrons are injected from the n-type region and holes from the p-type region into the active region. These charge carriers recombine, releasing energy in the form of photons. The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, hyper red at around 650 nm. The black face package absorbs ambient light, while the white segment diffusers help scatter the emitted red light, creating the high-contrast, bright white-on-black appearance of the illuminated character.

12. Technology Trends and Context

AlInGaP technology represents a significant advancement in visible LED performance, particularly for red, orange, and yellow wavelengths. It offers higher efficiency and better temperature stability than the older GaAsP (Gallium Arsenide Phosphide) technology. The trend in alphanumeric displays has been towards higher integration, such as multi-digit modules with built-in controllers (e.g., MAX7219 compatible modules) and a shift towards dot-matrix displays or OLEDs for greater flexibility in showing graphics and custom fonts. However, discrete segment displays like the LTP-587JD remain highly relevant for applications where cost, simplicity, extreme brightness, and long-term reliability under harsh conditions are paramount. The underlying trend across all LED technologies continues to be improvements in luminous efficacy (lumens per watt), allowing for brighter displays at lower power levels, which is critical for portable and energy-conscious applications.