LTP-14088KD-J LED Dot Matrix Display Datasheet - 1.50-inch Height - Hyper Red 650nm - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-14088KD-J is a solid-state, single-plane 8x8 dot matrix LED display module. Its primary function is to provide alphanumeric and symbolic character display capabilities in a compact, reliable format. The core advantage of this device lies in its use of advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) Hyper Red LED chips, which are epitaxially grown on a GaAs substrate. This technology offers superior luminous efficiency and color purity for red emission compared to older technologies like standard GaAsP. The display features a black face with white dot color, providing excellent contrast for readability. It is designed for low power consumption and offers a wide viewing angle, making it suitable for various information display applications where clear visibility is paramount. The device is categorized for luminous intensity, ensuring consistency in brightness across units, and is packaged in a lead-free format compliant with RoHS directives.

2. In-Depth Technical Parameter Analysis

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. At a standard test condition of an average forward current of 32mA with a 1/16 duty cycle, the typical average luminous intensity per dot is 2475 µcd (microcandelas), with a minimum specified value of 1020 µcd. The peak emission wavelength (λp) is typically 650 nanometers (nm), falling within the deep red spectrum. The dominant wavelength (λd) is specified at 639 nm. The spectral line half-width (Δλ) is 20 nm, indicating a relatively narrow bandwidth and pure color emission. A critical parameter for display uniformity is the Luminous Intensity Matching Ratio, which is specified as 2:1 maximum for dots within a similar light area. This means the brightest dot in a group should not be more than twice as bright as the dimmest, ensuring acceptable visual consistency across the matrix.

2.2 Electrical Characteristics

The electrical parameters define the operating boundaries and power requirements. The forward voltage (VF) for any single LED dot is between 2.1V and 2.8V, depending on the drive current. At a standard test current of 20mA, VF ranges from 2.1V (min) to 2.6V (max). At a higher peak current of 80mA, this range shifts to 2.3V to 2.8V. The reverse current (IR) for any segment is a maximum of 100 µA when a reverse voltage (VR) of 5V is applied. These parameters are crucial for designing the appropriate constant current or multiplexed driving circuitry.

2.3 Absolute Maximum Ratings and Thermal Considerations

Adherence to absolute maximum ratings is essential for device reliability and longevity. The average power dissipation per dot must not exceed 70 milliwatts (mW). The peak forward current per dot is rated at 90 mA, but this is specified under pulsed conditions with a frequency of 1 kHz and an 18% duty cycle. The average forward current per dot has a derating curve; it is 25 mA at 25°C and decreases linearly by 0.28 mA for every degree Celsius increase in ambient temperature. The device can operate and be stored within a temperature range of -35°C to +105°C. For assembly, soldering conditions are specified as 260°C for 3 seconds at a point 1/16 inch (approximately 1.6mm) below the seating plane.

3. Binning and Categorization System

The LTP-14088KD-J employs a categorization system primarily for luminous intensity. As indicated in the features and electrical characteristics, units are binned based on their measured average luminous output. The datasheet provides a minimum (1020 µcd) and typical (2475 µcd) value, suggesting that production parts are tested and grouped according to their actual intensity, likely into different output grades or categories. This allows designers to select parts with consistent brightness for their application. While the document does not specify explicit bins for wavelength or forward voltage, the provided min/max ranges for these parameters (e.g., VF, λp) define the acceptable limits for all shipped units, ensuring they fall within a functionally compatible window.

4. Performance Curve Analysis

The datasheet references a section for Typical Electrical/Optical Characteristic Curves. While the specific graphs are not provided in the text excerpt, such curves typically included in full datasheets are vital for design. These would normally include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with current, helping to optimize drive current for desired brightness and efficiency.
• Forward Voltage vs. Forward Current: Essential for calculating power dissipation and designing voltage supplies for the driver circuit.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates how light output decreases as temperature rises, which is critical for applications in varying thermal environments.
• Spectral Distribution: A graph showing the intensity of light emitted across different wavelengths, centered around the 650nm peak.

Designers should consult these curves to understand the non-linear relationships between current, voltage, temperature, and light output, enabling robust system design.

5. Mechanical and Package Information

5.1 Physical Dimensions and Tolerances

The device has a matrix height of 1.50 inches (37.0 mm). The package drawing (referenced but not detailed in the text) would provide critical dimensions for PCB footprint design, including overall length, width, height, and pin spacing. Key tolerances noted include: ±0.25mm for most dimensions, a pin tip shift tolerance of ±0.4mm, and limits on foreign material, ink contamination, bending, and bubbles within the LED segments (specified in mils). These ensure mechanical reliability and consistent optical appearance.

5.2 Pin Configuration and Internal Circuit

The display has a 16-pin configuration. The pinout is clearly defined: Pins 1, 2, 5, 7, 8, 9, 12, and 14 are connected to the cathodes of specific rows (e.g., Cathode Row 1, 2, 3...8). Pins 3, 4, 6, 10, 11, 13, 15, and 16 are connected to the anodes of specific columns (e.g., Anode Column 1, 2, 3...8). The internal circuit diagram shows a standard common-cathode configuration for an 8x8 matrix. Each of the 64 LEDs (dots) is formed at the intersection of one anode column line and one cathode row line. To illuminate a specific dot, its corresponding anode pin must be driven high (with a current-limiting resistor), and its corresponding cathode pin must be pulled low.

6. Soldering and Assembly Guidelines

The primary assembly instruction provided is for the soldering process. The device can withstand wave or reflow soldering with the condition that the solder temperature at a point 1/16 inch (1.6mm) below the seating plane does not exceed 260°C for more than 3 seconds. This is a standard IPC-compliant profile for lead-free soldering. Designers must ensure their PCB assembly process adheres to this thermal profile to prevent damage to the LED chips or the plastic package. The wide storage and operating temperature range (-35°C to +105°C) provides flexibility for handling and use in various environments, but standard ESD (Electrostatic Discharge) precautions should always be observed during handling.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

This 8x8 dot matrix display is ideal for applications requiring compact, low-to-medium resolution alphanumeric or simple graphic displays. Common uses include: industrial control panel status indicators, simple message boards, test and measurement equipment readouts, educational electronics kits, and prototype devices. Its compatibility with standard character codes (ASCII) makes it straightforward to interface with microcontrollers for displaying text.

7.2 Key Design Considerations

• Drive Circuitry: The display requires multiplexed driving due to its matrix structure. A microcontroller with sufficient I/O pins or dedicated LED driver ICs (like MAX7219 or HT16K33) must be used to sequentially scan the rows and columns. The peak current ratings (90mA pulsed) must be respected in the driver design.
• Current Limiting: External current-limiting resistors are mandatory for each anode column (or integrated into the driver IC) to set the forward current for the LEDs, typically between 20-32mA for average brightness, based on the duty cycle.
• Power Dissipation: The 70mW per dot limit and the current derating with temperature must be calculated for the worst-case operating condition, especially if multiple dots are lit simultaneously for extended periods.
• Viewing Angle: The wide viewing angle is beneficial but should be considered during mechanical enclosure design to ensure the display is oriented correctly for the end-user.
• Stacking: The feature of being stackable horizontally implies mechanical compatibility for creating wider multi-character displays, requiring careful alignment and interconnection in the PCB design.

8. Technical Comparison and Differentiation

The key differentiating factor of the LTP-14088KD-J is its use of AlInGaP Hyper Red LED technology. Compared to older red LED technologies like standard GaAsP or GaP, AlInGaP offers significantly higher luminous efficiency. This means it can produce the same or greater light output (measured in µcd) at a lower drive current, directly contributing to the "low power requirement" feature. It also generally provides a more saturated and pure red color (around 650nm) with better consistency. When compared to other 8x8 displays of similar physical size, its categorized luminous intensity and RoHS compliance are additional competitive advantages for quality-conscious and environmentally regulated markets.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between peak wavelength (650nm) and dominant wavelength (639nm)?
A: Peak wavelength is the wavelength at which the emitted optical power is greatest. Dominant wavelength is the single wavelength of monochromatic light that matches the perceived color of the emitted light. The slight difference is normal and accounts for the shape of the LED's emission spectrum.

Q: Can I drive this display with a 5V microcontroller without a driver IC?
A: Direct connection is not recommended. The forward voltage is ~2.6V, but you must use current-limiting resistors. More importantly, driving an 8x8 matrix directly from MCU pins is inefficient and will exceed the MCU's current sourcing/sinking capabilities. A dedicated multiplexing driver is almost always required.

Q: What does "1/16 Duty" mean in the luminous intensity test condition?
A: It means the LED is pulsed on for 1/16th of the time and off for 15/16ths. The specified luminous intensity is an average value measured under this condition. In a multiplexed 8x8 display, each row is typically active for 1/8th of the time (1/8 duty), so the drive current may need adjustment to achieve the desired average brightness.

Q: How do I interpret the 2:1 Luminous Intensity Matching Ratio?
A: This is a uniformity specification. It means that within a group of LEDs (e.g., all dots in the matrix), the brightest dot will not be more than twice as bright as the dimmest dot when measured under identical conditions. This ensures a reasonably even appearance.

10. Practical Design and Usage Example

Consider designing a single-character display for a temperature monitor. A microcontroller reads a sensor and needs to show a number from 0 to 99. Two LTP-14088KD-J displays can be stacked horizontally. The microcontroller, via an SPI or I2C LED driver IC, would multiplex the displays. The driver IC handles the row scanning and column data shifting, pulling cathode rows low sequentially while providing the correct pattern of anode currents for each column based on the character font stored in the microcontroller's memory. The drive current would be set via an external resistor to, for example, 25mA per dot average, ensuring operation within the 70mW power dissipation limit. The black face provides good contrast in an indoor panel. The design must include thermal management if the enclosure might reach high ambient temperatures, as the light output will decrease and current may need to be derated.

11. Operating Principle Introduction

The LTP-14088KD-J operates on the fundamental principle of a light-emitting diode (LED). When a forward voltage exceeding the diode's threshold (approx. 2.1-2.6V) is applied across an individual LED junction (anode to cathode), electrons and holes recombine in the active region of the AlInGaP semiconductor chip. This recombination releases energy in the form of photons, producing light at a wavelength characteristic of the semiconductor material's bandgap—in this case, red light around 650nm. The 8x8 matrix structure is formed by connecting 64 individual LED chips in a grid pattern. External electronics use a multiplexing technique to control this grid. By rapidly switching (scanning) which row cathode is active (connected to ground) and which column anodes are supplied with current, the illusion of a stable image is created through persistence of vision. This method drastically reduces the number of required control pins from 64 (one per LED) to just 16 (8 rows + 8 columns).

12. Technology Trends and Context

Discrete LED dot matrix displays like the LTP-14088KD-J represent a mature and reliable technology. While newer display technologies like OLEDs or high-resolution LCDs offer finer detail and full color, LED dot matrices maintain strong positions in applications requiring high brightness, wide viewing angles, extreme reliability, long lifetime, simplicity, and operation across a wide temperature range—often at a lower cost. The trend within this segment is towards higher efficiency LEDs (like the AlInGaP used here), lower power consumption, lead-free and environmentally friendly packaging, and sometimes towards surface-mount device (SMD) packages for automated assembly, though through-hole types like this one remain popular for prototyping and certain industrial uses. The core multiplexing drive principle remains standard, but modern integrated driver chips offer more features like built-in character fonts, brightness control, and simpler digital interfaces (SPI/I2C).