LTP-18088KD LED Dot Matrix Display Datasheet - 1.85 Inch Height - Hyper Red (650nm) - 2.6V Forward Voltage - 40mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-18088KD is a solid-state dot matrix display module designed for applications requiring clear, bright alphanumeric or symbolic information presentation. Its core function is to provide a reliable and efficient visual output interface.

1.1 Core Advantages and Target Market

This device is built around several key advantages that define its application space. It features a low power requirement, making it suitable for battery-powered or energy-conscious devices. The excellent character appearance and high brightness & contrast ensure readability in various ambient lighting conditions, from dim indoor settings to brighter environments. A wide viewing angle allows the displayed information to be seen clearly from off-axis positions, which is critical for public information displays or multi-user equipment. Finally, its solid-state reliability, inherent to LED technology, offers long operational life and resistance to shock and vibration compared to mechanical displays. These features make it ideal for industrial instrumentation, test equipment, point-of-sale terminals, transportation information boards, and other embedded systems requiring a robust, clear display.

2. Technical Specifications Deep Dive

The performance of the LTP-18088KD is characterized by a detailed set of electrical, optical, and mechanical parameters.

2.1 Device Description and Technology

The display has a matrix height of 1.85 inches (47.0 mm) and is organized as an 8 x 8 dot matrix. It utilizes Aluminium Indium Gallium Phosphide (AlInGaP) Hyper Red LED chips. These chips are fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. The package features a black face with white segments, a combination that significantly enhances the contrast ratio by absorbing ambient light and making the illuminated red segments stand out more prominently.

2.2 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Average Power Dissipation per Dot: 40 mW
• Peak Forward Current per Dot: 90 mA
• Continuous Forward Current per Dot: 15 mA (at 25°C), derating linearly at 0.2 mA/°C above 25°C.
• Reverse Voltage per Dot: 5 V
• Operating Temperature Range: -35°C to +85°C
• Storage Temperature Range: -35°C to +85°C
• Solder Temperature: 260°C for 3 seconds, measured 1/16 inch (approx. 1.6mm) below the seating plane.

2.3 Electrical & Optical Characteristics (at T_A=25°C)

These are the typical and guaranteed performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): 1650 μcd (Min), 3500 μcd (Typ) at I_P=32mA, 1/16 Duty Cycle.
• Peak Emission Wavelength (λ_p): 650 nm (Typ) at I_F=20mA.
• Spectral Line Half-Width (Δλ): 20 nm (Typ) at I_F=20mA.
• Dominant Wavelength (λ_d): 639 nm (Typ) at I_F=20mA.
• Forward Voltage per Dot (V_F): 2.1V (Min), 2.6V (Typ) at I_F=20mA; 2.3V (Min), 2.8V (Typ) at I_F=80mA.
• Reverse Current per Dot (I_R): 100 μA (Max) at V_R=5V.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max) at I_P=32mA, 1/16 Duty Cycle. This specifies the maximum allowable variation in brightness between the brightest and dimmest dots in the matrix.

Note: Luminous intensity measurement follows the CIE (Commission Internationale de l'\'Eclairage) eye-response curve using an appropriate sensor and filter combination.

3. Binning System Explanation

The datasheet indicates the device is categorized for luminous intensity. This means units are tested and sorted (binned) based on their measured light output. This allows designers to select displays with consistent brightness levels for a uniform appearance in their application, which is crucial when multiple displays are used side-by-side. The matching ratio of 2:1 further guarantees that within a single display, no dot is more than twice as bright as another, ensuring visual uniformity of the formed characters or graphics.

4. Performance Curve Analysis

While the PDF references typical characteristic curves, the provided electrical/optical data allows for analysis. The forward voltage shows a predictable increase with current (from 2.6V typ at 20mA to 2.8V typ at 80mA), which is standard LED behavior. The dominant wavelength of 639 nm and peak at 650 nm firmly place this in the hyper-red spectrum, offering high visual impact. The wide operating temperature range (-35°C to +85°C) suggests stable performance across harsh environments, though the forward current must be derated at high ambient temperatures as per the maximum ratings.

5. Mechanical & Package Information

5.1 Package Dimensions and Stackability

The mechanical drawing provides critical dimensions for PCB footprint design and enclosure integration. A key feature highlighted is that the module is stackable both vertically and horizontally. This implies the mechanical design includes features (like flush edges or specific mounting points) that allow multiple displays to be placed adjacent to each other to create larger multi-character or multi-line displays without unsightly gaps or alignment issues.

5.2 Pin Connection and Internal Circuit

The device has a 24-pin configuration. The pinout table clearly defines the function of each pin: Anode for columns and Cathode for rows. Several pins are marked \"NO CONNECTION\" (N/C). The internal circuit diagram, typical for a matrix display, shows the 64 LEDs (8x8) arranged with their anodes connected in columns and cathodes in rows. This common matrix architecture minimizes the number of required driver pins (16 for 64 LEDs) but requires multiplexed driving.

6. Soldering & Assembly Guidelines

The primary assembly instruction provided is for soldering: 260°C for 3 seconds, measured 1/16 inch below the seating plane. This is a standard reflow soldering profile parameter. Designers must ensure their PCB assembly process adheres to this to prevent thermal damage to the LED chips or the plastic package. The storage temperature range (-35°C to +85°C) should also be respected during handling and before assembly.

7. Application Suggestions

7.1 Typical Application Scenarios

The combination of high brightness, wide viewing angle, and solid-state construction makes the LTP-18088KD suitable for: Industrial Control Panels (status indicators, fault codes), Test and Measurement Equipment (readouts, bargraphs), Public Information Displays (in transportation, simple message boards), Consumer Electronics (audio equipment displays, appliance status), and Prototyping & Educational Kits.

7.2 Design Considerations

• Drive Circuitry: Must use constant current drivers or appropriate current-limiting resistors for each column/row to set the forward current (e.g., 20mA for typical brightness).
• Multiplexing: The matrix requires multiplexed driving. The controller must cycle through the rows (or columns) fast enough to avoid visible flicker (typically >100Hz). The peak current per dot (90mA) allows for higher pulsed currents during multiplexing to achieve the desired average brightness.
• Power Calculation: With 64 dots, a maximum average power of 40mW per dot, and a duty cycle defined by the multiplexing scheme, the total module power dissipation must be calculated to ensure adequate thermal management.
• ESD Protection: As with all semiconductor devices, standard ESD precautions should be observed during handling and assembly.

8. Technical Comparison & Differentiation

The key differentiator for the LTP-18088KD is its use of AlInGaP (Hyper Red) technology. Compared to older GaAsP or standard red GaP LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current, or similar brightness at lower power. The black face/white segment design enhances contrast more effectively than traditional gray or beige packages. Its stackable design is a practical mechanical advantage for building larger displays seamlessly.

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 point of maximum power in the emitted spectrum. Dominant wavelength is the perceived color point, calculated from the spectrum and the CIE color matching functions. For a monochromatic source like this red LED, they are close but not identical.

Q: How do I achieve the typical luminous intensity of 3500 μcd?
A: The test condition is a peak current (I_P) of 32mA at a 1/16 duty cycle. In a multiplexed 8-row matrix, a 1/8 duty cycle is more common. To achieve a similar average brightness, the peak current during its active time slot may need adjustment based on the driver's duty cycle and required average current per LED.

Q: Can I drive it with a 5V microcontroller pin directly?
A: No. The forward voltage is ~2.6V, and a series current-limiting resistor is mandatory. Connecting 5V directly would destroy the LED due to excessive current. Furthermore, microcontroller pins typically cannot source/sink the cumulative current required for a whole column or row in a multiplexed setup; external drivers (transistors or dedicated LED driver ICs) are necessary.

10. Design and Usage Case Example

Scenario: Designing a simple 4-digit numeric display for a counter.
Four LTP-18088KD displays would be placed side-by-side (facilitated by the stackable design). A microcontroller would be used to manage the display. Since each 8x8 matrix can form recognizable numbers, the controller's firmware would contain a font map. The microcontroller, via external transistor arrays or a dedicated LED driver IC, would multiplex the displays. It would cycle through the four displays (a time-division multiplex) and within each display, cycle through the 8 rows (row scanning). The peak current per LED would be set by the driver circuitry to achieve the desired brightness, considering the total multiplexing duty cycle (e.g., 1/32 if scanning 4 displays * 8 rows). The power supply must be sized to deliver the total average current for all illuminated dots.

11. Operating Principle Introduction

The LTP-18088KD operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold is applied across an AlInGaP LED chip, electrons and holes recombine in the active region, releasing energy in the form of photons (light). The specific composition of the AlInGaP semiconductor alloy determines the bandgap energy, which defines the wavelength (color) of the emitted light—in this case, hyper red. The 64 individual LED chips are arranged in a matrix with common anode columns and common cathode rows. By selectively applying a positive voltage to a specific column (anode) and grounding a specific row (cathode), only the LED at the intersection of that row and column turns on. By rapidly sequencing through this process (multiplexing), all desired dots can be illuminated to form a stable image.

12. Technology Trends

Display technology is continuously evolving. While discrete LED dot matrices like the LTP-18088KD remain relevant for specific embedded applications due to their robustness, simplicity, and high brightness, several trends are notable. There is a move towards surface-mount device (SMD) LED arrays for higher density and automated assembly. Integrated LED driver matrices with built-in controllers (like I2C or SPI interfaces) are simplifying design complexity. For color applications, RGB LED matrices are becoming more common. Furthermore, in many consumer applications, small OLED or TFT LCD modules are displacing monochrome LED dot matrices where full graphics, color, and lower power in always-on scenarios are required. However, for applications demanding extreme brightness, long lifetime, wide temperature range, and simplicity, AlInGaP-based dot matrix displays continue to hold a strong position.