LTP-1457AKY LED Display Datasheet - 1.2-inch (30.42mm) Matrix Height - AlInGaP Amber Yellow - 5x7 Dot Array - English Technical Document

1. Product Overview

The LTP-1457AKY is a single-digit, alphanumeric display module designed for applications requiring clear, legible character output. Its core component is a 5x7 dot matrix configuration, providing the resolution necessary for standard ASCII and EBCDIC character sets. The defining visual characteristic is its amber yellow emission, achieved through the use of AlInGaP (Aluminum Indium Gallium Phosphide) LED chips. This semiconductor material is known for its high efficiency and good visibility. The physical presentation features a gray faceplate with white dots, offering a high-contrast background for the illuminated elements, which enhances readability under various lighting conditions.

The device is engineered for low power consumption and solid-state reliability, making it suitable for integration into a wide range of electronic equipment. Its single-plane construction and wide viewing angle ensure that the displayed information is visible from multiple perspectives. A key mechanical feature is its horizontal stackability, allowing multiple units to be placed side-by-side to form multi-character displays without significant gaps, which is essential for creating messages or numerical readouts.

2. Technical Specifications Deep Dive

2.1 Optical Characteristics

The optical performance is central to the display's functionality. The primary source is AlInGaP LED chips grown on a non-transparent GaAs substrate. The typical peak emission wavelength (λp) is 595 nm, with a dominant wavelength (λd) of 592 nm, firmly placing the output in the amber yellow spectrum. The spectral line half-width (Δλ) is 15 nm, indicating a relatively pure color emission. The average luminous intensity (Iv) per dot is specified with a minimum of 2100 μcd and a typical value of 3800 μcd under a test condition of 80 mA peak current and a 1/16 duty cycle. The luminous intensity matching ratio between dots is 2:1 maximum, ensuring uniform brightness across the character matrix.

2.2 Electrical Characteristics

The electrical parameters define the operating boundaries and conditions for the display. The forward voltage (Vf) for any single LED dot typically ranges from 2.05V to 2.6V at a forward current (If) of 20 mA. The reverse current (Ir) is limited to a maximum of 100 μA when a reverse voltage (Vr) of 5V is applied. These parameters are critical for designing the correct driving circuitry to ensure longevity and performance.

2.3 Absolute Maximum Ratings

These ratings specify the limits beyond which permanent damage may occur. The average power dissipation per dot must not exceed 25 mW. The peak forward current per dot is rated at 60 mA, but only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). The average forward current per dot has a derating factor of 0.17 mA/°C starting from 25°C. The maximum reverse voltage per dot is 5V. The device is rated for an operating and storage temperature range of -35°C to +85°C. The solder temperature must not exceed 260°C for more than 3 seconds at a point 1.6mm below the seating plane during assembly.

3. Mechanical and Packaging Information

3.1 Physical Dimensions

The display has a matrix height of 1.2 inches (30.42 mm). The overall package dimensions are provided in a detailed drawing within the datasheet, with all measurements in millimeters. Standard tolerances for these dimensions are ±0.25 mm unless otherwise specified. The package is designed to facilitate the horizontal stacking feature mentioned in the overview.

3.2 Pin Configuration and Internal Circuit

The device interface consists of 14 pins. The pinout is as follows: Pin 1: Cathode Row 5; Pin 2: Cathode Row 7; Pin 3: Anode Column 2; Pin 4: Anode Column 3; Pin 5: Cathode Row 4; Pin 6: Anode Column 5; Pin 7: Cathode Row 6; Pin 8: Cathode Row 3; Pin 9: Cathode Row 1; Pin 10: Anode Column 4; Pin 11: Anode Column 3 (Note: Duplicate function with Pin 4, likely a datasheet error or specific internal connection); Pin 12: Cathode Row 4 (Duplicate of Pin 5); Pin 13: Anode Column 1; Pin 14: Cathode Row 2.

The internal circuit diagram shows a standard common-cathode configuration for the 5x7 matrix. The seven row lines (cathodes) and five column lines (anodes) intersect at the 35 LED dots. To illuminate a specific dot, its corresponding row cathode must be driven low (grounded) while its column anode is driven high (supplied with current through a current-limiting resistor). This matrix arrangement minimizes the number of required driver pins (12 for a 5x7 matrix instead of 35 for individual dots).

4. Application Suggestions and Design Considerations

4.1 Typical Application Scenarios

This display is ideal for applications requiring a single, highly visible alphanumeric character. Common uses include status indicators on industrial control panels, digital readouts on test and measurement equipment, single-character displays in embedded systems for debugging or mode indication, and as building blocks for multi-digit panels in instruments like clocks, counters, or simple message boards.

4.2 Design and Driving Considerations

Driving a 5x7 matrix requires a multiplexing scheme. Since only one row should be active at a time to prevent ghosting and excessive current draw, a microcontroller or dedicated display driver IC is necessary to cycle through the seven rows rapidly (typically at a rate >60 Hz to avoid flicker). The column data for the active row is sent simultaneously. The average forward current per dot must be calculated based on the peak current and the duty cycle (1/7 for a standard row-at-a-time multiplex). For example, to achieve a desired average dot current of 10 mA, the peak current during its active row time would need to be 70 mA (10 mA * 7 rows). This must be checked against the absolute maximum rating for peak current (60 mA at 1/10 duty). Therefore, careful calculation of the multiplexing scheme and current-limiting resistors is essential. The wide operating temperature range allows use in non-climate-controlled environments.

5. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. While the specific graphs are not detailed in the provided text, such curves generally include:

• Forward Current vs. Forward Voltage (I-V Curve): This shows the relationship between the current through an LED and the voltage across it. It is non-linear, with a turn-on voltage (around 2V for AlInGaP) after which current increases rapidly with small voltage increases. This curve is vital for selecting the appropriate current-limiting resistor value in a constant-voltage drive circuit.
• Luminous Intensity vs. Forward Current: This curve demonstrates how the light output increases with increased current. It is generally linear over a range but will saturate at very high currents. Operating within the linear region is important for brightness control via pulse-width modulation (PWM).
• Luminous Intensity vs. Ambient Temperature: This shows the derating of light output as the junction temperature of the LED increases. For AlInGaP, efficiency typically decreases with rising temperature, meaning the display may appear dimmer in high-temperature environments if not compensated for by the drive current.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the concentration of light output around the dominant wavelength (592 nm) and the width of the spectrum (15 nm half-width).

Designers should consult these curves to optimize drive conditions for brightness, efficiency, and longevity across the intended operating temperature range.

6. Soldering and Assembly Guidelines

The critical parameter for assembly is the solder heat tolerance. The leads can withstand a maximum temperature of 260°C for a maximum duration of 3 seconds, measured at a point 1.6 mm (1/16 inch) below the seating plane of the package. This is a standard rating for wave soldering or reflow processes. It is crucial to adhere to this limit to prevent damage to the internal wire bonds or the LED chips themselves. Standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly, as LEDs are sensitive to static electricity. Storage should be within the specified temperature range of -35°C to +85°C in a low-humidity environment.

7. Technical Comparison and Differentiation

The LTP-1457AKY's primary differentiators are its use of AlInGaP technology and its specific mechanical form factor. Compared to older GaAsP or GaP LED technologies, AlInGaP offers higher luminous efficiency, resulting in brighter output for the same electrical input, and better color purity. The amber yellow color is often chosen for its high visual impact and perceived brightness by the human eye. The 1.2-inch character height is a specific size that may be larger than common 0.56-inch or 0.8-inch displays, making it suitable for applications where viewing distance is greater or visibility is paramount. The horizontal stackability is a practical feature not always present in similar displays, simplifying the design of multi-character arrays.

8. Frequently Asked Questions (Based on Technical Parameters)

Q: How do I drive this display with a microcontroller?
A: You need at least 12 GPIO pins (7 for rows, 5 for columns). Implement a scanning routine that activates one row (cathode low) at a time while applying the pattern for that row to the 5 column (anode) pins via current-limiting resistors. The scanning must be fast enough to avoid flicker (>60 Hz frame rate).

Q: What value of current-limiting resistor should I use?
A: It depends on your supply voltage (Vcc) and desired operating current. Use the formula: R = (Vcc - Vf) / If. For a 5V supply and a typical Vf of 2.3V at 20 mA, R = (5 - 2.3) / 0.02 = 135 Ω. Use the nearest standard value (e.g., 130 Ω or 150 Ω). Remember this is for constant-on operation; for multiplexed operation, the peak current will be higher.

Q: Can I use this display outdoors?
A: The operating temperature range (-35°C to +85°C) is quite wide, suggesting robustness. However, the datasheet does not specify an IP (Ingress Protection) rating for water or dust resistance. For outdoor use, the display would likely need to be behind a protective window or within a sealed enclosure to prevent moisture and dirt ingress, which could damage the electronics or obscure the face.

Q: Why are there duplicate pin functions (e.g., Pin 4 & 11, Pin 5 & 12)?
A: This is likely an error in the provided pin connection table excerpt. In a standard 5x7 matrix, only 12 unique signals (5 columns + 7 rows) are needed. The duplicates may be internally connected to the same node to provide alternative PCB routing options or may be a documentation mistake. The internal circuit diagram is the authoritative source for connectivity.

9. Operating Principle Introduction

The fundamental principle is based on semiconductor electroluminescence. When a forward voltage exceeding the diode's turn-on voltage is applied across the AlInGaP p-n junction, electrons and holes recombine in the active region, releasing energy in the form of photons. The specific composition of the Aluminum, Indium, Gallium, and Phosphide layers determines the bandgap energy, which directly correlates to the wavelength (color) of the emitted light—in this case, amber yellow. The 5x7 matrix is an addressing technique that reduces the number of required control lines from 35 (one per dot) to 12 (rows + columns) by arranging the LEDs in a grid. Illumination is controlled by selectively activating the intersection points of powered rows and columns.

10. Technology Trends and Context

Displays like the LTP-1457AKY represent a mature, reliable technology for single and low-digit alphanumeric output. While larger graphic displays and OLEDs have become prevalent for complex information, discrete LED dot matrix modules remain highly relevant in industrial, instrumentation, and embedded applications due to their simplicity, ruggedness, high brightness, wide viewing angles, and excellent longevity. The shift from older LED materials to AlInGaP, as seen in this device, was a significant trend that improved efficiency and color range. Current trends in similar display segments might include the integration of the driver circuitry onto the module itself (requiring only serial data and power inputs), the use of even more efficient materials like InGaN for different colors, and designs optimized for automated assembly processes. The core advantages of solid-state reliability, low power, and high visibility ensure this technology's continued use in specific niches.