LTP-2057AKY LED Dot Matrix Display Datasheet - 2.0 Inch (50.8mm) Height - AlInGaP Amber Yellow - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-2057AKY is a monochrome dot matrix display module designed for alphanumeric character presentation. Its primary function is to provide a clear, legible display of characters and symbols in various electronic devices. The core technology behind this display is the use of Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material for the LED chips, which is known for producing high-efficiency light in the amber yellow spectrum. The device features a gray face and white dot color, which enhances contrast and readability under different lighting conditions.

The display is built as a 5 columns by 7 rows matrix, resulting in a total of 35 individually addressable dots. This configuration is standard for displaying ASCII characters and simple symbols. The "2.0 inch" specification refers to the character height, which is 50.8 millimeters, making it suitable for applications where information needs to be read from a moderate distance. The device operates on an X-Y (row-column) selection principle, allowing for multiplexed driving to control individual dots efficiently.

2. Technical Parameters Deep Objective Interpretation

2.1 Photometric and Optical Characteristics

The key photometric parameter is the Average Luminous Intensity (Iv), which has a typical value of 3600 microcandelas (µcd) under a test condition of a 32mA pulse current and a 1/16 duty cycle. This indicates a high brightness level suitable for indoor and many outdoor applications. The Dominant Wavelength (λd) is specified as 592 nanometers (nm), firmly placing the emitted light in the amber yellow region of the visible spectrum. The Spectral Line Half-Width (Δλ) is 15 nm, which describes the spectral purity or the narrowness of the emitted light's wavelength band; a smaller value indicates a more monochromatic light source. The device offers excellent character appearance due to high brightness and high contrast, as highlighted in its features.

2.2 Electrical Parameters

The electrical characteristics define the operating boundaries and conditions for the display. The Forward Voltage (Vf) per segment is typically 2.6V at a forward current (If) of 20mA. At a higher pulse current of 80mA, the Vf increases to a typical 2.8V. This positive temperature coefficient is normal for LED behavior. The Reverse Current (Ir) for any dot is a maximum of 100 microamperes (µA) when a reverse voltage (Vr) of 5V is applied, indicating the leakage current in the off-state. The Luminous Intensity Matching Ratio is specified as 2:1 maximum, which means the brightness difference between the brightest and dimmest dot in the array should not exceed this ratio, ensuring uniform appearance.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings specify the limits beyond which permanent damage to the device may occur. The Average Power Dissipation per dot must not exceed 70 milliwatts (mW). The Peak Forward Current per dot is rated at 60mA, while the Average Forward Current per dot is 25mA at 25°C. Crucially, this average current rating derates linearly by 0.33 mA per degree Celsius above 25°C. This derating curve is essential for thermal management design; as ambient temperature increases, the maximum allowable continuous current must be reduced to prevent overheating and ensure long-term reliability. The Operating and Storage Temperature Range is from -35°C to +85°C, defining the environmental conditions for use and non-operation. The maximum soldering temperature is 260°C for a maximum of 3 seconds, which is a standard reflow soldering profile requirement.

3. Mechanical and Packaging Information

The physical dimensions of the display package are provided in a detailed drawing (referenced in the datasheet). All dimensions are specified in millimeters with a standard tolerance of ±0.25 mm unless otherwise noted. This includes the overall length, width, height, the spacing between pins, and the position of the dot matrix area relative to the package edges. The package houses the 5x7 LED array and provides the mechanical structure and electrical connections via pins.

4. Pin Connection and Internal Circuit

The device has a 14-pin configuration. The pinout is clearly defined: Pins are assigned as anodes for specific columns and cathodes for specific rows. For example, Pin 1 is the cathode for Row 5, Pin 3 is the anode for Column 2, and so on. This specific arrangement is critical for designing the external drive circuitry. The internal circuit diagram shows that the LED dots are arranged in a common-cathode matrix configuration. Each LED's anode is connected to a column line, and its cathode is connected to a row line. To illuminate a specific dot, its corresponding column line must be driven high (anode positive), and its row line must be driven low (cathode grounded).

5. Soldering and Assembly Guidelines

The datasheet provides a key parameter for the assembly process: the solder temperature. The device can withstand a maximum temperature of 260°C for a maximum duration of 3 seconds, measured at 1.6mm (1/16 inch) below the seating plane of the package. This information is vital for setting up a reflow soldering oven profile. A standard lead-free reflow profile with a peak temperature around 250°C is typically compatible. Prolonged exposure to temperatures above this limit can damage the internal wire bonds, the LED chips, or the plastic package material.

6. Application Suggestions

6.1 Typical Application Scenarios

This 5x7 dot matrix display is ideal for applications requiring simple, fixed-font alphanumeric readouts. Common uses include industrial control panels for displaying setpoints, status codes, or error messages. It can be found in test and measurement equipment, consumer electronics like older audio equipment or appliances, and various instrumentation panels. Its amber yellow color is often chosen for its good visibility and lower perceived brightness strain in low-light environments compared to pure green or blue.

6.2 Design Considerations

Designing with this display requires careful attention to the drive circuitry. Since it is a multiplexed matrix, a microcontroller or dedicated display driver IC is necessary to sequentially scan the rows and columns. Current-limiting resistors are mandatory for each column (anode) line to set the forward current for the LEDs, typically to the recommended 20mA average. The derating curve for forward current must be respected based on the expected maximum ambient temperature inside the product enclosure. Heat sinking or ventilation might be necessary if operating near the upper temperature limit. The multiplexing scheme also affects the apparent brightness; a higher duty cycle or peak current may be used to compensate for the reduced on-time per LED, but always within the absolute maximum ratings.

7. Technical Comparison and Differentiation

The primary differentiating factor of the LTP-2057AKY is its use of AlInGaP LED technology. Compared to older technologies like standard Gallium Phosphide (GaP) LEDs used for amber/yellow, AlInGaP offers significantly higher luminous efficiency. This translates to higher brightness for the same drive current or lower power consumption for the same brightness level. The "high brightness & high contrast" feature is a direct result of this material advantage. The gray face with white dots further enhances the contrast ratio, making the characters appear sharper and more defined, especially in brightly lit conditions.

8. Frequently Asked Questions Based on Technical Parameters

Q: What is the purpose of the 1/16 duty cycle in the luminous intensity test condition?
A: The 1/16 duty cycle (e.g., a pulse) is used because the display is designed for multiplexed operation. In a 5x7 matrix, a common multiplexing scheme might scan one row at a time. If all 7 rows are scanned equally, each row (and thus each LED) is active for approximately 1/7 of the time. The 1/16 duty in the test is a standardized condition to measure the peak brightness of a single LED when it is briefly turned on, which is relevant for the perceived brightness in a multiplexed system.

Q: How do I interpret the Forward Voltage specification having two different current values?
A: The Forward Voltage (Vf) is not a constant; it increases with current. The datasheet provides two data points: a typical value at the standard operating current (20mA) and another at a higher pulse current (80mA) that might be used in multiplexed systems to achieve higher perceived brightness. Designers must ensure their driver circuit can provide the necessary voltage, especially when using higher pulse currents.

Q: Why is current derating above 25°C necessary?
A: LEDs generate heat internally. The semiconductor junction has a maximum operating temperature. As the ambient temperature rises, the ability of the package to dissipate this internal heat decreases. To prevent the junction temperature from exceeding its safe limit, which would drastically reduce lifespan or cause immediate failure, the maximum allowable continuous current must be reduced. The derating factor of 0.33 mA/°C provides the guideline for this reduction.

9. Practical Design and Usage Case

Consider designing a simple temperature controller with a digital readout. A microcontroller would read a temperature sensor, perform a control algorithm, and drive the LTP-2057AKY display to show the current temperature (e.g., " 23 C"). The microcontroller's I/O ports, configured with appropriate current-sinking and sourcing capabilities, would be connected to the display's rows and columns via current-limiting resistors. Firmware would implement a scanning routine: it would set one row line low (active) while placing the pattern for that row on the five column lines, wait a short time, then move to the next row. This cycle repeats rapidly, creating a persistent visual image. The amber color provides clear visibility on the control panel. The designer must calculate the resistor values based on the supply voltage and desired LED current (e.g., 20mA), considering the Vf drop and the microcontroller's output voltage.

10. Principle Introduction

The operating principle is based on electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold is applied across the AlInGaP LED chip, electrons and holes recombine in the active region, 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, amber yellow at 592 nm. The transparent GaAs substrate allows more light to escape, contributing to higher external efficiency. The 5x7 matrix arrangement is a practical method to form characters by selectively illuminating a subset of the 35 available dots.

11. Development Trends

While discrete 5x7 dot matrix displays like the LTP-2057AKY remain in use for specific applications, the broader trend in display technology has shifted towards integrated modules. These include LCDs (Liquid Crystal Displays) and OLEDs (Organic Light-Emitting Diodes) that offer full dot-addressable graphics, higher resolution, and the ability to display more complex information. For LED-based alphanumeric displays, surface-mount device (SMD) packages and multi-digit modules with integrated controllers have become more common, simplifying design and assembly. However, the fundamental advantages of LEDs—high brightness, long lifetime, and robustness—ensure they continue to be relevant, particularly in harsh environments or where visibility in direct sunlight is required. The AlInGaP material system itself has seen continuous improvement in efficiency and has been largely succeeded by even more efficient materials like InGaN for blue/green/white and AlInGaP for red/amber, but it represents a significant historical step in high-brightness visible LED development.