LTP-2057AKA LED Dot Matrix Display Datasheet - 2.0 Inch (50.8mm) Height - Super Orange (621nm) - 33mW per Dot - English Technical Document

1. Product Overview

The LTP-2057AKA is a single-digit, alphanumeric display module built using a 5x7 dot matrix configuration. Its primary function is to visually represent characters and symbols, commonly used for status indicators, simple readouts, and information panels in various electronic devices. The core advantage of this device lies in its utilization of AlInGaP (Aluminum Indium Gallium Phosphide) LED technology for the light-emitting elements, specifically in a "Super Orange" color. This material system offers benefits in terms of efficiency and color stability compared to older technologies. The display features a gray faceplate with white-colored dots, providing a high-contrast background for the emitted light, which enhances readability. The device is designed for applications requiring a medium-sized, reliable, and low-power character display.

2. In-Depth Technical Parameter Analysis

2.1 Optical Characteristics

The optical performance is central to the display's function. The key parameter, Average Luminous Intensity (Iv), is specified with a minimum of 2100 μcd, a typical value of 4600 μcd, and no maximum limit under the test condition of a pulsed forward current (Ip) of 32mA at a 1/16 duty cycle. This pulsed driving method is standard for multiplexed displays to achieve perceived brightness while managing power and heat. The color is defined by its Peak Emission Wavelength (λp) of 621 nanometers (nm), placing it in the orange-red region of the spectrum. The Spectral Line Half-Width (Δλ) is 18 nm, indicating the spectral purity or the narrowness of the emitted light band. The Dominant Wavelength (λd) is 615 nm, which is the wavelength perceived by the human eye and may differ slightly from the peak wavelength. A Luminous Intensity Matching Ratio of 2:1 is specified, meaning the brightness variation between the brightest and dimmest segments in the array should not exceed this ratio, ensuring uniform appearance.

2.2 Electrical Characteristics

The electrical parameters define the operating limits and conditions for the display. The Absolute Maximum Ratings set the boundaries for safe operation: an Average Power Dissipation of 33 milliwatts (mW) per dot, a Peak Forward Current of 90mA per dot, and an Average Forward Current per dot that derates linearly from 13mA at 25°C by 0.17mA/°C. This derating is crucial for thermal management at elevated ambient temperatures. The maximum Reverse Voltage per dot is 5 Volts (V). The Forward Voltage (Vf) for any single LED dot is typically 2.6V at 20mA, with a maximum of 2.8V at a higher test current of 80mA. The Reverse Current (Ir) is a maximum of 100 microamperes (μA) at the full 5V reverse bias.

2.3 Thermal and Environmental Specifications

The device is rated for an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. This wide range makes it suitable for industrial and automotive environments subject to temperature extremes. A critical assembly parameter is the maximum solder temperature of 260°C for a maximum duration of 3 seconds, measured at a point 1.6mm (1/16 inch) below the seating plane of the component. This guideline is essential for preventing thermal damage during the reflow soldering process.

3. Mechanical and Packaging Information

The display has a stated matrix height of 2.0 inches (50.8 mm). The provided package dimensions drawing (referenced in the datasheet) would detail the exact physical outline, pin locations, and overall size. Tolerances for these dimensions are typically ±0.25 mm unless otherwise noted. The device uses a standard pin connection interface for integration into a circuit board.

4. Pin Connection and Internal Circuit

The LTP-2057AKA has a 14-pin interface. The pinout is specifically arranged for X-Y (matrix) addressing: Pins are designated as either Anode for Columns or Cathode for Rows. For example, Pin 1 is Cathode for Row 5, Pin 3 is Anode for Column 2, and so on. This arrangement allows a microcontroller to selectively illuminate any single dot in the 5x7 grid by activating the corresponding column (anode) and row (cathode) lines. The internal circuit diagram (referenced in the datasheet) would visually depict this matrix structure, showing the 35 individual LEDs (5 columns x 7 rows) with their anodes connected in column groups and cathodes connected in row groups.

5. Performance Curve Analysis

The datasheet references a section for Typical Electrical/Optical Characteristic Curves. These graphs are invaluable for design engineers. They would typically include plots such as Forward Current vs. Forward Voltage (I-V curve) for a single LED element, showing the non-linear relationship and the turn-on voltage. Luminous Intensity vs. Forward Current curves would illustrate how light output increases with current, potentially showing saturation effects. There might also be curves showing the variation of Luminous Intensity or Forward Voltage with Ambient Temperature, which is critical for designing stable circuits over the specified temperature range. Analyzing these curves allows for optimizing drive current for desired brightness and understanding thermal effects on performance.

6. Soldering and Assembly Guidelines

As mentioned in the Absolute Maximum Ratings, the primary assembly constraint is the soldering temperature profile. The device can withstand a peak temperature of 260°C for up to 3 seconds during reflow soldering. It is critical to ensure the temperature measured at the package leads does not exceed this limit to prevent damage to the internal wire bonds, LED chips, or plastic package. Standard industry reflow profiles for lead-free soldering (which peaks around 240-250°C) are generally compatible, but the profile must be verified. Manual soldering with an iron should be performed quickly and with careful temperature control to localize heat. Proper ESD (Electrostatic Discharge) handling procedures should always be followed with LED components.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

This 5x7 dot matrix display is ideal for applications requiring a single, clear alphanumeric character. Common uses include: panel meters for voltage, current, or temperature readouts; status displays on industrial equipment (showing error codes or mode indicators); consumer appliances like microwave ovens or washing machines; and test/measurement instrumentation. Its compatibility with standard ASCII and EBCDIC character codes simplifies programming with microcontrollers.

7.2 Design Considerations

Drive Circuitry: The display requires multiplexed drive electronics. A microcontroller with sufficient I/O pins or coupled with external driver ICs (like shift registers or dedicated LED driver chips) is necessary to sequentially scan the rows and columns. The datasheet's test condition of 1/16 duty cycle at 32mA pulse current provides a starting point for calculating the required current-limiting resistors. The average current per LED will be much lower (e.g., 32mA / 16 = 2mA average if only one dot is on, but this scales with the number of simultaneously lit dots in a row).
Power Supply: The forward voltage of ~2.6V means the drive voltage must be higher than this, typically 3.3V or 5V systems are used. The power supply must be able to handle the peak current demands during multiplexing.
Viewing Angle: The datasheet mentions a "wide viewing angle," which is a characteristic of the LED chip and diffused lens design. For optimal placement, consider the primary viewing direction of the end-user.
Stacking: The feature of being "stackable horizontally" means multiple units can be placed side-by-side to form multi-character displays. Mechanical alignment and electrical interconnection between modules need to be designed.

8. Technical Comparison and Differentiation

The key differentiator for the LTP-2057AKA is its use of AlInGaP LED technology for the orange color. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red/orange LEDs, AlInGaP offers significantly higher luminous efficiency (more light output per unit of electrical power) and better performance maintenance at elevated temperatures. The "Super Orange" 621nm wavelength provides a vibrant, highly visible color. The gray face with white dots offers a professional, high-contrast appearance when unpowered, which can be a design advantage over all-black or all-red displays. The 2.0-inch character height is a specific size that may be chosen over smaller (e.g., 0.8-inch) or larger displays based on viewing distance requirements.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: How do I calculate the current-limiting resistor value for this display?
A: You must design for the pulsed (peak) current, not the average. Using the test condition as a reference (32mA at Vf typ. 2.6V), and assuming a 5V drive supply: R = (V_supply - Vf) / I_peak = (5V - 2.6V) / 0.032A = 75 Ohms. Use the maximum Vf (2.8V) for a safer, dimmer calculation: R = (5V - 2.8V) / 0.032A = ~68 Ohms. A standard 68 or 75 Ohm resistor would be suitable. The power rating of the resistor must be calculated based on the average current, not the peak.

Q: What does a 1/16 duty cycle mean for driving this display?
A: In a multiplexed 5x7 matrix, one common scanning method is to activate one row (cathode) at a time while supplying data to the 5 columns (anodes) for that row. With 7 rows, if each row is activated sequentially and equally, the duty cycle for any single LED is 1/7. The datasheet's 1/16 duty cycle suggests a different or more conservative multiplexing scheme, possibly involving blanking periods. The driver circuit must pulse the LED at the specified peak current (e.g., 32mA) for its allotted time slice to achieve the rated average luminous intensity.

Q: Can I drive this display with a constant DC current instead of multiplexing?
A: Technically, yes, but it is highly inefficient and not recommended. Driving all 35 dots simultaneously at even a low current like 5mA would require a total current of 175mA and generate significant heat, likely exceeding the package's power dissipation limits. Multiplexing is the standard and intended method of operation.

10. Practical Design and Usage Example

Consider designing a simple temperature readout displaying a value from 0 to 99 degrees Celsius. This would require two LTP-2057AKA displays stacked horizontally. A microcontroller (e.g., an ATmega328P) would be connected to the 14 pins of each display (28 I/O pins total). To save I/O, the column (anode) lines of both displays could be connected in parallel (5 shared lines), and the row (cathode) lines would be controlled separately for each display (7+7=14 lines). This uses 19 I/O pins. Alternatively, external 8-bit shift registers could be used to drastically reduce the microcontroller I/O requirement. The software would contain a font map, translating the digits 0-9 into the corresponding pattern of lit dots for the 5x7 grid. It would then scan through the 7 rows, for each display, sending the appropriate column data for the rows of the characters to be shown. The scanning must be fast enough (typically >60Hz) to avoid visible flicker.

11. Operating Principle Introduction

The LTP-2057AKA operates on the principle of a passive matrix LED array. It contains 35 independent AlInGaP semiconductor LED junctions arranged in a grid of 5 columns and 7 rows. Each LED is formed at the intersection of a column anode line and a row cathode line. When a forward voltage exceeding the diode's turn-on voltage (~2.6V) is applied between a specific column (positive) and a specific row (negative), current flows through that single LED, causing it to emit photons—light—at a wavelength of approximately 621 nm (orange). By rapidly sequencing which row is grounded (cathode activated) and which columns are supplied with current (anode activated), different patterns of dots can be illuminated, forming characters or symbols. The human eye's persistence of vision blends these rapid flashes into a stable image.

12. Technology Trends and Context

Displays like the LTP-2057AKA represent a mature and reliable segment of optoelectronics. While newer technologies like organic LED (OLED) or high-resolution LCDs dominate complex graphical displays, simple LED dot matrix modules remain highly relevant for applications requiring robustness, long lifetime, wide temperature operation, high brightness, and low cost per character. The trend within this segment is towards higher efficiency LED materials (like AlInGaP used here, and InGaN for blue/green/white), which allow for lower power consumption or higher brightness. There is also a trend towards integrated solutions where the driver electronics are built into the display module itself, simplifying the system design for the end engineer. However, the basic passive matrix architecture, due to its simplicity and low cost, continues to be a mainstay for single and multi-character numeric and alphanumeric displays in industrial, automotive, and consumer contexts.