LTP-2057AKA LED Dot Matrix Display Specification Sheet - 2.0-inch (50.8 mm) Character Height - Super Orange (621 nm) - 33 mW per Dot - Technical Documentation

1. Product Overview

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

2. In-depth Technical Parameter Analysis

2.1 Optical Characteristics

Optical performance is the core of a display's functionality. The key parameter—average luminous intensity (Iv)—is specified with a minimum value of 2100 μcd and a typical value of 4600 μcd under test conditions of a pulsed forward current (Ip) of 32mA and a duty cycle of 1/16, with no maximum limit. This pulsed driving method is standard for multiplexed displays, aiming to achieve perceived brightness while managing power consumption and heat. The color is defined by its peak emission wavelength (λp) of 621 nanometers (nm), located in the orange-red region of the spectrum. The spectral line half-width (Δλ) is 18 nm, indicating 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. The specified luminous intensity matching ratio is 2:1, meaning the brightness variation between the brightest and dimmest segments in an array should not exceed this ratio to ensure a uniform appearance.

2.2 Electrical Characteristics

Electrical parameters define the operating limits and conditions of the display. Absolute maximum ratings set safe operating boundaries: average power dissipation per dot is 33 milliwatts (mW), peak forward current per dot is 90mA, and average forward current per dot starts at 13mA at 25°C and derates linearly at a rate of 0.17mA/°C. This derating is crucial for thermal management at higher ambient temperatures. Maximum reverse voltage per dot is 5 volts (V). The forward voltage (Vf) of any single LED dot is typically 2.6V at 20mA, with a maximum of 2.8V at the higher test current of 80mA. Under full 5V reverse bias, the reverse current (Ir) is a maximum of 100 microamperes (μA).

2.3 Thermal and Environmental Specifications

The operating temperature range of this device is rated from -35°C to +85°C, with the same storage temperature range. This broad range makes it suitable for industrial and automotive environments that may experience extreme temperatures. A key assembly parameter is a maximum soldering temperature of 260°C for a maximum duration of 3 seconds, measured 1.6 mm (1/16 inch) below the component mounting plane. This guideline is crucial for preventing thermal damage during reflow soldering.

3. Mechanical and Packaging Information

The nominal dot matrix height of this display is 2.0 inches (50.8 mm). The provided package dimension drawing (referenced in the datasheet) details the exact physical outline, pin locations, and overall dimensions. Unless otherwise specified, the tolerance for these dimensions is typically ±0.25 mm. The device uses a standard pin connection interface for integration onto a circuit board.

4. Pin Connections and Internal Circuitry

LTP-2057AKA has a 14-pin interface. The pin arrangement is specifically designed for X-Y (matrix) addressing: pins are designated as column anodes or row cathodes. For example, pin 1 is the cathode for row 5, pin 3 is the anode for column 2, and so on. This arrangement allows a microcontroller to selectively illuminate any single point in the 5x7 grid by activating the corresponding column (anode) and row (cathode) lines. The internal circuit diagram (referenced in the datasheet) will visually depict this matrix structure, showing 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 on typical electrical/optical characteristic curves. These graphs are invaluable for design engineers. They typically include plots such as forward current versus forward voltage for a single LED element (I-V curve), showing the non-linear relationship and turn-on voltage. The luminous intensity versus forward current curve will illustrate how light output increases with current, potentially showing saturation effects. There may also be curves showing the variation of luminous intensity or forward voltage with ambient temperature, which is crucial for designing stable circuits over the specified temperature range. Analyzing these curves allows for optimizing drive current to achieve desired brightness and understanding the impact of thermal effects on performance.

6. Soldering and Assembly Guide

As stated in the Absolute Maximum Ratings, the primary assembly constraint is the soldering temperature profile. The device can withstand a peak temperature of up to 260°C during reflow soldering for a maximum duration of 3 seconds. It is essential to ensure the temperature measured at the package leads does not exceed this limit to prevent damage to the internal wire bonds, LED chip, or plastic package. Standard industry reflow profiles for lead-free soldering (with peaks typically around 240-250°C) are generally compatible, but the profile must be verified. When using a soldering iron for manual soldering, the operation should be quick with careful temperature control to localize heat. When handling LED components, proper ESD (Electrostatic Discharge) handling procedures should always be followed.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

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

7.2 Design Considerations

Drive Circuit:The display requires multiplexed driving electronics. A microcontroller with sufficient I/O pins or combined with external driver ICs (such as shift registers or dedicated LED driver chips) must be used to sequentially scan the rows and columns. The test conditions of 1/16 duty cycle and 32mA pulse current in the datasheet provide a starting point for calculating the required current-limiting resistors. The average current per LED will be much lower (e.g., if only one is lit, 32mA / 16 = 2mA average current, but this scales with the number of points lit simultaneously in a row).
Power Supply:A forward voltage of approximately 2.6V means the driving voltage must be higher than this, typically using a 3.3V or 5V system. The power supply must be capable of handling the peak current demand during multiplexing.
Viewing Angle:The datasheet mentions "wide viewing angle," which is a characteristic of the LED chip and diffuser lens design. For optimal placement, consider the end-user's primary viewing direction.
Stacking:The feature "horizontally stackable" means multiple units can be placed side-by-side to form a multi-character display. Mechanical alignment and electrical interconnection between modules need to be designed.

8. Technical Comparison and Differentiation

The key differentiation of the LTP-2057AKA lies in its orange LED utilizing AlInGaP technology. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red/orange LEDs, AlInGaP offers significantly higher luminous efficacy (more light output per unit of electrical power) and better performance retention at high temperatures. The "Super Orange" 621nm wavelength provides a vibrant, highly visible color. The gray panel with white dot matrix presents a professional, high-contrast appearance when unpowered, which could be a design advantage over all-black or all-red displays. The 2.0-inch character height is a specific size that can be selected based on viewing distance requirements, rather than smaller (e.g., 0.8-inch) or larger displays.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: How to calculate the current limiting resistor value for this display?
A: You must design based on the pulse (peak) current, not the average current. Refer to the test conditions (32mA at typical Vf of 2.6V) and assume a 5V driving power supply: R = (V_supply - Vf) / I_peak = (5V - 2.6V) / 0.032A = 75 ohms. For a safer, dimmer calculation using the maximum Vf (2.8V): R = (5V - 2.8V) / 0.032A = ~68 ohms. Standard 68 or 75 ohm resistors are suitable. The resistor's power rating must be calculated based on the average current, not the peak current.

Q: What does a 1/16 duty cycle mean for driving this display?
A: In a multiplexed 5x7 matrix, a common scanning method is to activate one row (cathode) at a time while providing data for the 5 columns (anodes) of that row. For 7 rows, if each row is activated sequentially and for equal time, the duty cycle for any single LED is 1/7. The 1/16 duty cycle in the datasheet indicates a different or more conservative multiplexing scheme, possibly involving blanking periods. The drive circuit must pulse the LED at the specified peak current (e.g., 32mA) during its assigned 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 possible, but highly inefficient and not recommended. Even driving all 35 dots simultaneously at a low current like 5mA would require a total 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 Examples

考虑设计一个简单的温度读数显示器，显示0到99摄氏度的值。这将需要两个LTP-2057AKA显示器水平堆叠。一个微控制器（例如ATmega328P）将连接到每个显示器的14个引脚（总共28个I/O引脚）。为了节省I/O，可以将两个显示器的列（阳极）线并联连接（5条共享线），而行（阴极）线则分别控制每个显示器（7+7=14条线）。这使用了19个I/O引脚。或者，可以使用外部8位移位寄存器来大幅减少微控制器的I/O需求。软件将包含一个字体映射，将数字0-9转换为5x7网格中相应的点亮点图案。然后，它将为每个显示器扫描7行，发送要显示字符的相应行的列数据。扫描必须足够快（通常>60Hz）以避免可见闪烁。

11. Introduction to Working Principles

LTP-2057AKA operates based 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 turn-on voltage (approximately 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—with a wavelength of about 621 nanometers (orange). By rapidly switching which row is grounded (cathode activated) and which columns are powered (anode activated), different dot patterns can be illuminated to form characters or symbols. The persistence of vision in the human eye blends these rapid flashes into a stable image.

12. Technical Trends and Background

Displays like the LTP-2057AKA represent a mature and reliable field within optoelectronics. While newer technologies such as organic LEDs (OLEDs) or high-resolution LCDs dominate complex graphical displays, simple LED dot matrix modules remain highly relevant for applications requiring ruggedness, long life, wide-temperature operation, high brightness, and low per-character cost. Trends within this field include the adoption of higher-efficiency LED materials (like the AlInGaP used here, and InGaN for blue/green/white), enabling lower power consumption or higher brightness. Another trend is integrated solutions, where the driving electronics are built into the display module itself, simplifying system design for the end engineer. However, due to its simplicity and low cost, the basic passive matrix architecture remains mainstream for single- and multi-character numeric and alphanumeric displays in industrial, automotive, and consumer fields.