LTP-747KA LED Dot Matrix Display Datasheet - 0.7 Inch (17.22mm) Character Height - Red Orange - AlInGaP Technology - Simplified Chinese Technical Documentation

1. Product Overview

LTP-747KA is a single-character, 5x7 dot matrix alphanumeric display module. Its primary function is to provide clear, bright visual output for characters and symbols in various electronic applications. The core component of this display is a light-emitting diode (LED) chip made from advanced aluminum indium gallium phosphide (AlInGaP) semiconductor material, responsible for producing the iconic red-orange light output. This material technology is renowned for its high efficiency and excellent performance characteristics.

The device is constructed with a gray panel and features white dots or segments, which enhances the contrast and readability between the light-emitting elements and the background. The display is classified according to its luminous intensity, meaning the units are binned or sorted based on their measured light output to ensure consistent brightness within a specified range for applications requiring uniform illumination.

2. Detailed Technical Specifications

This section provides a detailed and objective analysis of the key technical parameters specified in the specification document.

2.1 Optical Characteristics

Optical performance is the core of display functionality. Key parameters are measured under specific test conditions, typically at an ambient temperature (T_A) of 25°C.

• Average Luminous Intensity (I_V):This is a metric that measures the perceived power of light emitted from a single point. When driven at a peak current (I_P) of 32mA with a 1/16 duty cycle, the typical value is 3400 microcandelas (µcd), with a minimum of 1650 µcd. The 1/16 duty cycle is a multiplexing scheme commonly used in dot matrix displays, where each row is active for only 1/16 of the time to manage power and heat.
• Peak Emission Wavelength (λ_p):The wavelength at which the intensity of the LED's emission spectrum reaches its maximum. For the LTP-747KA, this value is typically 621 nanometers (nm), placing it firmly within the red-orange region of the visible spectrum.
• Dominant Wavelength (λ_d):Wannan darajar ita ce 615 nm, wannan ita ce mafi kyawun bayyana kallon ido na mutum na launi ta hanyar tsawon zango guda. Saboda siffar fitar da haske na LED, ya ɗan bambanta da tsawon zango mafi girma.
• Ramin rabin faɗin layin haske (Δλ):Wannan ma'auni yawanci yana 18 nm, yana nuna faɗin fitar da haske a rabin mafi girman ƙarfinsa. Ƙunƙarar rabin faɗi tana nuna tsabtar haske da ƙarar launi.
• Matsayin daidaita ƙarfin haske (I_V-m):The maximum is specified as 2:1. This ratio defines the allowable brightness variation between the brightest and darkest points on the display. A lower ratio indicates better uniformity.

2.2 Electrical Characteristics

Understanding electrical behavior is crucial for proper circuit design and ensuring long-term reliability.

• Forward voltage (V_F):The voltage drop across an LED when it conducts current. At a forward current (I_F) of 20mA, the typical value is 2.6V, and the maximum value is 2.6V. The minimum value is 2.05V. This range must be considered when designing the current limiting circuit.
• Reverse current per point (I_R):The minute current that flows when a reverse voltage is applied. At a reverse voltage (V_R) of 5V, the maximum is specified as 100 µA. Exceeding the absolute maximum reverse voltage may cause damage.
• Average forward current per point:The recommended maximum continuous DC current for reliable operation is 13 mA. This is different from the peak current used in multiplexed operation.
• Peak forward current per point:The maximum instantaneous current a point can withstand is specified as 90 mA. In multiplexing applications, the instantaneous current can be higher than the average current but must not exceed this peak rating.

2.3 Absolute Maximum Ratings and Thermal Considerations

These ratings define the limits beyond which permanent damage to the device may occur. They are not conditions for normal operation.

• Average Power Dissipation per Point:The maximum power that a single LED point can continuously dissipate is 33 mW. Exceeding this value may cause overheating and shorten the service life.
• Operating and Storage Temperature Range:This device is rated to operate within an ambient temperature range of -35°C to +85°C. It can also be stored within this same temperature range.
• Current Derating:Above 25°C, the average forward current must be linearly reduced at a rate of 0.17 mA per degree Celsius. This is a key design rule to prevent thermal runaway at higher ambient temperatures.
• Soldering Temperature:During wave soldering or reflow soldering, the temperature at 1/16 inch (approximately 1.6 mm) below the package mounting plane must not exceed 260°C for more than 3 seconds. This prevents damage to the internal chip and bonding wires.

3. Grading and Classification System

The datasheet clearly states that the device is "classified by luminous intensity." This implies the existence of a grading process.

• Luminous Intensity Grading:After manufacturing, individual displays are tested and sorted into different bins based on their measured light output. This ensures customers receive products with consistent brightness levels. The datasheet provides min/typ/max values (1650/3400 µcd), but this excerpt does not detail specific bin codes or categories. In practice, ordering information specifies the required intensity bin.
• Wavelength/Color Binning:Although wavelength binning is not explicitly mentioned in this datasheet, LED manufacturers typically bin devices by dominant wavelength or peak wavelength to ensure color consistency, especially in multi-unit displays. λ_p(621 nm) and λ_dThe strict typical values at (615 nm) indicate that the AlInGaP material possesses excellent intrinsic color uniformity.

4. Performance Curve Analysis

The datasheet references "Typical Electrical/Optical Characteristic Curves." Although specific charts are not provided in the text, we can infer their standard content and significance.

• Forward Current vs. Forward Voltage (I_F-V_F) Curve:This graph illustrates the nonlinear relationship between the current passing through an LED and the voltage across its terminals. It is crucial for designing a correct drive circuit. The curve will show a "knee" voltage (typically around 2.6V), beyond which the current increases rapidly with a small increase in voltage.
• Luminous Intensity vs. Forward Current (I_V-I_F) Curve:This graph illustrates how light output increases with drive current. It is typically linear within a certain range but saturates at very high currents. It helps determine the operating point for the desired brightness.
• Luminous Intensity vs. Ambient Temperature (I_V-T_A) Curve:This figure shows the decrease in light output as the LED junction temperature increases. It quantifies the thermal derating effect, which is crucial for applications operating in high-temperature environments.
• Spectral Distribution Curve:A plot of relative intensity versus wavelength, showing a bell-shaped curve centered at 621 nm with a half-width of 18 nm.

5. Mechanical and Packaging Information

5.1 Physical Dimensions

The character height of this display is 0.7 inches, equivalent to 17.22 mm. The package dimension drawing (referenced but not shown in the text) will detail the overall length, width, height, pin pitch, and segment arrangement. Unless otherwise specified, the tolerance for all dimensions is defined as ±0.25 mm (0.01 inch). This level of precision is crucial for mechanical fit on a printed circuit board (PCB).

5.2 Pin Connections and Internal Circuitry

This device has 12 pins. The pin definitions are clear: Pin 1: Column 1 anode, Pin 2: Row 3 cathode, Pin 3: Column 2 anode, and so on. The internal circuit diagram shows that the rows use a common cathode configuration. This means each of the 7 rows is connected to the cathodes of all 5 LEDs in that row. The 5 column lines are connected to the anodes of the LEDs in each column. This matrix arrangement allows control of 35 independent points (5x7) using only 12 pins (5+7) through multiplexing technology.

5.3 Polarity Identification

Although not explicitly stated in the text, the pin numbers and internal circuit diagram provide the necessary information for polarity. The pin definition table is the authoritative guide for correctly connecting the anode and cathode. Incorrect polarity connection (applying forward bias to the cathode) will prevent the LED from lighting up and may damage it if the voltage exceeds the reverse voltage rating (5V).

6. Welding and Assembly Guide

The key guideline provided is the soldering temperature profile: the temperature measured 1.6 mm below the package body must not exceed 260°C for more than 3 seconds. This is a standard guideline for wave soldering or reflow soldering processes. For manual soldering, a temperature-controlled soldering iron should be used, and contact time with the pins should be minimized to prevent heat conduction along the pins and damage to the internal chip. Proper electrostatic discharge (ESD) precautions should be observed during handling and assembly to prevent damage to the semiconductor junction.

7. Application Suggestions

7.1 Typical Application Scenarios

Due to its 5x7 dot matrix format being highly suitable for generating alphanumeric characters, the LTP-747KA is ideal for applications requiring clear, single-character readouts. Examples include:

• Industrial control panels and instrumentation displays.
• Test and measurement equipment.
• Consumer appliances, such as microwave ovens, washing machines, or audio equipment.
• Point of sale terminals and basic information displays.
• Educational Kit for Learning Microcontrollers and Multiplexed Displays.

7.2 Design Considerations

• Driver circuit:A microcontroller or dedicated display driver IC is required to multiplex the rows and columns. The driver must be capable of sourcing/sinking the necessary peak current for columns and rows separately (up to 32mA per point under test conditions, but the design should refer to the absolute maximum ratings).
• Current limiting:Each anode (column) line must use an external current-limiting resistor to set the forward current and protect the LED. The resistor value is calculated using the formula R = (V_{Power Supply}- V_F) / I_F Calculation. The peak current (I) in multiplexed operation must be considered._P).
• Thermal Management:In high ambient temperature environments or high-brightness applications, ensure the average current is derated as specified (0.17 mA per degree Celsius above 25°C). Adequate spacing on the PCB aids natural convection cooling.
• Perspective:The datasheet claims to have a "wide viewing angle," which is very beneficial for applications where the display may be viewed from off-axis positions.

8. Technical Comparison and Differentiation

Although no direct comparison with other models is provided, according to its datasheet, the key differentiating factors of the LTP-747KA include:

• Material Technology (AlInGaP):Compared to older GaAsP or GaP LEDs, AlInGaP offers higher efficiency, better temperature stability, and superior brightness, thereby enabling the claim of "high brightness and high contrast."
• Dot Matrix vs. Segment Display:The 5x7 dot matrix offers greater flexibility than the standard 7-segment display because it can display the full ASCII character set, symbols, and simple graphics, rather than just numbers and a few letters.
• Intensity Classification:The binning of luminous intensity is a value-added feature for applications that require uniformity across multiple units.
• Contrast Enhancement:A gray panel with white dots is a design choice aimed at improving contrast when the LEDs are off, making the display appear more professional and readable under various lighting conditions.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between Peak Forward Current (90mA) and Test Condition Current (32mA)?

Peak Forward Current (90mA) is an Absolute Maximum Rating—the highest instantaneous current the LED can withstand without immediate damage. The 32mA used in the luminous intensity test is a typical operating condition measured in a multiplexed (1/16 duty cycle) system. In that case,averageThe current is much lower (32mA / 16 = 2mA). The design must ensure the instantaneous current remains below 90mA, and the average current per point stays below 13mA (considering temperature derating).

9.2 How to understand the 1/16 duty cycle specification?

This represents the standard multiplexing driving method. To control 7 rows with 5 columns, a common technique is to activate one row at a time, cycling rapidly through all 7 rows. If each row is on for an equal duration, its activation time is 1/7 of the total time. The 1/16 duty cycle is a conservative, standardized test condition that allows for comparison between different displays, even if the actual multiplexing scheme in your application is 1/7 or 1/8 duty cycle.

9.3 Me ya sa ake ba da kewayon ƙarfin lantarki mai gaba (matsakaicin 2.05V, na al'ada/mafi girma 2.6V)?

Forward voltage (V_F) has a natural variation due to manufacturing tolerances in the semiconductor material. Circuit design must accommodate this range. The current-limiting resistor should be calculated usingMaximum value V_F(2.6V) calculation, to ensure that even devices with high V_Fcan obtain sufficient voltage to turn on and achieve the required current. Using typical values for calculation may lead to the risk of insufficient drive for certain units.

10. Design and Use Case Examples

Scenario:Design a single-character temperature readout display for an industrial controller operating in environments up to 50°C.

1. Character Set:A 5x7 matrix can display digits 0-9 and letters, such as "C" for degrees Celsius.
2. Driver Selection:A microcontroller with at least 12 I/O pins or a dedicated display driver IC (e.g., MAX7219) will be used to handle the multiplexing timing.
3. Current Calculation:Set an average dot current required for a good brightness. Assume we choose an 8mA average. At 50°C, apply derating: Derating = (50°C - 25°C) * 0.17 mA/°C = 4.25 mA. Maximum allowed average current at 50°C = 13 mA - 4.25 mA = 8.75 mA. Our set target of 8mA is safe.
4. Resistance Calculation:For 1/7 multiplexing (7 rows), the peak current per point needs to reach 8mA * 7 = 56mA to achieve an average of 8mA. This is below the 90mA peak rating. Using a 5V supply and V_F(max)=2.6V, the current limiting resistor is R = (5V - 2.6V) / 0.056A ≈ 42.9Ω. A standard 43Ω resistor will be used.
5. PCB layout:The display placeholder will match the dimensional drawing. Sufficient space will be left around the package for airflow.

The LTP-747KA operates based on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's built-in potential is applied (anode positive relative to the cathode), electrons from the n-type AlInGaP layer recombine with holes from the p-type layer. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP alloy (aluminum, indium, gallium, phosphorus) determines the semiconductor's bandgap energy, which directly dictates the wavelength (color) of the emitted light—in this case, a red-orange color of approximately 621 nm. The chip is mounted on an opaque gallium arsenide (GaAs) substrate, which helps reflect light upward, improving the overall light extraction efficiency from the top surface of the device. The 5x7 matrix is formed by individually addressable LEDs arranged in this grid pattern, controlled by an external multiplexing circuit that rapidly sequences power to the rows and columns to create the visual illusion of a stable, fully illuminated character.

12. Technology Trends and Background

AlInGaP LED technology used in the LTP-747KA is a major advancement compared to earlier LED materials like GaAsP. It achieves higher brightness, higher efficiency, and better temperature stability, enabling LEDs to be used in a wider range of indicator and display applications. The trend in display technology subsequently shifted towards higher-density dot matrices, full-color RGB matrices, and the widespread application of organic LED (OLED) and micro-LED displays in high-resolution screens. However, single-character and multi-character alphanumeric dot matrix displays like the 5x7 format remain highly relevant in industrial, appliance, and instrumentation environments for cost-effective, reliable, and easily readable interfaces that do not require full graphical functionality. Regardless of scale or technology, the basic driving principles—multiplexing and current control—remain the cornerstone of LED display design.

AlInGaP LED technology, as used in the LTP-747KA, represented a significant advancement over earlier LED materials like GaAsP. It enabled higher brightness, improved efficiency, and better temperature stability, making LEDs viable for a wider range of indicator and display applications. The trend in display technology has since moved towards higher-density dot matrices, full-color RGB matrices, and the widespread adoption of organic LED (OLED) and micro-LED displays for high-resolution screens. However, single and multi-digit alphanumeric dot matrix displays like the 5x7 format remain highly relevant for cost-effective, reliable, and easily readable interfaces in industrial, appliance, and instrumentation contexts where full graphical capability is not required. The underlying drive principles—multiplexing and current control—remain fundamental to LED display design regardless of the scale or technology.