LTP-747KY LED Dot Matrix Display Datasheet - 0.7-inch Digit Height - AlInGaP Amber Yellow - 2.6V Forward Voltage - 25mW Power Dissipation - English Technical Document

1. Product Overview

The LTP-747KY is a compact, high-performance 5 x 7 dot matrix LED display module designed for applications requiring clear, legible alphanumeric or symbolic character output. Its primary function is to provide visual information in electronic devices. The core advantage of this device lies in its utilization of advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology for the LED chips, which offers superior efficiency and color purity compared to older technologies like standard GaAsP. The target market includes industrial control panels, instrumentation, medical equipment, consumer electronics, and any embedded system requiring a reliable, low-power information display.

The display features a digit height of 0.7 inches (17.22mm), providing excellent readability. It is characterized by continuous uniform segments, ensuring a consistent and professional character appearance. Key selling points highlighted in the datasheet are its low power requirement, high brightness and contrast, wide viewing angle, and solid-state reliability, which translates to long operational life and durability in various environments.

2. Technical Specifications Deep Dive

2.1 Optoelectronic Characteristics

The optoelectronic performance is central to the display's functionality. Measured at an ambient temperature (T_A) of 25°C, the key parameters are:

• Average Luminous Intensity (I_V): This parameter defines the perceived brightness of each lit dot. The typical value is 3400 µcd (microcandelas) under a test condition of I_P=32mA with a 1/16 duty cycle. The minimum specified is 1650 µcd. The use of a 1/16 duty cycle for measurement is standard for multiplexed displays and indicates the peak current during its active time slice.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λ_p): 595 nm. This is the wavelength at which the optical power output is maximum, placing it firmly in the amber-yellow region of the visible spectrum.
  • Dominant Wavelength (λ_d): 592 nm. This is the single wavelength that best matches the perceived color of the LED to the human eye, slightly lower than the peak wavelength.
  • Spectral Line Half-Width (Δλ): 15 nm. This indicates the spectral purity or the spread of the emitted light around the peak wavelength. A value of 15 nm is relatively narrow, contributing to a saturated, pure amber-yellow color.
• Luminous Intensity Matching Ratio (I_V-m): Maximum 2:1. This is a critical parameter for display uniformity. It specifies that the brightness of the dimmest dot in the array will be no less than half the brightness of the brightest dot, ensuring a consistent appearance across all segments of a character.

2.2 Electrical Parameters

The electrical specifications define the operating limits and conditions for safe and reliable use.

• Forward Voltage per Dot (V_F): Typically 2.6V, with a maximum of 2.6V at a forward current (I_F) of 20mA. The minimum is 2.05V. This voltage is relatively low, contributing to the low power consumption claim.
• Reverse Current per Dot (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This indicates the level of leakage current when the LED is reverse-biased.
• Current Ratings:
  • Peak Forward Current per Dot: 60 mA (absolute maximum).
  • Average Forward Current per Dot: 13 mA (absolute maximum at 25°C). This rating derates linearly at 0.17 mA/°C above 25°C, meaning the allowable continuous current decreases as temperature rises to prevent overheating.
• Average Power Dissipation per Dot: 25 mW (absolute maximum). This is the maximum power each individual LED dot can safely dissipate as heat.

2.3 Thermal and Environmental Ratings

These parameters ensure the device's robustness across different operating conditions.

• Operating Temperature Range: -35°C to +85°C. This wide range makes it suitable for use in harsh environments, from freezing cold to hot industrial settings.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: The device can withstand a soldering temperature of 260°C for 3 seconds at a distance of 1/16 inch (approximately 1.6mm) below the seating plane. This is a standard specification for wave or reflow soldering processes.

3. Mechanical and Packaging Information

3.1 Physical Dimensions

The datasheet includes a detailed package dimension drawing. All dimensions are provided in millimeters with a standard tolerance of ±0.25mm unless otherwise specified. The overall size, pin spacing, and segment window dimensions are defined in this drawing, which is crucial for PCB (Printed Circuit Board) layout and mechanical integration into a product enclosure.

3.2 Pin Connection and Internal Circuit

The device has a 12-pin configuration. The pinout is as follows: Pin 1 (Anode Column 1), Pin 2 (Cathode Row 3), Pin 3 (Anode Column 2), Pin 4 (Cathode Row 5), Pin 5 (Cathode Row 6), Pin 6 (Cathode Row 7), Pin 7 (Anode Column 4), Pin 8 (Anode Column 5), Pin 9 (Cathode Row 4), Pin 10 (Anode Column 3), Pin 11 (Cathode Row 2), Pin 12 (Cathode Row 1).

An internal circuit diagram is provided, which shows the matrix arrangement of the 35 LEDs (5 columns x 7 rows). Each column has a common anode connection, and each row has a common cathode connection. This matrix structure is fundamental to multiplexing, allowing control of 35 individual dots with only 12 pins, significantly reducing the required microcontroller I/O lines.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. While the specific graphs are not detailed in the provided text, standard curves for such a device would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): This graph shows the nonlinear relationship between the voltage applied across the LED and the resulting current. It is essential for designing the current-limiting circuitry.
• Relative Luminous Intensity vs. Forward Current: This curve illustrates how the brightness of the LED changes with the drive current. It is typically linear over a range but will saturate at higher currents.
• Relative Luminous Intensity vs. Ambient Temperature: This graph demonstrates the thermal derating of light output. As temperature increases, the luminous efficiency of an LED generally decreases.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the bell-shaped curve centered around 595 nm with the specified 15 nm half-width.

These curves are vital for engineers to optimize drive conditions for desired brightness, efficiency, and longevity under specific operating temperatures.

5. Application Suggestions

5.1 Typical Application Scenarios

The LTP-747KY is ideal for applications requiring compact, multi-digit numeric or limited alphanumeric displays. Examples include:

• Test and Measurement Equipment: Digital multimeters, frequency counters, power supplies for displaying readings.
• Industrial Controls: Panel meters for temperature, pressure, flow rate, or process variable display on machinery.
• Consumer Electronics: Display for audio equipment (e.g., tuner frequency), kitchen appliances, or older electronic toys.
• Medical Devices: Simple parameter displays on monitors or diagnostic equipment where reliability is paramount.

5.2 Design Considerations

• Drive Circuitry: Due to its matrix configuration, the display must be multiplexed. This requires a microcontroller or dedicated driver IC capable of scanning the columns and rows at a high enough frequency (typically >100Hz) to avoid visible flicker. Each column anode is driven sequentially while the appropriate row cathodes are pulled low to light the desired dots.
• Current Limiting: External current-limiting resistors are mandatory for each column or row line (depending on the drive topology) to ensure the forward current per dot does not exceed the absolute maximum ratings, especially the peak current. Calculations must consider the multiplexing duty cycle (e.g., 1/5 for a 5-column matrix).
• Power Dissipation: The total power dissipation of the display must be calculated based on the number of simultaneously lit dots, forward voltage, and current. Ensure adequate thermal management if operating near the maximum ratings or in high ambient temperatures.
• Viewing Angle: The wide viewing angle is beneficial for applications where the display may be viewed from off-axis positions.

6. Technical Comparison and Differentiation

The primary differentiator of the LTP-747KY is its use of AlInGaP LED technology on a non-transparent GaAs substrate. Compared to older red GaAsP LEDs, AlInGaP offers significantly higher luminous efficiency, meaning brighter output for the same electrical input power. The amber-yellow color (592-595 nm) provides excellent visibility and is often considered easier on the eyes than pure red in low-light conditions. The gray face with white dots enhances contrast by reducing reflected ambient light from the non-active areas of the display, further improving readability. The categorization for luminous intensity (binned) ensures a predictable minimum brightness level, which is an advantage over non-binned parts where brightness can vary more widely.

7. Frequently Asked Questions (Based on Technical Parameters)

Q: Why is the average forward current rating (13mA) lower than the test condition current (20mA for V_F)?
A: The 20mA test condition is a standard point for measuring parameters like forward voltage. The 13mA absolute maximum rating is the highest continuous current allowed per dot under normal operating conditions to ensure long-term reliability and stay within the power dissipation limits. In a multiplexed application, the instantaneous current during the active time slice can be higher (e.g., 32mA as per the I_V test), but the average over a full cycle must not exceed 13mA.

Q: What does "1/16 Duty" mean in the luminous intensity test condition?
A: It indicates the display was driven in a multiplexed mode where each specific dot is only actively powered for 1/16th of the total scan cycle time. The luminous intensity is measured during that active pulse. This mimics real-world operating conditions for a multiplexed display.

Q: How do I interpret the 2:1 Luminous Intensity Matching Ratio?
A: This is a quality control parameter. It means that within a single display unit, the dimmest dot will be at least half as bright as the brightest dot. A lower ratio (closer to 1:1) indicates better uniformity. A 2:1 ratio is acceptable for many applications, ensuring characters appear evenly lit.

8. Practical Design and Usage Case

Consider designing a simple 4-digit temperature meter using the LTP-747KY. A microcontroller would be required to read a temperature sensor, convert the value to BCD (Binary-Coded Decimal) or a custom font map, and drive the display. Since the LTP-747KY is a single-digit module, four units would be placed side-by-side. The microcontroller would need at least 12 I/O pins to control one display directly. To control four displays efficiently (48 pins), a multiplexing scheme would be expanded: the column lines of all four displays could be connected in parallel, and separate row control lines would be needed for each display, or vice-versa, using a combination of column and digit (module) selection. Alternatively, dedicated LED driver ICs with serial interfaces (like SPI or I2C) would greatly simplify the design, reducing microcontroller pin count and software complexity. The current-limiting resistors must be calculated based on the supply voltage, LED forward voltage, and the desired average current per dot, factoring in the multiplexing duty cycle (e.g., if scanning 4 digits, the duty cycle per digit is 1/4).

9. Operating Principle Introduction

The LTP-747KY operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's threshold (around 2V for AlInGaP) is applied, electrons from the n-type region and holes from the p-type region are injected into the active region where they recombine. In AlInGaP LEDs, this recombination releases energy primarily in the form of photons (light) with a wavelength corresponding to the bandgap energy of the material, which is engineered to be in the amber-yellow range (approx. 595 nm). The 5x7 matrix arrangement is a practical implementation for forming characters. By selectively lighting specific dots within this grid, any numeral, letter, or simple symbol can be displayed. The common-anode, common-cathode matrix configuration is a topological design that minimizes the number of required connection pins, making the package smaller and cheaper to interface with.

10. Technology Trends and Context

While discrete 5x7 dot matrix displays like the LTP-747KY remain relevant for specific, cost-sensitive, or legacy designs, the broader trend in display technology has shifted towards integrated solutions. Modern applications often use graphic OLEDs, TFT LCDs, or larger, higher-density LED matrix panels that offer full graphical capabilities, a wider color gamut, and easier interfacing via standard digital buses. However, for applications requiring only simple, bright, highly reliable, and low-power character output in potentially harsh environments, discrete LED dot matrix modules offer distinct advantages. The AlInGaP technology used here represents a mature and highly efficient material system for red, orange, amber, and yellow LEDs. Future developments in display technology focus on miniaturization (micro-LEDs), flexible substrates, and even higher efficiencies, but the fundamental principles of operation and the design considerations for driving matrix displays remain largely consistent.