LTP-757KY LED Dot Matrix Display Datasheet - 0.7-inch (17.22mm) Digit Height - Amber Yellow - English Technical Document

1. Product Overview

The LTP-757KY is a compact, high-performance 5x7 dot matrix LED display module. Its primary function is to provide clear, legible alphanumeric and symbolic character representation in various 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 is known for superior efficiency and color purity compared to older technologies. This results in excellent character appearance with high brightness and contrast, making it suitable for applications where readability is paramount, even under varying ambient light conditions. The device is categorized for luminous intensity, ensuring consistent performance across production batches. Its low power requirement and solid-state reliability make it an ideal choice for consumer electronics, industrial instrumentation, point-of-sale terminals, and other embedded systems requiring a durable and efficient display solution.

2. Technical Specifications Deep Dive

2.1 Optical Characteristics

The optical performance is defined by several key parameters measured at an ambient temperature (T_A) of 25°C. The Average Luminous Intensity (I_V) has a typical value of 3400 µcd under a test condition of I_P=32mA and a 1/16 duty cycle. This parameter indicates the perceived brightness of the display. The Peak Emission Wavelength (λ_p) is typically 595 nm, which falls within the amber yellow portion of the visible spectrum. The Spectral Line Half-Width (Δλ) is 15 nm, indicating a relatively narrow and pure color emission. The Dominant Wavelength (λ_d) is 592 nm. It is important to note that luminous intensity measurements use a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the values correlate with human visual perception. The Luminous Intensity Matching Ratio (I_V-m) is specified as a maximum of 2:1, which defines the allowable variation in brightness between individual segments or dots to ensure uniform appearance.

2.2 Electrical Characteristics

The electrical parameters define the operating limits and conditions for the device. The Forward Voltage per dot (V_F) typically ranges from 2.05V to 2.6V at a forward current (I_F) of 20mA. The Reverse Current per dot (I_R) is a maximum of 100 µA when a reverse voltage (V_R) of 5V is applied. These values are critical for designing the appropriate driving circuitry.

2.3 Absolute Maximum Ratings

These ratings specify the limits beyond which permanent damage to the device may occur. They are not for continuous operation. Key ratings include: Average Power Dissipation per dot (25 mW), Peak Forward Current per dot (60 mA), and Average Forward Current per dot (13 mA at 25°C, derating linearly at 0.17 mA/°C). The maximum Reverse Voltage per dot is 5V. The device can operate and be stored within a Temperature Range of -35°C to +85°C. The Solder Temperature rating specifies that the device can withstand 260°C for 3 seconds at a point 1/16 inch below the seating plane, which is crucial for reflow soldering processes.

3. Binning System Explanation

The datasheet indicates that the device is categorized for luminous intensity. This implies a binning system based on measured light output. While specific bin codes are not listed in this document, such a system typically groups devices into different intensity ranges (e.g., high-brightness, standard-brightness). This allows designers to select parts that meet specific brightness requirements for their application, ensuring consistency in the final product's display performance. Designers should consult the manufacturer's detailed binning documentation for precise selection criteria.

4. Performance Curve Analysis

The datasheet references Typical Electrical/Optical Characteristic Curves. Although the specific curves are not detailed in the provided text, such graphs typically included in full datasheets are essential for design. They would likely show the relationship between forward current (I_F) and forward voltage (V_F) for thermal and driver design, the relationship between luminous intensity and forward current to optimize brightness vs. power consumption, and the variation of luminous intensity with ambient temperature. Understanding these curves allows engineers to predict performance under non-standard conditions and design robust systems.

5. Mechanical and Package Information

The LTP-757KY features a specific package with a gray face and white dots for enhanced contrast. The digit height is 0.7 inches (17.22 mm). The provided Package Dimensions drawing (not fully detailed here) would show the exact physical outline, lead spacing, and overall size in millimeters, with standard tolerances of ±0.25 mm. This information is vital for PCB footprint design and ensuring proper fit within the end product's enclosure.

5.1 Pin Connection and Polarity

The device has a 12-pin configuration. The pinout is as follows: Pin 1 (Cathode Column 1), Pin 2 (Anode Row 3), Pin 3 (Cathode Column 2), Pin 4 (Anode Row 5), Pin 5 (Anode Row 6), Pin 6 (Anode Row 7), Pin 7 (Cathode Column 4), Pin 8 (Cathode Column 5), Pin 9 (Anode Row 4), Pin 10 (Cathode Column 3), Pin 11 (Anode Row 2), Pin 12 (Anode Row 1). The Internal Circuit Diagram shows a matrix arrangement where each LED dot (at the intersection of a row anode and a column cathode) can be individually addressed through multiplexing. Correct identification of anode and cathode pins is critical to prevent reverse bias and ensure proper circuit operation.

6. Soldering and Assembly Guidelines

The key assembly specification provided is the soldering temperature profile. The device can withstand a peak temperature of 260°C for a maximum of 3 seconds, measured 1/16 inch (approximately 1.6 mm) below the seating plane. This is a standard rating for lead-free reflow soldering processes. Designers must ensure their reflow oven profile complies with this limit to prevent thermal damage to the LED chips or the package. General handling precautions should be observed, such as avoiding mechanical stress on the leads and protecting the display face from scratches or contamination. Storage should be within the specified temperature range of -35°C to +85°C in a dry environment.

7. Packaging and Ordering Information

The part number is clearly identified as LTP-757KY. While specific packaging details (e.g., tape and reel, tube quantities) are not listed in this excerpt, the part number itself is the primary identifier for ordering. The "KY" suffix likely denotes the amber yellow color. Engineers should confirm the exact packaging format with the supplier or distributor when placing orders.

8. Application Recommendations

8.1 Typical Application Scenarios

This display is well-suited for applications requiring compact, low-power, and highly readable numeric or limited character output. Common uses include: digital panel meters, weighing scales, medical monitoring equipment, household appliance displays (ovens, thermostats), industrial control panels, and basic information displays in various electronic devices.

8.2 Design Considerations

• Drive Circuitry: A multiplexing driver circuit is required due to the 5x7 matrix configuration. This involves sequentially activating the row anodes while providing the appropriate column cathode signals to illuminate the desired dots. Integrated display driver ICs are commonly used for this purpose.
• Current Limiting: External current-limiting resistors are mandatory for each anode or column line (depending on the drive scheme) to ensure the forward current per dot does not exceed the absolute maximum ratings, especially the average current.
• Power Dissipation: The average power dissipation per dot (25 mW max) must be considered when designing for maximum brightness, especially if multiple dots are illuminated simultaneously for extended periods.
• Viewing Angle: The wide viewing angle is beneficial, but the mounting position within the final product should be evaluated to ensure optimal readability for the end-user.

9. Technical Comparison

The primary differentiator of the LTP-757KY is its use of AlInGaP LED technology. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) LEDs, AlInGaP offers significantly higher luminous efficiency, resulting in greater brightness for the same input current. It also provides better color saturation and stability over temperature and time. When compared to other package types (e.g., discrete LEDs arranged in a matrix), this integrated dot matrix module offers simplified assembly, guaranteed mechanical alignment of the dots, and a uniform optical appearance due to the gray face and white dots.

10. Frequently Asked Questions (FAQs)

Q: What is the purpose of the 1/16 duty cycle mentioned in the luminous intensity test condition?
A: The 1/16 duty cycle is a standard test method for multiplexed displays. It means each segment is pulsed on for 1/16th of the total cycle time. The specified luminous intensity value is an average measured under this condition, which simulates typical multiplexed operation. The peak current during the on-time is higher than the average current.

Q: How do I interpret the Luminous Intensity Matching Ratio of 2:1?
A: This ratio indicates that the brightest dot or segment in the display will be no more than twice as bright as the dimmest dot or segment under identical driving conditions. A lower ratio (e.g., 1.5:1) indicates better uniformity. This parameter is important for ensuring a consistent, non-patchy appearance across all characters.

Q: Can I drive this display with a constant DC current instead of multiplexing?
A: Technically, you could, but it is highly inefficient and impractical. Driving all 35 dots simultaneously at their typical current would require a very high total current and cause excessive power dissipation and heat. Multiplexing is the standard and intended method of operation, significantly reducing the number of required driver pins and overall power consumption.

11. Practical Design Case

Consider designing a simple digital voltmeter display. The microcontroller reads an analog voltage, converts it to a digital value, and needs to show a 3-digit reading (e.g., 5.12V). The LTP-757KY would be used for each digit. The design steps would involve: 1) Creating a PCB footprint matching the mechanical dimensions and pinout. 2) Selecting a multiplexing driver IC compatible with a 5x7 matrix and the microcontroller's interface (e.g., SPI, I2C). 3) Calculating current-limiting resistor values based on the driver's output voltage and the LED's typical forward voltage to achieve the desired average current (e.g., 10-15mA per dot). 4) Programming the microcontroller to decode the numeric value into the correct segment patterns for the 5x7 font and control the multiplexing timing. 5) Ensuring the power supply can handle the peak current demands during multiplexing cycles.

12. Technology Principle Introduction

The LTP-757KY is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material grown on a non-transparent GaAs (Gallium Arsenide) substrate. When a forward voltage is applied across the p-n junction of the LED chip, electrons and holes recombine, 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 (~592-595 nm). The non-transparent substrate helps improve contrast by absorbing stray light. The individual LED chips are arranged in a 5x7 grid and interconnected internally to form the matrix, with external pins providing access to the rows (anodes) and columns (cathodes).

13. Technology Trends

While AlInGaP remains a high-performance technology for red, orange, amber, and yellow LEDs, the broader LED industry continues to evolve. Trends include the pursuit of even higher luminous efficacy (lumens per watt) across all colors. For display applications, there is a move towards finer pitch matrices and full-color RGB capabilities. However, for monochromatic, character-based displays requiring high reliability, excellent readability, and cost-effectiveness, devices like the LTP-757KY based on mature technologies like AlInGaP continue to be a robust and widely adopted solution. The integration of drivers and controllers directly with the display module is also a common trend to simplify end-product design.