LTP-747KR LED Display Datasheet - 0.7-inch (17.22mm) Matrix Height - Super Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTP-747KR is a character display module designed for applications requiring clear, bright alphanumeric or symbolic information. Its core function is to present data through a grid of individually controllable light-emitting diodes (LEDs).

1.1 Core Advantages and Target Market

This device offers several key advantages for integration into electronic systems. Its primary benefit is high brightness and excellent contrast, facilitated by the use of AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for the Super Red LED chips. This material technology is known for high luminous efficiency in the red/orange spectrum. The display features a wide viewing angle, ensuring readability from various positions. It is categorized for luminous intensity, allowing for brightness matching in multi-unit applications. The device is also characterized by low power requirement and solid-state reliability, with no moving parts. Its lead-free package complies with RoHS (Restriction of Hazardous Substances) directives. The target market includes office equipment, communication devices, household appliances, and other general electronic equipment where reliable, legible character display is needed.

1.2 Device Description

The LTP-747KR is physically defined as a 0.7 inch (17.22 mm) matrix height 5x7 dot matrix display. This means the active display area has a height of 17.22mm and is composed of a grid of 5 columns and 7 rows of LED dots, totaling 35 addressable pixels. It utilizes AlInGaP Super Red LED chips fabricated on a non-transparent GaAs (Gallium Arsenide) substrate. The external appearance consists of a gray face with white dots, which enhances contrast when the LEDs are off.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the device's operational limits and performance characteristics as defined in the datasheet.

2.1 Absolute Maximum Ratings

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

• Average Power Dissipation per Dot: 33 mW. This is the maximum continuous thermal power each LED dot can handle.
• Peak Forward Current per Dot: 90 mA. The maximum instantaneous current pulse allowed.
• Average Forward Current per Dot: 13 mA at 25°C, derating linearly at 0.17 mA/°C. This defines the safe continuous DC current, which must be reduced as ambient temperature (Ta) increases above 25°C.
• Operating & Storage Temperature Range: -35°C to +85°C. The device can function and be stored within this full range.
• Solder Condition: 260°C for 5 seconds, measured 1/16 inch (approx. 1.59mm) below the seating plane. This is a critical parameter for wave or reflow soldering processes.

2.2 Electrical & Optical Characteristics

These are the typical and guaranteed performance parameters measured under specified test conditions (Ta=25°C).

• Average Luminous Intensity (Iv): 1650 (Min.) to 3400 (Typ.) ucd (microcandelas). Tested at a pulsed current (Ip) of 32mA with a 1/16 duty cycle. This pulsed testing is standard for multiplexed displays to prevent overheating while measuring peak light output.
• Peak Emission Wavelength (λp): 639 nm (Typical). The wavelength at which the spectral power output is maximum.
• Dominant Wavelength (λd): 631 nm (Typical). The single wavelength perceived by the human eye, defining the color (Super Red).
• Spectral Line Half-Width (Δλ): 20 nm (Typical). The bandwidth of the emitted light spectrum at half its maximum power.
• Forward Voltage per Dot (VF): 2.0V (Min.) to 2.6V (Max.) at a test current (IF) of 20mA. This range is important for driver circuit design to ensure proper current regulation.
• Reverse Current per Dot (IR): 100 µA (Max.) at a reverse voltage (VR) of 5V. The datasheet explicitly notes this test condition is for characterization only and the device must not be operated under continuous reverse bias.
• Luminous Intensity Matching Ratio: 2:1 (Max.). This specifies the maximum allowable ratio between the brightest and dimmest segments within a single unit under identical drive conditions, ensuring uniform appearance.
• Cross Talk: ≤ 2.5%. This defines the maximum percentage of unintended light emission from non-selected segments when the display is multiplexed.

3. Binning System Explanation

The datasheet indicates the device is categorized for luminous intensity. This implies that units are sorted (binned) based on measured light output into different groups or codes. The module marking includes a \"Z: BIN CODE\" field. Designers can use this to select displays with closely matched brightness for applications requiring visual consistency across multiple units. The datasheet does not detail the specific binning steps or code designations.

4. Performance Curve Analysis

The datasheet references a section for \"Typical Electrical/Optical Characteristics Curves.\" While the specific graphs are not provided in the excerpt, such curves typically include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): Shows how light output increases with current, usually in a non-linear relationship that saturates at high currents.
• Forward Voltage vs. Forward Current: Illustrates the diode's I-V characteristic.
• Relative Luminous Intensity vs. Ambient Temperature: Demonstrates the decrease in light output as junction temperature rises, a key consideration for thermal management.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the narrow band of red light emission centered around 631-639 nm.

These curves are essential for understanding device behavior under non-standard conditions and for optimizing driver design.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The mechanical drawing provides critical installation data. Key notes include: all dimensions are in millimeters with a general tolerance of ±0.25mm; pin tip shift tolerance is 0.4mm; and the recommended PCB hole diameter is Ø1.30mm. The drawing would detail the overall length, width, height, pin spacing, and seating plane location.

5.2 Pin Connection and Polarity

The device has a 12-pin configuration. The pinout is as follows: 1(A1), 3(A2), 7(A4), 8(A5), 10(A3) are Anode Columns. Pins 12(K1), 11(K2), 2(K3), 9(K4), 4(K5), 5(K6), 6(K7) are Cathode Rows. This arrangement allows for a multiplexed driving scheme where columns (anodes) are selectively powered and rows (cathodes) are selectively grounded to illuminate specific dots.

5.3 Internal Circuit Diagram and Polarity Identification

The internal circuit diagram shows the matrix layout: 5 anode columns and 7 cathode rows, with an LED at each intersection. The anode pins are common to all LEDs in a vertical column. The cathode pins are common to all LEDs in a horizontal row. To illuminate a specific dot, its corresponding anode column must be driven with positive current, and its corresponding cathode row must be connected to ground.

6. Soldering and Assembly Guide

6.1 Automated Soldering Profile

The specified condition is 260°C for 5 seconds, measured 1.6mm (1/16 inch) below the seating plane. This is a typical profile for wave soldering or certain reflow processes. The temperature of the component body itself must not exceed the maximum rating during assembly.

6.2 Manual Soldering

For hand soldering, the recommendation is 350°C ±30°C for a maximum of 5 seconds, again measured below the seating plane. The higher temperature compensates for the lower thermal transfer efficiency of an iron compared to a solder bath or oven.

6.3 Reliability Tests (Implied Storage & Handling)

The datasheet lists a comprehensive suite of reliability tests (Operation Life, High Temp/Humidity Storage, High/Low Temp Storage, Temperature Cycling, Thermal Shock, Solder Resistance, Solderability) performed according to MIL-STD and JIS standards. Passing these tests validates the device's robustness against environmental stresses and assembly processes, indirectly informing proper storage conditions (within the -35°C to +85°C range) and handling.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is suited for ordinary electronic equipment including but not limited to: instrumentation panels, point-of-sale terminals, industrial control readouts, consumer appliance displays, and basic communication devices where simple alphanumeric feedback is required.

7.2 Critical Design Considerations and Cautions

• Drive Method: Constant current driving is strongly recommended to ensure consistent brightness across all segments and over the device's lifetime, compensating for the forward voltage (VF) variation (2.0V-2.6V).
• Current Limiting: The circuit must be designed to never exceed the absolute maximum average current, especially considering ambient temperature derating. Excess current or high operating temperature leads to severe light degradation or failure.
• Reverse Voltage Protection: The driving circuit must incorporate protection (e.g., series diodes, clamping circuits) against reverse voltages and voltage spikes during power cycling to prevent damage from metal migration and increased leakage current.
• Multiplexing Design: When using a multiplexed drive scheme (necessary for a 5x7 matrix with only 12 pins), the peak pulsed current must be calculated to achieve the desired average luminous intensity while keeping the average current within limits. The 1/16 duty cycle mentioned in the test condition is a clue to a potential multiplexing ratio.
• Thermal Management: Ensure adequate ventilation or heatsinking if the display is operated at high ambient temperatures or high duty cycles to maintain performance and longevity.

8. Technical Comparison and Differentiation

While a direct comparison with other models is not in the datasheet, the LTP-747KR's key differentiators based on its specs are: the use of AlInGaP technology for Super Red (generally offering higher efficiency and stability than older technologies for red), a 0.7-inch character height for good readability at a moderate distance, and a categorized (binned) luminous intensity for consistency. Its 5x7 format is a standard for displaying full alphanumeric characters, unlike simpler 7-segment or 14-segment displays.

9. Frequently Asked Questions Based on Technical Parameters

Q: Can I drive this with a constant voltage source and a simple resistor?

A: It is possible but not optimal. Due to the VF range (2.0V-2.6V), using a fixed voltage and resistor would result in different currents and therefore different brightness levels across different units or even different segments within a unit. A constant current driver is recommended for uniform performance.

Q: The test condition uses 32mA pulsed current. What current should I use in my design?

A: You must design for the Average Forward Current rating (13mA at 25°C, derated with temperature). In a multiplexed design, if you use a 1/8 duty cycle, you could use a peak pulsed current of up to ~104mA (13mA * 8) to achieve the same average, but this must not exceed the Peak Forward Current rating of 90mA. A safer approach is to use a lower peak current. The 32mA test condition is for measurement purposes under controlled, brief pulses.

Q: What does \"lead-free package (according to RoHS)\" mean for my manufacturing?

A: It means the device uses solderable finishes (like tin) that are free of lead, complying with environmental regulations. Your assembly process (solder paste, flux) should also be lead-free compatible.

10. Practical Design and Usage Case

Scenario: Designing a simple temperature controller readout. The microcontroller would have two output ports: one configured as 5 outputs for the anode columns (via current-limiting transistors or a dedicated driver IC), and one configured as 7 outputs for the cathode rows (as sink drivers). Software would multiplex through the columns rapidly, lighting the appropriate row pins for each column to form characters like \"25 C\". The design must calculate the resistor values or constant-current setpoints based on the supply voltage and the desired average current (e.g., 10mA per dot), ensuring it stays within the derated limit for the maximum expected enclosure temperature (e.g., 50°C). Protection diodes would be placed on the driver outputs to clamp inductive spikes.

11. Operating Principle Introduction

The LTP-747KR operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward bias voltage exceeding the diode's forward voltage (VF) is applied across an LED dot (anode positive, cathode negative), electrons and holes recombine in the active region (the AlInGaP quantum wells). This recombination releases energy in the form of photons (light). The specific composition of the AlInGaP semiconductor alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, Super Red at ~631 nm. The non-transparent GaAs substrate absorbs stray light, improving contrast. The 5x7 matrix structure is formed by connecting the anodes of LEDs in vertical columns and the cathodes in horizontal rows, enabling control of 35 dots with only 12 pins through time-division multiplexing.

12. Technology Trends

Displays like the LTP-747KR represent a mature, cost-effective technology for monochromatic character output. General trends in indicator and small display technology include a continued shift towards higher efficiency LED materials (like improved AlInGaP and InGaN for other colors), integration of driver electronics directly into the display package (reducing external component count), and the growth of alternative technologies like OLEDs for thinner, flexible, or higher-contrast applications. However, for applications requiring high brightness, long lifetime, robustness, and low cost in standard formats, LED dot matrix displays remain a prevalent and reliable solution.