LTP-2058AKD LED Display Datasheet - 2.3-inch (58.42mm) Height - 5x8 Dot Matrix - Hyper Red (650nm) - English Technical Document

1. Product Overview

The LTP-2058AKD is a single-digit, alphanumeric display module designed for applications requiring clear, legible character output. Its core function is to visually represent ASCII or EBCDIC coded characters through a grid of individually addressable light-emitting diodes (LEDs).

Core Advantages & Target Market: The device's primary advantages include a substantial 2.3-inch (58.42 mm) character height for excellent visibility, a wide viewing angle provided by its single-plane design, and solid-state reliability inherent to LED technology. Its low power requirement and compatibility with standard character codes make it suitable for industrial control panels, instrumentation, point-of-sale terminals, and other embedded systems where durable, low-maintenance, and easily readable displays are needed.

2. Technical Specifications Deep Dive

This section provides an objective analysis of the device's key performance parameters as defined in the datasheet.

2.1 Photometric & Optical Characteristics

The optical performance is central to the display's function. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for its LED chips, which are fabricated on a non-transparent GaAs substrate. This technology is known for high efficiency in the red-orange spectrum.

• Luminous Intensity (I_V): The average luminous intensity per dot is specified with a minimum of 1650 µcd, typical of 3500 µcd, under a test condition of I_p=32mA and 1/16 duty cycle. This parameter defines the brightness of each individual LED dot.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λ_p): 650 nm (nanometers). This is the wavelength at which the LED emits the most optical power.
  • Dominant Wavelength (λ_d): 639 nm. This is the single wavelength perceived by the human eye, defining the color as \"Hyper Red.\"
  • Spectral Line Half-Width (Δλ): 20 nm. This indicates the spread of the emitted light's wavelength, with a smaller value representing a more pure, saturated color.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 maximum. This is a critical parameter for display uniformity, specifying that the brightness of the dimmest dot in an array will be no less than half the brightness of the brightest dot under the same driving conditions.

2.2 Electrical Parameters

Understanding the electrical limits and operating points is essential for reliable circuit design.

• Absolute Maximum Ratings: These are stress limits that must not be exceeded, even momentarily.
  • Average Power Dissipation per Dot: 40 mW.
  • Peak Forward Current per Dot: 90 mA.
  • Average Forward Current per Dot: 15 mA at 25°C, derating linearly at 0.2 mA/°C.
  • Reverse Voltage per Dot: 5 V. Exceeding this can damage the LED junction.
• Electrical/Optical Characteristics (at T_A=25°C): These are typical operating parameters.
  • Forward Voltage (V_F): Ranges from 2.1V (min) to 2.8V (max) depending on current. Typical is 2.6V at 20mA and 2.8V at 80mA.
  • Reverse Current (I_R): 100 µA maximum at V_R=5V.

2.3 Thermal Characteristics

Thermal management is implied through the derating specifications and temperature ranges.

• Operating Temperature Range: -35°C to +85°C. The device is designed to function within this ambient temperature span.
• Storage Temperature Range: -35°C to +85°C.
• Current Derating: The average forward current rating decreases linearly by 0.2 mA for every degree Celsius above 25°C. This is a direct thermal limitation to prevent overheating.
• Solder Temperature: Withstands 260°C for 3 seconds at 1/16 inch (approx. 1.6mm) below the seating plane during assembly.

3. Binning System Explanation

The datasheet indicates the device is \"categorized for luminous intensity.\" This refers to a binning process where manufactured units are sorted (binned) based on measured luminous intensity. This ensures designers can select parts with consistent brightness levels for their application, which is crucial for multi-digit displays where uniform appearance is desired. While specific bin codes are not listed in this document, typical bins would group LEDs with similar I_V values.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristic Curves.\" Although the specific graphs are not provided in the text, such curves typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward voltage (V_F) and forward current (I_F). It is non-linear, with a threshold voltage (around 1.8-2.0V for AlInGaP red) below which very little current flows.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, typically in a near-linear relationship within the recommended operating range before efficiency drops at very high currents.
• Temperature Dependence: Curves showing how forward voltage decreases and wavelength may shift slightly with increasing junction temperature.

These curves are vital for designing efficient constant-current drivers and understanding performance under varying thermal conditions.

5. Mechanical & Package Information

The physical construction defines the form factor and assembly interface.

• Package Type: A through-hole package with 14 pins.
• Matrix Description: 5 columns by 8 rows of LED dots, creating a grid capable of forming all alphanumeric characters and some symbols.
• Visual Design: Features a gray face (likely the package epoxy) with white segments (the illuminated dot areas), providing good contrast when off and a clean appearance when lit.
• Stackability: The device is designed to be stacked horizontally, allowing for the creation of multi-character displays by placing units side-by-side.
• Dimensions: All dimensions are in millimeters with a general tolerance of ±0.25 mm unless otherwise specified. The exact dimensional drawing is referenced in the datasheet.

5.1 Pin Connection & Polarity

The 14-pin interface uses a multiplexed anode-column and cathode-row scheme for matrix addressing, which reduces the required driver pins from 40 (5x8) to 13 (5+8).

Pinout: Pin 1: Cathode Row 6 Pin 2: Cathode Row 8 Pin 3: Anode Column 2 Pin 4: Anode Column 3 Pin 5: Cathode Row 5 Pin 6: Anode Column 5 Pin 7: Cathode Row 7 Pin 8: Cathode Row 3 Pin 9: Cathode Row 1 Pin 10: Anode Column 4 Pin 11: Anode Column 3 (Note: Duplicate function as Pin 4, likely a typo or specific internal connection) Pin 12: Cathode Row 4 Pin 13: Anode Column 1 Pin 14: Cathode Row 2

Internal Circuit: The internal diagram shows a common matrix configuration where each LED dot is formed at the intersection of an anode column line and a cathode row line. To illuminate a specific dot, its corresponding anode pin must be driven high (with current limiting) while its corresponding cathode pin is driven low.

6. Soldering & Assembly Guidelines

The key assembly specification provided is the soldering temperature profile: the device can withstand a peak temperature of 260°C for 3 seconds, measured 1/16 inch (1.6mm) below the seating plane. This is a standard wave or reflow soldering condition. Designers should ensure their PCB assembly process adheres to this limit to prevent package damage or LED degradation.

Storage Conditions: Components should be stored within the specified storage temperature range of -35°C to +85°C in a dry environment, typically in moisture-sensitive device (MSD) bags if required.

7. Application Suggestions

7.1 Typical Application Scenarios

• Industrial HMIs: Status displays on machinery, PLC operator panels.
• Test & Measurement Equipment: Digital readouts for multimeters, frequency counters, power supplies.
• Retail & Hospitality: Price displays, queue management systems, simple information boards.
• Embedded Systems: Where a simple, robust, and low-power character output is needed.

7.2 Design Considerations

• Driver Circuit: Requires a matrix scan driver IC or microcontroller with sufficient GPIO pins and current sourcing/sinking capability. Constant current driving is recommended for consistent brightness.
• Current Limiting: External resistors or a constant-current driver are mandatory to limit the current through each LED segment to within the specified average and peak limits.
• Multiplexing: Since it's a matrix display, it operates on a multiplexing (scanning) principle. The refresh rate must be high enough (typically >60Hz) to avoid visible flicker. The duty cycle affects the perceived brightness and peak current requirements.
• Viewing Angle: The wide viewing angle is beneficial for applications where the operator may not be directly in front of the display.
• Power Supply: Ensure the supply voltage is sufficient to overcome the LED forward voltage (V_F) plus the voltage drop across any current-limiting components and driver circuitry.

8. Technical Comparison & Differentiation

Compared to older technologies like incandescent or vacuum fluorescent displays (VFDs), this LED matrix offers:

• Superior Reliability & Lifetime: Solid-state construction with no filaments or glass envelopes, leading to much longer operational life and resistance to vibration.
• Lower Power Consumption: Especially at lower brightness levels.
• Faster Response Time: Instant on/off capability.
• Wider Operating Temperature Range: Suitable for harsh environments.

Compared to modern graphic OLED or TFT modules, it is:

• Simpler to Interface: Requires fewer control lines and simpler software.
• More Rugged and Cost-Effective for simple character-only applications.
• Highly Readable in high-ambient-light conditions due to its high contrast and emissive nature.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: How do I calculate the appropriate current-limiting resistor for a single dot? A: Use Ohm's Law: R = (V_supply - V_F) / I_F. For example, with a 5V supply, a typical V_F of 2.6V at 20mA: R = (5 - 2.6) / 0.02 = 120 Ω. Always use the maximum V_F from the datasheet for a conservative design to ensure current doesn't exceed limits.

Q2: What does \"1/16 DUTY\" mean in the test condition for luminous intensity? A: It means the measurement was taken with the LED pulsed on for 1/16th of the total scan cycle time. In a multiplexed 5x8 matrix, a common scanning scheme activates one row at a time. If all 8 rows are scanned, each row is active for 1/8 duty cycle. The 1/16 duty suggests a different scanning pattern or a measurement condition where the peak pulse current is higher, and the average power is kept within limits. The actual operating duty cycle depends on the driver design.

Q3: Can I connect these displays in parallel to make a multi-digit unit? A: They are designed to be stacked horizontally, meaning you place multiple units next to each other on a PCB. You cannot simply connect the pins in parallel because each unit contains a full 5x8 matrix. Each display requires its own set of column drivers, while the row drivers can often be shared across all units in a multi-digit design to simplify the scanning circuitry.

Q4: Why is the dominant wavelength (639nm) different from the peak wavelength (650nm)? A: This is due to the spectral response of the human eye. The LED emits light across a range of wavelengths centered at 650nm (peak). However, the human eye is more sensitive to wavelengths around 555nm (green) and less sensitive to deep red. The dominant wavelength is calculated by finding the single wavelength of pure monochromatic light that would appear to have the same color as the LED's broad spectrum output to a standard human observer. It's the \"perceived\" color point.

10. Operating Principle Introduction

The LTP-2058AKD is an active matrix LED display. Its fundamental principle is electroluminescence from a semiconductor P-N junction. When a forward voltage exceeding the diode's threshold is applied across an anode (column) and cathode (row), electrons and holes recombine in the active AlInGaP layer, releasing energy in the form of photons (light) at a wavelength determined by the material's bandgap. The 5x8 matrix arrangement allows any of the 40 dots to be individually addressed by selecting the correct combination of one column (power source) and one row (ground path). Multiplexing scans through rows rapidly, turning on the necessary columns for each row, to create the illusion of a stable, fully lit character.

11. Technology Trends

While discrete LED dot matrix displays like the LTP-2058AKD remain relevant for specific rugged or cost-sensitive applications, the broader trend in display technology is towards higher integration and functionality. Surface-mount device (SMD) LED arrays and integrated LED driver modules are becoming more common. Furthermore, for applications requiring graphics or more complex characters, segmented LED displays, OLEDs, and small TFT LCDs offer greater flexibility. The principle of matrix addressing remains fundamental, but implementation moves towards chip-on-board (COB) designs and interfaces like I2C or SPI, reducing the component count and simplifying system design compared to direct GPIO matrix driving.