LTP-14058AKD LED Dot Matrix Display Datasheet - 1.4-inch (35.76mm) Height - Hyper Red (650nm) - 40mW per Dot - English Technical Document

1. Product Overview

The LTP-14058AKD is a compact, single-plane dot matrix display module designed for alphanumeric character representation. Its core component is a 5 column by 8 row array of individual light-emitting diodes (LEDs), resulting in a total of 40 addressable dots. The physical height of the character matrix is specified as 1.4 inches (35.76 millimeters), providing good readability. The device is engineered for applications requiring reliable, low-power visual output with a wide viewing angle.

1.1 Core Advantages and Target Market

The primary advantages of this display stem from its solid-state LED technology and efficient design. Key features include low power requirement, which makes it suitable for battery-powered or energy-conscious devices. The wide viewing angle ensures the displayed information is visible from various positions relative to the screen. The device is categorized for luminous intensity, allowing for brightness matching in multi-unit applications. Its compatibility with standard character codes (USASCII and EBCDIC) and horizontal stackability make it ideal for embedded systems, industrial control panels, instrumentation, test equipment, and other applications where simple, robust character-based information display is needed.

2. Technical Specifications Deep Dive

This section provides a detailed, objective analysis of the device's key technical parameters as defined in the datasheet.

2.1 Photometric and Optical Characteristics

The display utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce Hyper Red light. The typical peak emission wavelength (λp) is 650 nanometers (nm). The dominant wavelength (λd) is specified at 639 nm. The spectral line half-width (Δλ), which indicates the purity or spread of the emitted color, is 20 nm. The average luminous intensity (Iv) per dot is specified with a minimum of 800 microcandelas (μcd), a typical value of 2600 μcd, and no maximum under the test condition of a peak current (Ip) of 32 mA at a 1/16 duty cycle. A luminous intensity matching ratio of 2:1 ensures reasonable uniformity in brightness between different dots on the same display.

2.2 Electrical Characteristics

The forward voltage (Vf) for any single LED dot is between 2.1V (min) and 2.6V (typ) at a forward current (If) of 20 mA. At a higher current of 80 mA, this range shifts to 2.3V to 2.8V. The reverse current (Ir) is a maximum of 100 microamperes (μA) when a reverse voltage (Vr) of 5V is applied. These parameters are critical for designing the appropriate current-limiting circuitry.

3. Absolute Maximum Ratings and Thermal Considerations

Exceeding these limits may cause permanent damage to the device. The average power dissipation per dot must not exceed 40 milliwatts (mW). The peak forward current per dot is limited to 90 mA, while the average forward current per dot is 15 mA at 25°C, derating linearly by 0.2 mA for every degree Celsius above 25°C. The maximum reverse voltage per dot is 5V. The device is rated for an operating and storage temperature range of -35°C to +85°C. For assembly, the maximum solder temperature is 260°C for a maximum duration of 3 seconds, measured 1.6mm below the seating plane.

4. Mechanical and Packaging Information

The datasheet includes a detailed package drawing with dimensions in millimeters. Tolerances are generally ±0.25 mm unless otherwise specified. This drawing is essential for PCB (Printed Circuit Board) footprint design and mechanical integration into the end product. The physical package houses the LED array and provides the electrical interface via pins.

4.1 Pin Connection and Internal Circuit

The device has a 14-pin interface. The pinout is as follows: 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 of Pin 4 function, likely a documentation note); Pin 12: Cathode Row 4; Pin 13: Anode Column 1; Pin 14: Cathode Row 2. An internal circuit diagram shows the matrix arrangement, confirming it is a common-cathode configuration where columns are anodes and rows are cathodes. This structure enables multiplexing to control all 40 dots with only 13 unique control lines (5 columns + 8 rows).

5. Application Guidelines and Design Considerations

5.1 Driving the Display

To illuminate a specific dot, its corresponding column (anode) must be driven high (with appropriate current limiting), and its corresponding row (cathode) must be driven low. To display characters, a microcontroller typically uses a multiplexing technique, sequentially activating one row at a time while presenting the pattern for that row on the five column lines. The 1/16 duty cycle mentioned in the test conditions suggests a multiplexing scheme, though the exact scanning frequency must be high enough to avoid visible flicker (typically >60 Hz). External drivers (transistors or dedicated LED driver ICs) are almost always required, as the microcontroller's GPIO pins cannot typically source/sink the required cumulative current.

5.2 Current Limiting and Power Supply

Based on the electrical characteristics, a current-limiting resistor must be placed in series with each anode column. The resistor value is calculated using Ohm's Law: R = (Vcc - Vf_led) / I_desired. Using a Vcc of 5V, a typical Vf of 2.6V, and a desired per-dot current of 20 mA, the resistor value would be approximately (5 - 2.6) / 0.02 = 120 Ohms. The power supply must be capable of delivering the peak current. In a multiplexed setup, the instantaneous current when one row is active is 5 dots * I_dot. If I_dot is 20mA, this is 100mA. The average current is significantly lower due to the duty cycle.

5.3 Thermal Management

While individual dots have a 40mW limit, the total power for the display must be considered. With all 40 dots on continuously at 20mA and 2.6V, total power would be 40 * 0.052W = 2.08W. In a multiplexed design at 1/8 duty cycle (for 8 rows), the average power is roughly 2.08W / 8 = 0.26W. Designers should ensure adequate PCB copper or other means to dissipate heat, especially in high ambient temperature environments, to stay within the operating temperature range.

6. Performance Analysis and Typical Curves

The datasheet references typical electrical/optical characteristic curves. While the specific graphs are not detailed in the provided text, such curves generally include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the nonlinear relationship, important for understanding the voltage drop across the LED at different drive currents.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, typically in a sub-linear fashion at higher currents.
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises, a critical factor for brightness consistency.
• Spectral Distribution: A plot of relative intensity vs. wavelength, centering around the 650nm peak and showing the 20nm half-width.

These curves are vital for high-performance design, allowing engineers to optimize drive current for desired brightness and efficiency while managing thermal effects.

7. Comparison and Differentiation

The LTP-14058AKD's primary differentiators are its use of AlInGaP Hyper Red technology and its specific mechanical form factor. Compared to older GaAsP or GaP red LEDs, AlInGaP offers higher efficiency and better brightness. The 1.4\" matrix height is a specific size that may be chosen for particular panel cutouts or readability distances. The horizontal stackability is a key mechanical feature for creating multi-character displays without complex interconnects. Its categorization for luminous intensity is an advantage for applications requiring uniform appearance across multiple units.

8. Frequently Asked Questions (Based on Technical Parameters)

8.1 How do I connect this to a microcontroller?

You cannot connect it directly. You need external drivers. Connect the 5 column (anode) pins to the microcontroller via current-limiting resistors and transistor switches (or a dedicated LED column driver IC) capable of sourcing the required current. Connect the 8 row (cathode) pins to transistor switches (or a dedicated LED row driver/sink IC) capable of sinking the cumulative current of a full row (e.g., 5 * I_dot). The microcontroller firmware then controls these drivers to multiplex the display.

8.2 What is the difference between peak wavelength and dominant wavelength?

Peak wavelength (650 nm) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (639 nm) is the single wavelength of monochromatic light that would match the perceived color of the LED's light. It is more closely related to human color perception. The difference indicates the spectrum is not perfectly symmetrical.

8.3 Can I run the LEDs at a higher current for more brightness?

You can increase current, but you must stay within the Absolute Maximum Ratings: average current per dot ≤ 15mA (derated above 25°C) and average power per dot ≤ 40mW. Exceeding these ratings will reduce reliability and lifespan. Furthermore, efficiency (light output per watt) often decreases at very high currents. Always consult the typical performance curves to understand the brightness gain versus the increased heat and stress on the device.

9. Practical Application Example

Scenario: Designing a simple 4-digit temperature readout for an industrial oven. Four LTP-14058AKD displays would be placed side-by-side, utilizing their horizontal stackability. A temperature sensor (e.g., thermocouple with ADC) provides data to a microcontroller. The microcontroller's firmware contains a font map for numbers (and possibly a \"C\" for Celsius). It uses a timer interrupt to run the display multiplexing routine. At each interrupt, it turns off all rows, selects the next row (1 through 8), and sets the pattern for that row across the four displays (20 column lines total) via the driver circuitry. The multiplexing rate is set to 200 Hz, giving a per-dot duty cycle of 1/8 and a refresh rate of 25 Hz per display, which is flicker-free. Current-limiting resistors are calculated for a 15mA per-dot current to ensure long-term reliability within the oven's elevated ambient temperature, with appropriate derating applied.

10. Technology Introduction and Trends

10.1 AlInGaP LED Technology

AlInGaP is a semiconductor material system used primarily for high-brightness red, orange, yellow, and green LEDs. Grown on a GaAs substrate, it offers significant advantages over older technologies like GaAsP, including higher quantum efficiency, better temperature stability, and longer operating life. The \"Hyper Red\" designation typically refers to a specific composition yielding a deep red color around 650-660nm, which is often chosen for applications where high visibility or specific wavelength response is needed.

10.2 Display Technology Context

Discrete LED dot matrix displays like the LTP-14058AKD represent a mature, highly reliable segment of display technology. While newer technologies like OLEDs or TFT LCDs offer higher resolution and full graphics capability, LED dot matrices retain strong advantages in extreme environments (wide temperature range, high brightness, long life), simplicity, and cost-effectiveness for dedicated character-based tasks. The trend in this niche is towards higher integration (e.g., displays with built-in controllers and serial interfaces) and the adoption of even more efficient LED materials, though the fundamental multiplexed matrix design remains unchanged.