LTS-50801KE 5-inch Red LED Display Datasheet - Digit Height 127.0mm - Forward Voltage 20-26V - Power 1400mW - English Technical Document

1. Product Overview

The LTS-50801KE is a high-visibility, single-digit, seven-segment display designed for applications requiring large, clear numeric readouts. Its primary function is to provide a bright, uniform, and reliable numeric display. The core advantages of this device stem from its use of advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) red LED chips, which are epitaxially grown on a Gallium Arsenide (GaAs) substrate. This technology delivers high luminous intensity and excellent color purity. The display features a black face with white segments, creating a high-contrast appearance that enhances readability even in brightly lit environments. Its low power requirement and solid-state construction make it suitable for long-term, reliable operation in various industrial, commercial, and instrumentation settings where large numeric data needs to be presented clearly from a distance.

2. In-Depth Technical Parameter Analysis

2.1 Optical Characteristics

The optical performance is central to this display's functionality. At a standard test current of 30mA per segment, the device offers a typical average luminous intensity of 242 millicandelas (mcd). The light emission is characterized by a peak wavelength (λp) of 632 nanometers (nm) and a dominant wavelength (λd) of 624 nm, both measured at a drive current of 60mA. This places the emitted light firmly in the red portion of the visible spectrum. The spectral line half-width (Δλ) is 20 nm, indicating a relatively narrow bandwidth and good color saturation. A key parameter for multi-digit or multi-segment uniformity is the luminous intensity matching ratio, specified at a maximum of 2:1 for segments within a similar light area when driven at 30mA. This ensures consistent brightness across all illuminated segments of a character.

2.2 Electrical Characteristics

The electrical parameters define the operating boundaries and conditions for the display. Each segment has a forward voltage (VF) ranging from a minimum of 20V to a maximum of 26V when driven at 60mA. The absolute maximum ratings are critical for design reliability: the maximum continuous forward current per segment is 75 mA at 25°C, with a derating factor applied as temperature increases. The peak forward current, permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width), is 270 mA. The maximum power dissipation per segment is 1400 mW. The device can withstand a reverse voltage (VR) of up to 50V per segment, with a typical reverse current (IR) of 300 µA under that condition. The operating and storage temperature range is specified from -35°C to +105°C, indicating robust environmental tolerance.

3. Binning System Explanation

The datasheet indicates that the device is categorized for luminous intensity. This implies a binning process where units are sorted and labeled based on their measured light output at a standard test current (likely 30mA as per the typical value). This allows designers to select displays with consistent brightness levels for their applications, ensuring visual uniformity in multi-digit displays or across different units in a product line. While specific bin code details are not provided in this excerpt, the mention of categorization highlights the manufacturer's control over this key optical parameter.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. Although the specific graphs are not detailed in the provided text, such curves typically illustrate the relationship between forward current (IF) and forward voltage (VF), the dependence of luminous intensity on forward current, and the variation of dominant wavelength with temperature or current. Analyzing these curves is essential for understanding the device's behavior under non-standard conditions, such as dimming via current control or operation across the full temperature range. They help designers optimize drive circuitry for efficiency and performance stability.

5. Mechanical and Package Information

The LTS-50801KE is a through-hole display package. The key mechanical specification is the 5-inch (127.0 mm) digit height, which refers to the physical size of the displayed numeral. The package dimensions drawing (referenced but not shown in detail) provides all critical measurements in millimeters, with a general tolerance of ±0.25 mm. A specific note mentions a pin tip shift tolerance of +0.4 mm, which is important for PCB layout and automated insertion processes to ensure proper fit and alignment.

5.1 Pin Configuration and Polarity Identification

The device has a common anode configuration. The internal circuit diagram shows all segment cathodes connected individually, with their anodes tied together to a common pin (Pin 8). The pin connection table is crucial for correct wiring:

• Pin 1: Segment E Cathode
• Pin 2: Segment D Cathode
• Pin 3: Comma Cathode
• Pin 4: Decimal Point (D.P.) Cathode
• Pin 5: Segment C Cathode
• Pin 6: Segment B Cathode
• Pin 7: Segment A Cathode
• Pin 8: Common Anode
• Pin 9: Segment F Cathode
• Pin 10: Segment G Cathode

6. Soldering and Assembly Guidelines

The absolute maximum ratings section provides specific soldering conditions. It states that during assembly, the soldering iron tip should be positioned 1/16 inch (approximately 1.6 mm) below the seating plane (the point where the display body meets the PCB). The acceptable soldering time is 3 seconds at a maximum temperature of 260°C. Alternatively, it specifies that the temperature of the unit itself during the assembly process must not exceed the maximum temperature rating listed (105°C). Adhering to these guidelines is critical to prevent thermal damage to the LED chips, the epoxy package, or the internal wire bonds, which could lead to immediate failure or reduced long-term reliability.

7. Packaging and Ordering Information

The primary ordering code is LTS-50801KE. The description clarifies this part number corresponds to an AlInGaP Red, Common Anode display. The datasheet is controlled under specification number DS30-2008-0049. While specific packaging quantities (e.g., tubes, trays, reels) are not mentioned in the excerpt, this information is typically found on separate packaging specifications or order guides. The device is noted as a lead-free package compliant with RoHS (Restriction of Hazardous Substances) directives.

8. Application Recommendations

8.1 Typical Application Scenarios

This large-digit display is ideal for applications where information needs to be read from a distance or in ambient light. Common uses include industrial process control panels, test and measurement equipment, public information displays, scoreboards, large clocks, and certain types of medical instrumentation. Its high brightness and contrast make it suitable for both indoor and sheltered outdoor environments.

8.2 Design Considerations

Designers must consider several factors. First, the drive circuitry must supply the required voltage (20-26V per segment) and limit the current to safe levels, typically using constant current drivers or appropriate series resistors calculated based on the supply voltage and the LED's forward voltage drop. The high forward voltage necessitates a power supply capable of delivering these levels. Heat dissipation should be managed, especially when operating near maximum current or at high ambient temperatures, considering the derating curve for continuous current. PCB layout must account for the pin spacing and the +0.4mm pin shift tolerance. For multi-digit displays, multiplexing is a common technique to control many segments with fewer driver lines, but refresh rates must be high enough to avoid visible flicker.

9. Technical Comparison and Differentiation

Compared to smaller seven-segment displays or those using older LED technologies like GaAsP (Gallium Arsenide Phosphide), the LTS-50801KE's use of AlInGaP technology provides significantly higher luminous efficiency and brightness. The black face/white segment design offers superior contrast compared to diffused or all-one-color packages. Its large 5-inch digit size fills a specific niche where smaller displays are inadequate. When compared to vacuum fluorescent displays (VFDs) or large LCDs of the era, this LED display offers superior ruggedness, wider operating temperature range, faster response time, and lower voltage requirements than VFDs, though it may consume more power than an LCD backlight in a static state.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the 2:1 luminous intensity matching ratio?

A: This ratio ensures that no segment within a single digit is more than twice as bright as any other segment when driven under the same conditions. This is crucial for achieving a uniform, professional-looking character without overly bright or dim segments.

Q: Why is the forward voltage so high (20-26V)?

A> The high forward voltage is a result of the series connection of multiple LED chips within each segment to achieve the necessary light output across the large 5-inch area. Driving several LED chips in series requires a proportionally higher voltage.

Q: How do I calculate the series resistor value?

A> Use Ohm's Law: R = (Vsupply - Vf_led) / If. For example, with a 28V supply, a typical Vf of 23V, and a desired If of 30mA: R = (28V - 23V) / 0.03A = 166.7 ohms. Use the next standard value (e.g., 180 ohms) and ensure the resistor's power rating is sufficient (P = If^2 * R = 0.03^2 * 180 = 0.162W, so a 0.25W resistor is adequate).

Q: Can I use PWM for dimming?

A> Yes, pulse-width modulation (PWM) is an effective method for dimming LEDs. It involves switching the current on and off at a frequency high enough to be imperceptible to the human eye (typically >100Hz). The duty cycle of the PWM signal controls the average current and thus the perceived brightness. This is preferable to analog dimming (reducing DC current) as it minimizes color shift.

11. Practical Use Case Example

Consider designing a large industrial timer for a manufacturing process line. The timer needs to display minutes and seconds, be readable from 10 meters away under factory lighting, and operate reliably 24/7. A system could be built using four LTS-50801KE displays (two for minutes, two for seconds). A microcontroller would manage the timing logic and segment data. Given the high forward voltage, a dedicated LED driver IC capable of constant current output at voltages up to 30-40V would be used to drive the multiplexed displays. The driver would be controlled via a serial interface from the microcontroller. The PCB would be designed with wide traces to handle the segment currents and sockets that accommodate the pin shift tolerance. The enclosure would include a tinted polycarbonate window to enhance contrast and protect the displays. The robust temperature rating ensures reliable operation near industrial machinery.

12. Technology Principle Introduction

The core light-emitting principle is based on electroluminescence in a semiconductor p-n junction. The LTS-50801KE uses AS-AlInGaP (Aluminum Indium Gallium Phosphide) material. When a forward voltage is applied across the p-n junction, electrons from the n-type region and holes from the p-type region are injected into the active region. When these charge carriers recombine, they release energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy of the semiconductor, which directly dictates the wavelength (color) of the emitted light. In this case, the composition is engineered to produce red light around 624-632 nm. The epitaxial layers are grown on a GaAs substrate, which provides a crystalline template matching the lattice constant of the active layers, crucial for achieving high internal quantum efficiency and brightness.

13. Technology Trends and Context

At the time of this datasheet (2008), AlInGaP technology represented a significant advancement over earlier GaAsP and GaP LEDs for red, orange, and yellow colors, offering vastly superior efficiency and brightness. Large seven-segment displays like this were common for dedicated numeric readouts. The trend since then has been towards greater integration and flexibility. Today, while discrete large-digit LEDs are still used, there is a strong shift towards dot-matrix LED panels and high-resolution fine-pitch LED screens, which can display not only numbers but also text, graphics, and animations, all controlled digitally. Furthermore, the efficiency of LED technology has continued to improve dramatically (e.g., with the advent of even more efficient materials and structures), allowing for brighter displays with lower power consumption and better thermal management. However, the fundamental design principles for driving and implementing such displays—managing current, voltage, heat, and multiplexing—remain highly relevant.