LTD-5260HR LED Display Datasheet - 0.52-inch Digit Height - Red Color - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-5260HR is a high-brightness, dual-digit, seven-segment LED display module. Its primary function is to provide clear, legible numeric readouts in a wide range of electronic equipment. The core advantage of this device lies in its combination of excellent character appearance, high brightness and contrast, and a wide viewing angle, making it suitable for applications where readability under various lighting conditions is paramount. It is designed for low power requirement and offers solid-state reliability, ensuring long-term performance in consumer electronics, industrial instrumentation, test equipment, and point-of-sale terminals.

2. Technical Specifications Deep Dive

2.1 Photometric and Optical Characteristics

The display utilizes high-efficiency red LED chips fabricated from GaAsP on a transparent GaP substrate. This material choice contributes to its performance. Key optical parameters measured at an ambient temperature (T_A) of 25°C include:

• Average Luminous Intensity (I_V): Ranges from a minimum of 800 μcd to a typical value of 2200 μcd when driven at a forward current (I_F) of 10mA. This high brightness ensures visibility.
• Peak Emission Wavelength (λ_p): Typically 635 nm (I_F=20mA), placing it in the standard red visible spectrum.
• Dominant Wavelength (λ_d): Typically 623 nm (I_F=20mA).
• Spectral Line Half-Width (Δλ): Typically 40 nm (I_F=20mA), defining the color purity.
• Luminous Intensity Matching Ratio (I_V-m): A maximum ratio of 2:1 between segments ensures uniform appearance across the display.

Luminous intensity measurements are performed using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring data relevance to human vision.

2.2 Electrical Characteristics

The electrical parameters define the operating limits and conditions for the device:

• Forward Voltage per Chip (V_F): Typically 2.6V, with a maximum of 2.6V at I_F=20mA. This parameter is critical for designing the current-limiting circuitry.
• Reverse Current per Chip (I_R): Maximum 100 μA at a reverse voltage (V_R) of 5V.
• Continuous Forward Current per Chip: Rated at 25 mA maximum at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum allowable continuous current decreases as ambient temperature rises above 25°C.
• Peak Forward Current per Chip: Can withstand 100 mA under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).

2.3 Thermal and Absolute Maximum Ratings

These ratings must not be exceeded to prevent permanent damage:

• Power Dissipation per Chip: 75 mW maximum.
• Operating Temperature Range: -35°C to +85°C.
• Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane of the package. This is crucial for wave or reflow soldering processes.
• Reverse Voltage per Chip: 5 V maximum.

3. Binning System Explanation

The datasheet indicates that the device is categorized for luminous intensity. This implies a binning system where units are sorted and sold based on their measured light output (in μcd) at a standard test current (10mA). Designers can select bins to ensure consistency in display brightness across multiple units in a product, which is essential for aesthetic and functional uniformity. The typical value of 2200 μcd represents a common bin, while the minimum of 800 μcd defines the lower limit of the sorting range.

4. Performance Curve Analysis

The datasheet references typical electrical/optical characteristic curves. While not displayed in the provided text, such curves typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the nonlinear relationship, essential for determining the required drive voltage for a target current.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, up to the maximum rated limits.
• Luminous Intensity vs. Ambient Temperature: Shows the derating of light output as temperature increases, which is critical for high-temperature environment applications.
• Spectral Distribution: A plot of relative intensity vs. wavelength, confirming the peak and dominant wavelengths and the spectral half-width.

These curves allow engineers to predict performance under non-standard conditions and optimize their drive circuitry.

5. Mechanical and Package Information

5.1 Package Dimensions

The device has a digit height of 0.52 inches (13.2 mm). The package dimensions are provided in millimeters, with standard tolerances of ±0.25 mm unless otherwise specified. The exact mechanical drawing would detail the overall length, width, height, segment size and spacing, and lead (pin) dimensions and positions.

5.2 Pin Configuration and Polarity Identification

The LTD-5260HR is a common cathode type display. It has 18 pins. The pin connection table clearly maps each pin number to its function:

• Pins 1-4, 15-18: Control the segments (A, B, C, D, E, F, G, DP) of Digit 1.
• Pins 5-13: Control the segments (A, B, C, D, E, F, G, DP) and the common cathode of Digit 2.
• Pin 14: Common cathode for Digit 1.

This configuration allows for multiplexing, where digits are illuminated one at a time at a high frequency to create the perception of both being on simultaneously, saving microcontroller I/O pins.

5.3 Internal Circuit Diagram

The provided diagram shows the internal electrical connection of the LED segments. It visually confirms the common cathode architecture, showing all cathodes of the LEDs for one digit tied together to a single pin, while the anodes of individual segments are brought out to separate pins. This is a standard configuration for simplifying drive circuitry.

6. Soldering and Assembly Guidelines

The key assembly specification is the soldering temperature profile: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This guideline is intended to prevent thermal damage to the LED chips and the plastic package during wave or reflow soldering processes. Designers must ensure their PCB assembly process adheres to this limit. Standard ESD (Electrostatic Discharge) precautions should be observed during handling. Storage should be within the specified temperature range of -35°C to +85°C in a low-humidity environment.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is ideal for any device requiring a clear, two-digit numeric readout. Common applications include:

• Digital multimeters and bench power supplies.
• Industrial process controllers and timers.
• Fitness equipment (e.g., treadmill, bike displays).
• Consumer appliances like microwave ovens or washing machines.
• Audio equipment (VU meters, channel level displays).

7.2 Design Considerations

• Current Limiting: External current-limiting resistors are mandatory for each segment anode or common cathode line to set the forward current to a safe value (e.g., 10-20 mA). The resistor value is calculated using R = (V_supply - V_F) / I_F.
• Drive Method: For microcontroller interfacing, a multiplexed drive is most efficient. This requires sourcing current to the segment anodes and sinking current through the active digit's common cathode pin. Ensure the microcontroller port pins or external driver ICs can handle the total segment current when multiple segments are lit.
• Viewing Angle: The wide viewing angle is beneficial for panels that may be viewed from the side.
• Brightness Control: Brightness can be adjusted by varying the forward current (within limits) or by using pulse-width modulation (PWM) on the drive signals.

8. Technical Comparison and Differentiation

Compared to older or lower-grade seven-segment displays, the LTD-5260HR's key differentiators are its high brightness and excellent character appearance due to continuous uniform segments. The use of GaAsP on GaP substrate technology typically offers good efficiency. Its categorization (binning) for luminous intensity is an advantage for production consistency over non-binned parts. The common cathode configuration is more common and often easier to interface with modern CMOS-based microcontrollers that are better at sinking current than sourcing it.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the "Luminous Intensity Matching Ratio" of 2:1?

A: This specifies that the brightness of the dimmest segment will be no less than half the brightness of the brightest segment within the same digit. This ensures visual uniformity, preventing some segments from appearing noticeably darker than others.

Q: How do I drive this display with a 5V microcontroller?

A: You will need current-limiting resistors. For a target I_F of 10mA and a typical V_F of 2.6V, the resistor value would be R = (5V - 2.6V) / 0.01A = 240 Ohms. A 220 Ohm or 270 Ohm standard resistor would be suitable. You must use a driver transistor or IC to handle the cathode current if multiplexing, as the total digit current (when all 8 segments are on) could be 80mA, exceeding most MCU pin limits.

Q: Can I use this display outdoors?

A: The operating temperature range extends to +85°C, which covers many environments. However, the datasheet does not specify an IP (Ingress Protection) rating for water or dust resistance. For outdoor use, the display would likely need to be behind a sealed window or within a protected enclosure to prevent moisture damage.

10. Practical Design and Usage Case

Case: Designing a Simple Two-Digit Counter.

A designer is creating a manual event counter with a reset button. The LTD-5260HR is chosen for its clarity and size. The system uses a low-power microcontroller. The design employs multiplexing: the MCU's I/O pins, through 220Ω resistors, connect to all 16 segment anode lines (A-G, DP for both digits). Two NPN transistors are used as low-side switches for the two common cathode pins (pins 13 & 14). The firmware cycles between turning on the transistor for Digit 1 and outputting the pattern for its segments, then doing the same for Digit 2, at a rate faster than 60Hz to avoid flicker. The current-limiting resistors protect the LEDs and the MCU pins. The high brightness ensures the count is readable in a well-lit room.

11. Operating Principle Introduction

A seven-segment display is an assembly of light-emitting diodes (LEDs) arranged in a figure-eight pattern. By selectively illuminating specific segments (labeled A through G), any numeric digit from 0 to 9 can be formed. An optional decimal point (DP) segment is also included. In a common cathode display like the LTD-5260HR, all the cathodes (negative terminals) of the LEDs for a single digit are connected internally to one common pin. To light a segment, a positive voltage must be applied to its individual anode pin (through a current-limiting resistor), while the common cathode pin for that digit is connected to ground (low logic level), completing the circuit.

12. Technology Trends

While discrete seven-segment LED displays remain vital for many applications, the broader trend in display technology is towards integration and flexibility. This includes the rise of dot-matrix LED displays and OLEDs that can show alphanumeric characters and graphics. However, the seven-segment format persists due to its extreme simplicity, low cost, high reliability, and perfect suitability for pure numeric output. Modern versions may feature lower power consumption, higher brightness efficiency (lumens per watt), and surface-mount packages for automated assembly. The fundamental electrical interface and operating principle, as exemplified by the LTD-5260HR, remain standard and widely understood.