LTD-5260JD 0.52-inch Hyper Red 7-Segment LED Display Datasheet - Digit Height 13.2mm - Forward Voltage 2.6V - Power 70mW - English Technical Documentation

1. Product Overview

The LTD-5260JD is a high-performance, 0.52-inch (13.2 mm) digit height, 7-segment LED display module. It is designed for applications requiring clear, bright numeric readouts. The device utilizes advanced Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor technology for its light-emitting chips, which are fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. This construction contributes to its key visual characteristics: a gray faceplate and white segment areas when unlit, which enhances contrast when the red segments are illuminated.

The display features a common cathode configuration, which is a standard design for simplifying drive circuitry in multi-digit applications. It includes a right-hand decimal point (D.P.) for each digit, allowing for the display of fractional numbers. The primary design goals for this component are excellent character appearance, high brightness, high contrast ratio, and a wide viewing angle, all achieved with relatively low power requirements typical of solid-state LED technology.

1.1 Core Advantages and Target Market

The core advantages of the LTD-5260JD stem from its AlInGaP hyper red LED technology. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP offers significantly higher luminous efficiency. This translates to higher brightness levels for a given forward current, or lower power consumption for a required brightness level. The \"hyper red\" designation indicates a deep, saturated red color with a dominant wavelength typically around 639 nm, which is highly visible to the human eye.

The device is categorized for luminous intensity, meaning units are binned or sorted based on their measured light output. This allows designers to select displays with consistent brightness across multiple units in a product, ensuring a uniform appearance. The solid-state reliability of LEDs means no filaments to burn out, resistance to vibration, and an extremely long operational lifetime, often exceeding 100,000 hours.

The target market for this display includes industrial instrumentation, test and measurement equipment, point-of-sale systems, automotive dashboards (for aftermarket or secondary displays), medical devices, and consumer appliances where a clear, reliable numeric readout is required. Its 0.52-inch digit size makes it suitable for panel mounting where space is a consideration but readability from a moderate distance is necessary.

2. In-Depth Technical Parameter Analysis

The datasheet provides comprehensive electrical, optical, and absolute maximum ratings which are critical for reliable circuit design and ensuring the longevity of the display.

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.

• Power Dissipation per Chip: 70 mW. This is the maximum power that can be continuously dissipated by an individual LED segment (chip) without causing overheating.
• Peak Forward Current per Chip: 90 mA. This is allowed only under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It is useful for multiplexing schemes or achieving brief periods of higher brightness.
• Continuous Forward Current per Chip: 25 mA at 25°C. This rating derates linearly at 0.33 mA/°C as the ambient temperature (Ta) increases above 25°C. For example, at 85°C, the maximum continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) = 25 mA - 19.8 mA = 5.2 mA. This derating is crucial for thermal management.
• Reverse Voltage per Chip: 5 V. Exceeding this voltage in reverse bias can break down the LED's PN junction.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This defines the reflow soldering profile constraints.

2.2 Electrical & Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and represent typical device performance.

• Average Luminous Intensity (I_V): 320 (Min), 700 (Typ), μcd (Microcandelas) at I_F=1mA. This is the primary measure of brightness. The wide range from min to typ indicates the binning process; designers must use the minimum value for worst-case brightness calculations.
• Peak Emission Wavelength (λ_p): 650 nm (Typ) at I_F=20mA. This is the wavelength at which the spectral output is strongest.
• Dominant Wavelength (λ_d): 639 nm (Typ) at I_F=20mA. This is the single wavelength perceived by the human eye, defining the color. The 639 nm value confirms the \"hyper red\" classification.
• Spectral Line Half-Width (Δλ): 20 nm (Typ). This indicates the color purity; a smaller value means a more monochromatic light.
• Forward Voltage per Segment (V_F): 2.1 (Min), 2.6 (Typ) Volts at I_F=20mA. This is critical for designing the current-limiting circuitry. The driver must supply at least 2.6V to ensure the LED turns on properly.
• Reverse Current per Segment (I_R): 100 μA (Max) at V_R=5V. This is the leakage current when the LED is reverse-biased.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max). This specifies that the brightness difference between any two segments within the same digit will not exceed a 2-to-1 ratio, ensuring uniform appearance.

3. Binning System Explanation

The datasheet explicitly states that the devices are \"categorized for luminous intensity.\" This refers to a binning or sorting process post-manufacturing. Due to inherent variations in the semiconductor epitaxial growth and chip fabrication processes, LEDs from the same production batch can have variations in key parameters like forward voltage (V_F) and luminous intensity (I_V).

For the LTD-5260JD, the primary binning criterion is luminous intensity, as indicated. Units are tested and sorted into different intensity bins (e.g., a bin for 320-400 μcd, another for 400-500 μcd, etc., at the test condition of 1mA). This allows manufacturers and distributors to offer parts with guaranteed minimum brightness levels. Designers sourcing these displays should specify the required intensity bin to ensure consistency across all units in their production run, which is vital for products using multiple displays where visual uniformity is important. The datasheet provides the minimum (320 μcd) and typical (700 μcd) values, defining the possible range.

4. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, the datasheet includes a section for \"Typical Electrical / Optical Characteristic Curves.\" Based on standard LED behavior, these curves would 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 sharp increase in current once the forward voltage exceeds the diode's threshold (around 2V for AlInGaP red). This curve is essential for designing constant-current drivers.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): Shows how brightness increases with current. It is generally linear at lower currents but may saturate at higher currents due to thermal effects and efficiency droop.
• Luminous Intensity vs. Ambient Temperature (I_V vs. T_A): Illustrates how light output decreases as the junction temperature rises. This is a critical derating curve for applications operating in high-temperature environments.
• Spectral Distribution: A plot of relative radiant power versus wavelength, showing the peak at ~650 nm and the half-width of ~20 nm, confirming the optical characteristics table.
• Forward Voltage vs. Ambient Temperature (V_F vs. T_A): Shows the negative temperature coefficient of V_F; the forward voltage drops slightly as temperature increases.

These curves allow engineers to predict performance under non-standard conditions and optimize their design for efficiency and reliability.

5. Mechanical & Packaging Information

The datasheet provides a detailed package dimensions drawing. Key mechanical features include:

• Overall Size: The drawing specifies the length, width, and height of the plastic package, as well as the lead spacing and dimensions. All dimensions are in millimeters with a standard tolerance of ±0.25 mm unless otherwise noted.
• Leadframe Design: The 18 pins are arranged on a 0.1-inch (2.54 mm) pitch, which is a standard DIP (Dual In-line Package) footprint, making it compatible with standard PCB sockets and layouts.
• Polarity Identification: The pin connection diagram serves as the primary polarity and pinout guide. The common cathode pins (13 and 14) are clearly identified. The physical package likely includes a notch, a dot, or a beveled corner to indicate pin 1 orientation, which should be cross-referenced with the pin diagram.
• Seating Plane: The note on solder temperature references a point 1.6mm below the seating plane, which is important for defining the package's thermal mass during reflow soldering.

6. Soldering & Assembly Guidelines

The absolute maximum ratings provide the key guideline for soldering: the package must not be exposed to temperatures exceeding 260°C for more than 3 seconds. This aligns with standard lead-free reflow soldering profiles (e.g., IPC/JEDEC J-STD-020).

Recommended Process: A standard infrared or convection reflow oven with a controlled temperature profile should be used. The profile should have a preheat zone to gradually raise the temperature, a soak zone to activate the flux and equalize temperatures, a peak reflow zone where the temperature at the package leads briefly reaches 240-250°C (staying below the 260°C limit), and a controlled cooling zone.

Hand Soldering: If hand soldering is necessary, a temperature-controlled soldering iron should be used. The iron tip temperature should be set typically between 300-350°C, but the contact time with each pin must be very short (less than 3 seconds) to prevent heat from traveling up the lead and damaging the internal wire bonds or the LED chip itself. Use of a heat sink clip on the lead between the joint and the package body is advisable.

Cleaning: After soldering, if cleaning is required, use solvents compatible with the plastic package material. Isopropyl alcohol is generally safe.

Storage Conditions: Store in a dry, anti-static environment within the specified temperature range of -35°C to +85°C. The devices should be kept in their original moisture-barrier bags until ready for use to prevent moisture absorption, which can cause \"popcorning\" during reflow.

7. Pin Connection & Internal Circuit

The pin connection table is exhaustive. The LTD-5260JD is a two-digit display with a common cathode for each digit. The internal circuit diagram would show that all anodes for a specific segment (e.g., segment \"A\") of a specific digit are independent, while the cathodes for all segments within a single digit are connected together internally.

Drive Method: This configuration is ideal for multiplexing. To display a number, the microcontroller would:

1. Set the pattern of anodes (pins 1-12, 15-18) high (through current-limiting resistors) for the segments that need to be lit.
2. Pull the corresponding digit's common cathode (pin 13 or 14) low to complete the circuit and illuminate the digit.
3. After a short period (e.g., 5ms), turn that digit off by setting its cathode high or floating.
4. Repeat the process for the next digit with its corresponding segment anode pattern and cathode.

By cycling through the digits rapidly (at a frequency >100Hz), persistence of vision creates the illusion that both digits are continuously lit. This method reduces the number of required microcontroller I/O pins and power consumption significantly compared to static (non-multiplexed) driving.

8. Application Suggestions

8.1 Typical Application Circuits

The most common application is a multiplexed drive circuit. A microcontroller's I/O ports, often augmented with external current-sinking drivers (like a ULN2003A Darlington array) to handle the cathode current, control the display. Each segment anode connects to the microcontroller (or a latch/decoder IC like a 74HC595) through a current-limiting resistor. The resistor value is calculated using R = (V_supply - V_F) / I_F. For a 5V supply, a typical V_F of 2.6V, and a desired I_F of 10 mA: R = (5 - 2.6) / 0.01 = 240 Ω. A 220 Ω or 270 Ω resistor would be standard choices.

8.2 Design Considerations

• Current Limiting: Always use series resistors for each segment anode. Never connect an LED directly to a voltage source.
• Peak Current in Multiplexing: When multiplexing, the instantaneous current during the brief on-time can be higher than the DC rating to achieve the same average brightness. For example, with a 1/4 duty cycle, you could use a 40 mA pulse to achieve an average of 10 mA. However, this pulse must not exceed the absolute maximum peak current rating of 90 mA and must respect the duty cycle and pulse width constraints.
• Viewing Angle: Position the display so the intended viewing direction is within the device's wide viewing angle, typically perpendicular to the face for maximum contrast.
• Dimming: Brightness can be controlled via PWM (Pulse Width Modulation) on the cathode drivers, adjusting the duty cycle of the multiplexing pulses.

9. Technical Comparison & Differentiation

The primary differentiator of the LTD-5260JD is its use of AlInGaP technology for hyper red emission. Compared to displays using older GaAsP or standard red AllnGaP:

• vs. GaAsP Red: AlInGaP offers substantially higher luminous efficiency (more light per mA), better temperature stability, and a longer wavelength (deeper red) which often appears brighter to the eye and has better performance through red filters.
• vs. Standard Red LED Displays: The \"hyper red\" 639 nm dominant wavelength provides superior contrast against the gray/white background, especially in ambient light conditions, compared to a standard ~625 nm red.
• vs. Contemporary Alternatives (e.g., OLED): While OLEDs offer flexibility and potentially higher contrast in dark environments, this LED display is superior in high-brightness environments (sunlight readability), offers a wider operating temperature range, and has proven long-term reliability and stability that surpasses early-generation OLEDs.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 3.3V microcontroller?
A: Yes, but you must check the forward voltage. The typical V_F is 2.6V. With a 3.3V supply, the voltage headroom for the current-limiting resistor is only 0.7V (3.3V - 2.6V). To achieve a 10 mA current, you would need a 70 Ω resistor (R = 0.7V / 0.01A). This is feasible, but the current will be more sensitive to variations in V_F and supply voltage. A 5V supply is more robust for driving these LEDs.

Q: Why is the luminous intensity given at 1mA but the V_F at 20mA?
A: The intensity at a low current (1mA) is a standard test condition for comparing brightness efficiency. The forward voltage is typically measured at a standard operating current (20mA), which is a common drive level for indicator LEDs. Designers use the 1mA data for low-power calculations and the 20mA V_F for standard drive circuit design.

Q: What does \"common cathode\" mean for my circuit?
A: It means all the cathodes (negative sides) of the LEDs in one digit are connected together inside the package. To light a segment, you apply a positive voltage (through a resistor) to its anode pin and connect the digit's common cathode pin to ground. This is the opposite of a \"common anode\" display, where you ground the segment pin and apply voltage to the common anode.

Q: How do I calculate the power dissipation for thermal management?
A: For one segment, power P = V_F * I_F. At 20mA and 2.6V, P = 52 mW per segment. If all 7 segments of a digit are on (plus the decimal point, making 8), the total power for that digit would be 8 * 52 mW = 416 mW. This power is dissipated as heat in the LED chips. You must ensure the average chip temperature does not exceed its limits by following the current derating curve and providing adequate ventilation or heatsinking if necessary, especially in high ambient temperatures.

11. Practical Design Case Study

Scenario: Designing a simple two-digit voltmeter display for a benchtop power supply, showing 0.0V to 19.9V.

Implementation:

1. Microcontroller: A low-cost 8-bit MCU with at least 10 I/O pins is chosen.
2. Driving Circuit: Two I/O port pins are configured to sink current for the two common cathodes (pins 13 & 14). These pins connect directly to the MCU if they can sink 20-40mA, or through a transistor/driver IC. Eight other I/O pins (or a serial-in/parallel-out shift register like 74HC595 to save pins) drive the segment anodes (A-G and DP for both digits, noting some are shared) through individual 220Ω current-limiting resistors.
3. Software: The firmware reads the voltage via an ADC, converts it to BCD (Binary Coded Decimal), and uses a look-up table to determine which segments to light for each digit (0-9). It implements a multiplexing routine that updates the display at a 200Hz rate (each digit on for ~2.5ms).
4. Brightness Control: A simple PWM adjustment of the multiplexing duty cycle is implemented, controlled by a potentiometer read by another ADC channel, allowing the user to dim the display in dark environments.

This case highlights the efficient use of I/O, proper current limiting, and the multiplexing technique enabled by the common cathode, two-digit design of the LTD-5260JD.

12. Technology Principle Introduction

The core light-emitting principle is electroluminescence in a semiconductor PN junction. The LTD-5260JD uses AlInGaP (Aluminium Indium Gallium Phosphide) as the active layer. When a forward voltage is applied, electrons from the N-type region and holes from the P-type region are injected into the active region. There, they recombine, releasing energy in the form of photons (light). The specific composition of the Al_xIn_yGa_1-x-yP alloy determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For hyper red at ~639 nm, the composition is carefully calibrated. The non-transparent GaAs substrate absorbs any downward-emitted light, improving contrast by preventing light from scattering out the back of the chip. The gray face and white segments are part of the plastic package molding, which acts as a diffuser and contrast-enhancing filter for the small, bright LED chips mounted behind it.

13. Development Trends

While discrete 7-segment LED displays like the LTD-5260JD remain relevant for many applications due to their simplicity, robustness, and cost-effectiveness, several trends are evident:

1. Integration: There is a move towards displays with integrated drivers (I2C or SPI interface) and controllers, reducing the component count and microcontroller overhead for the system designer.
2. Miniaturization & Higher Density: Displays with smaller digit heights (e.g., 0.3-inch) and multi-digit modules (4-digit, 8-digit) in single packages are common.
3. Color Variety: While red is traditional, bright green, blue, yellow, and full-color RGB 7-segment displays are available for specific aesthetic or functional needs.
4. Alternative Technologies: In applications where ultra-low power, thinness, or flexibility is paramount, OLED-based segment displays are an alternative, though they may trade off on maximum brightness, temperature range, or long-term reliability in certain conditions compared to inorganic LEDs.
5. Efficiency Improvements: Ongoing research in semiconductor materials, including new phosphor-converted LEDs and micro-LED technology, promises even higher efficiencies and new form factors, though these are more likely to impact next-generation display technologies rather than replace traditional segment LEDs in the near term for their core applications.

The LTD-5260JD represents a mature, optimized solution within its specific niche, balancing performance, reliability, and cost.