LTC-4627JR LED Display Datasheet - 0.4-inch Digit Height - Super Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-4627JR is a quadruple-digit, seven-segment alphanumeric LED display module. Its primary function is to provide a clear, bright numerical and limited character readout in various electronic devices. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce super red light emission. This material system, grown on a non-transparent GaAs substrate, is known for its high efficiency and excellent color purity in the red spectrum. The device features a gray face with white segment markings, enhancing contrast and readability under various lighting conditions. It is designed as a multiplex common anode type, which is a standard configuration for multi-digit displays to minimize the required driver pins.

1.1 Key Features and Advantages

• Compact and Readable: Features a 0.4-inch (10.0 mm) digit height, offering a good balance between size and visibility.
• Superior Optical Performance: Delivers high brightness and high contrast, ensuring clear character appearance. The continuous uniform segments provide a cohesive look.
• Energy Efficient: Has a low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Excellent Viewing Angle: Offers a wide viewing angle, allowing the display to be read from various positions.
• High Reliability: Benefits from solid-state reliability with no moving parts or filaments to wear out.
• Quality Assurance: Devices are categorized for luminous intensity, ensuring consistent brightness levels within specified bins.
• Environmental Compliance: The package is lead-free, manufactured in accordance with RoHS (Restriction of Hazardous Substances) directives.

1.2 Device Identification

The part number LTC-4627JR specifically denotes a super red, multiplex common anode display with a right-hand decimal point. This naming convention helps in precisely identifying the device's electrical configuration and optical characteristics.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operation should always be maintained within these boundaries.

• Power Dissipation per Segment: 70 mW maximum. Exceeding this can lead to overheating and failure.
• Peak Forward Current per Segment: 90 mA maximum, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is for multiplexing or brief testing.
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This rating derates linearly by 0.33 mA/°C as ambient temperature (Ta) increases above 25°C. For example, at 50°C, the maximum continuous current would be approximately 25 mA - (0.33 mA/°C * 25°C) = 16.75 mA.
• Operating & Storage Temperature Range: -35°C to +85°C.
• Soldering Condition: The device can withstand wave soldering with the solder bath 1/16 inch (≈1.6mm) below the seating plane for 3 seconds at 260°C. The unit's body temperature must not exceed its maximum rating during assembly.

2.2 Electrical & Optical Characteristics (Typical at 25°C)

These are the guaranteed performance parameters under specified test conditions.

• Average Luminous Intensity (I_V): 200-650 µcd at a forward current (I_F) of 1 mA. This wide range indicates the device is binned for intensity.
• Peak Emission Wavelength (λ_p): 639 nm (typical) at I_F=20mA, placing it in the super red region.
• Spectral Line Half-Width (Δλ): 20 nm (typical), defining the spectral purity.
• Dominant Wavelength (λ_d): 631 nm (typical) with a tolerance of ±1 nm.
• Forward Voltage per Segment (V_F): 2.0V to 2.6V at I_F=20mA, with a tolerance of ±0.1V. This is a critical parameter for driver design.
• Reverse Current per Segment (I_R): 100 µA maximum at a reverse voltage (V_R) of 5V. Note: This is a test condition; continuous reverse bias operation is prohibited.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 maximum at I_F=10mA. This specifies the maximum allowable brightness variation between segments.
• Cross Talk: ≤ 2.5%, meaning minimal unintended illumination of adjacent segments.

3. Binning System Explanation

The datasheet indicates the product is "Categorized for Luminous Intensity." This implies a binning process where displays are sorted based on measured light output at a standard test current (likely 1mA or 10mA). Designers can select devices from the same intensity bin (e.g., 400-500 µcd) to ensure uniform brightness across multiple displays in an assembly, avoiding the "hue uneven problems" mentioned in the cautions. While not explicitly detailed for wavelength/color or forward voltage in this document, such categorization is common in LED manufacturing to guarantee consistent performance.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristics Curves." Although the specific graphs are not provided in the text, standard curves for such a device would typically include:

• I-V (Current vs. Voltage) Curve: Shows the exponential relationship, highlighting the typical forward voltage (V_F) around 2.0-2.6V.
• Luminous Intensity vs. Forward Current (I_V vs. I_F): Demonstrates how light output increases with current, up to the maximum rated limits. It helps designers choose an operating point for desired brightness and efficiency.
• Luminous Intensity vs. Ambient Temperature: Shows the derating of light output as temperature increases, emphasizing the need for thermal management in high-temperature environments.
• Spectral Distribution: A plot of relative intensity vs. wavelength, centering around 639 nm (peak) and 631 nm (dominant), with the specified 20 nm half-width.

5. Mechanical & Package Information

5.1 Package Dimensions

The display has a standard dual in-line package (DIP) footprint. Key dimensional notes include:

• All dimensions are in millimeters (mm).
• General tolerances are ±0.25 mm unless specified otherwise.
• Pin tip shift tolerance is ±0.4 mm.
• Quality control limits for imperfections: foreign material on segment ≤10 mils, ink contamination ≤20 mils, bubbles in segment ≤10 mils.
• Bending of the reflector is limited to ≤1% of its length.

5.2 Pin Connection and Polarity

The device is a common anode type. This means the anodes of the LEDs for each digit are connected together internally. The pinout is as follows:

• Pins 1, 2, 6, 8: Common anodes for Digit 1, Digit 2, Digit 3, and Digit 4, respectively.
• Pin 4: Common anode for the left-side colon segments (L1, L2, L3).
• Cathodes (negative terminals) for individual segments (A, B, C, D, E, F, G, DP, L1, L2, L3) are spread across pins 3, 5, 7, 11, 13, 14, 15, 16.
• Pins 9, 10, 12 are marked as "No Connection" or "No Pin."

Internal Circuit Diagram: The schematic shows the multiplexed arrangement. Each digit's anode is separate, while the cathodes for the same segment position (e.g., all 'A' segments) are connected together. To illuminate a specific segment on a specific digit, its corresponding digit anode pin must be driven high (positive voltage), and the corresponding segment cathode pin must be driven low (ground or sink current). This multiplexing is done rapidly to create the illusion of all digits being on simultaneously.

6. Soldering, Assembly & Storage Guidelines

6.1 Soldering

The absolute maximum ratings specify a wave soldering profile: 260°C for 3 seconds with the solder bath 1/16" below the seating plane. For reflow soldering, a standard lead-free profile with a peak temperature not exceeding the device's maximum temperature rating should be used. Care must be taken to avoid mechanical stress on the display body during assembly.

6.2 Storage Conditions

Proper storage is crucial to prevent pin oxidation and performance degradation.

• For LED Displays (like LTC-4627JR): Store in original packaging. Recommended conditions: Temperature 5°C to 30°C, Humidity below 60% RH. If stored outside these conditions or if the moisture barrier bag has been open for more than 6 months, it is recommended to bake the devices at 60°C for 48 hours and use them within one week.
• General Principle: Avoid long-term storage of large inventories. Consume stock promptly to ensure freshness and prevent oxidation of the tin-plated leads.

7. Application Notes and Design Considerations

7.1 Critical Application Cautions

• Intended Use: For ordinary electronic equipment (office, communication, household). Not recommended for safety-critical applications (aviation, medical, transportation control) without prior consultation and approval, as failure could jeopardize life or health.
• Driver Design:
  • Constant Current Driving: Highly recommended over constant voltage to ensure consistent brightness and protect the LEDs from thermal runaway.
  • Voltage Range: The driver circuit must accommodate the full V_F range (2.0V-2.6V) to deliver the intended current to all devices.
  • Reverse & Transient Protection: The circuit must protect against reverse voltages and voltage spikes during power-up/shutdown to prevent damage from metal migration and increased leakage current.
  • Current Derating: Choose the operating current after considering the maximum ambient temperature, using the derating factor of 0.33 mA/°C above 25°C.
• Environmental: Avoid rapid temperature changes in humid environments to prevent condensation on the display.
• Mechanical: If using a front-panel film/graphic overlay, avoid having it press directly against the display surface, as it may shift. If the application involves drop/vibration testing, share the test conditions in advance for evaluation.
• Matching for Multi-Display Units: When assembling two or more displays in one unit, use devices from the same luminous intensity bin to ensure uniform appearance.

7.2 Typical Application Scenarios

The LTC-4627JR is well-suited for applications requiring a clear, medium-sized numeric readout, such as:

• Test and measurement equipment (multimeters, power supplies).
• Industrial control panels and timers.
• Consumer appliances (microwaves, ovens, audio equipment).
• Point-of-sale terminals and basic information displays.
• Hobbyist and prototyping projects.

8. Technical Comparison and Differentiation

Compared to older technologies like standard GaAsP or GaP red LEDs, the AlInGaP super red LED chips in the LTC-4627JR offer significantly higher brightness and efficiency. Compared to some modern white-lit or side-lit displays, it provides superior color saturation and viewing angle for pure red indications. Its 0.4-inch digit size fills a niche between smaller, harder-to-read displays and larger, more power-hungry ones. The common anode multiplex design is a cost-effective and pin-efficient standard for multi-digit displays, though it requires a more complex driver IC than static drive types.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: What driver IC should I use for the LTC-4627JR?
A: You need a multiplexing driver capable of sourcing current to the common anode pins and sinking current from the segment cathode pins. Common choices are dedicated LED driver ICs like the MAX7219 or TM16xx series, or a microcontroller with sufficient GPIO pins and current capability, using external transistors if needed.

Q2: How do I calculate the current-limiting resistor?
A: Use Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.6V) in your calculation to ensure the current never exceeds your chosen I_F even with device variation. For a 5V supply and a desired I_F of 10 mA: R = (5V - 2.6V) / 0.01A = 240 Ω. Always place resistors on the cathode (sink) side in a multiplexed circuit.

Q3: Can I use it outdoors?
A: The operating temperature range (-35°C to +85°C) allows for many outdoor environments. However, consider sunlight readability (the high contrast helps), potential condensation (avoid rapid temp changes), and sealing the display behind a protective window to prevent moisture and dirt ingress, as the device itself is not waterproof.

Q4: Why is constant current drive recommended?
A: An LED's forward voltage (V_F) varies with temperature and from device to device. A constant voltage source with a series resistor provides an approximate constant current, but it can vary. A true constant current source ensures the LED always gets the exact designed current, leading to consistent brightness and longer lifespan, especially important over the -35°C to +85°C range.

10. Design-in Case Study

Scenario: Designing a simple 4-digit counter/timer.
A designer selects the LTC-4627JR for its readability and standard interface. They use a microcontroller with a built-in timer and enough I/O. Four GPIO pins are configured as outputs to drive the digit anodes (pins 1,2,6,8) via small NPN transistors (e.g., 2N3904) to source the required current. Seven other GPIO pins (plus one for the decimal point) are configured as open-drain outputs and connected directly to the segment cathodes (A-G, DP), each with a 220Ω series resistor to ground to set the segment current to ~10-12mA from a 5V supply. The firmware implements a multiplexing routine, turning on one digit anode at a time while activating the appropriate segment cathodes for that digit, cycling through all four digits rapidly (>60Hz). The gray face/white segment provides excellent contrast behind a dark tinted acrylic window on the product's front panel.

11. Operating Principle

The LTC-4627JR operates on the principle of electroluminescence in a semiconductor P-N junction. When a forward bias voltage exceeding the diode's turn-on voltage (≈2.0V) is applied, electrons from the N-type AlInGaP layer recombine with holes from the P-type layer. This recombination event releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, super red at ~631-639 nm. The non-transparent GaAs substrate helps reflect light upward, improving overall light output efficiency. The seven-segment pattern is created by placing individual LED chips or chip arrays under each segment area and connecting them via the internal multiplexing matrix.

12. Technology Trends

While discrete seven-segment displays like the LTC-4627JR remain vital for specific applications due to their simplicity, high brightness, and wide viewing angle, the broader trend is towards integrated dot-matrix displays (both LED and OLED) and TFT LCDs. These offer greater flexibility in displaying characters, graphics, and animations. However, for applications where only numbers, a few letters, and extreme clarity/reliability are required, seven-segment technology continues to evolve. Trends include even higher efficiency materials, lower operating voltages, surface-mount device (SMD) packages for automated assembly, and displays with integrated drivers and communication interfaces (like I2C or SPI) to further simplify system design and reduce microcontroller pin count.