LTC-2623JF LED Display Datasheet - 0.28-inch Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-2623JF is a high-performance, quadruple-digit, seven-segment display module designed for applications requiring clear numeric readouts. Its primary function is to provide a visual numeric output in electronic devices. The core technology behind this display is the use of Aluminium Indium Gallium Phosphide (AlInGaP) semiconductor material for the LED chips, which are mounted on a non-transparent Gallium Arsenide (GaAs) substrate. This specific material choice is critical for achieving the device's characteristic Yellow Orange emission color with high efficiency and brightness. The display features a gray face and white segments, a combination engineered to maximize contrast and readability under various lighting conditions. It is categorized based on luminous intensity, allowing for selection consistency in production batches.

1.1 Core Advantages and Target Market

The device offers several key advantages that make it suitable for a range of professional and industrial applications. Its low power requirement is a significant benefit for battery-operated or energy-conscious devices. The excellent character appearance, high brightness, and high contrast ensure that the displayed numbers are easily legible from a distance and in ambient light. A wide viewing angle expands the usability of the device, allowing it to be read from various positions without significant loss of clarity. The solid-state reliability inherent to LED technology translates to long operational life and resistance to shock and vibration compared to mechanical or other display types. The primary target markets for this display include instrumentation panels, test and measurement equipment, industrial control systems, medical devices, and consumer electronics where reliable, clear, and efficient numeric display is required.

2. Technical Parameters Deep Objective Interpretation

The datasheet provides a comprehensive set of electrical and optical parameters that define the operational boundaries and performance of the LTC-2623JF display. Understanding these parameters is essential for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation per Segment: 70 mW. This is the maximum amount of power that can be safely dissipated as heat by an individual LED segment under continuous DC operation. Exceeding this limit risks thermal damage to the semiconductor junction.
• Peak Forward Current per Segment: 60 mA. This rating applies under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It allows for brief periods of higher current to achieve momentary peaks in brightness, useful for multiplexing schemes.
• Continuous Forward Current per Segment: 25 mA at 25°C. This is the maximum recommended current for continuous operation at room temperature. The datasheet specifies a derating factor of 0.33 mA/°C above 25°C, meaning the maximum allowable continuous current must be reduced as ambient temperature increases to prevent overheating.
• Reverse Voltage per Segment: 5 V. Applying a reverse bias voltage greater than this value can cause breakdown and damage the LED.
• Operating and Storage Temperature Range: -35°C to +85°C. The device is rated to function and be stored within this temperature range.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a critical parameter for the reflow soldering process during PCB assembly.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C, providing the expected behavior under normal operating conditions.

• Average Luminous Intensity (I_V): 320 to 800 μcd at I_F=1mA. This parameter measures the light output. The wide range indicates a binning process; devices are categorized based on their actual measured intensity.
• Peak Emission Wavelength (λ_p): 611 nm (typical) at I_F=20mA. This is the wavelength at which the optical output power is greatest. For this AlInGaP device, it falls in the yellow-orange region of the visible spectrum.
• Spectral Line Half-Width (Δλ): 17 nm (typical). This indicates the spectral purity or bandwidth of the emitted light. A smaller value means a more monochromatic (pure color) output.
• Dominant Wavelength (λ_d): 605 nm (typical). This is the single wavelength perceived by the human eye that best matches the color of the light source, closely related to the peak wavelength.
• Forward Voltage per Segment (V_F): 2.05V to 2.6V at I_F=20mA. This is the voltage drop across the LED when operating. It is crucial for designing the current-limiting circuitry. The range accounts for normal manufacturing variations.
• Reverse Current per Segment (I_R): 100 μA (max) at V_R=5V. This is the small leakage current that flows when the LED is reverse-biased within its maximum rating.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segments or digits within a single device, ensuring uniform appearance.

3. Mechanical and Packaging Information

The physical construction and dimensions of the display are critical for mechanical integration into an end product.

3.1 Package Dimensions

The LTC-2623JF has a standard dual in-line package (DIP) footprint suitable for through-hole PCB mounting. The key dimensional feature is the 0.28-inch (7.0 mm) digit height. All dimensions in the provided drawing are in millimeters, with standard tolerances of ±0.25 mm unless otherwise specified. Designers must refer to the exact dimensional drawing for precise placement of mounting holes and clearance for the display body.

3.2 Pin Connection and Polarity Identification

The device has a 16-pin configuration. It utilizes a multiplexed common anode architecture. This means the anodes of the LEDs for each digit are connected together internally (e.g., pin 1 is common anode for digit 1, pin 14 for digit 2, etc.), while the cathodes for each segment (A-G, DP, and colon segments L1-L3) are shared across digits. This design drastically reduces the number of required driver pins from 32 (4 digits * 8 segments) to 16, enabling efficient multiplexing. The pinout table clearly identifies each pin's function, including several No Connection (NC) pins and one position (pin 10) with no physical pin. Correct identification of the common anode pins and segment cathode pins is essential for proper circuit design and software control.

3.3 Internal Circuit Diagram

The internal circuit diagram visually represents the multiplexed common anode architecture. It shows the four common anode nodes (one per digit) and how each of the segment and colon cathodes connects to the corresponding LEDs across all four digits. This diagram is invaluable for understanding the electrical topology needed to drive the display correctly, confirming that to illuminate a specific segment on a specific digit, its corresponding common anode pin must be driven high (or connected to Vcc via a current source), while the desired segment cathode pin must be driven low (sinked to ground).

4. Soldering and Assembly Guidelines

Proper handling during assembly is crucial for reliability.

4.1 Reflow Soldering Parameters

The datasheet explicitly states the maximum allowable thermal profile for soldering: a peak temperature of 260°C for a maximum duration of 3 seconds, measured 1.6mm below the seating plane (typically at the PCB surface). This parameter must be strictly adhered to during reflow oven profiling. Exceeding these limits can damage the internal wire bonds, degrade the LED epoxy lens, or delaminate the package.

4.2 Precautions and Storage Conditions

• ESD (Electrostatic Discharge): Although not explicitly stated, LEDs are semiconductor devices and can be sensitive to ESD. Standard ESD handling procedures (use of grounded wrist straps, anti-static mats, and conductive packaging) are recommended.
• Cleaning: If cleaning is required after soldering, use methods and solvents compatible with the plastic package and epoxy lens. Avoid ultrasonic cleaning which may cause micro-cracks.
• Storage: The device should be stored within its specified temperature range of -35°C to +85°C, preferably in a low-humidity, anti-static environment to prevent moisture absorption and terminal oxidation.

5. Application Suggestions

5.1 Typical Application Scenarios

The LTC-2623JF is ideal for any application requiring a bright, reliable, multi-digit numeric display. Common uses include: digital multimeters and clamp meters, frequency counters, process timers and counters, temperature controllers, weighing scales, medical monitoring equipment (e.g., blood pressure monitors), automotive diagnostic tools, and industrial control panel readouts.

5.2 Design Considerations

• Current Limiting: LEDs are current-driven devices. A current-limiting resistor (or a constant current driver circuit) must be used in series with each common anode or segment cathode path (depending on the driving topology) to set the operating current. The resistor value is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. Use the maximum V_F from the datasheet (2.6V) for a conservative design.
• Multiplexing Drive Circuit: To control 4 digits with only 16 pins, a multiplexing technique is used. A microcontroller sequentially activates one digit's common anode at a time while outputting the segment pattern for that digit. This happens at a high frequency (typically >100Hz) to create the illusion of all digits being on simultaneously. The driver must be capable of sourcing the peak current for one digit's worth of illuminated segments.
• Viewing Angle and Mounting: Consider the intended user's viewing position. The wide viewing angle is beneficial, but the display should be mounted squarely to the viewing direction for optimal brightness.
• Heat Management: While the power dissipation is low, in high ambient temperature environments or when driving at higher currents, ensure adequate ventilation around the display to stay within the derated current limits.

6. Technical Comparison and Differentiation

The LTC-2623JF differentiates itself primarily through its use of AlInGaP technology and specific performance characteristics.

• vs. Standard GaAsP or GaP LEDs: AlInGaP technology offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. It also provides better temperature stability and longer lifetime.
• vs. Larger or Smaller Digit Displays: The 0.28-inch digit height offers a balance between readability and compactness, fitting between smaller 0.2-inch displays for portable devices and larger 0.5-inch or 1-inch displays for panel mounting.
• vs. Single-Color vs. Multi-Color Displays: This is a monochromatic Yellow Orange display. For applications requiring status indication (e.g., red for alarm, green for normal), a multi-color or bi-color display would be more suitable.
• vs. Common Cathode Configuration: The choice of common anode is often dictated by the driving circuitry. Microcontrollers with open-drain/sink capabilities are more common, making common anode displays a frequent choice as they allow the MCU to sink the segment current directly.

7. Frequently Asked Questions Based on Technical Parameters

Q: Why is there a range for Luminous Intensity (320-800 μcd)?
A: This indicates the device is sold in luminous intensity bins. Manufacturers test and sort LEDs based on their actual output. You can specify a tighter bin for more uniform displays in a production run.

Q: Can I drive this display with a 5V supply?
A: Yes, but you must use a current-limiting resistor. For example, to drive a segment at I_F=20mA with a V_F of 2.4V using a 5V supply: R = (5V - 2.4V) / 0.02A = 130 Ohms. A standard 120 or 150 Ohm resistor would be appropriate.

Q: What does \"Multiplex Common Anode\" mean for my software?
A: Your software must implement a display refresh routine. In a loop, it will: 1) Turn OFF all digit anode drives. 2) Output the segment pattern (cathode data) for Digit 1. 3) Turn ON the anode drive for Digit 1. 4) Wait a short time (e.g., 2-5ms). 5) Repeat steps 1-4 for Digit 2, then Digit 3, then Digit 4, and then loop back to Digit 1.

Q: The Peak Forward Current is 60mA, but Continuous is only 25mA. Can I use 60mA continuously?
A: No. The 60mA rating is for very short pulses (0.1ms width) at a low duty cycle (10%). Using 60mA continuously would far exceed the 70mW power dissipation rating and would quickly destroy the LED segment.

8. Practical Design and Usage Case

Case: Designing a 4-Digit Digital Voltmeter Readout
A designer is creating a benchtop power supply and needs a clear voltage readout. They select the LTC-2623JF for its brightness and readability. The microcontroller has 16 available I/O pins, which matches the display's pin count perfectly. The designer uses 8 pins configured as outputs to sink current for the segments (A, B, C, D, E, F, G, DP). Four other pins are configured as open-drain outputs to source current to the four common anodes (each via a small transistor to handle the cumulative segment current). The remaining 4 pins are unused NC pins. Software is written to multiplex the display, reading a value from the ADC and converting it to 7-segment patterns. Current-limiting resistors are placed on the common anode lines (or segment lines, depending on the chosen topology). The gray face/white segment design provides excellent contrast against the metal panel of the power supply.

9. Principle Introduction

The operating principle of the LTC-2623JF is based on electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage (approximately 2.0-2.6V for this AlInGaP material) is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. When these charge carriers recombine in the active region of the semiconductor, energy is released in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material. AlInGaP has a bandgap corresponding to light in the red to yellow-green spectrum; the exact composition in this device is tuned for Yellow Orange emission (605-611 nm). The seven-segment format is created by arranging multiple individual LED chips (or chip sections) in the classic \"8\" pattern, with each segment electrically isolated so it can be controlled independently or via the multiplexing scheme.

10. Development Trends

The evolution of displays like the LTC-2623JF follows broader trends in optoelectronics. There is a continuous drive towards higher efficiency, producing more light (lumens) per watt of electrical input, which is crucial for battery life and energy savings. Improved color rendering and saturation are also areas of development, though less critical for monochromatic numeric displays. For alphanumeric or multi-color applications, the trend is towards higher pixel density (more segments or dot-matrix elements in the same area) and the integration of multiple colors or full RGB capability into a single package. Another significant trend is the move from through-hole packages (like this DIP) to surface-mount device (SMD) packages, which allow for smaller, lighter, and more automated assembly. Furthermore, there is increasing integration of the drive electronics (such as constant current drivers, multiplexers, and even simple controllers) directly with the display module, simplifying the design task for the end engineer and reducing the component count on the main PCB.