LTP-4823KF LED Display Datasheet - 0.4-inch Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTP-4823KF is a dual-digit, 16-segment alphanumeric LED display module. Its primary function is to present alphanumeric characters (letters and numbers) in electronic devices. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material to produce a Yellow Orange light emission. This device is categorized as a common anode configuration, meaning the anodes of the LEDs for each digit are connected together internally, simplifying multiplexing drive circuits. The display features a gray face with white segments, which enhances contrast and readability under various lighting conditions.

1.1 Core Advantages and Target Market

The key advantages of this display stem from its AlInGaP technology and design. It offers high brightness and excellent contrast, making it suitable for applications where visibility is critical. The wide viewing angle ensures the display remains legible from various positions. Its solid-state construction provides high reliability and long operational life compared to other display technologies. The low power requirement is a significant benefit for battery-powered or energy-conscious applications. This display is typically targeted at industrial control panels, test and measurement equipment, point-of-sale terminals, instrumentation, and any embedded system requiring a clear, reliable numeric or limited alphanumeric readout.

2. Technical Parameter Deep Dive

This section provides an objective and detailed interpretation of the electrical and optical parameters specified in the datasheet.

2.1 Photometric and Optical Characteristics

The primary optical characteristic is the Average Luminous Intensity (Iv), measured in microcandelas (µcd). Under a standard test condition of a 1mA forward current (IF), the intensity ranges from a minimum of 500 µcd to a typical value of 1300 µcd. This parameter defines the perceived brightness of the segments. The light is characterized by a Peak Emission Wavelength (λp) of 611 nm and a Dominant Wavelength (λd) of 605 nm, both measured at IF=20mA. These values place the emission firmly in the yellow-orange region of the visible spectrum. The Spectral Line Half-Width (Δλ) is 17 nm, indicating the spectral purity of the emitted light. A narrower half-width generally means a more saturated color.

2.2 Electrical Characteristics

The key electrical parameter is the Forward Voltage per Segment (VF). At a drive current of 20mA, the typical forward voltage is 2.6V, with a minimum of 2.05V. This value is crucial for designing the current-limiting circuitry for the LEDs. The Reverse Current per Segment (IR) is specified at a maximum of 100 µA when a reverse voltage (VR) of 5V is applied, indicating the leakage current in the off state. The Luminous Intensity Matching Ratio for segments within a similar light area is 2:1 maximum. This means the brightest segment should not be more than twice as bright as the dimmest segment under the same conditions, ensuring uniform appearance.

2.3 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage may occur. The Average Power Dissipation per Segment must not exceed 70 mW. The Peak Forward Current per Segment is limited to 60 mA, while the Average Forward Current per Segment is rated at 25 mA at 25°C, derating linearly by 0.33 mA/°C above 25°C. This derating is essential for thermal management in high-temperature environments. The maximum Reverse Voltage per Segment is 5V. The device can operate and be stored within a Temperature Range of -35°C to +105°C.

3. Binning System Explanation

The datasheet includes a bin table for luminous intensity. Binning is a quality control process where LEDs are sorted (binned) based on measured performance parameters to ensure consistency. For the LTP-4823KF, LEDs are categorized into bins (F, G, H, J, K) according to their average luminous intensity measured at IF=1mA. The ranges are: F (321-500 µcd), G (501-800 µcd), H (801-1300 µcd), J (1301-2100 µcd), and K (2101-3400 µcd). This allows designers to select parts with a specific brightness level for their application, ensuring uniformity across multiple displays or matching a design's brightness requirement precisely.

4. Performance Curve Analysis

While the specific curves are not detailed in the provided text, typical performance curves for such devices would include:

• IV Curve (Current vs. Voltage): Shows the relationship between forward current and forward voltage. It is non-linear, with a turn-on voltage (around 2V for AlInGaP) after which current increases rapidly with small increases in voltage. This highlights the need for constant-current drive.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with drive current. It is generally linear over a range but will saturate at very high currents due to thermal and efficiency droop.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature of the LED increases. This curve is critical for applications operating over a wide temperature range.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~611 nm and the shape of the emission spectrum.

5. Mechanical and Package Information

The LTP-4823KF has a standard dual-digit LED display footprint. The package dimensions are provided in millimeters. Key mechanical notes include: all dimension tolerances are ±0.25 mm unless specified otherwise, and the pin tip shift tolerance is ±0.4 mm. The device features 20 pins in a single row. The internal circuit diagram shows it is a common anode configuration for two 16-segment characters, with a right-hand decimal point (D.P.). The pin connection table meticulously lists the cathode connection for each segment (A-U, D.P., and common anodes for Character 1 and Character 2). Pin 14 is noted as \"No Connection\" (N.C.).

6. Soldering and Assembly Guidelines

The datasheet specifies soldering conditions: the device can be subjected to a soldering iron temperature of 260°C for 3 seconds, with the iron tip positioned 1/16 inch (approximately 1.6 mm) below the seating plane of the package. It is crucial not to exceed this maximum temperature rating during assembly to prevent damage to the internal LED chips and the plastic package. For wave or reflow soldering, standard profiles for through-hole components should be followed, ensuring the peak body temperature does not exceed the maximum storage temperature of 105°C.

7. Application Suggestions

7.1 Typical Application Scenarios

This display is ideal for any device requiring a clear, two-digit readout with occasional alphabetic indicators. Common uses include: digital multimeters, frequency counters, timers, process controllers, medical devices (e.g., patient monitors), household appliances (e.g., ovens, thermostats), and automotive diagnostic tools.

7.2 Design Considerations

• Drive Circuit: As a common anode display, it is best driven by a multiplexing circuit. A microcontroller can sink current through the segment cathodes (via current-limiting resistors) while sequentially enabling the common anode pins for each digit.
• Current Limiting: Always use series resistors for each segment cathode or in the common anode path to limit the current to the desired value (e.g., 10-20 mA for full brightness). Calculate the resistor value using R = (Vcc - Vf) / If, where Vf is the forward voltage from the datasheet.
• Refresh Rate: When multiplexing two digits, ensure the refresh rate is high enough (typically >60 Hz) to avoid visible flicker.
• Viewing Angle: Position the display considering its wide viewing angle to maximize usability for the end-user.

8. Technical Comparison

Compared to older technologies like red GaAsP LEDs, the AlInGaP used in the LTP-4823KF offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. Compared to single-digit displays, this dual-digit unit saves board space and simplifies assembly. Versus dot-matrix displays, 16-segment units offer a simpler drive interface (20 pins vs. more for a matrix) but are limited to alphanumeric characters and a few symbols, not full graphics.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the \"No Connection\" pin (Pin 14)?
A: This pin is mechanically present but not electrically connected to any internal component. It is often included for mechanical stability during soldering or to maintain a standard pinout footprint across a family of similar devices.

Q: How do I interpret the \"Luminous Intensity Matching Ratio\" of 2:1?
A: This is a uniformity specification. It means that under identical driving conditions, the measured luminous intensity of any one segment should not be more than double the intensity of any other segment on the same display. This ensures a consistent look across all lit segments.

Q: Can I drive this display with a 5V supply?
A: Yes, but you must use a current-limiting resistor. With a typical Vf of 2.6V at 20mA, the required resistor value would be R = (5V - 2.6V) / 0.02A = 120 Ohms. Always verify the actual Vf from your specific batch and adjust the resistor value accordingly to achieve the desired current.

10. Practical Use Case

Scenario: Designing a Simple Digital Timer. The LTP-4823KF is perfect for displaying minutes and seconds (MM:SS). A microcontroller would control the display via multiplexing. One I/O port would control the 18 segment cathodes (through transistors or a driver IC), and two other I/O pins would control the two common anodes. The firmware would update the segment data and switch between the two digits rapidly. The high brightness ensures the timer is visible in a well-lit room, and the low power consumption is beneficial if the device is battery-operated.

11. Operating Principle

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the diode's turn-on voltage is applied across the anode and cathode of an LED segment, electrons and holes recombine in the active region (the AlInGaP layer). This recombination releases energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which in turn dictates the wavelength (color) of the emitted light, in this case, yellow-orange. Each of the 16 segments is an individual LED or a combination of LEDs, and by selectively illuminating these segments, alphanumeric characters can be formed.

12. Technology Trends

While 16-segment displays like the LTP-4823KF remain relevant for specific applications, the broader trend in information display is towards higher integration and flexibility. Dot-matrix OLED and LCD displays are becoming more cost-competitive and offer full alphanumeric and graphic capabilities. However, LED segment displays retain advantages in extreme environments (wide temperature range, high brightness) and for applications where simplicity, reliability, and long lifespan are paramount. The underlying AlInGaP technology continues to see improvements in efficiency and lifetime. Furthermore, there is a constant industry drive towards even lower power consumption and compliance with environmental regulations like RoHS, which this device already meets with its lead-free package.