LTD-323JD LED Display Datasheet - 0.3-inch Digit Height - Hyper Red 650nm - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTD-323JD is a high-performance, 0.3-inch (7.62 mm) digit height numeric display module. It is designed for applications requiring clear, bright, and reliable numerical readouts. The device features a black face with white segments, providing excellent contrast for optimal character appearance and wide viewing angles. Its solid-state construction ensures long-term reliability in various operating environments.

1.1 Core Advantages and Target Market

The primary advantages of this display include its high brightness, high contrast ratio, and low power requirement. The use of AlInGaP (Aluminum Indium Gallium Phosphide) Hyper Red LED chips on a non-transparent GaAs substrate is key to its performance, offering superior luminous efficiency and color purity compared to older technologies. This makes it suitable for a wide range of applications including industrial instrumentation, test and measurement equipment, consumer appliances, automotive dashboards (secondary displays), and point-of-sale terminals where clear, energy-efficient numeric indication is required.

2. Technical Parameter Deep Dive

This section provides a detailed, objective interpretation of the key technical parameters specified in the datasheet.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The typical peak emission wavelength (λp) is 650 nm, which falls within the hyper-red spectrum. The dominant wavelength (λd) is specified at 639 nm. The spectral line half-width (Δλ) is 20 nm, indicating a relatively narrow spectral bandwidth which contributes to color purity. The average luminous intensity (Iv) ranges from a minimum of 200 μcd to a maximum of 600 μcd under a test condition of 1mA forward current. A luminous intensity matching ratio of 2:1 (max) ensures reasonable uniformity between segments. It is important to note that the luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the values are relevant to human perception.

2.2 Electrical Parameters

The key electrical parameter is the forward voltage (Vf) per segment, which has a typical value of 2.6V at a forward current (If) of 20mA. The minimum value is 2.1V. The reverse current (Ir) per segment is a maximum of 100 μA when a reverse voltage (Vr) of 5V is applied. These parameters are critical for designing the appropriate current-limiting circuitry and ensuring proper biasing of the LEDs.

3. Absolute Maximum Ratings and Thermal Considerations

The absolute maximum ratings define the operational limits beyond which permanent damage may occur. The continuous forward current per segment is 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the allowable continuous current decreases as ambient temperature increases. The peak forward current per segment is 90 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). The maximum power dissipation per segment is 70 mW. The device can operate and be stored within a temperature range of -35°C to +85°C. For assembly, the maximum solder temperature is 260°C for a maximum of 3 seconds at 1.6mm below the seating plane, which is a standard reflow profile consideration.

4. 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 at a standard test current (likely 1mA). Bins are defined by minimum and maximum intensity values (e.g., 200-300 μcd, 300-400 μcd, etc.). Designers should specify the required bin or be aware of potential intensity variations when sourcing components for applications requiring uniform brightness across multiple displays. The datasheet does not specify voltage or wavelength binning for this part number.

5. Performance Curve Analysis

While the specific graphs are not detailed in the provided text, typical curves for such a device would include:

• IV Curve (Current vs. Voltage): Shows the exponential relationship between forward voltage and current. The knee voltage (where current begins to rise significantly) is typically around 1.8-2.0V for AlInGaP red LEDs.
• Luminous Intensity vs. Forward Current: A generally linear relationship at lower currents, potentially saturating at higher currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature increases. AlInGaP LEDs typically have a negative temperature coefficient for luminous intensity.
• Spectral Distribution: A plot of relative intensity vs. wavelength, showing the peak at ~650nm and the spectral half-width.

These curves are essential for understanding the device's behavior under non-standard operating conditions and for optimizing drive circuitry for efficiency and longevity.

6. Mechanical and Package Information

The device comes in a standard LED display package. All dimensions are provided in millimeters with a general tolerance of ±0.25 mm unless otherwise specified. The exact footprint and pin spacing are defined in the package drawing, which is crucial for PCB (Printed Circuit Board) layout. The segment arrangement is continuous and uniform.

6.1 Pin Configuration and Polarity Identification

The LTD-323JD has a duplex common anode configuration. This means there are two common anode pins (one for each digit in a multi-digit package; for a single digit, one may be used). The pinout is as follows: Pin 5 is the common anode for digit 2, and Pin 10 is the common anode for digit 1. The segment cathodes are connected to pins: A (pin 3), B (pin 9), C (pin 8), D (pin 6), E (pin 7), F (pin 4), and G (pin 1). Pin 2 is noted as \"No Pin\". Correct identification of anode and cathode pins is vital to prevent reverse biasing the LEDs.

7. Soldering and Assembly Guidelines

The key soldering parameter provided is the maximum allowable temperature of 260°C for 3 seconds, measured 1.6mm below the seating plane. This is compatible with standard lead-free reflow soldering profiles. Designers should ensure the thermal profile during assembly does not exceed this limit to avoid damaging the epoxy package or the internal wire bonds. Standard handling precautions for ESD (Electrostatic Discharge) sensitive devices should be observed. Storage should be within the specified -35°C to +85°C range in a dry environment.

8. Application Suggestions

8.1 Typical Application Scenarios

Ideal for any device requiring a bright, clear numeric display. Examples include digital multimeters, frequency counters, clock radios, kitchen appliance timers, HVAC controllers, medical device readouts, and industrial process monitors.

8.2 Design Considerations

• Current Limiting: Always use a series resistor (or constant current driver) for each segment or common anode to set the forward current. Calculate the resistor value based on the supply voltage (Vcc), the typical forward voltage (Vf ~2.6V), and the desired current (e.g., 10-20mA). R = (Vcc - Vf) / If.
• Multiplexing: For multi-digit displays, a multiplexed drive scheme is common to reduce pin count. The common anodes are switched sequentially while the corresponding segment data is applied. Ensure the peak current in this scheme does not exceed the absolute maximum rating.
• Viewing Angle: The wide viewing angle is beneficial but consider the intended user's line of sight during mechanical design.
• Heat Management: While power dissipation is low, ensure adequate ventilation in enclosed spaces, especially when operating near maximum ratings or at high ambient temperatures.

9. Technical Comparison

Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, the AlInGaP Hyper Red LED offers significantly higher luminous efficiency, resulting in greater brightness for the same drive current. It also provides better color saturation (purer red) and typically has a longer operational lifetime. Compared to white LEDs used with filters for red displays, the Hyper Red LED is more efficient as it emits the desired color directly, eliminating filter losses.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the \"No Pin\" connection?
A: This is typically an unused pin position in the package, often included for mechanical symmetry or because the package mold is used for multiple device variants with different pinouts. It must not be connected in the circuit.

Q: Can I drive this display with a 5V microcontroller pin directly?
A: No. The forward voltage is only ~2.6V. Connecting 5V directly would cause excessive current, destroying the LED. A current-limiting resistor is mandatory.

Q: What does \"categorized for luminous intensity\" mean for my design?
A: It means displays from different production batches may have slightly different brightness levels. If visual uniformity across multiple units is critical (e.g., in a multi-digit panel), you should specify a tight bin code or implement software brightness calibration.

Q: Is this display suitable for outdoor use?
A: The operating temperature range extends to -35°C to +85°C, which covers many environments. However, for direct sunlight exposure, consider the potential for UV degradation of the epoxy and ensure the brightness is sufficient for daylight readability. A conformal coating may be necessary for moisture protection.

11. Practical Design Case

Scenario: Designing a simple two-digit counter using the LTD-323JD, driven by a 3.3V microcontroller.
Implementation: Use a multiplexing technique. Connect the two common anode pins (Digit 1 and Digit 2) to two microcontroller GPIO pins configured as open-drain/source outputs. Connect the seven segment cathodes (A-G) to seven other GPIO pins through individual 33Ω current-limiting resistors (calculated for ~20mA: R = (3.3V - 2.6V) / 0.02A = 35Ω; 33Ω is a standard value). The software would alternately turn on one common anode at a time, while setting the segment pins for the digit to be displayed. The refresh rate should be above 60 Hz to avoid visible flicker.

12. Principle Introduction

The device operates on the principle of electroluminescence in a semiconductor p-n junction. When a forward voltage exceeding the bandgap energy is applied, electrons and holes recombine in the active region (the AlInGaP multi-quantum well structure), releasing energy in the form of photons. The specific composition of Aluminum, Indium, Gallium, and Phosphide determines the bandgap energy, and thus the wavelength (color) of the emitted light—in this case, hyper red at 650 nm. The non-transparent GaAs substrate absorbs stray light, improving contrast.

13. Development Trends

The trend in LED display technology continues towards higher efficiency, lower power consumption, and increased integration. While discrete 7-segment displays like the LTD-323JD remain relevant for specific applications, there is a shift towards dot-matrix OLED and micro-LED displays for more complex graphics and flexibility. However, for simple, high-reliability, high-brightness numeric readouts, AlInGaP and newer InGaN-based LED displays will continue to be widely used due to their robustness, long lifetime, and cost-effectiveness in volume production. Advances in packaging may lead to even thinner profiles and wider viewing angles.