LTD-323JF LED Display Datasheet - 0.3-inch (7.62mm) Digit Height - AlInGaP Yellow Orange - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The device is a 0.3-inch (7.62 mm) digit height alphanumeric LED display. It is designed to provide clear, high-visibility numeric or limited alphanumeric information in a compact form factor. The core technology utilizes Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor material to produce a yellow-orange emission. The display features a black face for high contrast and white segments for optimal light diffusion and appearance. It is categorized as a duplex common anode display, meaning two digits share common anode connections, which is a common configuration for multiplexing in driver circuits to reduce pin count.

2. Technical Parameter Deep Dive

This section provides a detailed, objective analysis of the key electrical and optical parameters specified in the datasheet.

2.1 Optical Characteristics

The optical performance is central to the display's function. The Average Luminous Intensity (Iv) is specified from 320 μcd (minimum) to 800 μcd (typical) at a forward current (IF) of 1 mA. This parameter indicates the perceived brightness of the lit segments. Designers should note the Luminous Intensity Matching Ratio (Iv-m) of 2:1 maximum. This ratio defines the allowable brightness variation between different segments of the same digit or between digits, ensuring visual uniformity. A lower ratio indicates better consistency.

The color characteristics are defined by wavelength. The Peak Emission Wavelength (λp) is 611 nm (typical), while the Dominant Wavelength (λd) is 605 nm (typical) at IF=20mA. The dominant wavelength is the single wavelength perceived by the human eye, which defines the color (yellow-orange in this case). The Spectral Line Half-Width (Δλ) of 17 nm (typical) indicates the spectral purity or the narrowness of the emitted light band; a smaller value indicates a more monochromatic light source.

2.2 Electrical Characteristics

The electrical parameters define the operating conditions and power requirements. The key parameter is the Forward Voltage per Segment (VF), which is 2.6V (typical) at a forward current of 20 mA. This value is crucial for designing the current-limiting resistor in series with each segment. The Reverse Current per Segment (IR) is specified as a maximum of 100 μA at a Reverse Voltage (VR) of 5V, indicating the device's leakage characteristics in the off-state.

2.3 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW. This limits the combined effect of forward current and voltage drop across the segment.
• Continuous Forward Current per Segment: 25 mA at 25°C, with a derating factor of 0.33 mA/°C. This means the maximum allowable continuous current decreases as ambient temperature (Ta) increases above 25°C.
• Peak Forward Current per Segment: 60 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is relevant for multiplexed driving schemes.
• Reverse Voltage per Segment: 5 V. Exceeding this can break down the LED junction.
• Operating & Storage Temperature Range: -35°C to +85°C.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is critical for wave or reflow soldering processes.

3. Binning System Explanation

The datasheet explicitly states that the device is "Categorized for Luminous Intensity." This indicates the presence of a binning system. In LED manufacturing, variations occur. Binning is the process of sorting LEDs into groups (bins) based on key parameters like luminous intensity and sometimes forward voltage or dominant wavelength. By purchasing a binned product, designers ensure greater consistency in brightness across all displays used in an assembly, which is essential for product quality. The datasheet's specified Iv range (320-800 μcd) likely represents the spread across different bins available.

4. Performance Curve Analysis

While the specific curves are not detailed in the provided text, typical LED datasheets include graphs crucial for design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

This curve shows the non-linear relationship between current and voltage. The forward voltage increases logarithmically with current. The typical VF value given (2.6V @ 20mA) is a point on this curve. Designers use this to ensure the driver circuit can provide sufficient voltage, especially at low temperatures where VF increases.

4.2 Luminous Intensity vs. Forward Current

This graph shows how brightness scales with current. It is generally linear over a wide range but will saturate at very high currents. It helps determine the operating current needed to achieve a desired brightness level.

4.3 Luminous Intensity vs. Ambient Temperature

LED light output decreases as junction temperature rises. This curve is vital for thermal management design. If the display is operated in a high-temperature environment or with inadequate heat dissipation, the brightness will be lower than specified at 25°C.

4.4 Spectral Distribution

A graph showing relative intensity across wavelengths would visualize the peak (611 nm) and half-width (17 nm), confirming the yellow-orange color point.

5. Mechanical and Packaging Information

The device has a specific physical footprint and pin arrangement. The Package Dimensions drawing (referenced but not shown in text) provides all critical mechanical measurements in millimeters, with a standard tolerance of ±0.25 mm. This drawing is essential for PCB layout, ensuring the footprint and keep-out areas are correctly designed.

5.1 Pin Connection and Internal Circuit

The Pin Connection table is provided. It is a 10-pin device. The internal circuit diagram shows a duplex common anode configuration. Pins 5 and 10 are the common anodes for Digit 2 and Digit 1, respectively. The other pins (1, 3, 4, 6, 7, 8, 9) are the cathodes for individual segments (G, A, F, D, E, C, B). Pin 2 is noted as "No Pin," likely meaning it is a mechanical placeholder with no electrical connection. The segment labeling (A-G) follows the standard 7-segment display convention.

6. Soldering and Assembly Guidelines

The key guideline provided is the Solder Temperature rating: a maximum of 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is a standard rating for wave or reflow soldering. Adherence is critical to prevent thermal damage to the LED chips, the epoxy encapsulant, or the internal wire bonds. Prolonged exposure to high temperature can cause delamination, discoloration, or catastrophic failure.

General Handling Notes: While not explicitly stated, standard ESD (Electrostatic Discharge) precautions should be observed during handling and assembly, as LED junctions are sensitive to static electricity. Storage should be within the specified temperature and humidity ranges to prevent moisture absorption, which can cause "popcorning" during soldering.

7. Packaging and Ordering Information

The part number is clearly identified as LTD-323JF. This naming convention likely encodes key attributes: "LTD" may signify a display type, "32" could relate to the 0.32-inch size (approximating 0.3-inch), and "JF" may indicate the color (yellow-orange) and package. The datasheet reference is Spec No.: DS30-2001-410. For ordering, the exact part number must be used. Specifics on reel packaging, tape width, or orientation are typically found on separate packaging specification sheets.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is suited for applications requiring compact, bright, and reliable numeric indication. Common uses include:

• Test and measurement equipment (multimeters, frequency counters).
• Industrial control panels and instrument readouts.
• Consumer appliances (microwaves, audio equipment).
• Automotive aftermarket dash displays.
• Point-of-sale terminals.

8.2 Design Considerations

• Driver Circuit: Use a constant current source or a voltage source with a series current-limiting resistor for each segment cathode. The resistor value is calculated as R = (Supply Voltage - VF) / IF. For a 5V supply and 20mA target current: R = (5V - 2.6V) / 0.02A = 120 Ω.
• Multiplexing: The common anode structure is ideal for multiplexing. By sequentially enabling one common anode (digit) at a time and driving the appropriate segment cathodes, multiple digits can be controlled with fewer I/O pins. The peak current rating (60mA) allows for higher pulsed currents to compensate for the reduced duty cycle, maintaining perceived brightness.
• Viewing Angle: The datasheet claims a "Wide Viewing Angle," which is beneficial for applications where the display may be viewed from off-axis positions.
• Contrast: The black face provides high contrast in both brightly lit and dim environments.

9. Technical Comparison

Compared to other LED display technologies available at the time of its release (2001), the AlInGaP material system used in the LTD-323JF offered distinct advantages over older technologies like GaAsP (Gallium Arsenide Phosphide):

• Higher Brightness & Efficiency: AlInGaP LEDs are significantly brighter and more efficient than GaAsP LEDs, especially in the red to yellow-orange spectrum.
• Better Temperature Stability: AlInGaP generally exhibits less luminous intensity drop with increasing temperature compared to GaAsP.
• Superior Reliability: The "Solid State Reliability" claim is supported by the robust nature of AlInGaP chips and the mature packaging technology.
• Compared to contemporary alternatives like vacuum fluorescent displays (VFDs), this LED display is simpler to drive, has a longer lifetime, and operates at lower voltages, but may have lower brightness in some conditions.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: What resistor should I use to drive a segment at 20mA from a 5V supply?
A: Using the typical VF of 2.6V, R = (5 - 2.6) / 0.02 = 120 Ω. Use the nearest standard value (e.g., 120 Ω or 150 Ω) and check the actual current.

Q: Can I drive this display with a 3.3V microcontroller?
A: Possibly, but you must check the forward voltage. At 20mA, VF is 2.6V typical, leaving only 0.7V for the current-limiting resistor. This requires a very small resistor value (35 Ω), making the current sensitive to variations in VF. It's better to operate at a lower current (e.g., 5-10mA) or use a dedicated LED driver IC with a boost converter.

Q: What does the 2:1 Luminous Intensity Matching Ratio mean?
A: It means the brightest segment/digit should be no more than twice as bright as the dimmest segment/digit within the same display unit. This ensures visual uniformity.

Q: How do I interpret the derating for Continuous Forward Current?
A: The maximum continuous current decreases by 0.33 mA for every degree Celsius above 25°C. At 85°C (the max operating temperature), the derating is (85-25)*0.33mA ≈ 19.8 mA. Therefore, the maximum allowed continuous current at 85°C is 25 mA - 19.8 mA = 5.2 mA per segment.

11. Practical Design Case

Scenario: Designing a simple 2-digit voltmeter readout using a microcontroller.

1. Circuit Design: Connect the two common anodes (pins 5 & 10) to two separate microcontroller I/O pins configured as open-drain/low-side switches. Connect all seven segment cathodes (pins 1,3,4,6,7,8,9) to seven other I/O pins via 120 Ω current-limiting resistors (for a 5V system).
2. Software (Multiplexing): In a timer interrupt routine (e.g., at 100Hz):
   a. Turn off both common anode pins (set high impedance or logic high if using a PNP transistor).
   b. Set the segment cathode pins to the pattern for Digit 1.
   c. Enable (drive low) the common anode for Digit 1 (pin 10).
   d. Wait a short delay (e.g., 5ms).
   e. Turn off Digit 1's anode.
   f. Set the segment cathode pins to the pattern for Digit 2.
   g. Enable the common anode for Digit 2 (pin 5).
   h. Wait 5ms.
   i. Repeat. The human eye perceives both digits as continuously lit.
3. Current Calculation: Each segment is on for a 50% duty cycle (one digit at a time). To achieve an average current of 10mA per segment, the pulsed current during its active time should be 20mA. This is within the 60mA peak rating.

12. Principle Introduction

The device operates on the principle of electroluminescence in a semiconductor p-n junction. The active material is AlInGaP (Aluminum Indium Gallium Phosphide). When a forward voltage exceeding the junction's built-in potential 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 AlInGaP alloy determines the bandgap energy, which directly defines the wavelength (color) of the emitted light—in this case, yellow-orange (~605-611 nm). The black face absorbs ambient light to improve contrast, while the white segment material helps scatter and evenly distribute the emitted light from the underlying LED chip.

13. Development Trends

While this is a legacy product, understanding its context highlights trends in display technology. Since its introduction, several key trends have emerged:

• Shift to SMD (Surface Mount Device) Packages: Modern equivalents are almost exclusively SMD types, allowing for automated pick-and-place assembly, smaller footprints, and lower profiles compared to through-hole displays like the LTD-323JF.
• Higher Density & Full Color: Displays have moved towards higher pixel density (dot matrix, OLED) and full-color capability (RGB LEDs), enabling graphics and a wider color gamut.
• Improved Efficiency: Newer LED materials and phosphor systems (like those used in white LEDs) offer significantly higher luminous efficacy (lumens per watt), reducing power consumption for the same brightness.
• Integrated Drivers: Many modern display modules come with integrated driver ICs (I2C, SPI interface), simplifying the interface for microcontrollers and reducing the number of required I/O pins.
• Alternative Technologies: For small, low-power numeric displays, segments made with OLED (Organic LED) technology offer ultra-thin profiles, very high contrast, and wide viewing angles, though lifetime and cost considerations vary.

The LTD-323JF represents a reliable, mature solution for applications where its specific form factor, brightness, and simple interface are perfectly adequate, especially in cost-sensitive or long-lifecycle designs.