LTC-5674JG LED Display Datasheet - 0.52-inch Digit Height - Green Color - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Documentation

1. Product Overview

The LTC-5674JG is a solid-state, triple-digit numeric LED display module. Its primary function is to provide clear, high-visibility numeric readouts in various electronic devices and instrumentation. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) LED chips mounted on a non-transparent GaAs substrate. This material system is known for its high efficiency and excellent color purity in the green spectrum. The device is characterized by a gray faceplate and white segments, which work in conjunction to enhance contrast and readability under different lighting conditions. The display is designed for applications requiring reliable, long-lasting, and energy-efficient numeric indication.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for professional and industrial applications. Its low power requirement is a significant benefit for battery-operated or energy-conscious devices. The excellent character appearance, combined with high brightness and high contrast, ensures legibility from a distance and in various ambient light conditions. The wide viewing angle allows for readability from off-axis positions, which is crucial in multi-user environments or when the display is not directly facing the user. The solid-state construction provides inherent reliability, with no moving parts and high resistance to shock and vibration. The device is categorized for luminous intensity, meaning units are binned and sorted based on their light output, allowing designers to select parts for consistent brightness across a product line. Finally, the lead-free package ensures compliance with modern environmental regulations like RoHS. The target market includes industrial control panels, test and measurement equipment, medical devices, automotive dashboards (for secondary displays), and consumer appliances where clear numeric data presentation is required.

2. Technical Parameter Deep-Dive and Objective Interpretation

This section provides a detailed, objective analysis of the key electrical and optical parameters specified in the datasheet, explaining their significance for design engineers.

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 electrical power that can be converted into heat (and light) by a single segment without causing damage. Exceeding this limit risks overheating the semiconductor junction, leading to reduced lifespan or catastrophic failure. Designers must ensure the driving circuit limits current to keep power dissipation below this value, especially at high ambient temperatures.
• Peak Forward Current Per Segment (60 mA @ 1 kHz, 10% duty cycle): This rating allows for pulsed operation at higher currents than the continuous rating. The 10% duty cycle (on for 10% of the time, off for 90%) and 1 kHz frequency prevent heat buildup. This can be used for multiplexing schemes or for achieving momentary higher brightness. It is critical that the average current over time does not exceed the continuous rating.
• Continuous Forward Current Per Segment (25 mA): The maximum DC current that can be applied to a segment indefinitely under specified conditions (presumably at 25°C). This is the primary parameter for designing constant-current drivers. The derating factor of 0.33 mA/°C above 25°C is crucial. For example, at 85°C, the maximum allowable continuous current would be: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) = 25 mA - 19.8 mA = 5.2 mA. This severe derating highlights the importance of thermal management in high-temperature environments.
• Reverse Voltage Per Segment (5 V): The maximum voltage that can be applied in the reverse direction (cathode positive relative to anode) before the LED junction breaks down. This is a relatively low value, typical for LEDs, emphasizing the need for protection in circuits where reverse voltage transients might occur (e.g., during power-up sequences or in inductive loads).
• Operating & Storage Temperature Range (-35°C to +85°C): Defines the ambient temperature limits for reliable operation and non-operational storage. Performance at temperature extremes will be affected (e.g., luminous intensity drops at high temperatures, forward voltage increases at low temperatures).

2.2 Electrical & Optical Characteristics

These are the typical and guaranteed performance parameters under specified test conditions.

• Average Luminous Intensity Per Segment (I_V): This is the key measure of brightness.
  • Min/Typ/Max: 200 / 577 / 6346 μcd @ I_F=10mA: The wide range from 200 to 6346 μcd indicates a significant binning process. The typical value of 577 μcd is the expected median performance. Designers must use the minimum value (200 μcd) for worst-case brightness calculations to ensure readability under all conditions. The high maximum value shows the potential brightness of selected units.
  • Test Condition Note: Luminous intensity is measured using a sensor filtered to match the CIE photopic (day-adapted) eye response curve (V(λ)). This ensures the measurement correlates with human perception of brightness, not just raw radiant power.
• Forward Voltage Per Segment (V_F): Typ/Max: 2.1 / 2.6 V @ I_F=20mA. This is the voltage drop across the LED when operating. The maximum value of 2.6V is critical for designing the power supply or driver circuitry; it must provide at least this voltage to ensure all units turn on properly. The variation (2.1V to 2.6V) is due to normal semiconductor manufacturing tolerances.
• Peak Emission Wavelength (λ_p): Typ: 571 nm @ I_F=20mA. This is the wavelength at which the LED emits the most optical power. 571 nm is in the green-yellow region of the visible spectrum. This parameter is fixed by the AlInGaP material composition.
• Dominant Wavelength (λ_d): Typ: 572 nm. Slightly different from peak wavelength, this is the single wavelength perceived by the human eye as matching the LED's color. It is the primary determinant of the displayed color.
• Spectral Line Half-Width (Δλ): Typ: 15 nm. This measures the spread of the emitted spectrum. A value of 15 nm indicates a relatively pure, narrowband green color, which is desirable for high color saturation.
• Reverse Current Per Segment (I_R): Max: 100 μA @ V_R=5V. This is the small leakage current that flows when the LED is reverse-biased at its maximum rating. It is generally negligible in circuit design.
• Luminous Intensity Matching Ratio (I_V-m): Max: 2:1 @ I_F=1mA. This is a critical parameter for multi-segment/displays. It guarantees that within a single device, the brightness of the dimmest segment will be no less than half the brightness of the brightest segment (a 2:1 ratio). This ensures uniform appearance of all digits and segments.

3. Binning System Explanation

The datasheet explicitly states the device is \"categorized for luminous intensity.\" This implies a binning process where manufactured units are tested and sorted into different groups (bins) based on their measured light output at a standard test current (likely 10mA or 20mA).

• Purpose: To provide designers with predictable and consistent brightness levels. By purchasing parts from a specific bin, an engineer can ensure that all displays in a production run have similar brightness, avoiding noticeable variations between units in a product.
• Evidence in Datasheet: The very wide range specified for Luminous Intensity (200 to 6346 μcd) strongly suggests this is the total spread across all bins. A specific order code or suffix (not detailed in this excerpt) would typically indicate the bin grade.
• Design Implication: For applications where brightness consistency is paramount (e.g., instrumentation panels), the designer must specify the required bin when ordering. Using a random mix of bins could lead to unacceptable brightness variation.

4. Performance Curve Analysis

While the provided PDF excerpt mentions \"Typical Electrical / Optical Characteristic Curves,\" the specific graphs are not included in the text. Based on standard LED behavior, we can infer the likely content and its importance.

4.1 Inferred Curve Information

• Forward Current (I_F) vs. Forward Voltage (V_F) Curve: This graph would show the exponential relationship typical of a diode. It helps designers understand the dynamic resistance of the LED and the precise voltage required for a given drive current, especially important when using simple resistor-based current limiting.
• Luminous Intensity (I_V) vs. Forward Current (I_F) Curve: This is crucial. It would show how brightness increases with current. It is typically linear over a range but will saturate at very high currents due to thermal effects and efficiency droop. This curve allows designers to trade off between brightness and power consumption/heat generation.
• Luminous Intensity (I_V) vs. Ambient Temperature Curve: This graph would quantify the brightness reduction as temperature increases. AlInGaP LEDs generally have better high-temperature performance than older technologies like GaP, but brightness still decreases. This data is essential for designing systems that operate reliably over the full temperature range.
• Relative Intensity vs. Wavelength (Spectrum) Curve: This would visually depict the narrow emission peak around 571-572 nm with the 15 nm half-width, confirming the color purity.

Importance: These curves provide dynamic performance data that the static tables cannot. They enable predictive modeling of the display's behavior under real-world, non-standard operating conditions.

5. Mechanical and Packaging Information

5.1 Physical Dimensions

The datasheet includes a \"PACKAGE DIMENSIONS\" diagram (details not in text). Key features of a typical 0.52-inch triple-digit display include the overall length, width, and height, the digit height (13.2mm), the segment width, and the spacing between digits. The seating plane and lead positions are defined. All dimensions have a tolerance of ±0.25 mm unless otherwise noted, which is standard for this type of component and must be accounted for in PCB footprint design and panel cutouts.

5.2 Pin Connection and Internal Circuit

The device has a common anode configuration. This means the anodes of all LEDs for a given digit are connected together internally. The pinout table is essential:

• Digits: Common anodes for Digit 1, 2, and 3 are available on pins 12, 13, 27, 28, 29 (note: pins 13 & 28 both for Digit 2; 12 & 29 both for Digit 1; 27 for Digit 3). This duplication provides layout flexibility.
• Segments: Individual cathodes for segments A through G are on pins 23, 16, 17, 18, 22, 21, 20 respectively.
• Decimal Points: Three separate cathode pins for the decimal point of each digit (DP1, DP2, DP3) on pins 26, 19/10, 24. Pin 19 and 10 are both connected to DP for Digit 2.
• No Connection (NC) Pins: Several pins (1-11, 15, 30) are marked \"NO CONNECTION.\" These have no internal electrical connection and can be left floating or used for mechanical stability during soldering.
• Internal Circuit Diagram: This would show the common anode for each digit connected to its pin(s), with each segment LED cathode connected to its respective pin. Understanding this is vital for designing the multiplexing driver circuit.

6. Soldering and Assembly Guidelines

The datasheet specifies a single soldering condition: 1/16 inch (approximately 1.6mm) below the seating plane for 3 seconds at 260°C.

• Interpretation: This is a wave soldering or hand soldering guideline. It indicates the leads can withstand immersion in solder at 260°C for a short duration. The \"below seating plane\" instruction prevents solder wicking up the lead too far, which could cause thermal or mechanical stress on the package.
• Reflow Soldering: The datasheet does not provide a reflow profile. For modern SMT assembly (though this appears to be a through-hole device), a standard lead-free reflow profile with a peak temperature around 245-260°C would likely be acceptable, but the maximum package body temperature must be monitored to stay within the storage temperature limit (85°C).
• General Precautions:
  • Avoid excessive mechanical stress on the leads during insertion.
  • Use appropriate flux and ensure complete cleaning if required to prevent corrosion.
  • Do not exceed the specified soldering time and temperature to avoid damaging the internal wire bonds or the LED chips.
• Storage Conditions: Store in the specified range of -35°C to +85°C, in a dry environment to prevent moisture absorption which could cause \"popcorning\" during soldering.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

• Industrial Control Panels: For displaying setpoints, process values (temperature, pressure, count), timer readouts.
• Test & Measurement Equipment: Digital multimeters, frequency counters, power supplies, oscilloscopes (for secondary readouts).
• Medical Devices: Patient monitors (for non-critical parameters), infusion pumps, diagnostic equipment.
• Automotive Aftermarket/Secondary Displays: Trip computers, boost gauges, voltage monitors.
• Consumer/Commercial Appliances: Microwave ovens, coffee makers, fitness equipment, point-of-sale terminals.

7.2 Critical Design Considerations

• Current Limiting: LEDs are current-driven devices. Always use a current-limiting resistor or a constant-current driver circuit. Calculate the resistor value using the maximum forward voltage (2.6V) and the desired current (≤25 mA derated for temperature) from your supply voltage (V_supply): R = (V_supply - V_{F_max}) / I_F.
• Multiplexing Drive: For a multi-digit common anode display, multiplexing is the standard driving technique. A microcontroller sequentially turns on one digit's common anode at a time while applying the cathode pattern for that digit's number. The refresh rate must be high enough (typically >60 Hz) to avoid visible flicker.
  • Current Calculation: In multiplexing, since each digit is only on for a fraction of the time (1/3 for a 3-digit display), the instantaneous segment current can be higher to achieve the same average brightness. If you want an average current of 10 mA per segment, and you have 3 digits multiplexed with equal duty cycle, you could use a peak instantaneous current of 30 mA. This must still respect the peak forward current rating (60 mA under pulsed conditions).
• Thermal Management: Consider the power dissipation (70 mW per segment max). If driving multiple segments in a digit continuously, the heat can add up. Ensure adequate airflow or heatsinking if operating near maximum ratings, especially in high ambient temperatures. Remember the current derating rule.
• Viewing Angle: Position the display so the intended viewing axis aligns with the device's optimal viewing angle (typically perpendicular to the face).
• ESD Protection: While not explicitly stated, LEDs are sensitive to electrostatic discharge. Implement standard ESD handling precautions during assembly.

8. Technical Comparison and Differentiation

While a direct comparison with other part numbers is not provided, we can highlight the inherent advantages of the AlInGaP technology used in this display compared to older or alternative technologies:

• vs. Traditional GaP (Gallium Phosphide) Green LEDs: AlInGaP offers significantly higher luminous efficiency, resulting in much brighter displays for the same drive current. It also generally has better high-temperature performance and color stability.
• vs. High-Brightness GaN (Gallium Nitride) Blue/White LEDs with Filters: To produce green light, one could use a blue GaN LED with a phosphor (making white) and a green filter, but this is inherently less efficient than a direct-emitting green LED like AlInGaP, as the filter absorbs most of the light. Direct emission provides purer color and higher efficiency for monochromatic green.
• vs. VFD (Vacuum Fluorescent Display) or LCD with Backlight: This LED display is solid-state, more rugged, has a wider operating temperature range, and requires simpler, lower-voltage DC drive electronics compared to VFDs (which need high voltage). Compared to LCDs, it offers superior viewing angles, brightness, and performance in low-temperature environments, though it consumes more power for multi-segment displays and is limited to emitting light, not forming arbitrary graphics.

9. Frequently Asked Questions (Based on Technical Parameters)

1. Q: Can I drive this display directly from a 5V microcontroller pin? A: No. A microcontroller pin typically sources/sinks 20-25mA max and is at 5V (or 3.3V). The LED forward voltage is ~2.1-2.6V. You must use a current-limiting resistor. For a 5V supply and targeting 20mA: R = (5V - 2.6V) / 0.020A = 120Ω. The MCU pin may not be able to source 20mA continuously; use a transistor or driver IC.
2. Q: Why is the luminous intensity range so large (200 to 6346 μcd)? A: This reflects the binning process. Units are sorted after production. You will purchase from a specific bin (e.g., a 1000-2000 μcd bin) to get consistent brightness. The datasheet shows the total possible spread.
3. Q: What does \"common anode\" mean for my circuit design? A: It means you control the display by switching the positive voltage (anode) to each digit on/off, while the microcontroller or driver IC grounds the appropriate cathode pins to light specific segments. This is the opposite of a common cathode display.
4. Q: The derating curve says I can only use 5.2 mA at 85°C. Will my display be too dim? A: Possibly. You must check the Luminous Intensity vs. Current and vs. Temperature curves. At lower current and higher temperature, brightness drops significantly. For high-temperature operation, you may need to select a higher-brightness bin initially or accept a dimmer display. Thermal management to reduce the LED junction temperature is key.
5. Q: How do I connect the decimal points? A: They are separate LEDs with their own cathodes (pins 26, 19/10, 24). Treat them like an extra segment (\"DP\"). To light the decimal on Digit 1, you would ground pin 26 while the anode for Digit 1 is powered.

10. Practical Design and Usage Case Study

Scenario: Designing a 3-digit temperature meter for an industrial oven.

1. Requirements: Display range 0-999°C. Operate in ambient up to 70°C. Must be clearly readable from 2 meters away in a well-lit factory.
2. Component Selection: The LTC-5674JG is suitable due to its temperature range (-35 to +85°C) and high brightness.
3. Brightness Calculation: At 70°C ambient, derate continuous current: 25 mA - ((70-25)*0.33) ≈ 25 - 14.85 = 10.15 mA max continuous. For multiplexing 3 digits, use a 1/3 duty cycle. To achieve a good average brightness, use a peak current of 25 mA (within the 60mA pulsed rating). Average current per segment = 25mA / 3 ≈ 8.3 mA, which is safe for the temperature.
4. Driver Circuit: Use a microcontroller with sufficient I/O pins. Employ 3 NPN transistors (or a P-channel MOSFETs) to switch the 3 common anode pins (Digits 1,2,3) to Vcc. Use current-limiting resistors on each of the 7 segment cathode lines (A-G). The decimal points may not be used. The microcontroller runs a multiplexing routine, turning on one digit transistor at a time and outputting the 7-segment code for that digit.
5. Thermal Consideration: Mount the display on the external panel where some airflow exists. Avoid placing it directly next to a major heat source on the PCB.
6. Result: A reliable, bright display that meets the environmental and readability requirements.

11. Technology Principle Introduction

The LTC-5674JG is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology grown on a GaAs (Gallium Arsenide) substrate. This material system has a direct bandgap corresponding to light emission in the red, orange, yellow, and green regions of the spectrum. The specific color (571-572 nm green) is achieved by precisely controlling the ratios of Aluminum, Indium, Gallium, and Phosphorus during crystal growth. When a forward voltage is applied across the p-n junction, electrons and holes recombine, releasing energy in the form of photons (light). The non-transparent GaAs substrate absorbs some of the emitted light, but modern chip designs and efficient extraction geometries allow for high external quantum efficiency. The \"gray face and white segments\" are part of the plastic package. The gray face (often a dark gray or black) acts as a low-reflectance background to improve contrast. The white segments are light-diffusing areas that sit directly over the tiny LED chips, spreading the point-source light evenly across the segment area to create a uniform, glowing appearance.

LED Specification Terminology

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