LTC-5675KG LED Display Datasheet - 0.52-inch Digit Height - AlInGaP Green - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-5675KG is a quadruple-digit, seven-segment alphanumeric display module. Its primary function is to provide clear, high-visibility numeric and limited alphanumeric information in various electronic devices and instrumentation. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) LED chips mounted on a non-transparent GaAs substrate, which is known for producing high-efficiency green light. The display features a gray faceplate with white segment markings, offering excellent contrast for the illuminated green segments. This design is targeted at applications requiring reliable, solid-state numeric readouts with low power consumption and superior visual performance, such as industrial control panels, test equipment, consumer appliances, and instrumentation where multiple digits are needed in a compact form factor.

1.1 Key Features and Advantages

• Digit Size: 0.52-inch (13.2 mm) character height, providing good readability.
• Segment Design: Continuous uniform segments for excellent character appearance and aesthetics.
• Optical Performance: High brightness and high contrast ratio for clear visibility under various lighting conditions.
• Viewing Angle: Wide viewing angle, ensuring the display is legible from off-axis positions.
• Power Efficiency: Low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Reliability: Solid-state reliability with no moving parts, leading to long operational life.
• Quality Control: Devices are categorized for luminous intensity, allowing for consistent brightness matching in multi-digit or multi-unit applications.
• Environmental Compliance: Lead-free package compliant with RoHS (Restriction of Hazardous Substances) directives.

2. Technical Specifications Deep Dive

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

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation outside these limits is not advised.

• Power Dissipation per Segment: 70 mW maximum. This limits the maximum continuous current based on the forward voltage.
• Peak Forward Current per Segment: 60 mA maximum, but only under pulsed conditions (1 kHz, 25% duty cycle). This rating is for multiplexing or brief surge conditions.
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This current derates linearly by 0.33 mA/°C as ambient temperature increases above 25°C. For example, at 85°C, the maximum allowable continuous current would be approximately: 25 mA - ((85°C - 25°C) * 0.33 mA/°C) = 5.2 mA.
• Reverse Voltage per Segment: 5 V maximum. Exceeding this can cause junction breakdown.
• Operating Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Storage Temperature Range: -35°C to +85°C.
• Soldering Conditions: 260°C for 3 seconds, with the stipulation that this is measured 1/16 inch (approx. 1.6mm) below the seating plane of the component. This is a typical reflow profile guideline.

2.2 Electrical & Optical Characteristics (Ta=25°C)

These are the typical operating parameters under specified test conditions.

• Average Luminous Intensity (I_V): This is the key brightness parameter.
  • Minimum: 320 µcd at I_F = 1 mA
  • Typical: 1050 µcd at I_F = 10 mA
  • Maximum: 11550 µcd at I_F = 10 mA. The wide range from min to max indicates the devices are binned (categorized). Designers must select from appropriate bins for uniform brightness.
• Peak Emission Wavelength (λ_p): 571 nm (typical) at I_F=20mA. This is in the green region of the visible spectrum.
• Spectral Line Half-Width (Δλ): 15 nm (typical). This indicates the spectral purity or bandwidth of the emitted green light.
• Dominant Wavelength (λ_d): 572 nm (typical). Slightly different from peak wavelength, this is the single wavelength perceived by the human eye to match the color of the source.
• Forward Voltage per Segment (V_F): 2.1V (min), 2.6V (typical) at I_F=20mA. This is crucial for designing current-limiting circuitry. The driver circuit must supply enough voltage to overcome this V_F.
• Reverse Current per Segment (I_R): 100 µA maximum at V_R=5V. A low value indicates good junction quality.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 maximum for segments within the "similar light area." This means the brightest segment should be no more than twice as bright as the dimmest segment within a single digit or specified group, ensuring visual uniformity.

Note on Measurement: Luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the values correspond to human brightness perception.

3. Binning System Explanation

The datasheet explicitly states the devices are "categorized for luminous intensity." This is a binning process.

• Luminous Intensity Binning: The wide spread in the I_V spec (320 to 11550 µcd at 10mA) implies multiple brightness bins exist. Manufacturers test and sort components into groups (bins) based on their measured output. This allows customers to purchase parts with guaranteed minimum brightness levels (e.g., a bin with I_V > 8000 µcd) for high-brightness applications, or standard bins for cost-sensitive designs. Using binned parts is essential for achieving uniform appearance across multiple displays or digits.
• Wavelength Consistency: While not explicitly stated as binned, the tight typical values for λ_p (571 nm) and λ_d (572 nm) suggest good process control, resulting in consistent green color across production batches.

4. Performance Curve Analysis

The datasheet references "Typical Electrical / Optical Characteristic Curves." While the specific graphs are not provided in the text, we can infer their standard content and importance.

• Forward Current vs. Forward Voltage (I-V Curve): This graph would show the exponential relationship. It is critical for determining the necessary supply voltage for a given drive current and for calculating power dissipation (P = V_F * I_F).
• Luminous Intensity vs. Forward Current: This curve shows how brightness increases with current. It is typically non-linear, with efficiency (lumens per watt) often decreasing at very high currents due to heating. The datasheet provides discrete points at 1mA and 10mA.
• Luminous Intensity vs. Ambient Temperature: For AlInGaP LEDs, light output generally decreases as junction temperature increases. This curve is vital for designing applications that operate over the full temperature range (-35°C to +85°C) to ensure adequate brightness at high temperatures.
• Spectral Distribution: A graph showing relative intensity vs. wavelength, centered around 571-572 nm with a ~15 nm half-width, confirming the green color output.

5. Mechanical and Package Information

5.1 Package Dimensions

The device uses a standard LED display package. The dimensional drawing (referenced but not detailed in text) would typically show:

• Overall length, width, and height of the module.
• Digit-to-digit spacing (pitch).
• Segment dimensions and spacing.
• Lead (pin) spacing, length, and diameter. The note states all dimensions are in millimeters with a general tolerance of ±0.25 mm unless specified otherwise.

5.2 Pin Configuration and Polarity

The LTC-5675KG is a common anode device. This means the anodes of all LEDs for each digit are connected together internally and brought out to a single pin per digit (Pins 10-13: Digit 1-4 Anode). The cathodes for each segment (A-G, DP) are shared across all digits and connected to their respective pins (Pins 27-30, 35-37 for segments A-G; Pins 31-34 for decimal points). This configuration is ideal for multiplexing.

Multiplexing Operation: To display a number, a microcontroller would:

1. Set the pattern of segment cathodes (A-G) for the desired character.
2. Turn ON (apply voltage to) the common anode pin for the specific digit where that character should appear.
3. Sequentially cycle through each digit's anode at a high frequency (e.g., 100Hz+), creating the perception of all digits being lit simultaneously. This greatly reduces the required driver pins and power consumption compared to static drive.

Internal Circuit Diagram: The referenced diagram visually confirms the common anode, multiplexed architecture, showing the four digit anodes and the seven+1 segment cathodes.

6. Soldering and Assembly Guidelines

• Reflow Soldering: The specified condition is 260°C for 3 seconds, measured 1.6mm below the component body. This aligns with typical lead-free reflow profiles (peak temperature 245-260°C).
• Precautions:
  • Avoid mechanical stress on the leads during handling.
  • Ensure the display is not subjected to temperatures exceeding the maximum storage temperature before or after soldering.
  • Follow standard ESD (Electrostatic Discharge) precautions during handling.
• Storage Conditions: Store within the specified temperature range of -35°C to +85°C in a dry environment to prevent moisture absorption, which could cause "popcorning" during reflow.

7. Application Suggestions

7.1 Typical Application Scenarios

• Industrial Instrumentation: Panel meters, process controllers, timer displays.
• Test and Measurement Equipment: Digital multimeters, frequency counters, power supplies.
• Consumer/Commercial Appliances: Microwave ovens, audio equipment, point-of-sale terminals.
• Automotive Aftermarket: Gauges and displays where high brightness is needed for daylight visibility.

7.2 Design Considerations

• Current Limiting: ALWAYS use series current-limiting resistors for each segment cathode or digit anode (depending on drive scheme). The resistor value is calculated as R = (V_supply - V_F) / I_F. For a 5V supply, V_F=2.6V, and I_F=10mA: R = (5 - 2.6) / 0.01 = 240 Ω.
• Multiplexing Driver: Use a microcontroller with sufficient I/O pins or dedicated LED driver ICs (e.g., MAX7219, TM1637) that handle multiplexing and current control. Driver ICs simplify design and often provide brightness control.
• Power Dissipation: Calculate total power, especially when driving all segments of multiple digits simultaneously during multiplexing. Ensure it does not exceed ratings and consider thermal management if operating at high ambient temperatures.
• Brightness Matching: For best visual results, specify a luminous intensity bin from your supplier, especially if using multiple displays.
• Viewing Angle: The wide viewing angle allows flexible mounting, but consider the primary user's sightline during mechanical design.

8. Technical Comparison and Differentiation

Compared to older technologies like standard GaP (Gallium Phosphide) green LEDs or filtered incandescent displays, the AlInGaP technology in the LTC-5675KG offers:

• Higher Efficiency and Brightness: AlInGaP provides superior luminous efficacy, resulting in brighter displays at lower currents.
• Better Color Saturation: The green color is typically more pure and vibrant.
• Improved Reliability: Solid-state LEDs have a much longer lifespan than incandescent or vacuum fluorescent displays (VFDs).
• Lower Power Consumption: Essential for portable and battery-powered devices.
• Compared to some modern blue-chip + phosphor white LEDs used behind filters, AlInGaP green is often more efficient for monochromatic green applications.

9. Frequently Asked Questions (Based on Technical Parameters)

1. Q: What is the difference between "peak wavelength" and "dominant wavelength"?
   A: Peak wavelength is the single wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength is the single wavelength of monochromatic light that would match the perceived color of the source. They are often close but not identical, with dominant wavelength being more relevant for human perception.
2. Q: Can I drive this display with a 3.3V microcontroller without a driver IC?
   A: Possibly, but carefully. The typical V_F is 2.6V at 20mA. At 3.3V, the voltage headroom for the current-limiting resistor is only 0.7V. For a 10mA current, you would need a 70Ω resistor. This is feasible, but variations in V_F and supply voltage could cause significant current variation. A dedicated LED driver or transistor buffer is more robust.
3. Q: Why is the continuous current derated with temperature?
   A: As the LED junction temperature rises, its internal efficiency drops and the risk of thermal runaway increases. Derating the current prevents excessive heat generation, ensuring long-term reliability and preventing brightness degradation or failure.
4. Q: What does "categorized for luminous intensity" mean for my design?
   A: It means you should work with your distributor to select a specific brightness bin (e.g., a minimum I_V value). If you don't, you may receive parts from different bins, leading to noticeable brightness differences between digits or between different units of your product.

10. Design and Usage Case Study

Scenario: Designing a 4-digit DC voltage panel meter.

1. Microcontroller Selection: Choose an MCU with at least 12 digital I/O pins (4 digit anodes + 7 segment cathodes + 1 decimal point) or use an I/O expander.
2. Drive Circuit: Implement multiplexing in firmware. The MCU will cycle through digits 1-4 rapidly. For each digit, it sets the segment pattern on the cathode pins and enables the corresponding anode pin via a small NPN transistor (since the anode current for a fully lit digit '8' could be 8 segments * 10mA = 80mA, exceeding most MCU pin limits).
3. Current Limiting: Place eight 220Ω resistors (one for each segment cathode A-G and DP). This limits current per segment to ~10-11mA with a 5V supply and typical V_F.
4. Brightness Control: Implement software PWM (Pulse Width Modulation) on the digit enable time to globally dim the display if needed.
5. Result: A compact, efficient, and bright display showing voltage readings from 0.000 to 19.99V, with excellent readability in indoor and outdoor lighting conditions due to the high-contrast, high-brightness AlInGaP segments.

11. Technology Principle Introduction

The LTC-5675KG is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology. This material system is grown epitaxially on a non-transparent GaAs (Gallium Arsenide) substrate. When a forward voltage is applied across the p-n junction of the AlInGaP layers, electrons and holes recombine, releasing energy in the form of photons. The specific composition of the Al, In, Ga, and P atoms in the active layer determines the bandgap energy, which directly dictates the wavelength (color) of the emitted light. For this device, the composition is tuned to produce green light centered around 572 nm. The non-transparent substrate means light is primarily emitted from the top surface of the chip, which is suitable for the segment-based display structure. The individual LED chips are wire-bonded and assembled into the standard seven-segment pattern within the plastic package.

12. Technology Trends and Context

AlInGaP technology represents a mature and highly optimized solution for high-efficiency red, orange, amber, and green LEDs. In the display landscape:\p>

• For Monochromatic Displays: AlInGaP remains a top choice for pure green, red, and amber due to its efficiency and color purity, often outperforming blue-chip+phosphor white LEDs filtered to these colors.
• Market Context: While dot-matrix OLEDs and TFT-LCDs dominate in full-color, high-information-content displays, seven-segment LED displays like the LTC-5675KG maintain a strong position in applications requiring simple, very bright, low-cost, reliable, and low-power numeric readouts.
• Future Developments: Trends include further efficiency improvements, even tighter brightness and color binning for high-end applications, and the integration of driver electronics and communication interfaces (like I2C) directly into the display module, simplifying system design. However, the fundamental seven-segment form factor and AlInGaP technology for standard colors are likely to remain relevant for many years in their target applications.