LTS-547AJG 0.52-inch AlInGaP Green LED Display Datasheet - Digit Height 13.2mm - Forward Voltage 2.6V - English Technical Document

1. Product Overview

The LTS-547AJG is a high-performance, single-digit, seven-segment alphanumeric display module designed for applications requiring clear, bright numeric indication. Its primary function is to provide a highly legible digital readout. The core technology utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor material for the light-emitting chips, which is known for producing high-efficiency green light. The device features a gray face with white segment markings, optimizing contrast for improved readability under various lighting conditions. It is constructed as a common cathode type display, meaning all the cathodes of the individual LED segments are connected internally to common pins, simplifying the driving circuit design. This display is categorized as a lead-free component, complying with environmental directives such as RoHS.

1.1 Core Advantages and Target Market

The display offers several key advantages that make it suitable for a wide range of industrial and consumer applications. Its high brightness and excellent contrast ratio ensure visibility even in brightly lit environments. The wide viewing angle allows the displayed character to be read from various positions without significant loss of luminance or clarity. The device boasts solid-state reliability, meaning it has no moving parts and is resistant to shock and vibration compared to other display technologies. It features a low power requirement, making it ideal for battery-powered or energy-efficient devices. The continuous, uniform segments provide a clean and professional character appearance. Typical target markets include test and measurement equipment, industrial control panels, medical devices, automotive dashboards (for secondary displays), consumer appliances, and any electronic device requiring a compact, reliable numeric readout.

2. Technical Parameter Deep Dive

This section provides a detailed, objective interpretation of the key electrical and optical parameters specified in the datasheet. Understanding these parameters is crucial for proper circuit design and ensuring long-term reliability.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation at or beyond these limits is not guaranteed and should be avoided.

• Power Dissipation per Segment: 70 mW maximum. This is the maximum power that can be safely dissipated as heat by a single LED segment under continuous operation. Exceeding this can lead to overheating and accelerated degradation of the LED chip.
• Peak Forward Current per Segment: 60 mA maximum, but only under specific pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). This rating is for brief, high-current pulses used in multiplexing schemes, not for continuous DC operation.
• Continuous Forward Current per Segment: 25 mA maximum at 25°C. This is the key parameter for designing the DC drive current. Crucially, this rating derates linearly above 25°C at a rate of 0.33 mA/°C. For example, at an ambient temperature (Ta) of 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 derating is essential for thermal management.
• Reverse Voltage per Segment: 5 V maximum. Applying a reverse bias voltage higher than this can cause breakdown and failure of the LED junction.
• Operating & Storage Temperature Range: -35°C to +105°C. The device can function and be stored within this broad temperature range.
• Solder Temperature: Maximum 260°C for a maximum of 3 seconds, measured 1.6mm below the seating plane. This is critical for wave soldering or reflow processes to prevent damage to the plastic package or internal bonds.

2.2 Electrical & Optical Characteristics

These are the typical operating parameters measured at Ta=25°C and specified test conditions. They define the expected performance of the device.

• Average Luminous Intensity (I_V): 320 μcd (min), 750 μcd (typ) at I_F=1mA. This is a measure of the light output. The wide range indicates a binning process; devices are categorized based on their actual measured intensity.
• Peak Emission Wavelength (λ_p): 571 nm (typ) at I_F=20mA. This is the wavelength at which the emitted light intensity is highest, placing it in the green region of the visible spectrum.
• Spectral Line Half-Width (Δλ): 15 nm (typ). This indicates the spectral purity or the spread of wavelengths emitted. A value of 15nm is typical for an AlInGaP green LED, resulting in a relatively pure green color.
• Dominant Wavelength (λ_d): 572 nm (typ). This is the single wavelength perceived by the human eye that best matches the color of the light emitted, very close to the peak wavelength.
• Forward Voltage per Segment (V_F): 2.05V (min), 2.6V (max) at I_F=20mA. This is the voltage drop across the LED when operating. Designers must ensure the driving circuit can provide sufficient voltage to overcome this drop at the desired current. The variation requires current-limiting, not voltage-limiting, drive methods.
• Reverse Current per Segment (I_R): 100 μA (max) at V_R=5V. This is the small leakage current that flows when the LED is reverse-biased within its maximum rating.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (max). This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device when driven under identical conditions (I_F=1mA). A ratio of 2:1 ensures uniform appearance of the digit.

3. Binning System Explanation

The datasheet indicates that the device is \"Categorized for Luminous Intensity.\" This refers to a binning or sorting process performed during manufacturing. Due to inherent variations in the semiconductor epitaxial growth and chip fabrication process, LEDs from the same production batch can have slightly different optical and electrical characteristics. To ensure consistency for the end user, manufacturers test and sort (bin) the LEDs into groups with closely matched parameters. For the LTS-547AJG, the primary binned parameter is Luminous Intensity, as evidenced by the Min (320 μcd) and Typ (750 μcd) values. Devices are tested at the standard condition (I_F=1mA) and grouped into intensity bins. Customers may be able to order specific bins for applications requiring tight brightness matching across multiple displays. The forward voltage (V_F) also has a specified range (2.05V to 2.6V), which may involve secondary binning or is guaranteed as a maximum/minimum specification.

4. Performance Curve Analysis

While the provided PDF excerpt mentions \"Typical Electrical / Optical Characteristic Curves\" on the final page, the specific curves are not included in the provided text. Typically, such a datasheet would include graphs that are essential for in-depth design analysis. Based on standard LED datasheet conventions, the following curves would be expected and their analysis is provided:

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

This graph shows the relationship between the current flowing through the LED and the voltage across it. For an LED, this is an exponential curve. The \"knee\" voltage is where current begins to increase significantly—this is close to the typical V_F of 2.6V at 20mA. The curve demonstrates why LEDs must be driven with a current-limited source; a small increase in voltage beyond the knee results in a large, potentially destructive, increase in current. The curve's slope also relates to the dynamic resistance of the LED.

4.2 Luminous Intensity vs. Forward Current

This plot shows how light output (intensity) increases with drive current. For AlInGaP LEDs, the relationship is generally linear over a moderate current range but can sub-linear at very high currents due to efficiency droop (heating and other non-radiative effects). This curve helps designers choose an operating current that delivers the required brightness without excessively stressing the LED or reducing its efficiency.

4.3 Relative Luminous Intensity vs. Ambient Temperature

This is one of the most critical curves for reliability. It shows how the light output decreases as the ambient (or junction) temperature increases. AlInGaP LEDs are particularly sensitive to temperature, with output dropping significantly as temperature rises. This curve, combined with the current derating specification, informs thermal management decisions. If the display is used in a hot environment, both the current may need to be reduced (derating) and the expected brightness will be lower.

4.4 Spectral Distribution

A graph plotting relative intensity against wavelength. It would show a peak around 571-572 nm with a characteristic width (the 15 nm half-width). This curve confirms the green color point and is important for applications where specific color coordinates are required.

5. Mechanical & Package Information

5.1 Package Dimensions

The device has a standard single-digit seven-segment outline. Key dimensions from the drawing (not fully detailed in text) typically include overall height, width, and depth, digit height (specified as 0.52 inch or 13.2 mm), segment dimensions, and lead (pin) spacing. The notes specify that all dimensions are in millimeters with a standard tolerance of ±0.25 mm unless stated otherwise. A specific note mentions a pin tip shift tolerance of +0.4 mm, which is important for PCB hole placement and wave soldering processes to ensure proper alignment.

5.2 Pinout and Polarity Identification

The display has 10 pins on a 0.1-inch (2.54 mm) pitch, arranged in two rows. The pin connection table is provided:

• Pin 1: Anode for segment E
• Pin 2: Anode for segment D
• Pin 3: Common Cathode 1
• Pin 4: Anode for segment C
• Pin 5: Anode for Decimal Point (D.P.)
• Pin 6: Anode for segment B
• Pin 7: Anode for segment A
• Pin 8: Common Cathode 2
• Pin 9: Anode for segment F
• Pin 10: Anode for segment G

The device uses a common cathode configuration. There are two common cathode pins (3 and 8), which are internally connected. This allows for flexibility in PCB routing and can help distribute current. To illuminate a segment, its corresponding anode pin must be driven to a positive voltage relative to the common cathode(s), which must be connected to ground (or a lower voltage). The decimal point is a separate LED with its own anode (pin 5).

5.3 Internal Circuit Diagram

The schematic provided in the datasheet visually confirms the common cathode architecture. It shows eight independent LED chips (segments A-G plus the decimal point). All cathodes (negative sides) are tied together and brought out to pins 3 and 8. Each anode (positive side) is brought out to its respective pin. This diagram is essential for understanding how to interface the display with a microcontroller or driver IC.

6. Soldering & Assembly Guidelines

Adherence to these guidelines is critical to prevent damage during the PCB assembly process.

• Soldering Method: The device is suitable for wave soldering or reflow soldering processes.
• Temperature Profile: The absolute maximum solder temperature is 260°C. This temperature must not be exceeded at the lead/solder joint interface. For reflow, the standard profile for lead-free assemblies (peak temp ~245-250°C) is appropriate, but the time above liquidus must be controlled.
• Exposure Time: The maximum exposure time at the peak temperature is 3 seconds. Prolonged exposure can melt the plastic package or damage the internal wire bonds.
• Measurement Point: The temperature is measured 1.6 mm below the seating plane (the point where the lead exits the plastic body). This is often cooler than the PCB pad temperature.
• Cleaning: If cleaning is required, use solvents that are compatible with the LED's plastic package material to avoid cracking or clouding.
• Handling: Avoid mechanical stress on the leads. Use proper ESD (Electrostatic Discharge) precautions during handling and assembly.
• Storage Conditions: Store in a dry, anti-static environment within the specified temperature range (-35°C to +105°C). Avoid exposure to excessive moisture; if the devices are stored in high-humidity environments, baking may be required before soldering to prevent \"popcorning\" during reflow.

7. Application Suggestions

7.1 Typical Application Circuits

The LTS-547AJG requires an external current-limiting mechanism. The simplest drive method uses a microcontroller GPIO pin connected to the segment anode through a current-limiting resistor, with the common cathode connected to ground. The resistor value is calculated using R = (V_supply - V_F) / I_F. For a 5V supply and a desired I_F of 20mA with a typical V_F of 2.6V: R = (5 - 2.6) / 0.02 = 120 Ω. A 120Ω resistor would be used. For multiplexing multiple digits, dedicated driver ICs (like the MAX7219 or TM1637) or transistor arrays are used to sink the higher combined cathode current.

7.2 Design Considerations

• Current Limiting: Always use series resistors or constant-current drivers. Never connect an LED directly to a voltage source.
• Multiplexing: When driving multiple digits, the peak pulsed current rating (60mA at 1/10 duty) can be used for the segment anodes, but the average current per segment must not exceed the continuous DC rating when averaged over time.
• Heat Dissipation: Consider the operating environment. If the display is in an enclosed space or a high ambient temperature, derate the operating current accordingly using the 0.33 mA/°C rule to ensure longevity.
• Viewing Angle: The wide viewing angle is an advantage, but for optimal readability, position the display so the typical viewer's line of sight is roughly perpendicular to the face.
• PCB Layout: Ensure the footprint matches the dimensional drawing. The two common cathode pins can be tied together on the PCB to reduce trace resistance and improve current distribution.

8. Technical Comparison & Differentiation

Compared to other seven-segment display technologies, the LTS-547AJG offers specific advantages:

• vs. Red GaAsP or GaP LEDs: AlInGaP technology offers significantly higher luminous efficiency, resulting in brighter displays for the same drive current. Green light (around 570nm) is also near the peak sensitivity of the human photopic vision curve, making it appear subjectively brighter than red at the same radiant power.
• vs. LCD Displays: LEDs are emissive (produce their own light), making them clearly visible in darkness without a backlight. They have a much faster response time, wider operating temperature range, and are not susceptible to image retention or slow response in cold temperatures.
• vs. VFD (Vacuum Fluorescent Displays): LEDs are more rugged, require much lower operating voltages (3-5V vs. 20-50V for VFDs), and have a simpler drive circuitry. They also do not require filament power.
• Within AlInGaP Displays: The LTS-547AJG's key differentiators are its specific 0.52\" digit height, common cathode configuration, gray face/white segment design for contrast, and its guaranteed categorization for luminous intensity, providing a level of brightness consistency.

9. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this display with 3.3V logic?
A: Yes, but you must check the forward voltage. With a typical V_F of 2.6V, there is only 0.7V headroom (3.3V - 2.6V). A current-limiting resistor would be very small: R = (3.3 - 2.6)/0.02 = 35 Ω. At low currents (e.g., 5mA), it works fine. For full brightness at 20mA, ensure your 3.3V rail is stable and can supply the current. A constant-current driver is recommended for 3.3V systems.

Q2: Why are there two common cathode pins?
A: Two pins are used to distribute the total cathode current, which can be the sum of up to 8 segments (if all are on). This reduces current density in a single pin/PCB trace, improves reliability, and provides layout flexibility.

Q3: How do I calculate the power consumption of the display?
A: For one segment: P = V_F * I_F. At typical 20mA and 2.6V, P_segment = 52 mW. For the entire digit with all 7 segments on (no decimal), P_total ≈ 7 * 52 mW = 364 mW. Always ensure this is below the total package dissipation capability, considering thermal derating.

Q4: What does \"lead-free package\" mean for my assembly process?
A: The device's leads are plated with a finish compatible with lead-free soldering (e.g., tin-silver-copper). You must use lead-free solder paste and a corresponding higher-temperature reflow profile (peak ~245-250°C) during assembly.

10. Practical Design Case Study

Scenario: Designing a simple digital thermometer for an indoor/outdoor weather station. The unit must display temperatures from -35°C to 105°C (matching the display's operating range). It will be battery-powered for portability.

Design Choices:
1. Display Selection: The LTS-547AJG is suitable due to its wide temperature range, high brightness (readable outdoors), and low power requirement (important for battery life). The green color is easy on the eyes.
2. Drive Circuit: Use a low-power microcontroller (e.g., an ARM Cortex-M0+ or PIC) in sleep mode most of the time, waking up to update the display. To save power and pins, use a dedicated LED driver IC with built-in multiplexing and constant-current outputs. This allows driving multiple digits (for tens and ones place) efficiently.
3. Current Setting: For indoor use, set the segment current to 5-10 mA to conserve battery. For outdoor use in bright light, a button could temporarily increase the current to 15-20 mA for maximum brightness. The driver IC's current setting must be programmed accordingly.
4. Thermal Consideration: If the unit is placed in direct sunlight, the internal temperature could exceed 50°C. According to the derating formula, at 50°C, the max continuous current is 25 mA - ((50-25)*0.33) = 25 - 8.25 = 16.75 mA. Our maximum setting of 20mA would exceed this, so the design should limit the \"high brightness\" mode to a duty cycle or pulse width that keeps the average current within the derated limit at high ambient temperatures.

11. Technology Introduction

The LTS-547AJG is based on AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology. This material system is grown epitaxially on a non-transparent GaAs (Gallium Arsenide) substrate. AlInGaP is a direct bandgap semiconductor whose bandgap energy can be tuned by varying the ratios of Aluminum, Indium, Gallium, and Phosphorus. For green emission around 570-580 nm, specific compositions are used. The non-transparent GaAs substrate absorbs some of the generated light, which is a drawback compared to devices using transparent substrates (like GaP for some older green LEDs). However, modern AlInGaP-on-GaAs processes achieve very high internal quantum efficiency, and the light is primarily emitted from the top surface of the chip. The gray face and white segments of the package are not part of the semiconductor; they are part of the plastic molding. The gray face reduces ambient light reflection, while the white segments diffuse and scatter the green light from the underlying LED chip, creating a uniform, bright segment appearance.

12. Technology Trends

The field of LED displays continues to evolve. For discrete seven-segment displays like the LTS-547AJG, trends focus on increased efficiency, higher brightness, and broader color gamuts. While AlInGaP dominates the high-efficiency red, orange, amber, and green spectrum, newer materials like InGaN (Indium Gallium Nitride) are now capable of producing efficient green and even yellow LEDs, potentially offering different color points and efficiency characteristics. There is also a trend towards higher integration, such as displays with built-in controllers (I2C or SPI interfaces) that drastically simplify the microcontroller interface. Furthermore, the demand for ever-lower power consumption drives the development of LEDs that deliver usable brightness at currents below 1 mA for ultra-low-power IoT devices. Environmental regulations continue to push for the elimination of hazardous substances beyond lead, influencing plating and packaging materials.