LTC-561JD LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Red - 2.6V Forward Voltage - Low Power Consumption - English Technical Document

1. Product Overview

The LTC-561JD is a high-performance, triple-digit, seven-segment LED display module. Its primary design focus is enabling clear numeric readouts in applications where power efficiency is a critical concern. The device utilizes advanced AlInGaP (Aluminum Indium Gallium Phosphide) LED chip technology, which is renowned for its high luminous efficiency and excellent color purity, particularly in the red spectrum. This specific material system, grown on a non-transparent GaAs substrate, contributes to the display's high brightness and contrast ratio.

The display features a gray face with white segment markings, a combination chosen to maximize contrast and readability under various lighting conditions. A key innovation of this product is its optimization for low-current operation. The segments are meticulously tested and binned to ensure excellent uniformity and performance even when driven at currents as low as 1 mA per segment. This makes it exceptionally suitable for battery-powered devices, portable instrumentation, and any system where minimizing power draw is essential. The package is lead-free, complying with RoHS environmental directives.

1.1 Key Features and Advantages

• Digit Height: 0.56 inches (14.2 mm), offering a clear and easily readable numeric display.
• Excellent Segment Uniformity: Rigorous testing and binning ensure consistent brightness and color across all segments and digits.
• Low Power Requirement: Specifically engineered to operate efficiently at very low drive currents, extending battery life.
• High Brightness and Contrast: The AlInGaP technology and gray-face/white-segment design deliver superior optical performance.
• Wide Viewing Angle: Provides clear visibility from a broad range of perspectives.
• Solid-State Reliability: LEDs offer long operational life and high resistance to shock and vibration compared to other display technologies.
• Binned for Luminous Intensity: Products are categorized based on measured light output, allowing for precise matching in multi-display applications.
• Lead-Free Package: Manufactured in compliance with RoHS regulations.

1.2 Device Identification and Configuration

The part number LTC-561JD identifies a specific configuration: a multiplexed common anode display with AlInGaP high-efficiency red LEDs. It includes a right-hand decimal point (DP) for each digit. This common anode configuration is typical for multiplexed drives, where the anodes (common for each digit) are switched sequentially while the appropriate segment cathodes are enabled.

2. Technical Parameters: In-Depth Objective Interpretation

2.1 Absolute Maximum Ratings

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

• Power Dissipation per Segment: 70 mW maximum. Exceeding this can lead to overheating and accelerated degradation of the LED chip.
• Peak Forward Current per Segment: 90 mA, but only under pulsed conditions (1/10 duty cycle, 0.1 ms pulse width). This rating is for short-term surges, not continuous operation.
• Continuous Forward Current per Segment: 25 mA at 25°C. This current derates linearly at 0.33 mA/°C as ambient temperature (Ta) 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. This derating is crucial for thermal management.
• Operating & Storage Temperature Range: -35°C to +85°C. The device is rated for industrial temperature ranges.
• Solder Conditions: Wave or reflow soldering should be performed with the body of the display 1/16 inch (approx. 1.6 mm) above the solder wave or reflow profile, for a maximum of 3 seconds at 260°C. The temperature of the LED package itself must not exceed its maximum rating during this process.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C under standardized test conditions.

• Average Luminous Intensity (I_V): 320 to 700 ucd (microcandelas) at a forward current (I_F) of 1 mA. This wide range indicates the device is binned; specific units will fall into a subset of this range. The test at 1 mA highlights its low-current capability.
• Peak Emission Wavelength (λ_p): 656 nm (typical). This is the wavelength at which the optical power output is greatest, characteristic of deep red AlInGaP LEDs.
• Spectral Line Half-Width (Δλ): 22 nm (typical). This measures the spread of the emitted spectrum; a smaller value indicates a more monochromatic (pure color) light.
• Dominant Wavelength (λ_d): 640 nm (typical). This is the single wavelength perceived by the human eye, defining the color. It is slightly shorter than the peak wavelength.
• Forward Voltage per Chip (V_F): 2.1V to 2.6V at I_F=20 mA. Designers must ensure the driving circuit can provide sufficient voltage across this entire range to achieve the desired current. A tolerance of ±0.1V is specified.
• Reverse Current per Segment (I_R): 100 µA maximum at a reverse voltage (V_R) of 5V. Important: This parameter is for test purposes only. The device is not designed for continuous operation under reverse bias, which can cause damage.
• Luminous Intensity Matching Ratio: 2:1 maximum within a similar light output bin at I_F=10 mA. This means the dimmest segment should be no less than half as bright as the brightest segment within the same unit or matched batch, ensuring visual uniformity.
• Cross Talk: ≤2.5%. This refers to unwanted illumination of a segment when an adjacent segment is driven, caused by internal optical or electrical leakage.

3. Binning System Explanation

The LTC-561JD employs a binning system primarily for Luminous Intensity. As noted in the characteristics, the average luminous intensity ranges from 320 to 700 ucd. Units are tested and sorted into specific intensity bins. This allows designers to select displays with consistent brightness levels, which is especially critical when multiple displays are used side-by-side in a single product to avoid noticeable brightness differences (hue unevenness). The datasheet recommends choosing displays from the same bin for multi-unit applications. While not explicitly detailed for this model, binning may also involve forward voltage (V_F) to some degree, given its specified tolerance, ensuring easier current matching in multiplexed or parallel drive scenarios.

4. Mechanical and Package Information

4.1 Package Dimensions and Drawing

The display has a standard dual in-line package (DIP) footprint. Key dimensions include an overall module size of approximately 37.70 mm (length) x 15.24 mm (width). The digit height is 14.22 mm (0.560 inches). The pins are on a 2.54 mm (0.100 inch) pitch, which is the standard spacing for through-hole components. The seating plane is clearly defined, and the drawing includes an 8-degree draft angle on the sides. Pin 1 is typically marked on the package, and the part number, date code, and bin code are also indicated on the top surface.

4.2 Pin Connection and Internal Circuit

The device has a 12-pin configuration. It uses a multiplexed common anode design. The internal circuit diagram shows three common anode pins, one for each digit (Digit 1, Digit 2, Digit 3: pins 12, 9, 8 respectively). The seven segment cathodes (A, B, C, D, E, F, G) and the decimal point (DP) cathode are shared across all digits and connected to their respective pins. Pin 6 is noted as \"No Connection\" (N/C). This pinout is standard for driving the display in a time-division multiplexed manner, where each digit is illuminated in rapid sequence.

5. Performance Curve Analysis

The datasheet references typical performance curves, which are essential for detailed design. While the specific graphs are not fully detailed in the provided text, standard curves for such a device would typically include:

• I-V (Current-Voltage) Curve: Shows the relationship between forward current and forward voltage, highlighting the turn-on voltage (~2V) and the dynamic resistance of the LED.
• Luminous Intensity vs. Forward Current (I_V vs I_F): This curve is crucial for determining the drive current needed to achieve a desired brightness. It is typically linear over a range but may saturate at high currents.
• Luminous Intensity vs. Ambient Temperature (I_V vs T_a): Shows how light output decreases as the junction temperature of the LED increases. This informs thermal design and current derating.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at 656 nm and the spectral half-width of 22 nm.

Designers should consult the full datasheet graphs to optimize efficiency, brightness, and longevity for their specific operating conditions.

6. Soldering, Assembly, and Storage Guidelines

6.1 Soldering

The recommended soldering condition is a maximum of 3 seconds at 260°C, with the display body positioned at least 1.6 mm above the seating plane. This prevents excessive heat from traveling up the pins and damaging the internal LED chips and epoxy. Standard wave or reflow soldering profiles for through-hole components can be used, provided the package temperature limit is not exceeded. Avoid applying mechanical force to the display body during assembly.

6.2 Storage Conditions

For long-term storage, the product should remain in its original packaging. The recommended environmental conditions are a temperature between 5°C and 30°C and a relative humidity below 60% RH. Storing outside these conditions, particularly in high humidity, can lead to oxidation of the tin-plated pins, potentially requiring re-plating before use in automated assembly processes. Condensation should be avoided.

7. Application Suggestions and Design Considerations

7.1 Typical Application Scenarios

• Portable and Battery-Powered Equipment: Multimeters, handheld testers, medical monitors, where low current draw is paramount.
• Industrial Instrumentation: Panel meters, process controllers, timer displays.
• Consumer Electronics: Appliances, audio equipment, fitness equipment displays.
• Automotive Aftermarket Displays: Where wide temperature range and reliability are needed (subject to specific qualification).

7.2 Critical Design Considerations

• Drive Method: Constant current driving is strongly recommended over constant voltage driving. It ensures consistent luminous intensity regardless of variations in forward voltage (V_F) between segments or units and over temperature.
• Current Limiting: The circuit must be designed to limit the current to each segment to a safe value, considering both continuous and peak ratings, and must account for thermal derating at high ambient temperatures.
• Multiplexing Circuitry: For the common anode design, a suitable driver IC (like a multiplexing LED driver or a microcontroller with sufficient current sink/source capability) is required to sequentially enable each digit's anode while sinking current through the desired segment cathodes. The refresh rate must be high enough to avoid perceptible flicker (typically >60 Hz).
• Reverse Voltage Protection: The driving circuit should incorporate protection (e.g., diodes in series or parallel) to prevent the application of reverse bias or voltage transients during power cycling, which can cause metal migration and failure.
• Thermal Management: While the device itself does not have a thermal pad, ensuring adequate airflow and avoiding placement near other heat sources on the PCB will help maintain lower junction temperatures, preserving light output and lifespan.
• Optical Interface: If using a front panel or filter, ensure there is a small air gap and do not let it press directly against the display's surface, especially if a decorative film is applied, as this can cause the film to shift.

8. Technical Comparison and Differentiation

The LTC-561JD's primary differentiation lies in its low-current optimization. Many standard seven-segment displays are characterized at 10 mA or 20 mA. The fact that this device specifies key parameters like luminous intensity at 1 mA and guarantees segment matching at such a low drive level is a significant advantage for power-sensitive designs. Furthermore, the use of AlInGaP technology offers higher efficiency and potentially better color stability over temperature and lifetime compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs. Its common anode, multiplexed pinout is industry-standard, ensuring compatibility with a wide range of driver circuits and microcontrollers.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this display with a 5V microcontroller pin directly?
A: Not directly for constant illumination. The forward voltage is ~2.6V max. A series current-limiting resistor is required. For multiplexing, you will need external transistors to switch the common anodes (which may be at higher current) and likely buffer the segment cathodes, as microcontroller pin current limits are often too low for multiple segments.

Q: What does \"binned for luminous intensity\" mean for my design?
A: It means you can order parts from a specific brightness range. If your design uses multiple displays, ordering from the same bin code ensures they will all have similar brightness, avoiding a patchy appearance. For a single display, any bin within the 320-700 ucd range will work, but brightness will vary.

Q: The max continuous current is 25mA at 25°C. What current should I use for normal operation?
A: For reliability and longevity, it is common practice to drive LEDs below their absolute maximum rating. A typical operating current might be 10-20 mA, depending on the required brightness and thermal environment. Use the I_V vs. I_F curve to select the current that gives your target brightness.

Q: Why is reverse bias so dangerous for LEDs?
A: LEDs are not designed to block reverse voltage like regular diodes. Applying even a moderate reverse voltage (like the 5V test condition) can cause high leakage currents and, over time, lead to electromigration within the semiconductor chip, creating short circuits or increasing leakage permanently.

10. Practical Design and Usage Case

Case: Designing a Low-Power Digital Timer
A designer is creating a battery-operated kitchen timer that must run for months on a single set of AA batteries. The LTC-561JD is selected for its display. The microcontroller operates at 3.3V. The design uses a dedicated LED driver IC with constant current outputs configured for 2 mA per segment. This low current is sufficient for indoor brightness thanks to the display's high efficiency at low current. The driver handles the multiplexing, cycling through the three digits at 200 Hz. The common anode pins are driven by the driver's digit drivers, and the segment pins are connected to its constant current sinks. A Schottky diode is placed in series with the power supply to each common anode to protect against accidental reverse polarity from the driver. The average current consumption for the display is kept below 5 mA, making it ideal for extended battery life.

11. Operating Principle Introduction

A seven-segment LED display is an array of light-emitting diodes arranged in a figure-eight pattern. Each of the seven segments (labeled A through G) is an individual LED (or a series/parallel combination of LED chips). An additional LED is used for the decimal point (DP). In a common anode configuration like the LTC-561JD, the anodes of all LEDs for a single digit are connected together to one common pin. The cathodes of each segment type (A, B, C, etc.) are connected together across all digits. To illuminate a specific segment on a specific digit, the common anode for that digit is connected to a positive supply voltage (through a current-limiting circuit), and the cathode for the desired segment is connected to ground (or a current sink). To display numbers, multiple segments are illuminated simultaneously. To control multiple digits with fewer pins, multiplexing is used: the controller rapidly cycles through each digit, lighting the appropriate segments for that digit only during its time slice. The human eye's persistence of vision blends these rapid flashes into a stable, multi-digit number.

12. Technology Trends and Developments

The trend in display technology, including segmented LED displays, continues towards higher efficiency, lower power consumption, and improved integration. While the core AlInGaP technology for red/orange/yellow is mature, process improvements yield slightly higher efficacy over time. There is a growing emphasis on \"drop-in\" compatibility and driver integration. Some newer displays may incorporate built-in current limiting resistors or even simple logic (like BCD-to-7-segment decoders) to simplify the interface for microcontrollers. Furthermore, the demand for wider color gamuts and new applications (like ultra-low-power IoT devices) pushes for displays that maintain readability in sunlight (high contrast) or offer even lower minimum operating currents. The principles of multiplexing and drive, however, remain fundamentally consistent for this class of component.