LTC-571JD LED Display Datasheet - 0.56-inch Digit Height - AlInGaP Red - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTC-571JD is a high-performance, triple-digit, seven-segment LED display module designed for applications requiring clear, bright numeric readouts. Its primary function is to provide a visual numeric output in electronic devices such as test equipment, industrial controls, instrumentation panels, and consumer appliances. The core advantage of this device lies in its utilization of advanced AlInGaP (Aluminum Indium Gallium Phosphide) LED chip technology, which offers superior luminous efficiency and color purity compared to traditional materials. This results in the key features highlighted in the datasheet: high brightness, excellent character appearance with continuous uniform segments, high contrast, and a wide viewing angle. The device is categorized for luminous intensity, ensuring consistency in brightness levels across production batches, which is crucial for multi-digit displays where uniformity is paramount. The target market includes designers and manufacturers of professional and industrial electronic equipment where reliability, readability under various lighting conditions, and long operational life are critical requirements.

2. Technical Parameters Deep Dive

2.1 Photometric and Optical Characteristics

The optical performance is central to this display's functionality. The Average Luminous Intensity (Iv) is specified with a minimum of 340 µcd, a typical value of 700 µcd, and no maximum limit under a test condition of a 1mA forward current (IF). This high brightness ensures visibility. The light emitted is in the red spectrum, with a Peak Emission Wavelength (λp) of 656 nm and a Dominant Wavelength (λd) of 640 nm, both measured at IF=20mA. The Spectral Line Half-Width (Δλ) is 22 nm, indicating a relatively pure color emission. It is important to note that the luminous intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the values correspond to human visual perception.

2.2 Electrical Characteristics and Absolute Maximum Ratings

The device's electrical limits define its safe operating area. The Absolute Maximum Ratings must not be exceeded to prevent permanent damage. Key limits include: a Power Dissipation per Segment of 70 mW, a Peak Forward Current per Segment of 110 mA (under pulsed conditions: 1/10 duty cycle, 0.1ms pulse width), and a Continuous Forward Current per Segment of 25 mA at 25°C, derating linearly at 0.33 mA/°C above 25°C. The maximum Reverse Voltage per Segment is 5 V. The Forward Voltage per Segment (VF) has a typical value of 2.6V with a maximum of 2.6V at IF=20mA, while the Reverse Current per Segment (IR) is a maximum of 100 µA at VR=5V. The Luminous Intensity Matching Ratio between segments is specified at a maximum of 2:1, ensuring visual uniformity across the display.

2.3 Thermal and Environmental Specifications

Reliability across temperature is a key feature. The device is rated for an Operating Temperature Range of -35°C to +85°C and an identical Storage Temperature Range. This wide range makes it suitable for harsh environments. For assembly, the maximum Solder Temperature is 260°C for a maximum duration of 3 seconds, measured at 1.6mm below the seating plane, which is a standard guideline for wave or reflow soldering processes to avoid thermal damage to the LED chips or package.

3. Binning System Explanation

The datasheet explicitly states that the device is "Categorized for Luminous Intensity." This indicates the implementation of a binning or sorting system. In LED manufacturing, inherent variations occur. Binning is the process of sorting produced LEDs into groups (bins) based on specific measured parameters like luminous intensity, forward voltage, or dominant wavelength. For the LTC-571JD, the primary binning criterion is luminous intensity. This ensures that customers receive displays where all digits and segments have closely matched brightness levels, preventing one digit from appearing noticeably dimmer or brighter than another in a multi-digit unit. This is critical for aesthetic and functional uniformity in the final product. While the datasheet does not detail the specific bin codes or ranges, the mention of categorization assures the user of this quality control step.

4. Performance Curve Analysis

The datasheet includes a section for "Typical Electrical / Optical Characteristic Curves." These graphs are essential for in-depth design analysis. Although the specific curves are not detailed in the provided text, typical curves for such a device would include: Forward Current vs. Forward Voltage (I-V Curve): This shows the relationship between the current through the LED and the voltage drop across it. It is non-linear, and designers use this to select appropriate current-limiting resistors. Luminous Intensity vs. Forward Current (L-I Curve): This graph shows how light output increases with current. It is generally linear over a range but will saturate at higher currents. Luminous Intensity vs. Ambient Temperature: This curve shows how light output decreases as the junction temperature of the LED increases. Understanding this derating is crucial for designs operating at high ambient temperatures. Spectral Distribution: A plot of relative intensity versus wavelength, showing the shape and purity of the red emission peak around 640-656 nm.

5. Mechanical and Package Information

The mechanical design ensures reliable mounting and electrical connection. The device features a standard package with a digit height of 0.56 inches (14.2 mm). The package dimensions are provided in a detailed drawing with all measurements in millimeters and standard tolerances of ±0.25 mm unless otherwise noted. This allows for precise PCB (Printed Circuit Board) footprint design. The pin connection diagram is critical for correct wiring. The LTC-571JD is a multiplex common cathode type with a right-hand decimal point. The 12-pin assignment is as follows: Pin 1: Anode E, Pin 2: Anode D, Pin 3: Anode D.P. (Decimal Point), Pin 4: Anode C, Pin 5: Anode G, Pin 6: No Connection, Pin 7: Anode B, Pin 8: Common Cathode for Digit 3, Pin 9: Common Cathode for Digit 2, Pin 10: Anode F, Pin 11: Anode A, Pin 12: Common Cathode for Digit 1. The internal circuit diagram shows that each digit's segments share a common cathode connection, which is standard for multiplexed displays to minimize the number of required driver pins.

6. Soldering and Assembly Guidelines

Proper handling is vital for reliability. The key guideline provided is the solder temperature limit: 260°C maximum for 3 seconds at 1.6mm below the seating plane. This is compatible with standard lead-free reflow soldering profiles. Designers should ensure their PCB assembly process adheres to this limit to prevent thermal stress on the LED chips, which can cause reduced light output, color shift, or catastrophic failure. For manual soldering, a temperature-controlled iron should be used with minimal contact time. The device should be stored in the original moisture-barrier bag in a controlled environment (within the specified -35°C to +85°C range) before use to prevent moisture absorption, which can cause "popcorning" during reflow.

7. Packaging and Ordering Information

The part number is LTC-571JD. While specific packaging details (e.g., tape and reel, tube quantities) are not listed in the provided excerpt, standard industry practice for such displays is to ship them in anti-static tubes or trays to protect the pins and face. The "Spec No." DS30-2001-188 and "Effective Date" 06/12/2001 are revision control identifiers. The model naming convention "LTC-571JD" likely follows an internal coding system where "LTC" may denote a display product line, "571" specifies the size and type, and "JD" could indicate color, binning, or other variants.

8. Application Suggestions

8.1 Typical Application Scenarios

This display is ideal for any device requiring a clear, multi-digit numeric readout. Common applications include: digital multimeters and clamp meters, frequency counters, process timers and controllers, power supply unit displays, medical monitoring equipment, automotive diagnostic tools, and point-of-sale terminals. Its high brightness and wide viewing angle make it suitable for applications where the display may be viewed from an angle or under bright ambient light.

8.2 Design Considerations and Circuit Implementation

Designing with the LTC-571JD requires a multiplexing driver circuit due to its common cathode architecture. A microcontroller or dedicated display driver IC (like a MAX7219 or similar) is typically used. The driver sequentially activates each digit's common cathode (pins 8, 9, 12) at a high frequency (e.g., 100Hz-1kHz) while supplying the appropriate segment anode data (pins 1,2,3,4,5,7,10,11) for that digit. This method reduces the number of required I/O pins from (7 segments + 1 DP) * 3 digits = 24 to 7 segments + 1 DP + 3 digits = 11. Current-limiting resistors are mandatory for each segment anode line to set the forward current (e.g., 10-20 mA per segment). The resistor value can be calculated using R = (Vcc - Vf) / If, where Vf is the typical forward voltage (2.6V). For a 5V supply and 15mA target current: R = (5 - 2.6) / 0.015 = 160 ohms. A 150 or 180 ohm resistor would be suitable. Designers must ensure the peak current per segment does not exceed the 110mA pulsed rating and that the average power dissipation per segment, considering the multiplex duty cycle, stays below 70mW.

9. Technical Comparison and Differentiation

The LTC-571JD differentiates itself primarily through its use of AlInGaP LED technology. Compared to older technologies like standard GaAsP (Gallium Arsenide Phosphide) red LEDs, AlInGaP offers significantly higher luminous efficiency. This means it produces more light output (higher brightness) for the same amount of electrical current, or it can achieve the same brightness at a lower current, enhancing power efficiency. The "Hi-Eff. Red" designation underscores this advantage. Furthermore, AlInGaP LEDs generally have better temperature stability and longer lifetime. The "continuous uniform segments" feature indicates a high-quality mask or diffuser design that eliminates gaps or uneven lighting within each segment, providing a professional, high-quality appearance that is superior to displays with visibly segmented or dotted patterns.

10. Frequently Asked Questions (FAQ)

Q: What is the purpose of the "No Connection" pin (Pin 6)?
A: This pin is mechanically present but electrically isolated. It is likely included for mechanical symmetry and stability during the molding process or to maintain a standard pin spacing. It must not be connected to any circuit trace.

Q: How do I calculate the average current per segment in a multiplexed configuration?
A: The average current is the peak current multiplied by the duty cycle. For a 3-digit multiplex with equal time per digit, the duty cycle for each digit is 1/3. If you drive each segment with 20mA when its digit is active, the average current per segment is 20mA * (1/3) ≈ 6.67mA. This average current is used for power dissipation calculations.

Q: Can I drive this display with a constant (non-multiplexed) current?
A: Technically yes, by connecting all common cathodes together and driving each segment anode independently. However, this would require 11 driver lines (8 anodes + 3 cathodes tied together) and is less efficient in terms of component count and microcontroller I/O usage compared to multiplexing. The electrical ratings still apply.

Q: What does "gray face and white segments" mean?
A> This describes the appearance of the display when it is off. The face (background) is gray, which helps improve contrast when the red segments are illuminated. The segments themselves are white, which is the color of the diffusing material or mask through which the red LED light shines, creating a bright red emission when powered.

11. Practical Design and Usage Case

Consider designing a simple 3-digit voltmeter using a microcontroller with an analog-to-digital converter (ADC). The microcontroller reads a voltage (0-5V), converts it to a 3-digit number (0.00 to 5.00), and drives the LTC-571JD. The driver code would implement time-division multiplexing. In a loop, it would: 1) Set the segment pattern for the hundreds digit on the anode ports, then enable the cathode for Digit 1 (pin 12). 2) Wait a short delay (e.g., 2ms). 3) Disable Digit 1, set the segment pattern for the tens digit, and enable the cathode for Digit 2 (pin 9). 4) Repeat for the units/decimal digit using Digit 3 (pin 8) and the decimal point anode (pin 3). The cycle repeats rapidly, creating the illusion of a stable, continuously lit 3-digit number. Proper current-limiting resistors on each anode line, calculated for a peak current of 15-20mA, are essential. This design efficiently uses only a handful of the microcontroller's I/O pins.

12. Technical Principle Introduction

The LTC-571JD is based on solid-state semiconductor light emission. The core component is the AlInGaP LED chip. When a forward voltage exceeding the diode's junction potential (around 2.1-2.6V) is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light). The specific composition of the AlInGaP alloy determines the bandgap energy, which directly corresponds to the wavelength (color) of the emitted light—in this case, red (~640-656 nm). The chips are mounted on a non-transparent GaAs substrate, which helps reflect light outward, improving efficiency. The light from the tiny LED chips passes through a shaped plastic package with a white diffusing material for the segments and a gray filter for the background, creating the recognizable seven-segment numeral shapes. The common cathode multiplexing architecture is an electrical design choice that connects all the LEDs for one digit to a shared negative terminal, allowing individual digit control.

13. Technology Trends and Evolution

While the LTC-571JD represents a mature and reliable technology, the broader field of display technology continues to evolve. The trend in seven-segment displays has been towards higher efficiency and integration. Modern variants may use even more advanced semiconductor materials or chip-scale packaging for slightly better performance or smaller bezels. However, the fundamental multiplexed LED segment display remains highly relevant due to its simplicity, robustness, low cost for numeric-only output, and excellent visibility. The core principles embodied in this datasheet—efficient materials (AlInGaP), careful binning for uniformity, and clear mechanical/electrical specifications—remain the foundation for reliable display component design. For new designs, engineers might also evaluate fully integrated modules with built-in controllers or consider dot-matrix OLEDs for alphanumeric flexibility, but for pure numeric applications requiring high brightness and long life, displays like the LTC-571JD continue to be a optimal and proven solution.