LTS-4817SKR-P LED Display Datasheet - 0.39-inch Digit Height - Super Red - 2.6V Forward Voltage - English Technical Document

1. Product Overview

The LTS-4817SKR-P is a surface-mount device (SMD) designed as a single-digit numeric display. Its core function is to provide clear, bright numeric readouts in various electronic applications. The device utilizes AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology on a GaAs substrate to produce its characteristic Super Red color. This material choice is key to achieving high brightness and efficiency within the red spectrum. The display features a gray face with white segments, a combination engineered to maximize contrast and readability, especially in ambient light conditions. It is specifically designed to be suitable for reverse mount assembly processes, offering flexibility in PCB design and final product aesthetics.

1.1 Key Features and Advantages

• Digit Size: Features a 0.39-inch (10.0 mm) digit height, offering a balance between visibility and board space efficiency.
• Segment Quality: Provides continuous, uniform segments for consistent character appearance without gaps or irregularities.
• Power Efficiency: Designed for low power requirement, making it suitable for battery-powered or energy-conscious applications.
• Optical Performance: Delivers high brightness and high contrast, ensuring excellent legibility. The wide viewing angle maintains visibility from various perspectives.
• Reliability: Benefits from solid-state reliability with no moving parts, leading to long operational life.
• Binning: Devices are categorized (binned) for luminous intensity, allowing for consistent brightness matching in multi-digit displays.
• Compliance: The package is lead-free, manufactured in accordance with RoHS (Restriction of Hazardous Substances) directives.

1.2 Device Identification

The part number LTS-4817SKR-P decodes the device's key attributes: a single-digit display with Super Red emission, common anode configuration, and a right-hand decimal point. This specific configuration is critical for proper circuit design and pin mapping.

2. Technical Specifications Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the limits beyond which permanent damage to the device may occur. Operating the device continuously at or near these limits is not recommended.

• Power Dissipation per Segment: 70 mW maximum.
• Peak Forward Current per Segment: 90 mA (under pulsed conditions: 1/10 duty cycle, 0.1ms pulse width).
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly at 0.28 mA/°C as ambient temperature increases above 25°C.
• Temperature Range: Operating and storage temperature range is -35°C to +105°C.
• Soldering Tolerance: Can withstand iron soldering at 260°C for 3 seconds, measured 1/16 inch below the seating plane.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured at an ambient temperature (Ta) of 25°C.

• Luminous Intensity (I_V): Ranges from 500 µcd (min) to 1600 µcd (typ) at a forward current (I_F) of 1 mA. At I_F=10 mA, the typical intensity is 20,800 µcd. Intensity is measured using a filter matching the CIE photopic eye-response curve.
• Wavelength: Peak emission wavelength (λ_p) is 639 nm (typ). Dominant wavelength (λ_d) is 631 nm (typ). The spectral line half-width (Δλ) is 20 nm (typ). These define the pure red color output.
• Forward Voltage (V_F): Per LED chip, typically 2.6V with a maximum of 2.6V at I_F=20 mA. The minimum is 2.05V.
• Reverse Current (I_R): Maximum 100 µA at a reverse voltage (V_R) of 5V. This parameter is for test purposes only; the device is not intended for continuous reverse bias operation.
• Intensity Matching Ratio: The ratio of luminous intensity between segments in similar light areas is 2:1 maximum at I_F=1 mA, ensuring uniform appearance.
• Crosstalk: Specified to be ≤ 2.5%, minimizing unwanted light leakage between adjacent segments.

2.3 Binning System Explanation

The datasheet indicates the devices are \"categorized for luminous intensity.\" This means the LEDs are tested and sorted (binned) based on their measured light output at a standard test current. This process ensures that when multiple digits are used in a single display (like a clock or meter), all digits will have a consistent brightness level, preventing one digit from appearing noticeably dimmer or brighter than its neighbors. Designers can specify a bin code to guarantee this uniformity.

3. Performance Curve Analysis

The datasheet references typical performance curves which graphically represent the relationship between key parameters. While the specific graphs are not detailed in the provided text, standard curves for such a device would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship, crucial for designing current-limiting circuitry.
• Luminous Intensity vs. Forward Current: Demonstrates how light output increases with current, up to the maximum rated limits.
• Luminous Intensity vs. Ambient Temperature: Illustrates the decrease in light output as the junction temperature rises, highlighting the importance of thermal management.
• Spectral Power Distribution: A graph showing the relative intensity of light emitted across different wavelengths, centering around the 639 nm peak.

These curves allow engineers to predict device behavior under non-standard conditions (different currents, temperatures) and optimize their design for performance and reliability.

4. Mechanical and Package Information

4.1 Package Dimensions

The device has specific physical dimensions with a tolerance of ±0.25 mm unless otherwise noted. Key dimensional notes include limits on foreign material within segments (≤10 mil), surface ink contamination (≥20 mils), bubbles in segments (≤10 mil), bending of the reflector (≤1% of its length), and maximum plastic pin burr (0.14 mm). A detailed dimensioned drawing is essential for creating the PCB footprint.

4.2 Internal Circuit and Pinout

The display has a common anode configuration. The internal circuit diagram shows ten pins connecting to the anodes and cathodes of the seven segments (A-G) and the decimal point (DP).

Pin Connection Table:

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

Pin 3 and Pin 8 are both connected to the common anode internally. This dual-anode pin design helps in current distribution and thermal management.

4.3 Recommended Soldering Pattern

The datasheet provides two distinct PCB land pattern (footprint) designs: one for normal mounting and one for reverse mounting. The reverse mount pattern includes a cutout in the PCB. Using the correct pattern is critical for proper solder joint formation, mechanical stability, and achieving the intended visual effect (flush mounting for reverse mount).

5. Soldering and Assembly Guidelines

5.1 SMT Soldering Instructions

The device is intended for surface-mount technology (SMT) assembly. Critical instructions include:

• Reflow Soldering (Primary Method): Maximum of two reflow cycles. A cooling period to normal temperature is required between cycles.
  • Pre-heat: 120–150°C
  • Pre-heat Time: 120 seconds maximum
  • Peak Temperature: 260°C maximum
  • Time Above Liquidus: 5 seconds maximum
• Hand Soldering (Iron): Should be limited to one-time repair. Maximum iron temperature is 300°C with a maximum soldering time of 3 seconds per joint.

Exceeding these thermal profiles or cycle counts can damage the plastic package or the internal LED die.

5.2 Moisture Sensitivity and Storage

The SMD displays are shipped in moisture-proof packaging. They must be stored at ≤30°C and ≤60% Relative Humidity (RH). Once the sealed bag is opened, the components begin to absorb moisture from the air. If the parts are not used immediately and are not stored in a controlled dry environment (e.g., a dry cabinet), they must be baked before the reflow soldering process to prevent \"popcorning\" or package cracking caused by rapid vapor expansion during heating.

Baking Conditions (only once):

• Parts in Reel: 60°C for ≥48 hours.
• Parts in Bulk: 100°C for ≥4 hours or 125°C for ≥2 hours.

6. Packaging and Ordering Information

6.1 Packing Specifications

The device is supplied on tape-and-reel for automated pick-and-place assembly. The datasheet details dimensions for both the packing reel and the carrier tape.

• Reel Dimensions: Provided for standard reel sizes.
• Carrier Tape Dimensions: Separate specifications are given for normal mount and reverse mount devices, reflecting their different orientations in the tape. Key tape specifications include cumulative pitch tolerance, camber limits, and compliance with EIA-481-C standards.
• Quantities: A standard 13-inch reel contains 800 pieces. The minimum order quantity for remnants is 200 pieces.
• Leader/Trailer Tape: The reel includes a leader (minimum 400 mm) and trailer (minimum 40 mm) for machine handling.

6.2 Labeling and Traceability

The carrier tape includes markings for Part Number, Date Code, and Bin Code, providing full traceability for manufacturing and quality control purposes.

7. Application Notes and Design Considerations

7.1 Typical Application Scenarios

The LTS-4817SKR-P is ideal for applications requiring a bright, reliable, single-digit numeric display in a compact SMD format. Common uses include:

• Consumer electronics: digital scales, kitchen timers, audio equipment displays.
• Industrial equipment: panel meters, instrument readouts, control system status indicators.
• Automotive aftermarket: gauge clusters, trip computers.
• Medical devices: portable monitors where low power and high contrast are key.
• Appliances: microwave ovens, washing machines, thermostats (especially with reverse mount for a sleek, integrated look).

7.2 Critical Design Considerations

• Current Limiting: LEDs are current-driven devices. A series current-limiting resistor or constant-current driver circuit is mandatory for each segment or common anode to prevent exceeding the maximum continuous forward current, especially considering the derating with temperature.
• Thermal Management: While power dissipation is low per segment, the combined heat from multiple segments in a multi-digit design or operation in high ambient temperatures must be considered. Adequate PCB copper area and ventilation help maintain junction temperature within safe limits.
• Reverse Mount Aesthetics: When using the reverse mount option, ensure the PCB cutout is precisely machined and the recommended land pattern is followed to achieve a clean, flush appearance with the front panel.
• ESD Protection: Although not explicitly stated in this datasheet, AlInGaP LEDs can be sensitive to electrostatic discharge (ESD). Standard ESD handling precautions should be observed during assembly.

8. Technical Comparison and Differentiation

The LTS-4817SKR-P differentiates itself through several key attributes:

• Material Technology (AlInGaP): Compared to older technologies like GaAsP, AlInGaP offers significantly higher luminous efficiency and better temperature stability for red and amber colors, resulting in brighter displays with more consistent color over temperature and lifetime.
• Reverse Mount Capability: Not all SMD LED displays are designed or characterized for reverse mounting. This device's specified mechanical tolerances and provided footprint make it a reliable choice for this design approach.
• Intensity Binning: The guaranteed intensity matching (2:1 ratio) is a critical feature for multi-digit displays, eliminating the brightness mismatch that can occur with unbinned parts.
• Wide Viewing Angle & High Contrast: The combination of the chip technology, gray face, and white segments is engineered to provide superior readability from wide angles compared to displays with different color combinations.

9. Frequently Asked Questions (FAQ)

Q1: What is the difference between \"peak wavelength\" and \"dominant wavelength\"?
A1: Peak wavelength (λ_p) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λ_d) is the single wavelength of monochromatic light that matches the perceived color of the LED. For a narrow-spectrum red LED like this, they are close (639 nm vs. 631 nm), but λ_d is more relevant to human color perception.

Q2: Why are there two common anode pins (3 and 8)?
A2: Having two anode pins helps distribute the total forward current (which is the sum of all illuminated segments) across two PCB traces and solder joints. This improves current handling, reduces trace heating, and enhances mechanical connection reliability.

Q3: Can I drive this display with a microcontroller pin directly?
A3: No. A typical microcontroller GPIO pin cannot source or sink enough current (25 mA per segment, potentially over 175 mA for all segments if the digit '8' is displayed) and would be damaged. You must use external drivers (like transistor arrays or dedicated LED driver ICs) controlled by the microcontroller.

Q4: What does \"derating linear from 25°C\" mean for continuous forward current?
A4: It means the maximum safe continuous current decreases as temperature increases above 25°C. The derating factor is 0.28 mA/°C. For example, at 50°C ambient, the max current would be: 25 mA - [0.28 mA/°C * (50°C - 25°C)] = 25 mA - 7 mA = 18 mA per segment.

Q5: Is baking always required after opening the bag?
A5: Baking is required only if the components have been exposed to ambient humidity outside the specified storage conditions (≤30°C/60% RH) for a period that allows moisture absorption, and before they undergo reflow soldering. If used immediately or stored in a dry environment, baking may not be necessary. Consult the MSL (Moisture Sensitivity Level) label on the bag for specific exposure time limits.