LTD-322JS LED Display Datasheet - 0.3-inch Digit Height - Yellow - 2.6V Forward Voltage - 70mW Power Dissipation - English Technical Document

1. Product Overview

The LTD-322JS is a solid-state numeric display device designed for applications requiring clear, bright, and reliable numerical readouts. It belongs to the category of light-emitting diode (LED) displays, specifically utilizing AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor technology to produce yellow light emission. The primary function of this component is to visually represent numeric digits (0-9) and some alphanumeric characters through individually addressable segments.

Its core application areas include industrial instrumentation, consumer electronics panels, test and measurement equipment, and any embedded system requiring a compact, low-power numeric display. The device is characterized by its 0.3-inch (7.62 mm) digit height, which offers a good balance between readability and board space consumption. The display features a black face with white segments, providing high contrast for optimal character appearance under various lighting conditions.

The underlying technology employs AlInGaP LED chips fabricated on a non-transparent Gallium Arsenide (GaAs) substrate. This material system is known for its high efficiency and stability in producing yellow and amber wavelengths. The device is configured as a duplex common cathode display, meaning it contains two digits (or two independent display units) sharing common cathode connections, which simplifies multiplexing drive circuitry.

2. In-Depth Technical Parameter Analysis

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 for reliable performance.

• Power Dissipation per Segment: 70 mW. This is the maximum allowable power that can be dissipated by a single illuminated segment without causing thermal damage. Exceeding this limit risks degrading the LED's internal quantum well structure and bonding wires.
• Peak Forward Current per Segment: 60 mA. This rating applies under pulsed conditions with a 1/10 duty cycle and a 0.1 ms pulse width. It allows for brief periods of overcurrent to achieve higher instantaneous brightness, useful for multiplexed displays or strobe effects, but must be carefully managed to avoid exceeding the average power rating.
• Continuous Forward Current per Segment: 25 mA at 25°C. This is the maximum DC current recommended for continuous operation. A linear derating factor of 0.33 mA/°C is specified, meaning the allowable continuous current decreases as ambient temperature (Ta) rises above 25°C. For example, at 50°C, the maximum continuous current would be approximately 25 mA - (0.33 mA/°C * 25°C) = 16.75 mA.
• Reverse Voltage per Segment: 5 V. LEDs are diodes and have a relatively low reverse breakdown voltage. Applying a reverse bias greater than 5V can cause avalanche breakdown, potentially destroying the segment.
• Operating & Storage Temperature Range: -35°C to +85°C. This defines the environmental conditions the device can withstand during operation and non-operational storage. Performance within the electrical/optical characteristics table is typically specified at 25°C.
• 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 and internal die bonds.

2.2 Electrical & Optical Characteristics

These parameters are measured under standard test conditions (Ta=25°C) and represent the typical performance of the device.

• Average Luminous Intensity (I_V): 320 μcd (Min), 800 μcd (Typ) at I_F=1mA. Luminous intensity is a measure of the perceived power of light emitted in a particular direction. The wide range (Min to Typ) indicates a binning process. The measurement uses a filter approximating the CIE photopic eye-response curve (V(λ)), ensuring the value correlates with human brightness perception.
• Peak Emission Wavelength (λ_p): 588 nm (Typ) at I_F=20mA. This is the wavelength at which the spectral power distribution of the emitted light reaches its maximum. For AlInGaP yellow LEDs, this typically falls in the 585-595 nm range.
• Spectral Line Half-Width (Δλ): 15 nm (Typ) at I_F=20mA. This parameter, also called Full Width at Half Maximum (FWHM), describes the bandwidth of the emitted spectrum. A value of 15 nm indicates a relatively monochromatic yellow light, which is characteristic of direct-bandgap semiconductors like AlInGaP.
• Dominant Wavelength (λ_d): 587 nm (Typ) at I_F=20mA. Dominant wavelength is the single wavelength perceived by the human eye that best matches the color of the light. It is closely related to, but not always identical to, the peak wavelength.
• Forward Voltage per Segment (V_F): 2.05V (Min), 2.6V (Typ) at I_F=20mA. This is the voltage drop across the LED when conducting the specified current. Designers must ensure the driving circuit can provide sufficient voltage to overcome this drop, plus any drops in series resistors or driver transistors.
• Reverse Current per Segment (I_R): 100 μA (Max) at V_R=5V. This is the leakage current when the diode is reverse-biased at its maximum rated voltage.
• Luminous Intensity Matching Ratio (I_V-m): 2:1 (Max) at I_F=1mA. This specifies the maximum allowable ratio between the brightest and dimmest segment within a single device or between devices from the same batch. A ratio of 2:1 ensures visual uniformity across the display.

3. Binning System Explanation

The datasheet indicates the device is "Categorized for Luminous Intensity." This implies a binning or sorting process based on key performance parameters.

• Luminous Intensity Binning: The specified minimum (320 μcd) and typical (800 μcd) values for I_V suggest products are sorted into different intensity bins. This allows purchasers to select parts suitable for their specific brightness requirements, potentially affecting cost. Designers must account for the minimum value to guarantee visibility in their application.
• Forward Voltage Sorting: While not explicitly stated as a binned parameter, the range given for V_F (2.05V to 2.6V) is typical for production spread. For applications where consistent voltage drop is critical (e.g., battery-powered devices with tight voltage headroom), manufacturers may offer voltage-sorted parts upon request.
• Wavelength Consistency: The tight specifications for λ_p (588 nm Typ) and λ_d (587 nm Typ) indicate good process control, resulting in consistent yellow color across production lots. Significant binning for color is less common for monochromatic LEDs like this yellow type compared to white LEDs.

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 significance.

• Forward Current vs. Forward Voltage (I-V Curve): This graph would show the exponential relationship typical of a diode. For the LTD-322JS, the curve would pass through the point I_F=20mA, V_F=~2.6V. The curve's slope in the operating region helps determine dynamic resistance, important for analog dimming or pulsed operation.
• Luminous Intensity vs. Forward Current (I-L Curve): This plot shows how light output increases with current. For LEDs, it is generally linear over a wide range below saturation. The curve would show intensity at 1mA (for I_V spec) and illustrate the relationship up to the maximum continuous current (25mA).
• Luminous Intensity vs. Ambient Temperature: This curve is crucial for thermal management. The light output of AlInGaP LEDs typically decreases as junction temperature increases. Understanding this derating allows designers to compensate optically or electrically in high-temperature environments.
• Spectral Distribution: A graph showing relative intensity versus wavelength, centered around 588 nm with a FWHM of approximately 15 nm. This confirms the monochromatic nature of the output.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The device's physical outline is defined in a package drawing. All dimensions are in millimeters with a standard tolerance of ±0.25 mm (0.01 inch) unless otherwise noted. Key dimensions typically include the overall length, width, and height of the package, the digit-to-digit spacing (pitch), the segment size and spacing, and the lead (pin) spacing and dimensions. This information is essential for PCB footprint design, ensuring proper fit, and planning for overlays or windows in the end-product enclosure.

5.2 Pin Connection and Polarity

The LTD-322JS has a 10-pin configuration. It is a common cathode type, meaning the cathodes (negative terminals) of the LEDs for each digit are connected together internally.

• Pin 1: Anode G (Segment G)
• Pin 2: No Connection (N/C)
• Pin 3: Anode A (Segment A)
• Pin 4: Anode F (Segment F)
• Pin 5: Common Cathode for Digit 2
• Pin 6: Anode D (Segment D)
• Pin 7: Anode E (Segment E)
• Pin 8: Anode C (Segment C)
• Pin 9: Anode B (Segment B)
• Pin 10: Common Cathode for Digit 1

The internal circuit diagram shows the standard 7-segment plus decimal point (DP) layout for each digit, with individual anodes for each segment and common cathodes for each digit. This configuration is ideal for multiplexing.

6. Soldering & Assembly Guidelines

Adherence to the specified soldering profile is critical to prevent thermal damage.

• Reflow/Wave Soldering: The maximum allowable solder temperature is 260°C, measured 1.6mm below the package body (seating plane). The exposure time at this peak temperature must not exceed 3 seconds. Standard lead-free (SnAgCu) reflow profiles with a peak temperature of 240-250°C are generally safe if the time above liquidus is controlled.
• Hand Soldering: If manual soldering is necessary, a temperature-controlled iron should be used. Contact time per lead should be minimized, ideally to less than 3 seconds, using a tip temperature not exceeding 350°C.
• Cleaning: After soldering, if cleaning is required, use solvents compatible with the LED's epoxy lens material. Avoid ultrasonic cleaning, as high-frequency vibrations can damage the internal wire bonds.
• Storage Conditions: Store in a dry, anti-static environment within the specified temperature range (-35°C to +85°C). Moisture Sensitivity Level (MSL) is not specified in this datasheet but should be confirmed with the manufacturer for modern assembly processes involving reflow.

7. Application Suggestions

7.1 Typical Application Circuits

The common cathode configuration is designed for multiplexed driving. A typical circuit involves using a microcontroller or dedicated display driver IC.

• Multiplexing (Scanning): The two common cathodes (pins 5 & 10) are connected to NPN transistors or NFETs (sinking current). The segment anodes are connected to current-limiting resistors and then to microcontroller pins or a driver IC's segment outputs. The microcontroller rapidly turns on one digit's cathode at a time while energizing the appropriate segment anodes for that digit. A refresh rate of >60 Hz per digit prevents visible flicker.
• Current Limiting: A series resistor is mandatory for each segment anode (or a current-regulated driver) to set the forward current. The resistor value is calculated as R = (V_supply - V_F) / I_F. For a 5V supply and a target I_F of 20mA with V_F=2.6V, R = (5 - 2.6) / 0.02 = 120 Ω. The resistor power rating should be at least I_F² * R = 0.048W, so a standard 1/8W (0.125W) resistor is sufficient.
• Brightness Control: Brightness can be adjusted by varying the forward current (via PWM on the series resistor or using a variable current source) or by varying the duty cycle in the multiplexing routine.

7.2 Design Considerations

• Viewing Angle: The datasheet claims a "Wide Viewing Angle." For optimal readability, the display should be mounted perpendicular to the primary viewing direction. Consider the angular intensity distribution if viewing from an oblique angle is required.
• Contrast Enhancement: The black face/white segment design provides inherent contrast. For outdoor or high-ambient-light use, a neutral density filter or a dedicated contrast enhancement filter may be needed.
• Thermal Management: While power dissipation is low (max 70mW per segment), in multiplexed operation, the average power per segment is lower. However, if all segments of a digit are on simultaneously at high current, ensure adequate ventilation or heatsinking if the ambient temperature is high, respecting the current derating curve.
• ESD Protection: LEDs are susceptible to Electrostatic Discharge (ESD). Handle with appropriate ESD precautions. Incorporating TVS diodes or series resistors on I/O lines connected to the display can improve system-level ESD robustness.

8. Technical Comparison & Differentiation

The LTD-322JS, based on its specifications, holds several advantages and trade-offs compared to other display technologies.

• vs. Larger/Smaller LED Displays: The 0.3-inch digit is a mid-size option. Larger digits (e.g., 0.5\

  LED Specification Terminology

  Complete explanation of LED technical terms

  Photoelectric Performance

  Term	Unit/Representation	Simple Explanation	Why Important
  Luminous Efficacy	lm/W (lumens per watt)	Light output per watt of electricity, higher means more energy efficient.	Directly determines energy efficiency grade and electricity cost.
  Luminous Flux	lm (lumens)	Total light emitted by source, commonly called "brightness".	Determines if the light is bright enough.
  Viewing Angle	° (degrees), e.g., 120°	Angle where light intensity drops to half, determines beam width.	Affects illumination range and uniformity.
  CCT (Color Temperature)	K (Kelvin), e.g., 2700K/6500K	Warmth/coolness of light, lower values yellowish/warm, higher whitish/cool.	Determines lighting atmosphere and suitable scenarios.
  CRI / Ra	Unitless, 0–100	Ability to render object colors accurately, Ra≥80 is good.	Affects color authenticity, used in high-demand places like malls, museums.
  SDCM	MacAdam ellipse steps, e.g., "5-step"	Color consistency metric, smaller steps mean more consistent color.	Ensures uniform color across same batch of LEDs.
  Dominant Wavelength	nm (nanometers), e.g., 620nm (red)	Wavelength corresponding to color of colored LEDs.	Determines hue of red, yellow, green monochrome LEDs.
  Spectral Distribution	Wavelength vs intensity curve	Shows intensity distribution across wavelengths.	Affects color rendering and quality.

  Electrical Parameters

  Term	Symbol	Simple Explanation	Design Considerations
  Forward Voltage	Vf	Minimum voltage to turn on LED, like "starting threshold".	Driver voltage must be ≥Vf, voltages add up for series LEDs.
  Forward Current	If	Current value for normal LED operation.	Usually constant current drive, current determines brightness & lifespan.
  Max Pulse Current	Ifp	Peak current tolerable for short periods, used for dimming or flashing.	Pulse width & duty cycle must be strictly controlled to avoid damage.
  Reverse Voltage	Vr	Max reverse voltage LED can withstand, beyond may cause breakdown.	Circuit must prevent reverse connection or voltage spikes.
  Thermal Resistance	Rth (°C/W)	Resistance to heat transfer from chip to solder, lower is better.	High thermal resistance requires stronger heat dissipation.
  ESD Immunity	V (HBM), e.g., 1000V	Ability to withstand electrostatic discharge, higher means less vulnerable.	Anti-static measures needed in production, especially for sensitive LEDs.

  Thermal Management & Reliability

  Term	Key Metric	Simple Explanation	Impact
  Junction Temperature	Tj (°C)	Actual operating temperature inside LED chip.	Every 10°C reduction may double lifespan; too high causes light decay, color shift.
  Lumen Depreciation	L70 / L80 (hours)	Time for brightness to drop to 70% or 80% of initial.	Directly defines LED "service life".
  Lumen Maintenance	% (e.g., 70%)	Percentage of brightness retained after time.	Indicates brightness retention over long-term use.
  Color Shift	Δu′v′ or MacAdam ellipse	Degree of color change during use.	Affects color consistency in lighting scenes.
  Thermal Aging	Material degradation	Deterioration due to long-term high temperature.	May cause brightness drop, color change, or open-circuit failure.

  Packaging & Materials

  Term	Common Types	Simple Explanation	Features & Applications
  Package Type	EMC, PPA, Ceramic	Housing material protecting chip, providing optical/thermal interface.	EMC: good heat resistance, low cost; Ceramic: better heat dissipation, longer life.
  Chip Structure	Front, Flip Chip	Chip electrode arrangement.	Flip chip: better heat dissipation, higher efficacy, for high-power.
  Phosphor Coating	YAG, Silicate, Nitride	Covers blue chip, converts some to yellow/red, mixes to white.	Different phosphors affect efficacy, CCT, and CRI.
  Lens/Optics	Flat, Microlens, TIR	Optical structure on surface controlling light distribution.	Determines viewing angle and light distribution curve.

  Quality Control & Binning

  Term	Binning Content	Simple Explanation	Purpose
  Luminous Flux Bin	Code e.g., 2G, 2H	Grouped by brightness, each group has min/max lumen values.	Ensures uniform brightness in same batch.
  Voltage Bin	Code e.g., 6W, 6X	Grouped by forward voltage range.	Facilitates driver matching, improves system efficiency.
  Color Bin	5-step MacAdam ellipse	Grouped by color coordinates, ensuring tight range.	Guarantees color consistency, avoids uneven color within fixture.
  CCT Bin	2700K, 3000K etc.	Grouped by CCT, each has corresponding coordinate range.	Meets different scene CCT requirements.

  Testing & Certification

  Term	Standard/Test	Simple Explanation	Significance
  LM-80	Lumen maintenance test	Long-term lighting at constant temperature, recording brightness decay.	Used to estimate LED life (with TM-21).
  TM-21	Life estimation standard	Estimates life under actual conditions based on LM-80 data.	Provides scientific life prediction.
  IESNA	Illuminating Engineering Society	Covers optical, electrical, thermal test methods.	Industry-recognized test basis.
  RoHS / REACH	Environmental certification	Ensures no harmful substances (lead, mercury).	Market access requirement internationally.
  ENERGY STAR / DLC	Energy efficiency certification	Energy efficiency and performance certification for lighting.	Used in government procurement, subsidy programs, enhances competitiveness.