LTP-3362JS 0.3-inch Dual-Digit Alphanumeric LED Display Datasheet - Digit Height 7.62mm - Yellow Color - English Technical Document

1. Product Overview

The LTP-3362JS is a dual-digit, 17-segment alphanumeric LED display module designed for applications requiring clear character and symbol presentation. Its primary function is to provide a highly legible visual output for numeric digits, alphabetic characters, and specific symbols. The core advantage of this device lies in its use of advanced AS-AlInGaP (Aluminum Indium Gallium Phosphide) Yellow LED chips, which are epitaxially grown on a GaAs substrate. This technology delivers high brightness and excellent color purity. The display features a black face with white segments, creating a high-contrast appearance that enhances readability under various lighting conditions. Its 0.3-inch (7.62 mm) digit height makes it suitable for medium-distance viewing in instrumentation, industrial control panels, point-of-sale terminals, and test equipment where space is at a premium but clarity is paramount.

1.1 Key Features and Target Market

The device is categorized by its luminous intensity, ensuring consistent brightness levels across production batches. Its wide viewing angle ensures the display remains readable from various positions, a critical factor in panel-mounted applications. The solid-state reliability of LED technology offers a long operational lifespan with minimal maintenance. This display is targeted at engineers and designers working on embedded systems, industrial human-machine interfaces (HMIs), medical devices, and consumer electronics that require a robust, low-power, and highly visible alphanumeric readout.

2. In-Depth Technical Parameter Analysis

A thorough understanding of the electrical and optical parameters is essential for proper circuit design and ensuring optimal display performance.

2.1 Photometric and Optical Characteristics

The optical performance is central to the display's functionality. The average luminous intensity per segment is specified with a minimum of 320 µcd, a typical value of 800 µcd, and no stated maximum when driven at a forward current (I_F) of 1mA. This high brightness level, measured using a sensor filtered to match the CIE photopic eye-response curve, ensures excellent visibility. The device emits yellow light with a peak wavelength (λ_p) of 588 nm and a dominant wavelength (λ_d) of 587 nm at I_F=20mA, placing it firmly in the yellow region of the visible spectrum. The spectral line half-width (Δλ) is 15 nm, indicating a relatively pure color emission. The luminous intensity matching ratio between segments is 2:1 maximum, which helps maintain a uniform appearance across the display.

2.2 Electrical and Thermal Parameters

The electrical characteristics define the drive requirements and operational limits. The absolute maximum ratings are critical for preventing device failure. The power dissipation per segment must not exceed 70 mW. The peak forward current per segment is 60 mA, but this is only permissible under pulsed conditions (1 kHz, 10% duty cycle). The continuous forward current per segment is derated from 25 mA at 25°C at a rate of 0.33 mA/°C, meaning the allowable continuous current decreases as ambient temperature rises. The reverse voltage per segment must not exceed 5 V. The forward voltage (V_F) per segment typically ranges from 2.0V to 2.6V at I_F=20mA. The reverse current (I_R) is a maximum of 100 µA at V_R=5V. The device is rated for an operating and storage temperature range of -35°C to +85°C.

3. Binning System Explanation

The datasheet indicates that the devices are \"categorized for luminous intensity.\" This implies a binning process where displays are sorted based on their measured light output at a standard test current (likely 1mA or 20mA). This ensures that end-users receive products with consistent brightness levels. While not explicitly detailed for wavelength/color or forward voltage in this document, such categorization is common practice in LED manufacturing to guarantee color uniformity and electrical performance matching, which is especially important in multi-digit or multi-segment applications to avoid visible differences between segments.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical / Optical Characteristic Curves,\" which are essential for detailed design work. Although the specific graphs are not provided in the text, typical curves for such a device would include:

• Relative Luminous Intensity vs. Forward Current (I-V Curve): This graph shows how light output increases with drive current, typically in a sub-linear fashion, helping designers choose the optimal current for desired brightness and efficiency.
• Forward Voltage vs. Forward Current: This curve is crucial for designing the current-limiting circuitry and calculating power dissipation.
• Relative Luminous Intensity vs. Ambient Temperature: This shows the derating of light output as temperature increases, which is vital for applications in high-temperature environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, confirming the peak and dominant wavelengths and the spectral width.

Designers should consult the full datasheet from the manufacturer for these precise graphical data.

5. Mechanical and Package Information

5.1 Physical Dimensions and Pinout

The LTP-3362JS comes in a standard LED display package. The dimensions are provided in millimeters with a general tolerance of ±0.25 mm. The pin connection diagram is critical for PCB layout. The device has 20 pins in a dual-in-line package (DIP). It features a multiplex common cathode configuration, with Pin 4 serving as the common cathode for Digit 1 and Pin 10 as the common cathode for Digit 2. The remaining pins are anodes for the individual segments (A through U, plus DP for the decimal point) and special segments (e.g., S, T for slash). Pin 14 is noted as \"No Connection\" (N/C). The internal circuit diagram shows the multiplexed arrangement, where segments with the same letter designation on different digits are internally connected to a single anode pin, and the digits are selected by energizing their respective common cathode.

5.2 Polarity Identification and Mounting

The device uses a common cathode configuration. Proper polarity must be observed during installation. The package likely includes a notch, dot, or other marking to indicate Pin 1. The black face and white segments provide a clear visual indicator of the viewing side.

6. Soldering and Assembly Guidelines

The absolute maximum ratings specify soldering conditions: the leads can be subjected to 260°C for 3 seconds, measured 1/16 inch (approximately 1.59 mm) below the seating plane. This is a typical specification for wave soldering. For reflow soldering, a standard lead-free profile with a peak temperature around 260°C is suitable, but the specific time above liquidus should be minimized. Care must be taken to avoid excessive thermal stress. During handling, standard ESD (electrostatic discharge) precautions should be observed to protect the LED chips. For storage, the recommended range is -35°C to +85°C in a dry environment.

7. Packaging and Ordering Information

The part number is LTP-3362JS. The \"JS\" suffix likely denotes specific characteristics such as color (Yellow) and package style. Standard packaging for such components is often in anti-static tubes or trays, and then placed in reels or boxes for automated assembly. The exact packaging quantity (e.g., 50 pieces per tube) would be specified in separate packaging documentation. The datasheet revision is A, and the effective date is 09/11/2003.

8. Application Recommendations

8.1 Typical Application Scenarios

The LTP-3362JS is ideal for any application requiring a compact, two-character alphanumeric readout. Common uses include: digital multimeters and clamp meters, frequency counters, process timers, battery charger status displays, audio equipment tuners and level meters, and industrial controller status/error code displays.

8.2 Design Considerations and Circuit Implementation

Designing with this display requires a multiplexing driver circuit due to its common cathode, multiplexed anode structure. A microcontroller with sufficient I/O pins or a dedicated LED driver IC (like a MAX7219 or HT16K33) is necessary. The driver must source current to the segment anode pins and sink current from the digit cathode pins. Current-limiting resistors are mandatory for each segment anode line to set the desired forward current (e.g., 20 mA for maximum brightness). The resistor value can be calculated using R = (V_CC - V_F) / I_F. With a V_CC of 5V and a typical V_F of 2.3V at 20mA, the resistor would be approximately 135 Ohms. The multiplexing frequency should be high enough to avoid visible flicker, typically above 100 Hz. Designers must also consider the total power dissipation, especially when driving multiple segments simultaneously at high current.

9. Technical Comparison and Differentiation

Compared to older technologies like vacuum fluorescent displays (VFDs) or simpler red GaAsP LEDs, the AlInGaP yellow LED used in the LTP-3362JS offers superior efficiency, higher brightness, better color stability over temperature, and longer lifetime. Compared to contemporary white or blue GaN-based LEDs with filters, the direct yellow emission of AlInGaP is more efficient and provides better color saturation. Its key differentiators are the specific yellow color point, high contrast due to the black face, and the 17-segment format which allows for a more comprehensive alphanumeric set than a standard 7-segment display, while remaining more cost-effective and simpler to drive than a full dot-matrix display.

10. Frequently Asked Questions (FAQ)

Q: What is the difference between peak wavelength and dominant wavelength?
A: 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 emitted light. For a narrow spectrum like this LED, they are very close (587nm vs 588nm).

Q: Can I drive this display with a constant DC current without multiplexing?
A: Technically, yes, but it is highly inefficient and not the intended use. You would need to connect each segment's anode to a current-limited voltage source and each digit's cathode to ground. This would require 18 drivers for the segments plus 2 for the digits, totaling 20 drivers for a 2-digit display, which is impractical. Multiplexing significantly reduces the required driver count.

Q: How do I calculate the power dissipation for the whole display?
A: In a multiplexed setup, power is calculated based on the average current. If driving at I_F per segment with a duty cycle (D) for each digit (D=1/Number of digits for equal brightness), the average power per segment is V_F * I_F * D. Sum this for all illuminated segments.

Q: What does \"Luminous Intensity Matching Ratio\" mean?
A: It specifies the maximum allowable ratio between the brightest and dimmest segment in a device (e.g., 2:1). A ratio of 2:1 means the dimmest segment must be at least half as bright as the brightest segment, ensuring uniformity.

11. Practical Design and Usage Examples

Case Study 1: Digital Timer Interface. A designer uses the LTP-3362JS to show minutes and seconds (MM:SS) on a custom timer circuit. They use a low-power microcontroller to manage the multiplexing. To conserve power, they drive the LEDs at 10mA instead of 20mA, accepting a lower but still sufficient brightness. The black face ensures readability even under bright workshop lighting.

Case Study 2: Sensor Readout Unit. In a temperature and humidity data logger, the display shows codes like \"tH\" for temperature high alarm or numeric values. The 17-segment capability allows displaying letters \"C\" or \"F\" for temperature units. The wide operating temperature range matches the environmental requirements of the logger itself.

12. Technical Principle Introduction

The LTP-3362JS is based on semiconductor electroluminescence. The AS-AlInGaP (Aluminum Indium Gallium Phosphide) material system is a direct bandgap semiconductor. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. They recombine radiatively, releasing energy in the form of photons. 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, yellow (~587-588 nm). The epitaxial layers are grown on a GaAs substrate. The black epoxy package body absorbs ambient light to improve contrast, while the lens shape is designed to optimize the viewing angle.

13. Technology Trends and Evolution

AlInGaP technology represents a mature and highly efficient solution for red, orange, amber, and yellow LEDs. Current trends in display technology are moving towards higher density, full-color capability, and integration. While discrete segment displays like the LTP-3362JS remain vital for specific applications, there is a broader shift towards organic LED (OLED) and micro-LED displays for high-resolution graphical interfaces. However, for simple, low-cost, high-reliability, and high-brightness alphanumeric readouts, LED segment displays continue to be widely used. Future developments may include even higher efficiency materials, integrated driver circuits within the display package (reducing external component count), and a wider range of package sizes and colors to meet diverse design needs. The principle of multiplexing to reduce pin count remains a fundamental and enduring technique in display driver electronics.