LTP-1057AHR LED Display Datasheet - 1.24 Inch (31.5mm) Matrix Height - 5x7 Dot Matrix - Red Orange Color - English Technical Document

1. Product Overview

The LTP-1057AHR is a single-digit, alphanumeric display module designed for applications requiring clear, legible character output. Its core function is to visually represent data, typically ASCII or EBCDIC coded characters, through an array of individually addressable light-emitting diodes (LEDs).

1.1 Core Features and Advantages

The device offers several key advantages for integration into electronic systems:

• Large Character Size: Features a 1.24-inch (31.5 mm) matrix height, ensuring excellent visibility from a distance and in various lighting conditions.
• Low Power Consumption: Engineered for efficient operation, making it suitable for battery-powered or energy-conscious applications.
• Excellent Readability: Provides a single-plane, wide viewing angle display with a red face and red dots for high contrast.
• High Reliability: As a solid-state device, it offers long operational life and robustness against shock and vibration compared to mechanical displays.
• Standard Interface: The 5x7 array with X-Y (row-column) select architecture is compatible with common microcontroller and driver IC interfaces.
• Design Flexibility: Modules are stackable horizontally, allowing for the creation of multi-digit displays.
• Quality Assurance: Devices are categorized (binned) for luminous intensity, ensuring consistency in brightness across multiple units in an assembly.
• Environmental Compliance: The package is lead-free, adhering to RoHS (Restriction of Hazardous Substances) directives.

1.2 Target Applications and Market

This display is intended for use in ordinary electronic equipment across various sectors. Typical application areas include, but are not limited to:

• Office Equipment: Instrument panels, status indicators on printers, copiers, or fax machines.
• Communication Equipment: Channel displays, signal strength indicators, or status readouts.
• Industrial Controls: Process parameter display, machine status, or timer readouts.
• Test and Measurement Gear: Digital readouts for multimeters, frequency counters, or power supplies.
• Consumer Electronics: Displays for audio equipment, appliances, or hobbyist projects.

It is crucial to note that this display is not designed for applications where failure could directly jeopardize life or health (e.g., aviation, medical life-support, critical transportation controls) without prior consultation and specific qualification.

2. Technical Specifications and Objective Interpretation

This section provides a detailed, objective analysis of the device's electrical and optical performance parameters.

2.1 Absolute Maximum Ratings

These are stress limits that must not be exceeded under any conditions, even momentarily. Operation beyond these limits may cause permanent damage.

• Power Dissipation per Segment: 75 mW. This limits the combined effect of forward current (I_F) and forward voltage (V_F).
• Peak Forward Current per Segment: 60 mA, but only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). This is for multiplexing schemes.
• Continuous Forward Current per Segment: 25 mA at 25°C. This rating derates linearly by 0.33 mA/°C as ambient temperature (T_a) increases above 25°C. For example, at 65°C, the maximum continuous current would be approximately: 25 mA - [ (65°C - 25°C) * 0.33 mA/°C ] = 25 mA - 13.2 mA = 11.8 mA.
• Temperature Ranges: Operating and storage temperatures are specified from -35°C to +85°C.
• Solder Temperature: A maximum of 260°C for a maximum of 3 seconds, measured 1.6mm (1/16 inch) below the seating plane of the device. This is critical for wave or reflow soldering processes.

2.2 Electrical and Optical Characteristics

These are the typical performance parameters measured under specified test conditions at an ambient temperature (T_a) of 25°C.

• Average Luminous Intensity (I_V): Ranges from 1780 µcd (minimum) to 4000 µcd (typical) when driven at a pulsed current (I_p) of 80 mA with a 1/16 duty cycle. This high pulsed current allows for bright perception in multiplexed applications.
• Wavelength Characteristics:
  • Peak Emission Wavelength (λ_p): 630 nm (red-orange spectrum). Measured at I_F=20mA.
  • Spectral Line Half-Width (Δλ): 40 nm. This indicates the spread of the emitted light's wavelength.
  • Dominant Wavelength (λ_d): 621 nm. This is the single wavelength perceived by the human eye to match the color of the emitted light.
• Forward Voltage per Segment (V_F): Ranges from 2.0 V (minimum) to 2.6 V (typical) at I_F=20mA. Circuit design must account for this range to ensure consistent current drive.
• Reverse Current per Segment (I_R): Maximum of 100 µA when a reverse voltage (V_R) of 5V is applied. The datasheet explicitly warns that this reverse voltage condition is for test purposes only and the device should not be continuously operated under reverse bias.
• Luminous Intensity Matching Ratio (I_V-m): Maximum of 2:1 between segments when driven at I_F=10mA. This specifies the maximum allowable brightness variation between different segments (dots) within the same display unit.

Important Note on Luminous Intensity Measurement: The intensity is measured using a sensor and filter combination that approximates the CIE photopic eye-response curve, ensuring the value correlates with human brightness perception.

3. Binning System Explanation

The datasheet indicates that devices are \"categorized for luminous intensity.\" This refers to a binning or sorting process.

• Luminous Intensity Binning: After manufacture, LEDs are tested and sorted into different groups (bins) based on their measured luminous intensity at a standard test current. This ensures that when a designer selects components from the same bin code, the displays will have very similar brightness levels. This is critical when assembling multiple displays side-by-side to avoid noticeable brightness differences (\"hot spots\" or \"dim spots\"). The datasheet recommends using displays from the same bin for multi-unit applications.
• Wavelength/Color Binning: While not explicitly detailed in the provided excerpt, it is common practice for LED manufacturers to also bin devices based on dominant wavelength (λ_d) or chromaticity coordinates to ensure color consistency. The specified λ_d of 621 nm is likely a central target value for this product.

4. Performance Curve Analysis

The datasheet references \"Typical Electrical/Optical Characteristics Curves.\" These graphical representations are essential for understanding device behavior under non-standard conditions. Although the specific curves are not provided in the text, they typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the nonlinear relationship between current and voltage. The curve will demonstrate the turn-on voltage and how V_F increases with I_F. This is vital for designing current-limiting circuitry.
• Luminous Intensity vs. Forward Current (I-L Curve): Illustrates how light output increases with drive current. It is generally linear over a range but will saturate at very high currents. This helps optimize the drive current for desired brightness versus efficiency and lifetime.
• Luminous Intensity vs. Ambient Temperature: Shows how light output decreases as the junction temperature of the LED increases. This derating curve is crucial for applications operating at high ambient temperatures.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~630 nm and the 40 nm half-width.

5. Mechanical and Package Information

5.1 Package Dimensions

The device has a defined physical outline. All dimensions are in millimeters, with standard tolerances of ±0.25 mm (0.01 inch) unless otherwise specified. The exact dimensional drawing is referenced in the datasheet.

5.2 Pin Connection and Internal Circuit

The display has a 14-pin configuration, with pins 11 and 12 being \"No Pin\" (NC). The internal circuit diagram shows a common-cathode architecture for the rows and individual anodes for the columns, forming the 5x7 matrix. The pinout is as follows:

• Pin 1: Cathode Row 5
• Pin 2: Cathode Row 7
• Pin 3: Anode Column 2
• Pin 4: Anode Column 3
• Pin 5: Cathode Row 4
• Pin 6: Anode Column 5
• Pin 7: Cathode Row 6
• Pin 8: Cathode Row 3
• Pin 9: Cathode Row 1
• Pin 10: Anode Column 4
• Pin 11: No Connection
• Pin 12: No Connection
• Pin 13: Anode Column 1
• Pin 14: Cathode Row 2

This pin arrangement must be carefully followed for proper display operation. The common-cathode design means to illuminate a specific dot, its corresponding column anode must be driven high (with current limiting), while its row cathode must be pulled low.

6. Soldering, Assembly, and Storage Guidelines

6.1 Soldering Process

The absolute maximum rating specifies a solder temperature profile: maximum 260°C for a maximum of 3 seconds, measured at a point 1.6mm below the package body. This is a standard rating for through-hole components for wave soldering. For reflow soldering of SMD variants (referenced in storage), a specific profile adhering to the package's Moisture Sensitivity Level (MSL) would be required.

6.2 Storage Conditions

Proper storage is essential to prevent pin oxidation and ensure solderability.

• For Through-Hole Displays (LTP-1057AHR): Store in original packaging at 5°C to 30°C and below 60% Relative Humidity (RH). Long-term storage is discouraged.
• For SMD LED Displays (Referenced):
  • In Sealed Bag: 5°C to 30°C, below 60% RH.
  • After Bag Opening: 5°C to 30°C, below 60% RH, for a maximum of 168 hours (7 days) if the MSL is Level 3. After this period, a bake-out at 60°C for 24 hours is recommended before soldering to remove absorbed moisture and prevent \"popcorning\" damage during reflow.
• General Recommendation: Consume inventory quickly and avoid large, long-term stockpiles.

7. Application Design Recommendations and Cautions

The datasheet provides critical guidance for reliable circuit design and use.

• Drive Method: Constant current driving is strongly recommended over constant voltage to ensure consistent luminous intensity and longevity, as the LED's forward voltage has a tolerance and varies with temperature.
• Circuit Protection: The driving circuit must protect against reverse voltages and transient voltage spikes during power-up/down sequences, as reverse bias can cause metal migration and failure.
• Current Limiting: The safe operating current must be chosen considering the maximum ambient temperature, applying the derating factor from the Absolute Maximum Ratings.
• Thermal Management: Avoid operating temperatures higher than recommended, as this accelerates light output degradation (lumen depreciation) and can lead to premature failure.
• Environmental Considerations: Avoid rapid temperature changes in high-humidity environments to prevent condensation on the display.
• Mechanical Handling: Do not apply abnormal force to the display body during assembly. If using a front-cover film, ensure it does not press tightly against the display surface, as the adhesive may cause the film to shift.
• Multi-Display Consistency: For applications using two or more displays, select units from the same luminous intensity bin to avoid uneven brightness (hue unevenness).

8. Operational Principle

The LTP-1057AHR is a dot-matrix LED display. It consists of 35 individual LED elements (5 columns x 7 rows) arranged in a rectangular grid. Each LED (dot) is a semiconductor p-n junction that emits red-orange light when forward biased—a phenomenon called electroluminescence. The specific color is determined by the bandgap energy of the semiconductor material used (GaAsP/GaP or AlInGaP/GaAs as noted). The display is multiplexed: by sequentially activating (sinking current to ground) one row cathode at a time while applying forward current to the appropriate column anodes for that row, an entire character can be displayed. This scan happens faster than the human eye can perceive, creating a stable image while significantly reducing the number of required driver pins compared to individually driving each of the 35 LEDs.

9. Common Design Questions and Answers

Q: What is the purpose of the 1/16 duty cycle rating for luminous intensity?
A: The display is designed for multiplexed operation. The 80mA pulsed current at a low duty cycle (e.g., 1/16) delivers a high instantaneous brightness. When averaged over time and combined with persistence of vision, this creates the perception of a bright, stable display while keeping the average power and heat dissipation per LED within safe limits.

Q: Why is reverse bias so dangerous for this LED display?
A: Applying a reverse voltage beyond the very low maximum (implied by the I_R test at 5V) can cause breakdown of the semiconductor junction. More insidiously, even lower reverse voltages over time can cause electromigration of metal atoms within the chip, leading to increased leakage current or a direct short circuit, permanently damaging the segment.

Q: How do I calculate the required current-limiting resistor for a segment?
A: Use the worst-case forward voltage (V_F max = 2.6V) from the datasheet. For a constant voltage supply (V_supply), the resistor value R = (V_supply - V_F) / I_F. Choose I_F based on desired brightness, ensuring it is below the derated continuous current limit for your operating temperature. For example, with a 5V supply, V_F=2.6V, and I_F=15mA: R = (5 - 2.6) / 0.015 = 160 Ohms. A constant current driver circuit is a more robust solution.

Q: Can I use this display outdoors?
A: The operating temperature range (-35°C to +85°C) allows for many outdoor conditions. However, the device is not inherently waterproof or sealed against dust and moisture. For outdoor use, it must be housed in a properly rated enclosure that protects it from the elements, manages condensation, and possibly includes a sunshield to maintain contrast in direct sunlight.