LTC-5685TBZ LED Display Datasheet - 0.56-inch Digit Height - Blue Color - 3.6V Forward Voltage - English Technical Document

1. Product Overview

The LTC-5685TBZ is a triple-digit, seven-segment alphanumeric display module utilizing blue light-emitting diode (LED) technology. It is designed for applications requiring clear, bright numeric readouts. The device features a black face with white segment diffusers, providing high contrast for excellent character legibility. The primary construction involves InGaN (Indium Gallium Nitride) epitaxial layers grown on a sapphire substrate, which is a standard for producing blue LEDs. This solid-state design offers inherent reliability advantages over other display technologies.

1.1 Key Features and Device Identification

The display offers several distinct advantages for integration into electronic systems. Its 0.56-inch (14.22 mm) digit height strikes a balance between visibility and compactness, suitable for panel meters, instrumentation, and consumer electronics. The device operates with low power requirements, contributing to energy-efficient designs. A high brightness output combined with the black face ensures a high contrast ratio, making the numerals easily readable even in well-lit conditions. The viewing angle is wide, allowing the display to be seen clearly from various positions. The components are binned for luminous intensity, meaning LEDs are sorted and grouped to ensure consistent brightness levels across production batches, which is critical for multi-digit displays to appear uniform. Furthermore, the package is compliant with lead-free manufacturing standards according to RoHS directives.

The specific part number, LTC-5685TBZ, identifies this as a common anode configuration device with a right-hand decimal point. The \"TBZ\" suffix typically denotes the color (Blue) and specific package or feature set.

2. Mechanical and Package Information

The physical dimensions of the display are critical for PCB (Printed Circuit Board) layout and enclosure design. While the exact dimensional drawing is referenced in the original document, key tolerances and assembly notes are provided. All primary dimensions are specified in millimeters with a standard tolerance of ±0.25 mm unless stated otherwise. For PCB mounting, a hole diameter of 1.00 mm is recommended for the pins. The pin tips have a positional shift tolerance of ±0.40 mm, which designers must account for in their pad layout. Quality control parameters are also defined, limiting foreign materials, bubbles within the segment area, and surface ink contamination to 10 mils (approximately 0.254 mm) each.

3. Electrical Configuration and Pinout

3.1 Internal Circuit Diagram

The internal schematic reveals the electrical structure of the display. Each segment (A through G and the decimal point for each digit) is formed by one or more blue LED chips. A critical component in the circuit is a Zener diode connected in parallel with the LED chips. This diode serves as a protective element, helping to clamp transient voltage spikes and providing a degree of electrostatic discharge (ESD) protection, which aligns with the specified high ESD threshold. The LED chips are specified with a dominant wavelength (λd) of 470 nm, placing the emission in the blue region of the visible spectrum.

3.2 Pin Connection Assignment

The device has 11 pins in a single-row configuration. The pinout is as follows:
Pin 1: Cathode for Digit 1, Segment A and Decimal Point
Pin 2: Cathode for Digit 2, Segment B
Pin 3: Cathode for Digit 3, Segment C
Pin 4: Cathode for Digit 4, Segment D
Pin 5: Cathode for Digit 1, Segment E
Pin 6: Cathode for Digit 2, Segment F
Pin 7: Cathode for Segment G (common across digits, but controlled via anode selection)
Pin 8: Common Anode for Digit 4
Pin 9: Common Anode for Digit 3
Pin 10: Common Anode for Digit 2
Pin 11: Common Anode for Digit 1
This common anode configuration means that to illuminate a segment, its corresponding cathode pin must be driven low (grounded) while the anode of the desired digit is driven high. Multiplexing is used to control the three digits independently by sequentially enabling each digit's anode while presenting the segment data for that digit on the cathode lines.

4. Absolute Maximum Ratings and Operating Limits

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.
Power Dissipation: The maximum power dissipation per LED chip is 70 mW. Exceeding this can lead to overheating and rapid degradation.
Forward Current: The continuous forward current per segment is rated at 20 mA at 25°C. This rating derates linearly above 25°C at a rate of 0.21 mA/°C. For example, at 85°C, the maximum continuous current would be lower. A peak forward current of 100 mA is allowed under pulsed conditions (15% duty cycle, 0.1 ms pulse width), which is useful for multiplexing or achieving higher momentary brightness.
Temperature Range: The device can operate and be stored within a temperature range of -35°C to +85°C.
Electrostatic Discharge (ESD): The Human Body Model (HBM) ESD threshold is 8000 V, indicating good inherent protection, but proper ESD handling procedures are still necessary.
Soldering: The device can withstand wave or reflow soldering with the condition that the temperature at the body of the unit does not exceed the maximum rating during assembly. A specific guideline is soldering for 3 seconds at 260°C, measured 1/16 inch (≈1.59 mm) below the seating plane.

5. Electrical and Optical Characteristics

These parameters are measured at an ambient temperature (Ta) of 25°C and define the typical performance under normal operating conditions.

5.1 DC Characteristics

Luminous Intensity (I_V): The average luminous intensity per segment ranges from 5400 µcd (minimum) to 9000 µcd (typical) when driven at a forward current (I_F) of 10 mA. This is a measure of the perceived brightness by the human eye, measured with a filter matching the CIE photopic response curve.
Forward Voltage (V_F): The voltage drop across a segment when conducting 20 mA is typically 3.6 V, with a minimum of 3.3 V. This parameter is crucial for designing the driving circuitry's voltage supply and current-limiting resistors.
Reverse Current (I_R): When a reverse voltage (V_R) of 5V is applied, the leakage current is a maximum of 100 µA. The datasheet explicitly notes that this reverse voltage condition is for test purposes only and the device must not be operated continuously under reverse bias.

5.2 Spectral Characteristics

Peak Wavelength (λ_p): The wavelength at which the emission intensity is highest is 468 nm (at I_F=20mA).
Dominant Wavelength (λ_d): This is the single wavelength that would produce the same color perception as the LED's broad spectrum. It ranges from 470 nm to 475 nm.
Spectral Half-Width (Δλ): This is the width of the emission spectrum at half its maximum intensity, typically 15 nm. A narrower half-width indicates a more spectrally pure color.

5.3 Matching and Binning

Luminous Intensity Matching Ratio: For segments within a \"similar light area,\" the ratio of the brightest to the dimmest segment should not exceed 2:1 when measured at a low current of 1 mA. This specification, combined with the factory binning process, ensures visual uniformity across all segments of the display.

6. Application Guidelines and Cautions

This section contains critical information for the reliable integration of the display into an end product.

6.1 Design and Usage Considerations

Intended Use: The display is designed for standard commercial and industrial electronics. It is not certified for safety-critical applications (aviation, medical life-support, etc.) without prior consultation and evaluation.
Driving Method: Constant current driving is strongly recommended over constant voltage driving. This ensures consistent brightness and protects the LEDs from thermal runaway, as the forward voltage of LEDs decreases with increasing temperature. The driving circuit must be designed to accommodate the full range of V_F (3.3V to 3.6V) to guarantee the target drive current is always delivered.
Current Derating: The operating current must be chosen based on the maximum expected ambient temperature in the application, considering the derating specified in the absolute maximum ratings.
Reverse Voltage Protection: Circuit design must actively prevent the application of reverse bias or large voltage transients during power-up/down sequences, as this can cause metal migration and lead to increased leakage or short circuits.
Thermal and Environmental: Avoid rapid temperature changes in humid environments to prevent condensation on the display. Do not apply mechanical force to the display body during assembly.
Optical Consistency: When using multiple displays in one assembly, it is recommended to use units from the same production bin to avoid noticeable differences in hue or brightness.
Testing: If the end product requires the display to undergo drop or vibration tests, the specific conditions should be shared for evaluation, as mechanical stress can affect the internal connections.

6.2 Storage and Handling Conditions

For long-term storage, the product should remain in its original packaging. The recommended storage environment is within a temperature range of 5°C to 30°C and a relative humidity below 60%. Storing outside these conditions, particularly in high humidity, can lead to oxidation of the component leads (pins), which may require re-processing before use and can affect solderability. Therefore, it is advised to manage inventory to avoid prolonged storage and to consume components in a timely manner.

7. Performance Curve Analysis

While the specific graphs are referenced in the datasheet, typical curves for such LEDs would include:
Forward Current vs. Forward Voltage (I-V Curve): This exponential curve shows the relationship between the current through the LED and the voltage across it. It highlights the need for current limiting.
Luminous Intensity vs. Forward Current: This curve is generally linear at lower currents but may saturate at higher currents due to thermal effects. It helps designers choose an operating point for desired brightness vs. efficiency.
Luminous Intensity vs. Ambient Temperature: This shows the derating of light output as the junction temperature increases, emphasizing the importance of thermal management.
Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~468 nm and the ~15 nm half-width, confirming the blue color characteristics.

8. Typical Application Scenarios

The LTC-5685TBZ is well-suited for a variety of applications requiring a clear, reliable numeric display. These include:
• Digital panel meters for voltage, current, or temperature readouts.
• Point-of-sale equipment and cash registers.
• Industrial control panels and timer displays.
• Test and measurement equipment.
• Consumer appliances like microwave ovens, audio amplifiers, or clock radios.
Its blue color offers a modern aesthetic and can be easier on the eyes in low-light conditions compared to very bright green or red displays.

9. Design Considerations and Comparison

When selecting this display, designers should consider its common anode configuration, which may require different driver ICs or microcontroller port configurations compared to common cathode types. The 3.6V typical forward voltage means a supply voltage of at least 5V is typically used to accommodate the drop across the current-limiting resistor and driver circuitry. Compared to older technologies like vacuum fluorescent displays (VFDs) or simpler incandescent displays, this LED display offers lower power consumption, longer lifetime, and greater shock and vibration resistance. Compared to LCDs, it provides superior brightness and viewing angles without requiring a backlight, though it may consume more power if many segments are lit simultaneously.