LTPL-A138DWAGB Flash LED Datasheet - CSP Package - 1.2x1.2mm - 3.2V - 5.7W Pulse - White - English Technical Document

1. Product Overview

The LTPL-A138DWAGB is a compact, high-power light-emitting diode (LED) specifically engineered as a flash light source. Its primary design objective is to deliver intense illumination in scenarios requiring high-resolution imaging under low ambient light conditions and at extended distances. The device utilizes a Chip Scale Package (CSP) architecture, which offers significant advantages in terms of miniaturization and thermal performance.

1.1 Key Features

• Ultra-Compact Form Factor: Features one of the smallest available chip scale packages, enabling high flux density in a minimal footprint.
• Flip-Chip Technology: Employs a direct-attach flip-chip design. This structure eliminates traditional wire bonds, reducing parasitic inductance and improving thermal conduction from the semiconductor junction directly to the substrate.
• High Efficacy at High Current: Engineered to maintain high luminous efficacy and output even when driven at very high current densities, which is critical for short-duration flash applications.
• Superior Thermal Management: The flip-chip design and CSP construction provide a low thermal resistance path, allowing for more efficient heat dissipation compared to conventional packaged LEDs.

1.2 Target Applications

• Camera phones and smartphones
• Portable handheld devices
• Digital still cameras (DSC)
• Other compact imaging systems requiring a powerful, momentary light source

2. Technical Parameters: In-Depth Objective Analysis

This section provides a detailed breakdown of the LED's operational limits and performance characteristics under defined conditions. All data is referenced to an ambient temperature (Ta) of 25°C unless otherwise specified.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed.

• Power Dissipation (Pulse Mode): 5.7 W. This is the maximum allowable power the package can handle during pulsed operation.
• Pulsed Forward Current (I_FP): 1500 mA maximum under a specific duty cycle (400ms ON, 3600ms OFF, D=0.1). This rating is for flash-type applications.
• DC Forward Current (I_F): 350 mA maximum for continuous DC operation.
• Junction Temperature (T_j): 125 °C maximum. The temperature of the semiconductor chip itself must not exceed this value.
• Operating Temperature Range: -40°C to +85°C. The ambient temperature range for reliable device operation.
• Storage Temperature Range: -40°C to +100°C. The safe temperature range for the device when not powered.

2.2 Electrical & Optical Characteristics

Typical performance parameters measured under standard test conditions. Measurement tolerances are ±10% for luminous flux and ±0.1V for forward voltage. Testing is performed using a 300ms pulse.

• Luminous Flux (Φ_V): 240 lm (Typical) at 1000mA. Minimum 180 lm, Maximum 280 lm. This is the total visible light output.
• Viewing Angle (2θ_1/2): 120 degrees (Typical). This defines the angular spread of the emitted light where intensity is half of the peak value.
• Correlated Color Temperature (CCT): 4000K to 5000K at 1000mA. This indicates the white light shade, falling within the \"neutral white\" range.
• Color Rendering Index (CRI): 80 (Minimum) at 1000mA. A measure of how accurately the light source reveals the true colors of objects compared to a natural reference.
• Forward Voltage (V_F1): 3.2V (Typical) at 1000mA. Ranges from 2.9V (Min) to 3.8V (Max). This is the voltage drop across the LED when driven at operating current.
• Forward Voltage (V_F2): Approximately 2.0V at a very low test current of 10µA.
• Reverse Current (I_R): 100 µA maximum at a reverse bias of 5V. Critical Note: This parameter is for informational (IR) testing only. The device is not designed for operation under reverse bias and applying such voltage in a circuit may cause failure.

3. Binning System Explanation

To ensure consistency in production, LEDs are sorted (binned) based on key performance parameters. This allows designers to select parts that meet specific application requirements for brightness and voltage.

3.1 Luminous Flux Binning

LEDs are categorized into bins based on their light output at 1000mA.

• Bin N0: Luminous flux range from 180 lm to 250 lm.
• Bin P1: Luminous flux range from 250 lm to 280 lm.

3.2 Forward Voltage Binning

All devices for this part number fall under a single forward voltage bin, Bin 4, with a range of 2.9V to 3.8V at 1000mA.

3.3 Chromaticity Binning

The document provides a chromaticity coordinate chart (CIE 1931 x,y) defining the acceptable color space for the 4000K-5000K white light output. The target chromaticity coordinates are provided, with a guaranteed tolerance of ±0.01 on both x and y coordinates. This ensures color consistency between different units.

4. Performance Curve Analysis

Graphical data provides deeper insight into the device's behavior under varying conditions. All curves are based on the LED mounted on a 2cm x 2cm Metal Core PCB (MCPCB) for thermal management.

4.1 Relative Spectral Power Distribution

This curve (Fig. 1) shows the intensity of light emitted across different wavelengths. For a white LED, this typically shows a blue peak from the InGaN chip and a broader yellow-green-red peak from the phosphor coating. The shape determines the CCT and CRI.

4.2 Radiation Pattern

This polar diagram (Fig. 2) visually represents the 120-degree viewing angle, showing how light intensity decreases from the center (optical axis).

4.3 Forward Current Derating

This crucial curve (Fig. 3) illustrates how the maximum allowable DC forward current must be reduced as the ambient temperature increases. To prevent the junction temperature from exceeding 125°C, the drive current must be lowered in hotter environments.

4.4 Forward Current vs. Forward Voltage (I-V Curve)

Figure 4 shows the non-linear relationship between current and voltage. The \"knee\" voltage is where the device begins to emit light significantly. The curve is essential for designing the correct driver circuitry.

4.5 Relative Luminous Flux vs. Forward Current

Figure 5 demonstrates how light output increases with drive current. It typically shows a sub-linear relationship at very high currents due to efficiency droop and thermal effects.

4.6 Relative Luminous Flux vs. Junction Temperature

This curve (implied by thermal context) would show the reduction in light output as the junction temperature rises, a phenomenon known as thermal quenching. Maintaining a low T_j is key to maintaining stable, high output.

5. Mechanical & Package Information

5.1 Package Dimensions

The device is a 1.2mm x 1.2mm Chip Scale Package. The optical center is marked, and an anode mark indicates polarity. All dimension tolerances are ±0.075mm. The lens color is Orange/White, and the emitted color is White via InGaN technology with phosphor conversion.

5.2 Recommended PCB Attachment Pad Layout

A detailed land pattern diagram is provided for Surface Mount Technology (SMT) assembly. Adherence to this pattern is critical for proper soldering, alignment, and thermal performance. A maximum stencil thickness of 0.10mm is recommended for solder paste application.

5.3 Polarity Identification

The package includes a clear anode (+) mark. Correct polarity connection is essential; reverse connection can damage the device.

6. Soldering & Assembly Guidelines

6.1 Recommended IR Reflow Profile (Pb-Free Process)

A detailed reflow soldering profile is specified for lead-free assembly processes, compliant with J-STD-020D.

• Peak Temperature (T_P): 250°C maximum.
• Time above Liquidus (T_L = 217°C): 60-150 seconds.
• Ramp-Up Rate: 3°C/second maximum.
• Ramp-Down Rate: 6°C/second maximum.
• Preheat: 150-200°C for 60-120 seconds.

Critical Notes: A rapid cooling process is not recommended. The lowest possible soldering temperature that achieves a reliable joint is always desirable to minimize thermal stress on the LED. The use of halogen-free and lead-free flux is mandated, and care must be taken to prevent flux from contacting the LED lens. Dip soldering is not a guaranteed or recommended assembly method for this component.

6.2 Cleaning

If cleaning is necessary after soldering, only specified chemicals should be used. The LED can be immersed in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. The use of unspecified chemicals may damage the package material or optical lens.

6.3 Moisture Sensitivity

This product is classified as Moisture Sensitivity Level (MSL) 3 per JEDEC standard J-STD-020. This means the package can be exposed to ambient conditions (≤30°C/60% RH) for up to 168 hours (7 days) before it must be soldered. If exceeded, baking is required to remove absorbed moisture and prevent \"popcorning\" damage during reflow.

7. Packaging & Handling

7.1 Tape and Reel Specifications

The components are supplied in embossed carrier tape on reels for automated pick-and-place assembly. Detailed dimensions for the tape pockets, cover tape, and reel (including 7-inch reel specifications) are provided. A standard 7-inch reel contains 6000 pieces. Packaging follows EIA-481 specifications.

7.2 Storage Conditions

Devices should be stored in their original, unopened moisture-barrier bags with desiccant in an environment controlled to within the specified storage temperature range (-40°C to +100°C) and low humidity.

8. Application Notes & Design Considerations

8.1 Intended Use

This LED is designed for use in ordinary electronic equipment such as consumer electronics, communication devices, and office equipment. It is not rated for safety-critical applications where failure could jeopardize life or health (e.g., aviation, medical life-support, transportation safety systems). Consultation with the manufacturer is required for such applications.

8.2 Thermal Management Design

Effective heat sinking is paramount. The recommended use of a Metal Core PCB (MCPCB) is explicitly stated for the performance curves. The PCB layout should maximize copper area connected to the thermal pads beneath the CSP to conduct heat away from the junction. The low thermal resistance of the flip-chip design is an advantage, but it must be coupled with an effective system-level thermal path.

8.3 Electrical Drive Considerations

For flash applications, a pulsed current driver capable of delivering up to 1500mA for short durations (e.g., <400ms) is required. The driver circuit must account for the forward voltage binning range (2.9V-3.8V) and include appropriate current regulation or limiting to prevent damage from over-current, especially as the LED's forward voltage decreases with rising temperature. Reverse voltage protection is strongly advised, as the device is not designed for reverse bias operation.

8.4 Optical Integration

The 120-degree viewing angle provides a broad illumination field. For camera flash applications, secondary optics (reflectors or lenses) may be used to shape the beam pattern to better match the camera's field of view, improving efficiency and reducing glare. The small package size facilitates integration into slim device designs.

9. Technical Comparison & Differentiation

The LTPL-A138DWAGB's primary differentiators lie in its packaging and drive capability:

• vs. Traditional PLCC LEDs: The CSP format is significantly smaller and offers superior thermal performance due to the direct thermal path of the flip-chip, allowing for higher drive currents in a smaller space.
• vs. Other CSP LEDs: The combination of very high pulsed current rating (1500mA) and high typical luminous flux (240lm) targets the demanding requirements of modern smartphone camera flashes, where both size and light output are critical.
• vs. Xenon Flashes: LED flashes offer advantages in size, power consumption, durability, and fast recycling time. This particular LED aims to bridge the output gap with xenon through high-current pulsed operation.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive this LED with a constant 1000mA DC current?
A1: The Absolute Maximum Rating for DC current is 350mA. Driving at 1000mA DC would exceed this rating and likely cause immediate thermal failure. The 1000mA specification is for pulsed operation, typically under a low duty cycle as defined in the datasheet.

Q2: What is the difference between Junction Temperature (Tj) and Ambient Temperature (Ta)?
A2: Ambient Temperature (Ta) is the temperature of the air surrounding the device. Junction Temperature (Tj) is the temperature at the semiconductor chip inside the package, which is always higher than Ta due to self-heating from electrical power loss (I_F * V_F). Proper heat sinking aims to minimize the difference (Tj - Ta).

Q3: Why is there a Bin P1 for flux if the maximum in the characteristics table is 280lm?
A3: The Electrical Characteristics table defines the guaranteed min/typ/max for the entire part number. The binning system (N0, P1) provides finer sorting within that overall range. A designer needing guaranteed higher output can specify Bin P1 parts (250-280lm), while a cost-sensitive design might use Bin N0 parts (180-250lm).

Q4: How critical is the reflow profile?
A4: Extremely critical. Exceeding the peak temperature (250°C) or time above liquidus can degrade the internal materials, phosphor, and solder joints, leading to reduced performance or early failure. Following the recommended profile ensures reliability.

11. Operational Principles

The LTPL-A138DWAGB is a phosphor-converted white LED. It is based on an Indium Gallium Nitride (InGaN) semiconductor chip that emits blue light when forward biased (electroluminescence). This blue light is partially absorbed by a cerium-doped yttrium aluminum garnet (YAG:Ce) phosphor layer deposited on or near the chip. The phosphor down-converts a portion of the blue photons into photons across a broad spectrum in the yellow-green-red region. The mixture of the remaining blue light and the phosphor-emitted yellow light is perceived by the human eye as white light. The specific ratios of blue to yellow emission are tuned to achieve the target Correlated Color Temperature (CCT) of 4000K-5000K.

12. Industry Trends & Context

The development of LEDs like the LTPL-A138DWAGB is driven by several key trends in consumer electronics:

• Miniaturization: The relentless push for thinner, smaller devices demands light sources with the smallest possible footprint, making CSP LEDs increasingly essential.
• Enhanced Mobile Imaging: Smartphone cameras continue to improve in low-light performance. This requires more powerful flash units that can deliver high-quality (high CRI) light in very short pulses to freeze motion and illuminate scenes adequately without draining the battery excessively.
• Thermal Management in Compact Spaces: As power densities increase in tiny packages, advanced thermal solutions like flip-chip on CSP become critical to maintain performance and longevity. Efficient heat dissipation is a primary design challenge.
• Automation & Reliability: The tape-and-reel packaging and detailed SMT guidelines reflect the industry's reliance on fully automated, high-volume manufacturing where process control is vital for yield and reliability.

This datasheet represents a component at the intersection of these trends, offering high optical power from a minuscule package suitable for the next generation of compact imaging devices.