LTR-S951-TB IR Emitter and Detector Datasheet - Side View Package - Vce 30V - English Technical Document

1. Product Overview

The LTR-S951-TB is a discrete infrared (IR) component integrating an emitter and detector within a single, compact side-view package. This device is designed for applications requiring non-contact sensing or detection through infrared light. The primary function involves the emitter generating infrared radiation and the detector, a phototransistor in this case, responding to incident IR light by modulating its collector current. Its core advantages include a space-saving side-view form factor, compatibility with automated assembly processes, and a design suitable for infrared reflow soldering, making it ideal for high-volume PCB manufacturing. The target markets encompass consumer electronics, industrial automation, security systems, and any application utilizing remote control or proximity sensing principles.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

The device is rated for a maximum power dissipation of 100 mW at an ambient temperature (TA) of 25°C. The collector-emitter voltage (V_CE) must not exceed 30 V, and the emitter-collector voltage (V_EC) must not exceed 5 V. These ratings define the absolute limits beyond which permanent damage may occur. The operational temperature range is specified from -40°C to +85°C, with a wider storage temperature range of -55°C to +100°C, ensuring reliability under various environmental conditions. The component is also rated for infrared reflow soldering with a peak temperature of 260°C for a maximum of 10 seconds.

2.2 Electrical and Optical Characteristics

Key electrical parameters are defined at TA=25°C. The collector-emitter breakdown voltage (V_(BR)CEO) is a minimum of 30V, measured with a reverse current (I_R) of 100µA and no irradiance (E_e=0). The collector dark current (I_CEO), which is the leakage current when no light is present, has a maximum value of 100 nA at V_CE=20V. This low dark current is crucial for achieving a high signal-to-noise ratio in sensing applications. The on-state collector current (I_C(ON)), which indicates the phototransistor's response to IR light, has a typical value of 5.5 mA when V_CE=5V and is illuminated with an irradiance of 0.5 mW/cm² from a 940nm source. The switching speed is characterized by rise and fall times (t_r, t_f) of 15 µs typical, under specified test conditions of V_CE=5V, I_C=1mA, and R_L=1kΩ. This speed is adequate for many remote control and data transmission protocols.

3. Performance Curve Analysis

The datasheet includes typical characteristic curves which are essential for circuit design. These curves graphically represent the relationship between key parameters under varying conditions. While specific plots are not detailed in the provided text, such curves typically include the collector current (I_C) versus collector-emitter voltage (V_CE) for different levels of irradiance, showing the phototransistor's output characteristics. Another common curve is the collector current versus irradiance (E_e) at a fixed V_CE, illustrating the device's sensitivity. These graphs allow designers to predict the component's behavior in their specific application, ensuring the circuit operates within the linear and safe regions of the phototransistor's performance.

4. Mechanical and Package Information

The LTR-S951-TB features a side-view package with a black dome lens. Detailed outline dimensions are provided in the datasheet, with all measurements in millimeters. Tolerances are typically ±0.1 mm unless otherwise specified. The side-view design allows the IR beam to be parallel to the PCB surface, which is useful for edge-sensing applications or when vertical space is constrained. The package is designed to be compatible with automatic placement equipment, facilitating efficient assembly. Separate sections provide suggested soldering pad layout dimensions for PCB design and the package dimensions for the tape and reel format used in automated handling.

5. Soldering and Assembly Guidelines

5.1 Storage Conditions

For unopened, moisture-proof packaging with desiccant, the device should be stored at ≤30°C and ≤90% Relative Humidity (RH) and used within one year. Once the original packaging is opened, the storage environment must not exceed 30°C or 60% RH. Components removed from their original packaging are recommended to undergo IR reflow soldering within one week. For longer storage outside the original bag, they should be kept in a sealed container with desiccant or in a nitrogen ambient. If stored unpackaged for more than one week, a bake at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

5.2 Soldering Process

The device is compatible with infrared reflow soldering processes. Recommended conditions include a pre-heat zone of 150–200°C, a pre-heat time of up to 120 seconds maximum, a peak temperature not exceeding 260°C, and a time above 260°C limited to 10 seconds maximum. Reflow should be performed a maximum of two times. For hand soldering with an iron, the tip temperature should not exceed 300°C, and the soldering time per lead should be limited to 3 seconds. The datasheet references JEDEC standard profiles as a basis for process setup, emphasizing the need to follow solder paste manufacturer specifications and perform board-specific characterization.

5.3 Cleaning

If cleaning is necessary after soldering, only alcohol-based solvents such as isopropyl alcohol should be used. Harsh or aggressive chemical cleaners should be avoided to prevent damage to the package or lens material.

6. Packaging and Ordering Information

The component is supplied in an 8mm tape on 13-inch diameter reels, compliant with EIA standards. Each reel contains 9000 pieces. The tape and reel specifications follow ANSI/EIA 481-1-A-1994. The packaging ensures compatibility with high-speed automated pick-and-place machines. Notes specify that empty component pockets are sealed with cover tape and that a maximum of two consecutive missing components is allowed on a reel.

7. Application Suggestions

7.1 Typical Application Scenarios

The LTR-S951-TB is suited for applications such as infrared receivers in remote control systems, PCB-mounted proximity or object detection sensors, and basic IR wireless data transmission links. The side-view package makes it particularly useful for sensing objects along the edge of a device or in slots.

7.2 Drive Circuit Design

The phototransistor detector is a current-output device. A typical application circuit involves connecting a load resistor (R_L) between the collector and the supply voltage (V_CC), with the emitter connected to ground. The output signal is taken from the collector node. The value of R_L influences the gain, bandwidth, and output voltage swing. The datasheet provides test conditions using R_L=1kΩ. For the IR emitter (if actively driven), it is crucial to use a series current-limiting resistor for each LED to ensure uniform intensity and prevent current hogging, as the forward voltage (V_f) can vary between devices. Driving LEDs in parallel without individual resistors is not recommended.

7.3 Design Considerations

Designers must consider the device's viewing angle (implied by the dome lens), sensitivity to the 940nm wavelength, and switching speed relative to their application's data rate. Ambient light immunity can be a concern; while the black lens helps, optical filtering or modulation of the IR source may be necessary in high-ambient-light environments. The placement on the PCB must align with the mechanical outline and suggested pad dimensions to ensure proper soldering and alignment for sensing.

8. Cautions and Reliability Notes

The product is intended for standard electronic equipment. For applications requiring exceptional reliability where failure could risk life or health (e.g., medical, aviation, transportation), specific consultation and qualification are necessary. The specifications and product appearance are subject to change without notice for product improvement.

9. Principle of Operation

The device operates on the principle of photoelectric effect in semiconductors. The infrared emitter is typically a Gallium Arsenide (GaAs) or similar material Light Emitting Diode (LED) that emits photons at a peak wavelength around 940nm when forward biased. The detector is a silicon phototransistor. When photons from the emitter (or another IR source) strike the base region of the phototransistor, they generate electron-hole pairs. This photogenerated current acts as a base current, which is then amplified by the transistor's current gain (β), resulting in a much larger collector current. This change in collector current in response to IR light is the fundamental sensing mechanism. The integrated package aligns the emitter and detector optically for reflective sensing modes, where an object reflects the emitted light back to the detector.