LTR-5888DHP1 Phototransistor Datasheet - Dark Green Package - Vce 30V - Pc 100mW - English Technical Documentation

1. Product Overview

The LTR-5888DHP1 is a high-sensitivity phototransistor designed for infrared (IR) detection applications. Its core function is to convert incident infrared light into an electrical current. A key feature is its special dark green plastic package, which is engineered to attenuate or cut visible light wavelengths. This design minimizes interference from ambient visible light sources, making the device particularly suitable for applications where the signal of interest is purely in the infrared spectrum, such as proximity sensing, object detection, and IR remote control receivers.

The device offers a wide operating range for the collector current and is characterized by fast switching times, enabling it to respond quickly to changes in IR illumination. This combination of optical filtering, sensitivity, and speed makes it a versatile component for various electronic systems requiring reliable IR detection.

2. In-Depth Technical Parameter Analysis

2.1 Absolute Maximum Ratings

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

• Power Dissipation (P_C): 100 mW. This is the maximum power the device can dissipate as heat at an ambient temperature (T_A) of 25°C. Exceeding this limit risks thermal runaway and failure.
• Collector-Emitter Voltage (V_CEO): 30 V. The maximum voltage that can be applied between the collector and emitter terminals when the base (light-sensitive region) is open.
• Emitter-Collector Voltage (V_ECO): 5 V. The maximum reverse voltage applicable between emitter and collector.
• Operating Temperature Range: -40°C to +85°C. The ambient temperature range over which the device is designed to function correctly.
• Storage Temperature Range: -55°C to +100°C. The temperature range for non-operational storage.
• Lead Soldering Temperature: 260°C for 5 seconds at a distance of 1.6mm from the package body. This defines the reflow soldering profile constraint to prevent package damage.

2.2 Electrical & Optical Characteristics

These parameters are specified at T_A=25°C and define the typical performance of the device.

• Breakdown Voltages: V_(BR)CEO (30V min) and V_(BR)ECO (5V min). These are the voltages at which the junction breaks down under specified test currents with no illumination (E_e = 0 mW/cm²).
• Collector-Emitter Saturation Voltage (V_CE(SAT)): 0.4V max at I_C = 100µA and E_e = 1 mW/cm². This is the voltage drop across the transistor when it is fully "on" (saturated) under illumination. A lower V_CE(SAT) is desirable for efficient switching.
• Switching Times: Rise Time (T_r) is 15 µs typical and Fall Time (T_f) is 18 µs typical, measured under V_CC=5V, I_C=1mA, and R_L=1kΩ. These times determine how fast the output can respond to a pulsed light input.
• Collector Dark Current (I_CEO): 100 nA max at V_CE=10V with no illumination. This is the small leakage current that flows when the device is in complete darkness. A lower dark current indicates better signal-to-noise ratio in low-light detection.
• Collector Current Ratio (R): 0.8 to 1.25. This parameter likely specifies the matching between two phototransistors or channels, important for differential sensing applications.

3. Binning System Explanation

The LTR-5888DHP1 employs a comprehensive binning system based on its On-State Collector Current (I_C(ON)). Binning is a quality control process that groups components with similar performance characteristics. Two binning tables are provided: one for the production setting range and one for the final guaranteed range.

The parameter I_C(ON) is defined as the average collector current under standardized conditions (V_CE = 5V, E_e = 1 mW/cm²). Devices are sorted into bins labeled A through H, each with a specific I_C(ON) range (e.g., Bin A: 0.20mA to 0.26mA for production setting). Each bin is associated with a distinct color marking (Red, Black, Green, Blue, White, Purple, Yellow, Orange). This allows designers to select devices with tightly controlled sensitivity for their specific circuit requirements, ensuring consistent system performance. For example, an application requiring a precise trigger threshold would benefit from using devices from a single, narrow bin.

4. Performance Curve Analysis

The datasheet includes several typical characteristic curves, which provide visual insight into device behavior under varying conditions.

• Figure 1: Collector Dark Current vs. Ambient Temperature: This graph shows how I_CEO increases exponentially with rising temperature. This is a critical consideration for high-temperature applications, as the increasing dark current can mask weak optical signals.
• Figure 2: Collector Power Dissipation vs. Ambient Temperature: This derating curve illustrates that the maximum allowable power dissipation (P_C) decreases as ambient temperature increases. At 85°C, the maximum power the device can handle is significantly less than the 100mW rating at 25°C. Designers must use this curve to ensure safe thermal operation.
• Figure 3: Rise & Fall Time vs. Load Resistance: This plot demonstrates that switching times (T_r and T_f) increase with higher load resistance (R_L). For applications requiring maximum speed, a lower value of R_L should be chosen, though this will affect the output voltage swing.
• Figure 4: Relative Collector Current vs. Irradiance: This is the fundamental transfer function of the phototransistor. It shows that the collector current increases linearly with the incident infrared irradiance (E_e) over a certain range. The slope of this line represents the device's responsivity or sensitivity.

5. Mechanical & Packaging Information

The device uses a special dark green plastic package. The package dimensions are provided in the datasheet with all measurements in millimeters. Key dimensional notes include: a tolerance of ±0.25mm unless specified otherwise, a maximum resin protrusion under the flange of 1.5mm, and lead spacing measured at the point where leads exit the package. The dark green material is crucial for its optical filtering properties, blocking visible light to enhance IR-specific performance.

6. Soldering & Assembly Guidelines

The primary guideline provided is related to soldering thermal stress. The leads can be subjected to a temperature of 260°C for a maximum duration of 5 seconds, measured at a point 1.6mm (0.063 inches) from the package body. This specification is critical for defining a safe reflow soldering profile. Exceeding this time-temperature limit can cause internal damage to the semiconductor die, wire bonds, or the plastic package itself, leading to immediate failure or reduced long-term reliability. Standard industry practices for handling moisture-sensitive devices (MSL) should also be followed unless otherwise stated.

7. Application Recommendations

7.1 Typical Application Scenarios

• Infrared Remote Control Receivers: Detecting modulated IR signals from TV remotes, air conditioners, etc.
• Proximity and Object Detection: Used in automatic faucets, hand dryers, paper towel dispensers, and robotics to sense the presence of an object.
• Industrial Counting and Sorting: Detecting objects on conveyor belts when paired with an IR emitter.
• Optical Encoders: Sensing slots or marks on a rotating disk for position or speed measurement.
• Smoke Detectors: In some optical chamber designs, to detect light scattered by smoke particles.

7.2 Design Considerations

• Biasing: The phototransistor can be used in either a switch (saturated) mode or a linear (active) mode. In switch mode (common-emitter configuration with a pull-up resistor), it provides a digital output. In linear mode (often with an operational amplifier), it provides an analog output proportional to light intensity.
• Load Resistor (R_L): The value of R_L in the collector circuit is a key design choice. A smaller R_L provides faster switching (see Fig. 3) but results in a smaller output voltage swing for a given photocurrent. A larger R_L gives a larger voltage swing but slower response.
• Ambient Light Rejection: While the dark green package helps, for environments with strong ambient IR (e.g., sunlight, incandescent bulbs), additional electrical filtering may be necessary. Using a modulated IR source and a demodulating receiver circuit is a highly effective technique.
• Thermal Management: Refer to Figure 2 (derating curve) to ensure the device's power dissipation remains within safe limits at the maximum expected operating ambient temperature.
• Binning Selection: Choose the appropriate sensitivity bin (A-H) based on the required signal level and the expected IR source intensity to optimize circuit performance and consistency.

8. Technical Comparison & Differentiation

The LTR-5888DHP1's primary differentiator is its dedicated dark green package for visible light suppression. Compared to clear or non-filtered phototransistors, it offers superior performance in environments with high ambient visible light, as it is less likely to be triggered falsely. Its combination of a relatively high V_CEO (30V), fast switching speed (µs range), and a detailed binning system for sensitivity makes it a robust and design-friendly choice for a wide array of IR sensing tasks. The comprehensive binning allows for precision matching in applications requiring multiple sensors or very consistent trigger points.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the purpose of the dark green package?
A: It acts as a visible light filter. It attenuates light in the visible spectrum (approx. 400-700nm) while allowing infrared wavelengths (typically >700nm) to pass through to the semiconductor chip. This improves the signal-to-noise ratio in IR-only applications.

Q: How do I interpret the two different binning tables?
A: The "Production Setting" table shows the tighter internal ranges used during manufacturing to sort devices. The "On State Range" table shows the wider, guaranteed specification range that the customer can rely on. Devices from a single production bin will have more consistent performance than those simply meeting the wider guaranteed range.

Q: Can I use this device in direct sunlight?
A: While the package filters visible light, sunlight contains a significant amount of infrared radiation. This can saturate the sensor. For outdoor use or in strong ambient IR, optical shielding, electrical filtering, or the use of a modulated IR source system is strongly recommended.

Q: What happens if I exceed the lead soldering temperature/time?
A: It can cause irreversible damage: melting of the package, breaking of internal wire bonds, or degradation of the semiconductor properties. Always adhere to the 260°C for 5 seconds guideline at 1.6mm from the body.

10. Practical Design Case Study

Scenario: Designing a Proximity Sensor for an Automatic Soap Dispenser.
The goal is to detect a hand placed ~5-10cm below a nozzle. An IR LED emitter is placed opposite the LTR-5888DHP1 detector, both facing the detection zone.

Design Steps:
1. Circuit Configuration: Use the phototransistor in common-emitter switch mode. Connect the emitter to ground, the collector to a pull-up resistor (R_L) connected to a supply voltage (e.g., 5V). The output signal is taken from the collector node.
2. Component Selection: Choose an IR LED with a wavelength matched to the peak sensitivity of the phototransistor. Select an R_L value (e.g., 10kΩ) that provides a good voltage swing. Based on the expected reflected IR intensity, select a phototransistor from Bin D or E for medium sensitivity.
3. Modulation (Optional but Recommended): To reject ambient light, drive the IR LED with a pulsed current (e.g., 38kHz). Follow the phototransistor output with a bandpass filter or a dedicated IR receiver IC tuned to the same frequency. This makes the system immune to constant ambient IR.
4. Threshold Detection: The output voltage at the collector will drop when a hand reflects the IR light onto the detector. A comparator or microcontroller's ADC can be used to detect this voltage change and trigger the soap pump.
5. Considerations: Account for the dark current increase with temperature (Fig. 1) when setting the detection threshold. Ensure the device's power dissipation is within limits per Fig. 2.

11. Operating Principle

A phototransistor is fundamentally a bipolar junction transistor (BJT) where the base region is exposed to light and is not connected to an electrical terminal. Incident photons with energy greater than the semiconductor's bandgap are absorbed in the base-collector junction region. This absorption creates electron-hole pairs. The electric field in the reverse-biased base-collector junction sweeps these charge carriers, generating a photocurrent. This photocurrent acts as the base current for the transistor. Due to the transistor's current gain (β or h_FE), the resulting collector current is the photocurrent multiplied by the gain (I_C ≈ β * I_photo). This internal amplification is what gives a phototransistor much higher sensitivity than a simple photodiode. The dark green package material absorbs most visible light photons, while infrared photons can pass through and be absorbed by the silicon to generate the signal current.

12. Technology Trends

The field of optoelectronics for sensing continues to evolve. Trends relevant to devices like the LTR-5888DHP1 include:
Integration: Moving towards integrated solutions that combine the photodetector, amplifier, and digital logic (like a Schmitt trigger or modulator/demodulator) into a single package (e.g., IR receiver modules).
Miniaturization: Development of phototransistors in smaller surface-mount packages to meet the demands of compact consumer electronics.
Enhanced Filtering: Use of more sophisticated interference filters deposited directly on the chip or package to provide sharper wavelength selectivity, improving rejection of unwanted ambient light sources.
Application-Specific Optimization: Devices are increasingly being characterized and binned for very specific applications (e.g., specific pulse detection for data communication, very low dark current for precision measurement), rather than as general-purpose components.