Phototransistor PD204-6B/L3 Datasheet - 3mm Package - Peak Sensitivity 940nm - English Technical Document

1. Product Overview

The PD204-6B/L3 is a high-speed, high-sensitivity silicon PIN photodiode housed in a standard 3mm plastic package. This device is spectrally matched to visible and infrared emitting diodes, with its peak sensitivity optimized for the 940nm wavelength, making it suitable for a variety of sensing applications requiring fast response and reliable performance.

Key advantages of this component include its fast response time, high photosensitivity, and small junction capacitance, which contribute to efficient signal detection. The product is compliant with RoHS and EU REACH regulations, and is manufactured as a lead-free (Pb-free) device.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device is designed to operate reliably within specified environmental and electrical limits. Exceeding these ratings may cause permanent damage.

• Reverse Voltage (VR): 32 V - The maximum voltage that can be applied in reverse bias across the photodiode terminals.
• Operating Temperature (Topr): -25°C to +85°C - The ambient temperature range for normal device operation.
• Storage Temperature (Tstg): -40°C to +100°C - The temperature range for safe storage when the device is not powered.
• Soldering Temperature (Tsol): 260°C for a maximum duration of 5 seconds, as per standard reflow soldering profiles.
• Power Dissipation (Pc): 150 mW at or below 25°C free air temperature.

2.2 Electro-Optical Characteristics

These parameters define the core performance of the phototransistor under standard test conditions (Ta=25°C).

• Spectral Bandwidth (λ0.5): 760 nm to 1100 nm. This defines the range of wavelengths where the device maintains at least half of its peak sensitivity.
• Peak Sensitivity Wavelength (λP): 940 nm (Typical). The device is most responsive to light at this infrared wavelength.
• Open-Circuit Voltage (VOC): 0.42 V (Typical) under an irradiance (Ee) of 1 mW/cm² at 940nm.
• Short-Circuit Current (ISC): 4.3 μA (Typical) under the same test condition (Ee=1mW/cm², λp=940nm).
• Reverse Light Current (IL): 3.9 μA (Min), 6 μA (Typ) at VR=5V, Ee=1mW/cm², λp=940nm. This is the photocurrent generated when the diode is reverse-biased and illuminated.
• Reverse Dark Current (ID): 10 nA (Max) at VR=10V in complete darkness (Ee=0mW/cm²). This is the small leakage current that flows even when no light is present.
• Reverse Breakdown Voltage (VBR): 32 V (Min) measured at a reverse current (IR) of 100μA in darkness.
• Total Capacitance (Ct): 10 pF (Typ) at VR=5V and a frequency of 1MHz. Lower capacitance enables faster switching speeds.
• Rise/Fall Time (tr/tf): 10 ns / 10 ns (Typ) with VR=10V and a load resistance (RL) of 100Ω, indicating a very fast response suitable for pulsed light detection.
• View Angle (2θ1/2): 45° (Typ). This defines the angular field of view over which the device maintains sensitivity.

Tolerances are specified as ±10% for luminous intensity, ±1nm for dominant wavelength, and ±0.1V for forward voltage in related applications.

3. Performance Curve Analysis

The datasheet provides several characteristic curves that illustrate device behavior under varying conditions. These are essential for design engineers to predict performance in real-world scenarios.

3.1 Power Dissipation vs. Ambient Temperature

This curve shows the maximum allowable power dissipation decreasing as the ambient temperature increases above 25°C. Designers must derate the power handling capability accordingly to ensure long-term reliability.

3.2 Spectral Sensitivity

The spectral response curve confirms the device's peak sensitivity at 940nm and its useful range from approximately 760nm to 1100nm. It highlights the device's suitability for applications using common infrared LEDs.

3.3 Reverse Dark Current vs. Ambient Temperature

Dark current increases exponentially with temperature. This curve is critical for applications operating at elevated temperatures, as higher dark current contributes to noise and can affect the signal-to-noise ratio in low-light conditions.

3.4 Reverse Light Current vs. Irradiance (Ee)

This plot demonstrates the linear relationship between the generated photocurrent (IL) and the incident light intensity (irradiance) over a specified range. It confirms the device's predictable and linear photometric response.

3.5 Terminal Capacitance vs. Reverse Voltage

The junction capacitance (Ct) decreases with increasing reverse bias voltage. A lower capacitance is desirable for high-speed applications, and this curve helps select an optimal operating bias point.

3.6 Response Time vs. Load Resistance

This curve shows how the rise and fall times (tr/tf) are affected by the value of the external load resistor (RL). Faster response is achieved with smaller load resistances, but this trades off against signal amplitude.

4. Mechanical and Package Information

4.1 Package Dimension

The device uses a standard 3mm radial leaded package. The dimensional drawing specifies the body diameter, lead spacing, and lead dimensions. All unspecified tolerances are ±0.25mm. The lens color is black.

4.2 Polarity Identification

The cathode (negative terminal) is typically indicated by a flat spot on the package body or a longer lead. Correct polarity must be observed during circuit assembly for proper reverse-bias operation.

5. Soldering and Assembly Guidelines

The component is suitable for standard PCB assembly processes.

• Reflow Soldering: The maximum soldering temperature is 260°C, and the time at or above this temperature must not exceed 5 seconds to prevent thermal damage to the plastic package and the semiconductor die.
• Hand Soldering: If hand soldering is necessary, a temperature-controlled iron should be used with minimal contact time (typically less than 3 seconds per lead).
• Cleaning: Use cleaning agents compatible with the plastic package material.
• Storage: Store in a dry, anti-static environment within the specified storage temperature range of -40°C to +100°C.

6. Packaging and Ordering Information

6.1 Packing Quantity Specification

The standard packing is as follows: 200-1000 pieces per bag, 4 bags per box, and 10 boxes per carton. This provides flexibility for both prototyping and volume production.

6.2 Label Form Specification

The product label contains key information for traceability and identification:

• CPN: Customer's Product Number
• P/N: Product Number (e.g., PD204-6B/L3)
• QTY: Packing Quantity
• CAT, HUE, REF: Ranks for Luminous Intensity, Dominant Wavelength, and Forward Voltage (if binned).
• LOT No: Manufacturing Lot Number for traceability.
• X: Month of production.

7. Application Suggestions

7.1 Typical Application Scenarios

The PD204-6B/L3 is well-suited for various optoelectronic sensing applications, including:

• Automatic Door Sensors: Detecting the interruption of an infrared beam to trigger door opening/closing mechanisms.
• Copiers and Printers: Used for paper detection, edge sensing, or toner level monitoring.
• Game Machines/Arcade Systems: For object detection, interactive controls, or position sensing.
• General Purpose Infrared Sensing: Remote control receivers, proximity sensors, and industrial automation where fast, reliable detection of 940nm IR light is required.

7.2 Design Considerations

• Bias Circuit: Operate the photodiode in reverse bias (photoconductive mode) for optimal speed and linearity. A reverse voltage of 5V to 10V is typical, as shown in the specifications.
• Load Resistor (RL): Choose RL based on the required trade-off between response speed (bandwidth) and output voltage swing. A transimpedance amplifier (TIA) circuit is recommended for converting the small photocurrent into a usable voltage while maintaining high speed and low noise.
• Optical Considerations: Ensure proper alignment with the light source (typically an IR LED at 940nm). The 45° view angle should be considered for the field of view. Using an optical filter can help block unwanted ambient light, especially visible light.
• Noise Reduction: For sensitive applications, shield the device and its circuitry from electrical noise. Keep traces short, use bypass capacitors, and consider the impact of dark current at high operating temperatures.

8. Technical Comparison and Differentiation

Compared to standard photodiodes or phototransistors with slower response times, the PD204-6B/L3 offers distinct advantages:

• High Speed: With rise/fall times of 10ns, it is significantly faster than many general-purpose phototransistors, enabling detection of rapidly modulated signals.
• PIN Structure: The PIN photodiode construction provides a wider depletion region than a standard PN photodiode, resulting in lower junction capacitance (10pF) and higher speed.
• Optimized Spectrum: The 940nm peak sensitivity is precisely matched to the output of common, low-cost infrared LEDs, maximizing system efficiency.
• Standard Package: The 3mm radial package is a common industry form factor, making it easy to integrate into existing designs and compatible with standard PCB footprints.

9. Frequently Asked Questions (Based on Technical Parameters)

9.1 What is the difference between operating in photovoltaic (zero bias) and photoconductive (reverse bias) mode?

In photovoltaic mode (V_R=0V), the photodiode generates a voltage (V_OC). This mode has zero dark current but slower response and less linearity. The PD204-6B/L3 specifications list VOC=0.42V. In photoconductive mode (with reverse bias, e.g., V_R=5V), an external voltage is applied. This reduces junction capacitance (enabling faster response, as seen in the 10ns tr/tf), improves linearity, and allows for a larger active region, but introduces dark current (I_D). For high-speed applications like those intended for this device, photoconductive mode is recommended.

9.2 How do I convert the photocurrent (I_L) into a measurable voltage?

The simplest method is to use a load resistor (R_L) in series. The output voltage is V_out = I_L * R_L. However, as R_L increases, the RC time constant (with the diode capacitance) increases, slowing the response (as shown in the Response Time vs. Load Resistance curve). For optimal performance, especially with small currents and need for speed, a transimpedance amplifier (TIA) is the preferred circuit. It provides a stable, low-impedance output voltage (V_out = -I_L * R_f) while keeping the photodiode at virtual ground, minimizing the effects of capacitance.

9.3 Why is the dark current important, and how does temperature affect it?

Dark current (I_D) is the noise current that flows when no light is present. It sets the lower limit of detectable light. The datasheet specifies a maximum of 10nA at 25°C. This current doubles approximately every 10°C rise in temperature. Therefore, in high-temperature environments or for very low-light detection, dark current can become a significant source of noise and must be accounted for in the circuit design (e.g., through temperature compensation or synchronous detection techniques).

9.4 Can this sensor be used with light sources other than 940nm?

Yes, but with reduced sensitivity. The spectral response curve shows significant sensitivity from 760nm to 1100nm. For example, it will respond to 850nm LEDs, but the generated photocurrent for the same light intensity will be lower than with a 940nm source. Always refer to the relative spectral sensitivity curve (if provided in full) or calculate responsivity at the desired wavelength for accurate design.

10. Practical Design Case Study

Design Case: Infrared Beam Break Sensor for Security Gate.

Objective: Create a reliable, fast sensor to detect when an object interrupts an invisible infrared beam, triggering a security alarm.

Implementation:

1. Transmitter: A 940nm infrared LED is driven by a pulsed current (e.g., 20mA pulses at 38kHz) to provide immunity against ambient light and reduce average power consumption.
2. Receiver: The PD204-6B/L3 is placed opposite the transmitter, aligned within its 45° view angle. It is reverse-biased at 5V through a load resistor.
3. Signal Conditioning: The small AC photocurrent signal from the photodiode (superimposed on the DC dark current) is fed into a high-gain, band-pass amplifier tuned to 38kHz. This filters out DC ambient light and low-frequency noise.
4. Detection: The amplified signal is then rectified and compared to a threshold. When the beam is unbroken, a strong 38kHz signal is present, and the comparator output is high. When an object breaks the beam, the signal disappears, causing the comparator to switch low and activate the alarm.

Why PD204-6B/L3 is Suitable: Its fast 10ns response time easily handles the 38kHz modulated signal. The high sensitivity at 940nm ensures a good signal-to-noise ratio from the matched IR LED. The low capacitance allows for a responsive circuit even with necessary filtering components.

11. Operating Principle

A PIN photodiode like the PD204-6B/L3 operates on the principle of the internal photoelectric effect. The device structure consists of a wide, lightly doped intrinsic (I) semiconductor region sandwiched between P-type and N-type regions. When photons with energy greater than the semiconductor's bandgap (e.g., infrared light at 940nm for silicon) strike the intrinsic region, they generate electron-hole pairs. When the diode is reverse-biased, the built-in electric field across the depletion region (which extends through the intrinsic layer) sweeps these charge carriers towards the respective terminals, generating a photocurrent (I_L) that is proportional to the incident light intensity. The wide intrinsic region reduces capacitance and allows for efficient collection of carriers generated over a larger volume, contributing to both speed and sensitivity.

12. Industry Trends and Context

Photodetectors like the PD204-6B/L3 are fundamental components in the growing field of optoelectronics and sensing. Current trends driving demand for such devices include:

• Automation and Industry 4.0: Increased use of non-contact sensors for position, presence, and quality control in manufacturing.
• Consumer Electronics: Integration into devices for proximity sensing (e.g., turning off smartphone screens during calls), ambient light sensing for display brightness control, and gesture recognition.
• Internet of Things (IoT): Low-power, reliable sensors for smart home devices, security systems, and environmental monitoring.
• Advancements: The general trend is towards higher integration (e.g., photodiodes with on-chip amplifiers), smaller packages (surface-mount devices), lower power consumption, and enhanced performance in specific wavelengths for applications like LiDAR, biomedical sensing, and optical communications. Devices like the PD204-6B/L3 represent a mature, reliable, and cost-effective solution for mainstream infrared sensing needs.

13. Disclaimer and Usage Notes

Critical usage guidelines derived from the datasheet disclaimer include:

1. Specifications are subject to change. Always refer to the latest official datasheet for design.
2. The product meets its published specifications for 12 months from the date of shipment under normal storage conditions.
3. Characteristic curves show typical performance, not guaranteed minimum or maximum values. Design with appropriate margins.
4. Strictly adhere to the Absolute Maximum Ratings. Operation beyond these limits can cause immediate or latent failure. The manufacturer assumes no liability for damage resulting from misuse.
5. The information is proprietary. Reproduction without permission is prohibited.
6. This component is not designed or qualified for safety-critical applications such as medical life-support, automotive control, aviation, or military systems. For such applications, contact the manufacturer for specially qualified products.