PD204-6C Photodiode Datasheet - 3mm Package - Peak Sensitivity 940nm - English Technical Document

1. Product Overview

The PD204-6C is a high-speed, high-sensitivity silicon PIN photodiode housed in a standard 3mm diameter plastic package. This device is specifically designed for applications requiring fast response times and reliable detection of visible and near-infrared light. Its spectral response is optimally matched to common visible and infrared emitting diodes (IREDs), making it a versatile component for various optoelectronic systems. The product is compliant with RoHS and EU REACH regulations and is manufactured using lead-free processes.

1.1 Core Features and Advantages

• Fast Response Time: Enables the detection of rapid optical signals, suitable for high-speed communication and sensing.
• High Photo Sensitivity: Provides a strong electrical signal from low levels of incident light, improving signal-to-noise ratio.
• Small Junction Capacitance: Contributes to the fast response time by reducing the RC time constant of the detection circuit.
• Standard Package: The 3mm plastic package is a common form factor, ensuring easy integration into existing designs and compatibility with standard sockets.
• Environmental Compliance: The device is Pb-free and adheres to RoHS and EU REACH standards.

1.2 Target Applications

The PD204-6C is suitable for a range of industrial and consumer applications where reliable light detection is required. Primary application areas include:

• Automatic Door Sensors: For presence detection and safety systems.
• Office Equipment: Such as copiers and printers for paper detection and edge sensing.
• Consumer Electronics: Including game machines for interactive or positional sensing.
• General Purpose Opto-isolation and Light Detection: In various electronic circuits.

2. Technical Specifications and Objective Interpretation

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.

• Reverse Voltage (V_R): 32 V - The maximum voltage that can be applied in reverse bias across the photodiode terminals.
• Operating Temperature (T_opr): -40°C to +85°C - The ambient temperature range for normal device operation.
• Storage Temperature (T_stg): -40°C to +100°C - The temperature range for non-operational storage.
• Soldering Temperature (T_sol): 260°C for a maximum of 5 seconds - Critical for PCB assembly to prevent thermal damage to the plastic package and semiconductor die.
• Power Dissipation (P_c): 150 mW at or below 25°C free air temperature - The maximum power the device can dissipate.

2.2 Electro-Optical Characteristics (T_a = 25°C)

These parameters define the device's performance under specified test conditions. Typical values represent the center of the distribution, while min/max values define the guaranteed limits.

• Spectral Bandwidth (λ_0.5): 400 nm to 1100 nm - The wavelength range where the responsivity is at least half of its peak value. This indicates a broad sensitivity from visible blue to near-infrared.
• Peak Sensitivity Wavelength (λ_P): 940 nm (Typical) - The wavelength of light at which the photodiode is most sensitive. This aligns perfectly with common 940nm infrared LEDs.
• Open-Circuit Voltage (V_OC): 0.42 V (Typical) at E_e=1 mW/cm², λ_p=940nm - The voltage generated by the photodiode under illumination when no current is drawn (open circuit).
• Short-Circuit Current (I_SC): 3.5 µA (Typical) at E_e=1 mW/cm², λ_p=940nm - The current generated by the photodiode under illumination when the terminals are shorted (zero voltage).
• Reverse Light Current (I_L): 3.5 µA (Typical) at V_R=5V, E_e=1 mW/cm², λ_p=940nm - The photocurrent generated when the diode is reverse-biased. This is the primary operating parameter in most circuits.
• Reverse Dark Current (I_D): 10 nA (Max) at V_R=10V, E_e=0 mW/cm² - The small leakage current that flows under reverse bias in complete darkness. A lower value is better for detecting weak light signals.
• Reverse Breakdown Voltage (V_BR): 32 V (Min), 170 V (Typical) at I_R=100µA - The voltage at which the reverse current increases sharply. The typical value is much higher than the absolute maximum rating, indicating a good safety margin.
• Total Capacitance (C_t): 5 pF (Typical) at V_R=5V, f=1MHz - The junction capacitance, which affects high-frequency response. Lower capacitance enables faster switching.
• Rise Time / Fall Time (t_r / t_f): 6 ns / 6 ns (Typical) at V_R=10V, R_L=100Ω - The time required for the output to transition from 10% to 90% (rise) and 90% to 10% (fall) of its final value in response to a light pulse. This confirms the high-speed capability.

3. Performance Curve Analysis

The datasheet provides several characteristic curves that illustrate device behavior under varying conditions. These are essential for detailed circuit design.

3.1 Spectral Sensitivity

The curve shows responsivity versus wavelength. It peaks around 940nm and has significant response from approximately 400nm to 1100nm. This broad response makes the device useful with various light sources, though it is optimized for near-IR.

3.2 Reverse Light Current vs. Irradiance (E_e)

This graph typically shows a linear relationship between photocurrent (I_L) and incident light power density (E_e) over a wide range. The slope of this line represents the responsivity (A/W) of the photodiode. Designers use this to calculate the expected signal current for a given light level.

3.3 Reverse Dark Current vs. Ambient Temperature

This curve demonstrates that dark current (I_D) increases exponentially with temperature. For high-precision or high-temperature applications, this leakage current can become a significant source of noise and offset error.

3.4 Terminal Capacitance vs. Reverse Voltage

The junction capacitance (C_t) decreases with increasing reverse bias voltage. A designer can trade off higher reverse voltage (and thus lower capacitance for speed) against higher dark current and power consumption.

3.5 Response Time vs. Load Resistance

The rise/fall time increases with larger load resistance (R_L) due to the larger RC time constant formed by the photodiode's junction capacitance and the load resistor. For maximum speed, a low-value load resistor or a transimpedance amplifier configuration is recommended.

4. Mechanical and Package Information

4.1 Package Dimension

The PD204-6C is housed in a standard 3mm diameter round plastic package. The dimensional drawing specifies the body diameter, lead spacing, and lead dimensions. A key specification is the tolerance of ±0.25mm on critical dimensions, which is standard for this type of component. The package features a water-clear lens, allowing broad spectrum transmission.

4.2 Polarity Identification

The cathode is typically identified by a longer lead, a flat spot on the package rim, or a marking on the package body. Correct polarity must be observed during installation, with the cathode connected to the more positive voltage in reverse-bias operation (the common mode).

5. Assembly and Handling Guidelines

5.1 Soldering Recommendations

The absolute maximum soldering temperature is 260°C for a duration not exceeding 5 seconds. This is compatible with standard lead-free reflow soldering profiles. Hand soldering should be performed quickly with a temperature-controlled iron to avoid thermal stress on the plastic package and the semiconductor junction.

5.2 Storage Conditions

The device should be stored within the specified storage temperature range of -40°C to +100°C in a dry environment. Moisture-sensitive devices should be kept in their original sealed packaging until use to prevent moisture absorption, which can cause \"popcorning\" during reflow soldering.

6. Packaging and Ordering Information

6.1 Packing Specification

The standard packing is 200 to 1000 pieces per bag, 4 bags per box, and 10 boxes per carton. This bulk packaging is typical for automated assembly processes.

6.2 Label Information

The product label contains critical information for traceability and verification: Customer Product Number (CPN), Product Number (P/N), Packing Quantity (QTY), and Lot Number (LOT No). It may also include bins for luminous intensity, dominant wavelength, and forward voltage, although these are more relevant for LEDs; for photodiodes, key parameters like dark current or responsivity might be binned.

7. Application Design Considerations

7.1 Circuit Configuration

The PD204-6C can be used in two primary modes:
Photovoltaic Mode: The diode is operated with zero bias (short circuit or connected to a high-impedance voltage amplifier). This mode offers very low dark current but has slower response due to higher junction capacitance and is non-linear for large signals.
Photoconductive Mode: The diode is reverse-biased (e.g., 5V or 10V as shown in the datasheet). This is the recommended mode for high-speed and linear operation. The reverse bias reduces junction capacitance (increasing speed) and widens the depletion region, improving quantum efficiency. A load resistor converts the photocurrent into a voltage signal.

7.2 Amplifier Interface

For best performance, especially with weak signals, a transimpedance amplifier (TIA) is used. The TIA converts the photocurrent directly into a voltage while maintaining a virtual ground at the photodiode cathode, which keeps the diode at a constant reverse bias (zero voltage across it). This configuration minimizes the effects of junction capacitance and provides excellent bandwidth and linearity. Care must be taken to select an op-amp with low input bias current and low noise, and to compensate the feedback network for stability.

7.3 Optical Considerations

To maximize performance, the optical path should be designed to match the photodiode's active area and angular response. Lenses, apertures, or filters may be used to control the field of view, reject unwanted wavelengths (like ambient light), or focus light onto the sensitive area. For applications with strong ambient light, an optical filter matched to the source wavelength (e.g., a 940nm bandpass filter) can dramatically improve the signal-to-noise ratio.

8. Technical Comparison and Differentiation

The PD204-6C's key differentiators in its class (3mm PIN photodiodes) are its combination of high speed (6ns rise/fall time) and good sensitivity (3.5 µA at 1 mW/cm²). Some competing devices may prioritize one characteristic over the other. The 940nm peak sensitivity is a standard for IR systems, but designers requiring peak response at other wavelengths (e.g., 850nm for some communications) would need to select a different variant. The relatively low dark current (10 nA max) is also a positive attribute for low-light detection.

9. Frequently Asked Questions (Based on Technical Parameters)

Q: What is the difference between short-circuit current (I_SC) and reverse light current (I_L)?
A: I_SC is measured with zero voltage across the diode (short circuit). I_L is measured under a specified reverse bias (e.g., 5V). In an ideal photodiode, they would be equal. In practice, I_L under moderate reverse bias is often very close to I_SC and is the parameter used for design in photoconductive mode.

Q: Why is the rise time specified with a 100Ω load resistor?
A: A small load resistor is used to minimize the RC time constant, allowing the measurement to reflect the intrinsic speed of the photodiode itself, not the speed limited by an arbitrarily chosen large resistor. In a real circuit, the effective load might be different.

Q: Can I use this photodiode with a blue (450nm) LED?
A: Yes, but not optimally. The spectral sensitivity curve shows it has lower responsivity at 450nm compared to 940nm. You will get a weaker signal for the same optical power. For best performance with a blue source, a photodiode with a peak sensitivity in the blue region should be selected.

10. Operational Principles

A PIN photodiode is a semiconductor device with a wide, lightly doped intrinsic (I) region sandwiched between P-type and N-type regions. When photons with energy greater than the semiconductor's bandgap are absorbed in the intrinsic region, they create electron-hole pairs. Under the influence of an internal built-in potential (in photovoltaic mode) or an applied reverse bias (in photoconductive mode), these charge carriers are swept apart, generating a measurable photocurrent that is proportional to the incident light intensity. The wide intrinsic region reduces junction capacitance (enabling high speed) and increases the volume for photon absorption (improving sensitivity), especially for longer wavelengths that penetrate deeper into the silicon.

11. Design and Use Case Example

Case: Object Detection in an Automatic Door
An infrared LED (emitting at 940nm) and the PD204-6C photodiode are placed on opposite sides of a doorway to form a transmitted beam sensor. The LED is pulsed at a few kHz to distinguish its signal from ambient light. The photodiode is reverse-biased at 5V through a load resistor. Under normal conditions (no obstruction), the photodiode generates a steady AC photocurrent. When a person or object breaks the beam, the signal drops. A subsequent amplifier, filter (to pass the modulation frequency), and comparator circuit detect this drop and trigger the door opening mechanism. The high speed of the PD204-6C ensures it can faithfully follow the modulated LED signal, and its 940nm peak sensitivity maximizes the received signal strength from the matched IR LED.

12. Industry Trends

The trend in photodiode technology for sensing applications continues toward higher integration, lower noise, and enhanced functionality. This includes devices with on-chip transimpedance amplifiers, ambient light rejection features, and digital output (via integrated ADCs). There is also development in materials beyond silicon (e.g., InGaAs) for extended infrared range detection. For standard industrial applications like those served by the PD204-6C, the focus remains on reliability, cost-effectiveness, and performance consistency in volume manufacturing. The drive for miniaturization also pushes for photodiodes in smaller surface-mount packages while maintaining or improving optical performance parameters.