PD70-01B/TR7 Silicon Planar PIN Photodiode Datasheet - 2.0x1.25x0.9mm - 32V Reverse Voltage - 940nm Peak Wavelength - English Technical Document

1. Product Overview

The PD70-01B/TR7 is a high-performance Silicon Planar PIN Photodiode designed for applications requiring fast response and high sensitivity to infrared light. Its compact size and robust performance across a wide temperature range make it a versatile component for various electronic systems.

1.1 Core Advantages and Target Market

This photodiode offers several key advantages, including a built-in daylight filter to reduce ambient light interference, high sensitivity at its peak wavelength, and very low junction capacitance enabling short switching times. Its small, surface-mount package is Pb-free and compliant with RoHS, REACH, and halogen-free standards. These features make it particularly suitable for consumer electronics, industrial control, and communication applications such as television and appliance remote controls, infrared audio transmission, video recorders, copiers, elevator sensors, and general-purpose measurement and control systems.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device is designed to operate reliably within specified limits. The maximum reverse voltage (VR) is 32V. It can function in an operating temperature (Topr) range of -25°C to +85°C and be stored (Tstg) from -40°C to +85°C. The maximum soldering temperature (Tsol) is 260°C for a duration not exceeding 5 seconds. The power dissipation (Pd) is rated at 150 mW at or below 25°C free air temperature.

2.2 Electro-Optical Characteristics

At a standard temperature of 25°C, the photodiode exhibits specific performance metrics. Its spectral bandwidth (λ0.5) ranges from 730 nm to 1100 nm, with peak sensitivity (λP) at 940 nm, placing it firmly in the near-infrared spectrum. Under an irradiance of 1 mW/cm² at 940 nm, the typical short-circuit current (ISC) is 35 µA, and the typical reverse light current (IL) at VR=5V is 25 µA (min. 17 µA). The reverse dark current (ID) at VR=10V is typically 5 nA, with a maximum of 30 nA. The reverse breakdown voltage (VBR) is minimum 32V, typically 170V at a current of 100 µA.

3. Performance Curve Analysis

The datasheet includes typical characteristic curves that provide deeper insight into device behavior beyond the tabulated minimum, typical, and maximum values.

3.1 Spectral Sensitivity

A graph (Fig.1) illustrates the normalized spectral response versus wavelength. The curve shows a sharp rise in sensitivity starting around 730 nm, peaking at 940 nm, and then gradually falling off towards 1100 nm. This confirms its optimization for infrared detection, particularly for common 940 nm IR emitters, while the daylight filter attenuates sensitivity in the visible spectrum.

3.2 Linearity of Response

Another graph (Fig.2) plots the Reverse Light Current (IL) against Irradiance (Ee). This curve is expected to show a highly linear relationship, indicating that the photocurrent output is directly proportional to the incident light power over the operational range, a critical feature for measurement and control applications.

4. Mechanical and Package Information

4.1 Package Dimensions and Polarity

The PD70-01B/TR7 comes in a compact surface-mount package. Detailed dimensional drawings are provided. The package body dimensions are approximately 2.0 mm in length, 1.25 mm in width, and 0.9 mm in height (excluding leads). The cathode is typically marked, often by a notch, a beveled edge, or a dot on the package. Designers must consult the detailed package drawing for the exact polarity identification marker and pad layout to ensure correct PCB footprint design and assembly orientation.

4.2 Carrier Tape and Reel Specifications

For automated assembly, the component is supplied in carrier tape and reel. The tape width, pocket dimensions, and reel diameter are specified to be compatible with standard pick-and-place equipment. The standard packing quantity is 1000 pieces per reel.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Profile

For Pb-free soldering, a specific temperature profile must be followed. The recommended profile includes a preheat stage, a soak zone, a peak reflow temperature not exceeding 260°C, and a controlled cooling phase. The total time above liquidus and the maximum peak temperature duration are critical to prevent thermal damage to the epoxy package and the semiconductor die. Reflow soldering should not be performed more than two times.

5.2 Hand Soldering and Rework

If hand soldering is necessary, extreme care must be taken. The soldering iron tip temperature should be below 350°C, and contact time with each terminal should be less than 3 seconds per solder joint using an iron with a capacity of 25W or less. A cooling interval of more than two seconds is required between soldering each terminal. For rework, a double-head soldering iron is recommended to simultaneously heat both terminals and avoid mechanical stress. The feasibility and impact of rework on device characteristics should be evaluated beforehand.

6. Storage and Handling Precautions

6.1 Moisture Sensitivity

This device is moisture-sensitive. The moisture barrier bag should not be opened until the components are ready for use. Before opening, storage conditions should be 30°C or less and 90% Relative Humidity (RH) or less. The total shelf life in the unopened bag is one year. After opening, the components must be stored at 30°C or less and 60% RH or less and used within 168 hours (7 days). If the silica gel desiccant indicates saturation or the storage time is exceeded, a baking treatment at 60 ±5°C for 24 hours is required before use.

6.2 Electrical Protection

A critical precaution is over-current protection. As a diode, it must be operated with a series current-limiting resistor when biased. Without this resistor, a small increase in applied voltage can cause a large, potentially destructive increase in current, leading to burnout. The resistor value must be calculated based on the operating voltage and the desired photocurrent or dark current.

7. Application Suggestions and Design Considerations

7.1 Typical Application Circuits

The PD70-01B/TR7 can be used in two primary configurations: photovoltaic mode (zero bias) and photoconductive mode (reverse bias). In photovoltaic mode, it generates a voltage/current when illuminated, suitable for simple light detection. In photoconductive mode (with a reverse bias voltage applied, e.g., 5V), the response speed is significantly faster, and the linearity is improved, making it ideal for high-speed pulse detection like in IR remote controls. A transimpedance amplifier (TIA) circuit is commonly used to convert the small photocurrent into a usable voltage signal.

7.2 Design Considerations

Key design factors include: Biasing: Choose the operating mode based on speed and linearity requirements. Bandwidth: The low capacitance (implied by fast switching time) allows for high bandwidth when paired with a suitable low-noise amplifier. Optical Filtering: The built-in daylight filter is beneficial, but for specific applications, additional external optical filters may be needed to block unwanted wavelengths. PCB Layout: Keep the photodiode and its amplifier close together to minimize parasitic capacitance and noise pickup. Ensure the anode and cathode are correctly oriented according to the package marking.

8. Technical Comparison and Differentiation

Compared to standard photodiodes or phototransistors, the PIN structure of the PD70-01B/TR7 offers distinct advantages. The intrinsic (I) region between the P and N layers reduces junction capacitance, enabling faster response times (short switching time). This makes it superior for high-speed data transmission via IR. Its high sensitivity and specified dark current parameters provide a good signal-to-noise ratio. The integrated daylight filter is a practical feature not found in all basic photodiodes, simplifying design for ambient light environments.

9. Frequently Asked Questions (FAQ)

9.1 What is the purpose of the daylight filter?

The daylight filter attenuates sensitivity in the visible light spectrum (approximately 400-700 nm). This reduces noise and interference from ambient light sources like sunlight or room lighting, allowing the device to more reliably detect the modulated infrared signals from a remote control or other IR source.

9.2 How do I choose the value of the series resistor?

The series resistor limits the current under both dark and illuminated conditions. In reverse bias mode, the resistor value (R) can be estimated using Ohm's Law: R ≈ (Supply Voltage - Diode Reverse Voltage Drop) / Maximum Expected Current. The current should be kept well below the maximum power dissipation limit. Start with a conservative value (e.g., 10kΩ) and adjust based on signal amplitude and speed requirements.

9.3 Can this sensor detect visible light?

While its spectral range starts at 730 nm (border of red visible light), its sensitivity in the visible spectrum is very low due to the daylight filter. It is primarily an infrared detector optimized for 940 nm. For visible light detection, a photodiode without an IR-blocking or daylight filter would be required.

10. Operating Principle Introduction

A Silicon PIN Photodiode is a semiconductor device that converts light into electrical current. When photons with energy greater than the bandgap of silicon strike the device, they generate electron-hole pairs in the depletion region. In a PIN structure, a wide intrinsic (I) region is sandwiched between the P-type and N-type regions. This wide I-region creates a larger depletion area for photon absorption and, crucially, reduces the junction capacitance. Under reverse bias, the electric field sweeps these charge carriers to the contacts, generating a photocurrent that is proportional to the incident light intensity. The "planar" process refers to the manufacturing technique, which typically yields devices with stable and consistent performance.