The **TSOP955..W** series (where ".." denotes the carrier frequency) belongs to a family of miniaturized IR receiver modules designed for infrared remote control systems. These parts are specifically engineered to provide high sensitivity and robust suppression of optical noise. --- ### 1. Device Overview The TSOP955..W consists of a **PIN photodiode** and a **preamplifier** integrated into a single lead frame. The internal block diagram typically includes a band-pass filter, an automatic gain control (AGC) circuit, and a demodulator to provide a clean TTL-compatible output. | Feature | Specification | | :--- | :--- | | **Supply Voltage (Vcc)** | 2.0 V to 3.6 V | | **Carrier Frequencies** | 30 kHz to 56 kHz (e.g., TSOP95538W is 38 kHz) | | **Supply Current** | ~0.35 mA | | **Transmission Distance** | Up to 40 meters | | **Output Type** | Active Low (CMOS/TTL) | --- ### 2. Key Internal Components To understand how the part works, it is essential to look at its functional blocks: * **Photo Detector:** Converts IR light pulses into electrical signals. * **Automatic Gain Control (AGC):** Automatically adjusts the sensitivity to ensure performance in different lighting conditions (e.g., sunlight or fluorescent bulbs). * **Band Pass Filter:** Only allows signals near the specific carrier frequency (e.g., 38 kHz) to pass, filtering out other light noise. * **Demodulator:** Removes the carrier frequency and sends the data envelope to the output pin. --- ### 3. Pin Configuration The TSOP955..W usually follows a standard 3-pin layout in a "Heimdall" (W) package. | Pin Number | Name | Description | | :--- | :--- | :--- | | 1 | **OUT** | Demodulated data output | | 2 | **GND** | Ground connection | | 3 | **Vs** | Power supply (2.0V - 3.6V) | --- ### 4. Application Circuit To use this part effectively, a simple RC filter is recommended on the power line to suppress ripples from the power supply. ```cpp // Schematic Representation // [Vs] ----[ 100 Ohm Resistor ]----+----[ Pin 3: Vs ] // | // [ 4.7uF Cap ] // | // [GND] --------------------------+----[ Pin 2: GND ] // // [MCU Input] <------------------------[ Pin 1: OUT ] ``` --- ### 5. Why the "W" Suffix? The **"W"** suffix refers to the **Heimdall package** design. It features a wide-angle lens and enhanced optical shielding. This package is often chosen for its compact surface-mount footprint and its ability to withstand high temperatures during reflow soldering.