## Overview of the LA5522 IC The **LA5522** is a monolithic integrated circuit specifically designed for **DC motor speed control**. It was manufactured by Sanyo (now part of ON Semiconductor) and is commonly found in vintage portable audio equipment, such as cassette recorders, walkmans, and radio-cassette players. --- ### 1. Key Technical Specifications | Parameter | Value / Description | | :--- | :--- | | **Function** | DC Motor Speed Governor | | **Package Type** | TO-126 (3-pin or 4-pin variants) | | **Operating Voltage Range** | Typically 1.8V to 10V | | **Reference Voltage** | Approx. 1.2V | | **Output Current** | Supports motors up to approx. 500mA - 700mA | | **Quiescent Current** | Low (approx. 2mA), making it ideal for battery power | --- ### 2. Functional Description The LA5522 regulates the speed of a DC motor by maintaining a constant relationship between the supply voltage and the Back-Electromotive Force (Back-EMF) generated by the motor. * **Speed Regulation:** It compensates for variations in battery voltage and mechanical load. * **Built-in Reference:** It contains an internal voltage reference to ensure stable RPM even as batteries drain. * **External Adjustment:** The speed is typically set using an external resistor or a potentiometer connected to the control pins. --- ### 3. Typical Pin Configuration (TO-126 Package) While variations exist, the standard layout for the LA5522 is as follows: 1. **Vcc (Pin 1):** Positive power supply input. 2. **Control/Adjustment (Pin 2):** Connected to an external resistor ($R_t$) to set the motor speed. 3. **Motor/Output (Pin 3):** Connects to the negative terminal of the DC motor. --- ### 4. Basic Application Circuit Example The following is a representation of how the LA5522 is wired in a standard circuit: ```text (+) Vcc ---------+--------- (Motor +) | [LA5522] Pin 1 (Vcc) Pin 3 (Motor -) ---- (Motor -) Pin 2 (Adj) | [Potentiometer] | (-) GND ---------+----------------------- ``` ### 5. Common Uses * **Micro-cassette recorders:** Maintaining steady tape speed. * **Walkmans:** Preventing "wow and flutter" during playback. * **Toys:** Regulating small DC motors in battery-operated models. ---