The **LA5515** is a monolithic integrated circuit (IC) specifically designed for **electronic speed control** of low-voltage DC motors. It was primarily used in portable audio equipment like radio-cassette recorders and portable tape players. --- ## 1. Technical Specifications The LA5515 belongs to Sanyo’s line of motor controllers. Below are the key electrical parameters: | Parameter | Typical Value | Unit | | :--- | :--- | :--- | | **Operating Voltage (Vcc)** | 1.8 to 8.0 | Volts | | **Max Output Current** | 700 | mA | | **Reference Voltage (Vref)** | 1.2 | Volts | | **Quiescent Current** | 4.0 | mA | | **Package Type** | SIP-4 / SIP-5 | - | --- ## 2. Key Internal Electronic Parts The IC integrates several functional blocks into a single silicon chip to minimize the need for external components: * **Voltage Reference:** Provides a stable 1.2V internal reference to ensure consistent motor speed regardless of battery discharge (within the operating range). * **Error Amplifier:** Compares the feedback voltage from the motor with the internal reference to adjust the drive current. * **Current Limiter:** Protects the IC from overheating or failure if the motor stalls (locked rotor condition). * **Bridge Rectifier/Protection Diodes:** Usually includes internal diodes to protect against back-EMF generated by the inductive load (the motor). --- ## 3. Application Circuit Components While the LA5515 handles the logic, it requires a few external parts to function in a circuit: 1. **Timing Resistor (Rt):** Sets the reference current for the speed control loop. 2. **Filter Capacitor (C):** Typically placed across the supply (Vcc to GND) to suppress electrical noise generated by the motor brushes. 3. **Speed Adjustment Potentiometer:** Usually connected in series with a resistor to the control pin to allow manual calibration of the motor RPM. --- ## 4. Features & Benefits * **Wide Operating Voltage:** It can function with as few as two 1.5V batteries (3V total), making it ideal for vintage handheld electronics. * **Low Current Consumption:** Designed for battery-operated longevity. * **Speed Stability:** Maintains RPM even if the load on the motor changes slightly (e.g., when the tape reaches the end of the reel). --- ## 5. Pin Configuration (Common SIP-4) | Pin No. | Name | Function | | :--- | :--- | :--- | | 1 | **Vcc** | Positive Power Supply | | 2 | **Control** | Speed adjustment/feedback input | | 3 | **Motor** | Output connection to the DC motor | | 4 | **GND** | Common Ground |