UC3845BVN

Product Overview

• Category: Integrated Circuit (IC)
• Use: Voltage Mode PWM Controller
• Characteristics: High-performance, versatile, and efficient
• Package: DIP-8 (Dual In-line Package with 8 pins)
• Essence: Regulates and controls the output voltage of power supplies
• Packaging/Quantity: Available in reels or tubes, quantity varies based on supplier

Specifications

• Input Voltage Range: 7V to 30V
• Output Voltage Range: 0V to 5.1V
• Operating Temperature Range: -40°C to +85°C
• Switching Frequency: Adjustable, typically 50kHz to 500kHz
• Maximum Duty Cycle: 100%
• Output Current: Up to 1A
• Protection Features: Overvoltage protection, undervoltage lockout, overcurrent protection

Pin Configuration

The UC3845BVN has a total of 8 pins arranged as follows:

1. VREF: Reference voltage input
2. COMP: Error amplifier output
3. FB: Feedback pin for regulating the output voltage
4. RT/CT: Timing resistor/capacitor connection
5. CT: Timing capacitor connection
6. GND: Ground reference
7. OUT: Output pin for driving external MOSFET
8. VCC: Power supply voltage input

Functional Features

• Voltage Mode Control: Regulates the output voltage by adjusting the duty cycle of the PWM signal
• Error Amplifier: Compares the feedback voltage with the reference voltage to generate an error signal
• Soft Start: Gradually increases the duty cycle during startup to prevent excessive inrush current
• Current Limiting: Protects the power supply from overcurrent conditions
• Frequency Adjustability: Allows the switching frequency to be tailored for specific applications

Advantages and Disadvantages

Advantages: - High-performance voltage regulation - Versatile and widely used in various power supply designs - Efficient power conversion - Protection features ensure safe operation

Disadvantages: - Limited output current capability (up to 1A) - Requires external components for complete power supply implementation

Working Principles

The UC3845BVN is a voltage mode PWM controller that regulates the output voltage of power supplies. It operates by comparing the feedback voltage from the output with a reference voltage. The error amplifier generates an error signal, which is then used to adjust the duty cycle of the PWM signal. By controlling the duty cycle, the output voltage is regulated.

During startup, the soft start feature gradually increases the duty cycle to prevent excessive inrush current. The controller also incorporates current limiting to protect the power supply from overcurrent conditions.

Application Field Plans

The UC3845BVN is commonly used in various power supply applications, including:

1. Switching Power Supplies: Used in computer power supplies, telecommunication equipment, and industrial power systems.
2. LED Drivers: Controls the brightness of LEDs in lighting applications.
3. Battery Chargers: Regulates the charging process for batteries in portable devices and electric vehicles.
4. Motor Control: Provides precise control of motor speed and direction in industrial automation and robotics.

Alternative Models

Here are some alternative models that can be used as substitutes for the UC3845BVN:

1. TL494CN
2. SG3525AN
3. UC3843AN
4. MC34063AP

These models offer similar functionality and can be used in various power supply designs.

In conclusion, the UC3845BVN is a versatile and efficient voltage mode PWM controller used in a wide range of power supply applications. Its high-performance characteristics, protection features, and adjustable switching frequency make it a popular choice among designers.