UC3845BNG

Product Overview

• Category: Integrated Circuit (IC)
• Use: PWM Controller
• Characteristics: High-performance, current-mode control, adjustable frequency, and duty cycle
• Package: DIP-8 (Dual In-line Package with 8 pins)
• Essence: Regulates the output voltage of power supplies
• Packaging/Quantity: Available in reels of 2,500 units

Specifications

• Input Voltage Range: 7V to 30V
• Output Voltage Range: 5V to 30V
• Maximum Duty Cycle: 50%
• Oscillator Frequency Range: 50kHz to 500kHz
• Operating Temperature Range: -40°C to +85°C

Pin Configuration

The UC3845BNG IC has the following pin configuration:

1. VREF: Reference voltage input for error amplifier.
2. COMP: Compensation pin for external compensation network.
3. CS: Current sense input for current-mode control.
4. SS/TR: Soft-start/Shutdown pin for controlling start-up and shutdown timing.
5. OUT: Output pin for connecting to the power switch.
6. GND: Ground reference for the IC.
7. RT/CT: Timing resistor and capacitor connection for setting oscillator frequency.
8. VCC: Power supply input for the IC.

Functional Features

• Current-Mode Control: Provides stable regulation by sensing the current flowing through the power switch.
• Adjustable Frequency and Duty Cycle: Allows flexibility in designing power supplies for various applications.
• Soft-Start Function: Enables controlled start-up to prevent excessive inrush current.
• Shutdown Capability: Facilitates easy system shutdown when required.

Advantages and Disadvantages

Advantages: - High-performance regulation for power supplies. - Flexibility in frequency and duty cycle adjustment. - Soft-start feature prevents excessive inrush current. - Shutdown capability for system control.

Disadvantages: - Limited maximum duty cycle of 50%. - Requires external compensation network for stability.

Working Principles

The UC3845BNG is a current-mode PWM controller that regulates the output voltage of power supplies. It operates by comparing the sensed current through the power switch with a reference voltage. Based on this comparison, it adjusts the duty cycle of the PWM signal to maintain stable output voltage. The adjustable frequency allows optimization for different applications, while the soft-start and shutdown features enhance system control.

Detailed Application Field Plans

The UC3845BNG is widely used in various applications, including:

1. Switching Power Supplies: Provides efficient regulation and control in AC-DC and DC-DC converters.
2. LED Lighting: Enables precise dimming control and constant current drive for LED applications.
3. Motor Control: Facilitates speed control and protection in motor drives.
4. Battery Chargers: Ensures accurate charging profiles for different battery chemistries.
5. Audio Amplifiers: Offers stable power supply regulation for audio equipment.

Detailed and Complete Alternative Models

1. UC3842BNG: Similar to UC3845BNG but with a lower maximum duty cycle of 47%.
2. UC3843BNG: Similar to UC3845BNG but with a lower operating frequency range of 40kHz to 400kHz.
3. UC3846BNG: Similar to UC3845BNG but with additional features like overvoltage protection and fault detection.

These alternative models provide options based on specific requirements and constraints.

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