UC3843 PWM Controller

Wiring Connections:

The typical connections for the UC3843 are as follows:

1. VCC (Pin 6): Connect to the supply voltage (8V to 40V).
2. GND (Pin 4): Connect to ground.
3. COMP (Pin 3): Connect to an external compensation network for stability.
4. RAMP (Pin 2): Connect a resistor-capacitor network for frequency modulation.
5. CS (Pin 1): Connect to a current sensing resistor for current limiting.
6. OUT (Pin 7): Connect to the gate of the power MOSFET for controlling output.
7. CT (Pin 5): Connect a timing capacitor to set the oscillation frequency.

Power:

• Operating Voltage: 8V to 40V DC
• Supply Current: around 10 mA (not including output load).

Input and Output:

• Input: Accepts a wide range of DC input voltages.
• Output: Controls the gate of a power transistor or MOSFET to regulate output voltage and current.

Physical Characteristics:

• Size: Compact design in DIP-8 or SOIC-8 packages.
• Weight: Lightweight, generally under 1 gram.
• Pin Configuration: 8-pin configuration for easy integration into circuits.

Technical Specifications:

• Operating Frequency: Adjustable from 100 kHz to 500 kHz, based on external components.
• Max Duty Cycle: around 80% for continuous operation.
• Input Voltage Range: Supports a wide range of input voltages for flexibility.

Additional Features:

• Adjustable Dead Time: Offers the ability to set dead time between switching cycles for improved efficiency.
• Noise Immunity: Designed to reduce susceptibility to noise in switching power applications.
• Versatile Applications: Suitable for applications like flyback converters, buck converters, and boost converters.

How to Use:

1. Circuit Design:
   • Connect the UC3843 as per the typical application circuit in your design.
   • Ensure to use appropriate external components for RAMP, COMP, and timing capacitor settings.
2. Power Supply Connection:
   • Connect the VCC pin to your input voltage supply and GND to ground.
3. Set the Frequency:
   • Use a resistor and capacitor connected to the RAMP pin to set the desired switching frequency.
4. Current Sensing:
   • Connect a resistor for current sensing to the CS pin to implement current limiting.
5. MOSFET Connection:
   • Connect the OUT pin to the gate of a power MOSFET to control output power to the load.
6. Testing the Circuit:
   • Power on the circuit and measure the output voltage and current.
   • Adjust external components as necessary to achieve desired performance.
7. Protection Features:
   • Ensure that the thermal shutdown feature is functional to protect the circuit under high temperature conditions.
8. Application Examples:
   • DC-DC Converters: Use in power supply circuits to convert voltages efficiently.
   • Battery Chargers: Implement in systems requiring controlled charging of batteries.
   • LED Drivers: Control the power delivered to LED arrays.

The UC3843 PWM Controller is an essential component for those working with power supply designs. Its high efficiency, flexibility, and built-in protection features make it a popular choice for a wide range of applications, from simple battery chargers to complex DC-DC converters. With its ease of use and reliability, the UC3843 is a solid foundation for any power management project.