UC3843D Integrated Circuits (ICs)

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UC3843D is a high-performance current-mode pulse width modulation (PWM) controller for DC-to-DC converter applications. It is a member of the UC38x family of PWM controllers. This family has been designed to control a wide variety of off-line, high frequency switching power supplies employed in modern electronics equipment. The UC3843D family is built on a 5V high-speed CMOS process and includes features such as high speed current-mode PWM control, precision regulated 5V operating voltage and temperature compensated oscillator.

Features:

• Internal Ripple Clock Controller
• Pre-Regulated 5V Operating Voltage
• Current Mode PWM Control
• High Speed Response for Critical Conduction Mode Operation
• Voltage/Temperature Compensated Oscillator
• Accurate Timing Synchronization
• Built-in Lead Protection

Application Fields:

UC3843D is typically used in flexible power supply designs such as SMPS, switching DC/DC converters, and variable frequency converters. It is also commonly found in a variety of semiconductor products such as brushless DC motor drives, telephone line interface circuits, active filters, and automotive electronic control systems. Furthermore, the UC3843D family is widely used when the output power needs to be exactly regulated and modulated.

Working Principle:

UC3843D works by modulating the voltage or current at the output of a switch-mode converter. The output can be varied by changing the duty cycle of the switch. It does this by controlling the switching of the transistors that drive the inductor, capacitor, or other elements in the converter circuit. The current-mode pulse width modulation allows the duty cycle to be varied faster than the duty cycle can be controlled by voltage-mode PWM controllers. It is this rapid duty cycle control that enables current mode PWM controllers to achieve much higher frequency in the converter circuit.

The logic thresholds in current-mode PWM controllers are temperature independent, which allows them to eliminate slow-start effects and overshoot associated with voltage-mode PWM controllers. This temperature independence also allows current-mode PWM controllers to provide better accuracy and stability in high temperature applications, such as automotive systems.

The UC3843D is designed to allow the user to control the system output through standard analog or digital feedback loops. This, coupled with its precision regulated 5V operating voltage, makes it an excellent choice for low-cost, high-performance, and powerful DC-to-DC converter designs.

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