UC3851DW

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PMICs, or Power Management Integrated Circuits, enable manufacturers to create more efficient and reliable devices, and are vital components to many electronic systems. UC3851DW (enhanced version) is a fixed-frequency PWM current mode controller that can meet the requirements of high-efficiency, low-component-count, and very-low-voltage applications. It has a wide range of application fields and working principles that make it a great choice in design projects.

Application Fields

The UC3851DW is a design solution for most of the power-conversion applications. Some of the applications of the IC are:

• Low-power isolated and non-isolated AC/DC converters
• Off-line or DC-to-DC switching power supplies
• Memristor converters
• Battery chargers
• DC-to-DC converters
• LED drivers
• Motor control
• High-power adapters

The UC3851DW has several features that make it suitable for both a broad range of power conversion applications, but also provides several flexibility options. This IC has been designed with low-voltage design solutions in mind, and has the capability to operate efficiently even in instances where input voltages are as low as 3.3V.

Working Principle

The UC3851DW is a current-mode PWM controller that is designed around the concept of simple latch-based architectures. Its circuits consist of a latch circuit, an error amplifier (EA), and a multiplier circuit. The multiplier acts as a multiplier for the duty cycle output of the PWM controller.

The UC3851DW has an internal oscillator, which is used to derive an internal fixed frequency for the PWM controller that is set with an external resistor and capacitor. This output frequency is available at the OV pin. An internal reference voltage is also available, whose value is established by the setting of an external reference voltage control pin (VOS).

The latch circuit detects the peak current of the power switch by monitoring the resistor divider across the inductor, and is used to limit the peak current of the power switch. The error amplifier compares the voltage at the OUT pin to a reference voltage set by the VOS pin. This comparison sets the target PWM duty cycle to match the load current requirement. The latched PWM output is then connected to the power switch. This provides a variable, pulse width-modulated (PWM) output.

The EA and multiplier are fed with the OUT signal, and the PWM output is controlled accordingly. This control loop is all done digitally, providing a simple and low-component, low-voltage design solution for all applications.

The UC3851DW is a great choice for most power-conversion applications, especially those that require high-efficiency and very low-voltage designs. It has a wide range of application fields and working principles that make it a great choice for most design projects.

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