UC2833DW

The UC3843DW is a linear regulator controller integrated circuit (IC) produced by ON Semiconductor Corporation. This IC is a member of the UC3800 series, and is employed in a variety of applications such as voltage regulators and power supplies.

Application Field

The UC3843DW linear regulator controller enables supply output currents of up to 1.25A, making it well-suited to numerous applications such as DC-DC converters, AC-DC power supplies, auxiliary power supplies with automatic shutdown, pre-regulator designs, voltage supervisors and regulators for microprocessor-based systems, switched-regulator designs and active voltage-dropout regulators.

Working Principle

The UC3843DW linear regulator controller is composed of seven main blocks: error amplifier, current sense amplifier, voltage reference, main power switch, pulse width modulator (PWM), current control feedback loop, and soft start circuitry.

The error amplifier is the first block in the IC and it is responsible for establishing the difference between the reference voltage and its output in order to make adjustments to the output voltage. It is then compared to the reference voltage, which provides a constant adjusting point in order to maintain a predetermined output voltage.

The current sense amplifier measures current levels that flow through the main power switch, making sure it remains within acceptable values. If the current level passes this limit, the device implements measures that limit its current until the preset threshold is reached.

The voltage reference block provides a precise regulated reference voltage, typically 2.5V. This voltage is used by the error amplifier to establish adjustments to the output voltage in order to keep it stable.

The main power switch is connected to the output terminals and it is responsible for controlling the amount of current that is allowed to pass through them in order to regulate the output voltage.

The PWM block is responsible for regulating the switch’s on/off time and for generating a control signal for the main power switch. The PWM operates in a closed loop with the error amplifier and the current sense amplifier, in order to regulate the main power switch’s on/off period, maintaining the amount of current within acceptable levels.

The current-limit feedback loop is responsible for maintaining the current flowing through the switching transistor within predetermined values, to prevent any damage to the load and switching transistor.

The soft start circuit is used to gradually increase the output voltage, avoiding the inrush current associated with large capacitive loads. The soft start time and amplitude can be easily adjusted.

Conclusion

The UC3843DW linear regulator controller integrated circuit is a key component in many voltage regulator and power supply designs. It is comprised of several subcomponents, but the main blocks are the error amplifier, current sense amplifier, voltage reference, main power switch, pulse width modulator, current control feedback loop and soft start circuitry, all of which work together to ensure the output voltage is regulated according to the predetermined values.