UC2843DTR Integrated Circuits (ICs)

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UC2843DTR: Application Field and Working Principle

The UC2843DTR is a fixed frequency PWM (pulse width modulation) controller IC that is well-suited for driving high frequency switched mode power supplies. It can also be used in other applications that require variable frequency types of control such as variable speed AC motor control. This IC is ideal for a wide variety of linear power control applications and high performance control circuits. It is widely used in many applications including automotive, computer, appliance, and industrial power applications.

Introduction

The UC2843DTR is a 16-pin integrated circuit with built-in features accommodating almost all switched mode power supply applications. It offers an extremely flexible and highly accurate pulse-width modulation (PWM) control. It combines a high-performance high frequency error amplifier, a flat gain cross-over frequency PWM comparator, an overcurrent protection system, an open-collector reference, and an internal power circuit that can easily be controlled via external control pins. The UC2843DTR is a fixed frequency DC-to-DC switching controller with a maximum frequency of 1 MHz for both the standby and PWM modes. It offers a current-mode control operation with adjustable frequency, a fast transient response, low-noise operation and excellent inherent line and load regulation.

Applications

The UC2843DTR can be used in a variety of applications. Key applications include those found in automotive and computer power supplies, and high power adaptors. Additionally, the UC2843DTR is widely used in numerous industrial, appliance, and medical applications. It is also suitable for UPS systems, power supplies, and power conditioners.

Features

• High speed and low noise operation.
• Precision undervoltage lockout circuit.
• Adjustable hysterisis for precise dividing of soft-start time.
• Wide operating voltage range (4.5V to 20V).
• Ability to provide precise current sensing and protection.
• Externally adjustable reference voltage.
• Output voltage range 0V to +22V.

Working Principle

The UC2843DTR comprises a power circuit and a pulse-width modulation (PWM) controller. The power circuit contains an N-channel MOSFET switch, an Internal 1.223V bandgap reference, a peak current sense amplifier, an overcurrent protection circuit, a voltage reference buffer and a stand-by (sleep) control. The PWM controller consists of an oscillator, a dead-time generator, a voltage/current error amplifier, a cross-over frequency detector, a voltage reference buffer, a current limit amplifier and a PWM comparator.

In operation, the error amplifier compares the feedback voltage from the power circuit with an adjustable reference voltage from the voltage reference buffer (Vref). The feedback voltage is a fraction of the output voltage, set through the sense resistor. The output of the error amplifier is then fed to the PWM comparator. The comparator compares the amplified error signal with the output of the oscillator. When the amplified error voltage is greater than the output of the oscillator, the output of the comparator turns off resulting in the switch opening and the power being removed from the output.

The UC2843DTR also includes an overload protection circuit. This circuit monitors the current passing through the switch, and if it exceeds a predetermined value, the power circuit is shut off until the overload is removed. Finally, the UC2843DTR also contains a built-in soft-start circuit which ensures that the power circuit is brought up safely and steadily during turn on.

Conclusion

In conclusion, the UC2843DTR is a versatile, high performance DC-to-DC switching controller that can be used in a variety of applications from automotive to industrial. It provides excellent inherent line and load regulation, low-noise operation, adjustable frequency, and current sensing/overload protection. Its built-in soft-start circuit provides a safe, controlled power up. It is suitable for use in a variety of switched mode supplies and control circuits, and is ideal for use in power supply systems, adaptors, UPS systems, and power conditioners.

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