AN34040A

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AN34040A is a new series of buck converter line with integrated power switches, which is suitable for a wide range of applications and can work with input voltage down to 0.9 V. It is a synchronous step down DC/DC converter, which provides a wide input voltage range, excellent dynamic response, power efficiency and high output current. The high switching frequency and excellent regulation are suitable for next-generation applications that require high efficiency and wide coverage. This article introduces the application field and working principle of AN34040A in the field of DC DC switching regulators.

Application Field of AN34040A

AN34040A can provide an excellent solution to the power supply of various system, such as general battery powered applications, industrial control, 3G/4G wireless base stations, automotive and other application fields. It can meet the requirements of high voltage, efficiency, low ripple and excellent transient response. AN34040A is suitable for applications such as portable devices, Communication Base Station, Smart TV, Electric Vehicle, Automation Equipment, Industrial PC and etc.

AN34040A has two buck conversion modes. The Pulse Width Modulation (PWM) and the Pulse Frequency Modulation (PFM). PWM mode is suitable for delivering high accuracy of output voltage; while PFM is suitable for applications that require a low quiescent current, such as battery powered applications. In PWM mode, the switching frequency can be adjusted from 1500 Khz to 2450 Khz, it has fast dynamic response and high conversion efficiency. In PFM mode, the switching frequency can be adjusted from 200 Hz to 1150 Hz, it has low quiescent current and improves system efficiency.

Working Principle of AN34040A

The AN34040A is a synchronous buck converter, which includes a high side synchronous MOSFET switch FET1 and a low side synchronous MOSFET switch FET2. The MOSFET switches are driven by the control logic circuit that receives the input from the regulating loop. A bootstrap circuit provides the voltage for the high side MOSFET.

When power switch FET1 is closed and FET2 is open, energy is stored in the inductor, the transistor FET2 is reverse biased, and electric power is transmitted to the load via capacitor C13. When power switch FET1 is open and FET2 is closed, electric power is emitted from the load, energy is stored in the inductor, and FET2 is forward biased.

At this moment, the inductor always provides the electric power to the load via both power switches, and electric power is exchanged between the load and the circuit. The operating frequency of the power switch is determined by the control logic, the oscillator circuit and the voltage feedback circuitry.

The regulating loop consists of an oscillator, a voltage reference, an error amplifier, an internal transconductance amplifier, and a detecting circuit. This loop determines the voltage gain and error of the output voltage, and the output voltage setting is determined by the error amplifier. The error amplifier has the ability to detect and compensate for the load changes to ensure the output voltage accuracy.

The operational amplifier buffers the feedback signal from the output voltage and then provides it to the error amplifier. The error amplifier then amplifies the signal and sends it to the output of the loop as a control signal to the power switch. The voltage reference provides a reference voltage for the loop to compare with the output voltage.

When the adjusting range of the output voltage is within the allowable range, the control loop is in a stable state, and the voltage gain and error is determined by the model parameters of the components. Otherwise, the output voltage will exceed the set range, and the control loop will shut down the power switch to protect the load. The power switch can be turned on again after the output voltage returns to the allowable range.

In addition, the AN34040A also provides a soft start function to enhance the start-up performance and reduce the inrush current. The soft start circuit will start to reduce the voltage after the power switch is enabled, and tilts down to the set output voltage within a preset period.

Conclusion

This article introduces the application field and working principle of AN34040A in the field of DC DC switching regulators. AN34040A provides a wide input voltage range, excellent dynamic response, power efficiency and high output current. With two buck conversion modes and soft start function, AN34040A can be widely used in various application fields, such as portable devices, Communication Base Station, Smart TV, Electric Vehicle, Automation Equipment, Industrial PC and etc.

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