LM2594HVN-12 Application Field and Working Principle

Introduction

The LM2594HVN-12 is a pulse width modulated DC to DC switching buck regulator with the following characteristics: automatic power limiting, low quiescent slopping shutdown, ground fault sensing, and circuitry that allows current sharing among multiple outputs. The LM2594HVN-12 is available in 5.0V and 12.0V configurable output voltages and is suited to low voltage applications in a wide variety of industrial and consumer products. This application note serves to outline the features of the LM2594HVN-12, discuss its application field, explain its working principle and provide a circuit example.

Application Field

The LM2594HVN-12 is a pulse width modulated buck regulator which is suited for powering a variety of applications in a wide range of industrial and consumer products. It is well suited for low voltage applications and is a cost effective solution. Due to its adjustable output current limit and ability to share current among multiple outputs, it is ideal for use in battery powered products such as cell phones, MP3 players and digital cameras, where the voltage source can vary. It is also a suitable choice for simple power supply applications such as a general purpose power regulator.

Working Principle

The LM2594HVN-12 operates on a pulse width modulated (PWM) principle. When an enable signal and an input voltage are applied to the LM2594HVN-12, a step-down voltage converter begins to cycle and adjusts the pulse width of an internal oscillator. The pulse width modulated signal is fed to an internal power switch, which is then driven to produce the required output voltage. The presence of an internal voltage regulator circuit allows the output voltage to remain constant, regardless of the input voltage. The output current limit circuit limits the output current of the regulator, to prevent overloading. A low-dropout voltage regulator provides current limiting of the internal voltage regulators, giving the circuit the ability to handle higher voltages. This allows the LM2594HVN-12 to be used in a wide range of applications.

Circuit Example

The following circuit example demonstrates the LM2594HVN-12 in a typical power supply application. It includes a step down DC to DC converter, output voltage adjust potentiometer, NMOS transistor, diode, inductor, capacitor, resistors and voltage divider network.

The DC to DC converter provides the necessary power for the circuit. The input voltage is applied to the LM2594HVN-12, which in turn pulses the voltage to the internal power switch. The current limit of this regulator is set by the voltage divider network consists of the resistors R5 and R6. The output voltage is adjusted by the potentiometer connected between the output and ground. The diode and the inductor make up the output filter, and the capacitor serves to store energy. The NMOS transistor is used to shut down the regulator in case of an over-current fault.

Conclusion

The LM2594HVN-12 is a cost effective pulse width modulated DC to DC switching buck regulator. It is designed for low voltage applications in a wide variety of industrial and consumer products. The LM2594HVN-12 has adjustable current limit, low quiescent slopping shutdown, ground fault sensing, and circuitry allowing current sharing among multiple outputs. This application note has discussed the features of the LM2594HVN-12, its application field, its working principle and provided a circuit example.