FAN5307S18X Application Field and Working Principle

Introduction

The FAN5307S18X is a high frequency, wide input voltage range synchronous step-down DC-DC converter. It is a low side N-channel MOSFET switch with switch current up to 5A. It features fast transient response with a high level of efficiency. Typical applications of the FAN5307S18X include battery powered and automotive applications, as well as a general purpose step-down converter.

Application Fields

The FAN5307S18X is ideal for a variety of applications where a wide voltage input range, fast transient response and high efficiency are needed. Typical applications include battery powered applications, automotive applications, and general purpose step-down converters. This device can also be used to provide a regulated output voltage in a variety of DC-DC conversion applications, such as: distributed power systems, telecom, battery charging and automotive systems.

Working Principle

The FAN5307S18X consists of a synchronous rectifier stage, an error amplifier, an on-off control comparator, and an internal linear regulator. The device is designed with a low side N-channel MOSFET power switch. The MOSFET switch is driven by an internal high frequency oscillator to ensure a fast transient response, and minimize power loss. The power switch is turned off/on with an internal on-off control comparator. The voltage error between the output voltage and the internal reference is amplified by an internal error amplifier to provide a control signal for the on-off control comparator.

The FAN5307S18X also features pulse-frequency modulation (PFM) and pulse-width modulation (PWM). The device automatically selects the most appropriate mode to optimize efficiency and transient response characteristics. In PFM mode, the power switch is turned off once the output voltage reaches the regulation voltage, and the device will only pulse when high load current is needed. In PWM mode, the power switch is turned off/on at a fixed frequency, allowing high efficiencies to be achieved with low load currents. Furthermore, the FAN5307S18X features over current protection (OCP), thermal shutdown (TSD) and under voltage lockout (UVLO).

Conclusion

The FAN5307S18X is a wide input voltage range synchronous step-down DC-DC converter with a low side N-channel MOSFET switch, fast transient response, and high efficiency. It is targeted for battery powered and automotive applications, as well as a general purpose step-down converter. The device also features PFM and PWM modes, as well as OCP, TSD, and UVLO protection.