SPX3940AT-L-5-0/TR

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SPX3940AT-L-5-0/TR Application Field and Working Principle

The SPX3940AT-L-5-0/TR is a low-dropout linear voltage regulator with three terminals. Designed to regulate high-current, low-voltage applications, the SPX3940AT-L-5-0/TR offers peak efficiency up to 95 percent, input operating current up to 5 A, output voltage range of 5 V to 50 V, and adjustable output voltage from 0 V to maximum output voltage.

The SPX3940AT-L-5-0/TR is ideal for use in applications requiring a low-dropout, low-noise linear regulator, such as automotive systems, power converters/inverters, power supplies, and many other applications.This device is available in a small and compact QFN package for space-constrained applications.

Working Principle of SPX3940AT-L-5-0/TR

The linear voltage regulator operates in a closed-loop mode, where a small reference voltage is used to control the output voltage of the device. The SPX3940AT-L-5-0/TR consists of two transistors in series, with the base of each transi stor connected to each output. A small reference voltage Vref is provided to the base of one transistor and the emitter of the other transistor. Output voltage is set by varying the Vref voltage. The output voltage is limited by the voltage drop across the base-emitter junction of the two transistors, thus the regulator is referred to as a low-dropout (LDO) regulator.

The input voltage needed to maintain the output voltage can be calculated by monitoring the voltage at the base of the transistors. When the input voltage is lower than the output voltage, the base of the transistor is too low to be held on and the output voltage will start to drop as the input voltage is decreased further. The regulated output voltage can be of any voltage between 0 V and the maximum input voltage of the regulator.

The output voltage of the SPX3940AT-L-5-0/TR is adjustable. It can be adjusted by varying the voltage at the Vref pin with an external resistance. This will change the reference voltage, which will in turn change the output voltage of the regulator accordingly. The SPX3940AT-L-5-0/TR also features an over-current protection (OCP) mechanism which will protect the device from damage due to excessive output current.

Applications of SPX3940AT-L-5-0/TR

The SPX3940AT-L-5-0/TR is ideal for applications requiring a low-dropout, low-noise linear regulator such as automotive systems, power converters/inverters, power supplies and many more. The SPX3940AT-L-5-0/TR is also well suited for applications requiring high efficiency and low noise performance such as smart phones, portable media players, and other portable devices.

The SPX3940AT-L-5-0/TR can also be used in battery-powered applications in automotive, industrial and portable electronics due to its low dropping output and low quiescent current. Other applications of the SPX3940AT-L-5-0/TR include local on-card voltage regulation and support of low voltage digital circuits such as DSPs, microcontrollers, FPGAs and ARM cores.

Conclusion

The SPX3940AT-L-5-0/TR is a robust low dropout voltage regulator from STMicroelectronics designed for high-current, low-voltage power conversion and local on-card voltage regulation applications. It offers peak efficiency up to 95 percent and output voltage range of 5 V to 50 V, adjustable output voltage form 0 V to maximum output voltage and over-current protection.

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