L4931ABD120

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The L4931ABD120 is part of a family of three-terminal adjustable, low dropout regulators, specially designed for powering portable devices from Li-Ion batteries, providing them with a precisely regulated output voltage and low quiescent current. It is characterized by very low drop-out voltage, high ripple rejection and extremely low quiescent current, making it suitable for very low power applications, especially in battery powered devices.

The L4931ABD120 combines P-Channel high performance MOSFET pass elements with a built-in bandgap reference circuit. This type of regulator device provides the required output voltage independent of the input voltage, and is adjustable via external two resistors. Its output voltage can thus be set to any value between 1.22 V and 15 V.

As an example of the application of this device, let us consider a typical radio module that requires a regulated voltage of 3 V. Its power supply circuit may include the L4931ABD120, a battery consisting of one or several Li-Ion cells, and two external resistors for adjusting the output voltage. Once the module is powered up, the L4931ABD120 will start regulating its output voltage to 3 V, no matter what the battery voltage may be.

The main advantages of this device compared to other voltage regulator circuits, such as linear or switching regulators, are its smaller size, very low drop-out voltage, very low quiescent current, and the fact that it does not require bulky inductors for its operation.

As for its working principle, the L4931ABD120 is designed to regulate the output voltage with an extremely low voltage drop across the regulator itself (from its input to output pin), usually ranging from 0.3 V to 0.5 V. This is achieved by adjusting the transistor\'s gate voltage according to the bandgap reference generated by the reference circuit, in such a way that the difference between its input voltage and the output voltage is kept as low as possible.

The working principle of the L4931ABD120 is based on a principle known as negative feedback, in which the input voltage and output voltage are continuously compared and the output voltage is adjusted accordingly in order to maintain the desired ratio between them. In other words, if the input voltage increases, the output voltage will automatically be adjusted to reach the same ratio as before, thus avoiding any large drop in the regulator’s output voltage.

The L4931ABD120 is particularly well suited for portable devices such as cellular phones, digital cameras and MP3 players, where size, low drop-out voltage and very low quiescent current are of utmost importance. It is also useful in a wide range of other applications, such as power supplies and battery powered systems, where a precisely regulated output voltage is required.

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