L4943

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The L4943, a member of the STMicroelectronics Power Management Long Life series, is a high-sensitivity low dropout linear voltage regulator specifically designed for low voltage applications with high current outputs. The device can provide an adjustable output voltage from 1.2 to 5.0 V with an output current of up to 1 A. The L4943 is particularly suitable for mobile to battery applications.

This high power linear regulator is a three-terminal regulator with a typical drop-out voltage of 40 mV when operating at 1 A, making it one of the lowest drop-out regulators available. The internal reset circuit is used to protect the device and output from overload conditions, while the over-current protection limits the device’s output current to a safe level. The full-on/off control ensures the L4943 will remain in regulation over the full range of input voltages.

The main application field of the L4943 is mobile to battery applications, such as laptop or notebook computers, PDAs, and digital cameras, where function requirements and performance cannot be satisfied with other solutions available in the market. The ability to dissipate power up to 20W into a 12V-regulated output makes it ideal for such applications. The L4943 also has excellent thermal behavior and achieves high efficiency. Other application fields include precision instrumentation, tools and test equipment, process control and electrical systems.

Working principle-wise, the L4943 is based on a combination circuit composed of a voltage reference, an error amplifier, a current limiter, a thermal protection circuit, and three transistors (NPN, PNP, and multiple PNP). Its operation can be divided into three basic stages.

Firstly, a voltage reference is used to determine the output desired. This voltage is amplified by the error amplifier, producing a virtual output voltage which is compared to the actual output voltage. If the difference is above a certain threshold, the NPN and PNP transistors are activated, thus allowing the current to flow through the resistors from the input to the output, until the desired output voltage is achieved. The multiple PNP transistors form the basis for the current limiter circuit, which regulates the maximum current going through the regulator.

Once the output voltage has been set, the device enters the second stage which is the control stage. The output voltage is again compared to the input voltage. If the output voltage is higher than the input voltage, the device will not allow current to flow, thus preventing over-current conditions, even at high temperatures. If, on the other hand, the output voltage is lower than the input voltage, the device will not allow current to flow, thus protecting the device and output from over-voltage conditions. The third stage occurs when the over-current protection and over-voltage protection is activated. The device will shut off, preventing any further current from flowing, and protecting the device from any over-current conditions.

Overall, the L4943 is a high-performance, low-dropout linear voltage regulator for mobile to battery applications. The device is simple to use and has excellent temperature stability, allowing it to achieve high efficiency and reliable operation. With its wide variety of features and applications, this low dropout regulator is the perfect choice for a range of applications.

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