L4999BB1TR

PMIC, or power management integrated circuits, are specialized chips designed to control the flow of electricity for specific applications. Among them, voltage regulators are used to regulate and maintain a preset output voltage to protect power systems from input voltage fluctuations. The L4999BB1TR is one such voltage regulator, and its applications and operating principle are discussed in this article.

Application Field
The L4999BB1TR is a 3-terminal integrated voltage regulator with a heavy load capacity. It features low quiescent current (2 mA typical), excellent line and load regulation, and a temperature range of -40℃ to +125℃. It is designed for applications requiring high output current and low noise. These include post-regulators for switch mode power supplies (SMPS), unregulated power supplies, and CRT display power supplies.

Typical Application Circuit
Figure 1 shows a typical application circuit for the L4999BB1TR voltage regulator. An input voltage source such as a power supply or AC adapter provides current to the regulator via the Input pin, while the Output pin drives the load. The Enable pin provides shutdown control. With the Enable pin pulled low, the regulator is in shutdown mode, allowing the device to be disabled and saving energy.

Working Principle
The L4999BB1TR voltage regulator uses a linear, fixed-frequency regulator topology to maintain a stable output voltage. The output voltage is set with an external precision voltage divider consisting of resistors R1 and R2. The internal voltage reference of the device is compared with the output feedback voltage via an error amplifier, and the output voltage is regulated by an onboard transistor. When the device is in operation, current flows through both the Load and R2, while R1 acts as a load resistor, creating a voltage drop across it and increasing the feedback voltage to the error amplifier. The error amplifier then compares the reference voltage and the feedback voltage, and adjusts the base current to the transistor to set the output voltage to the desired level.

Conclusion
The L4999BB1TR voltage regulator is ideal for applications requiring high output current, low noise, and excellent line and load regulation. The device features a heavy load capacity and temperatures ranging from -40℃ to +125℃. Furthermore, its typical quiescent current of only 2 mA makes it an excellent choice for power-sensitive applications. It uses a linear, fixed-frequency regulator topology to maintain a stable output voltage, and its onboard transistor adjusts the base current to keep the output voltage at the desired level.