LM1771USD/NOPB

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LM1771USD/NOPB is a microcontroller unit (MCU) of voltage regulator which is a DC-DC switching controller in PMIC – Voltage Regulators. It is a synchronous flyback controller developed by Texas Instruments (TI), providing high-accuracy output voltage regulation, low power consumption and excellent light load efficiency. It is built on the company’s process of CMOS, which is able to combine low quiescent current, high voltage accuracy and low cost. This type of voltage regulator is suitable for normal core voltage, clock voltage, PWM peripheral voltage and light load applications.

The main application fields of LM1771USD/NOPB are line regulation, clock regulation and PWM applications for Point-Of-Load (POL) converters. Not only can it be used for various industrial and consumer electronics, but also automotive long-distance communication, home automation, and other high-reliability applications. Its features include wide input voltage range 15V-36V, adjustable constant frequency current mode, ultra-low quiescent current, gain-scheduled compensation, and enhanced light load efficiency over a wide range of line levels.

Working Principle

The LM1771USD/NOPB is an integrated circuit (IC) with synchronous and flyback functions, making it a very flexible DC-DC converter controller. Its core architecture is a voltage mode constant frequency current mode buck-boost with integrated load switches. It is also adjustable and provides up to 98.5% peak efficiency at normal loads and offers improved light load efficiency compared with other DC-DC controllers. The main principle of its operation is based on the peak current mode control. In the circuit, the voltage mode control regulates the output voltage, while the current mode control regulates the peak inductor current.

The power conversion cycle of LM1771USD/NOPB can be divided into two parts: the energy transference part and the energy recovery part. During the energy transfer cycle, the power is switched from the input stage to the output stage by a high-side switch which is activated by a signal from the controller. The controller then turns on the low-side switch and turns off the high-side switch. This allows the inductor and output capacitor to replenish the energy stored in the input capacitor and the output capacitor.

The LM1771USD/NOPB also includes an Adaptive Voltage Position (AVP) circuit that accurately regulates the output voltage and protects the output voltage from excess voltage. AVP adjusts the operating frequency over a wide input voltage range and is capable of detecting the output voltage deviation. When the output voltage variation exceeds the programmed window, AVP will increase the operating frequency in order to maintain the output voltage.

Protection Features

The LM1771USD/NOPB provides an excellent protective function to ensure safe and reliable operation with low voltage operation, short-circuit protection, thermal shutdown, and over-current protection. The low voltage protection will inactive the controller once the input voltage drops below 8V. If the output voltage exceeds the maximum drive voltage, the controller will be in a fault mode and the output will be shut down.

In order to prevent the controller from experiencing thermal shutdown, the device has included a thermal shutdown circuit which will automatically turn off the device to prevent it from exceeding the normal operating temperature. It also has included an over-current protection which will detect if the current exceeds the maximum level of preset. When this happens, the controller will enter the fault state and the output will be turned off.

Conclusion

The LM1771USD/NOPB is a high-performance, low power microcontroller unit (MCU) which is a synchronous flyback controller developed by Texas Instruments (TI) under PMIC – Voltage Regulators. It is widely used for various industrial and consumer electronics and automotive long-distance communication applications. The main features of LM1771USD/NOPB include wide input voltage range 15-36V, adjustable constant frequency current mode, ultra-low quiescent current, gain-scheduled compensation and enhanced light load efficiency. Not only can it provide accurate output voltage regulation, but also protection features like short circuit protection, thermal shutdown, and over-current protection. It is a very powerful and reliable voltage regulator that can help our life to be more convenient and safer.

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