LM1770SMFX/NOPB

PMIC - Voltage Regulators - DC DC Switching Controllers

The LM1770SMFX/NOPB is Texas Instruments\' synchronous rectified step-down voltage regulator controller. This product is designed to provide efficient operation, easy implementation, and superior line and load regulation. It is also an ideal controller for electronics requiring significant power savings as it offers high efficiency and power switching.

Application Field

The LM1770SMFX/NOPB is used in a wide range of applications, including the following:

• Highly optimized computing systems
• Highly integrated consumer electronics products
• Portable consumer electronics products
• Industrial control systems
• Automotive electronics
• Telecommunications systems

The controller is capable of providing 0.75 to 3A output current with adjustable or fixed voltage outputs. The high voltage range (up to 52V) and the output voltage accuracy of 0.5% also benefit industry in creating buck regulators that meet their performance requirements.

Working Principle

The LM1770SMFX/NOPB features synchronous rectification, burst-mode operation, and cycle-by-cycle current limit. It operates in a conventional buck converter configuration, with the power switches (M1,M2) connected in series between the supply voltage, Vin, and the output voltage, Vout. A pair of passive components (L1,C1) is connected at the output for current buffering and energy storage. The schematic diagram of the LM1770SMFX/NOPB is shown in Figure 1.

Figure 1: Schematic diagram of the LM1770SMFX/NOPB

A PWM signal, generated by the error amp, drives the pulse width modulator that regulates the switching of M1, M2 in the do1wns tep. This PWM signal also provides a functional block that enables burst mode operation. In this switching mode, power transistors operate in bursts at a fixed frequency (typically 200kHz) to reduce power losses under light loads. As the load decreases, burst mode frequency and duty cycle are automatically reduced to conserve power. The inductor current waveform during burst mode operation is shown in Figure 2.

Figure 2: Inductor current waveform in the burst mode

The LM1770SMFX/NOPB also features a cycle-by-cycle current limit circuit. This integral current limit circuit senses inductor surge current and reduces pulse-width as required. This current limit circuit also features an over-voltage protection circuit and a voltage slope compensation circuit. The voltage slope compensation circuit enables the controller to maintain a constant output for a wide range of load and input conditions. The circuit also includes an enable pin, which can be used to enable/disable the controller when the enable signal is low.

In summary, the LM1770SMFX/NOPB offers a high performance, feature-rich voltage regulator controller that is suitable for a wide range of applications. The controller offers high efficiency, adjustable or fixed output voltage, and over-voltage protection. Additionally, the controller is capable of supporting synchronous rectification and burst mode operation.