LM3674MFX-1.5/NOPB

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LM3674MFX-1.5/NOPB Application Field and Working Principle

The LM3674MFX-1.5/NOPB is a simple, versatile and highly efficient synchronous switching regulator targeted at 2MHz small-outline package point-of-load, distributed DC/DC converters, and 48V intermediate bus converter products. This switching regulator belongs to the family of PMIC (Power Management Integrated Circuits) and has been categorized under Voltage Regulators and DC DC Switching Regulators.

The key features of this device are low external component count, constant switching frequency for low noise and EMI, synchronous rectification for improved efficiency, current limit and short-circuit protection, an enable pin, programmable soft-start, slew rate control, programmable hysteresis, and precision output voltage trim. Response time is extremely fast due to the integration of an internal PWM comparator, current limit comparator, error amplifier, driver, and logic. In addition, it features an adjustable output current limit of 300mA or 500mA and a low (1.5mV) voltage dropout at the enable pin.

The LM3674MFX-1.5/NOPB has been designed to work as a low side totem-pole switching regulator, where the power management IC drives an external N-Channel MOSFET in a synchronous rectification configuration. In this configuration, switching losses are minimized and efficiency is increased. The device can also produce a negative voltage or current output, depending on the external components chosen. As the switching frequency is constant, the losses due to gate charge are minimized and thus provide for improved efficiency between input and output voltage.

The working principle of the LM3674MFX-1.5/NOPB includes several stages. The first stage is of a current limit comparator that compares the current set point with the voltage at the external sense resistor connected to the IS pin. A PWM comparator is then used to compare the Error Amplifier output to a Ramp signal generated by an internal oscillator. This comparison sets the PWM signal at the 12th pin. After this the high side switch is enabled to supply the load with the required current. Finally, the Lowside FET is enabled for energy storage and the cycle is repeated.

In conclusion, LM3674MFX-1.5/NOPB is a simple, versatile and highly efficient synchronous switching regulator used in point-of-load and distributed DC/DC converters. It provides an adjustable output current limit, low voltage dropout at the enable pin, an enable pin, programmable soft-start and slew rate control, programmable hysteresis, and precision output voltage trim. The device works on the principle of PWM comparator, error amplifier, driver and logic which results in fast response time and efficient energy storage.

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