LM2677SX-ADJ Integrated Circuits (ICs)

LM2677SX-ADJ Application Field and Working Principle

The LM2677SX-ADJ is a DC-DC switching regulator series from Texas Instruments, designed for power management, appropriate for a number of different applications. This device is part of the Power Management Integrated Circuit (PMIC) family. It belongs to the Voltage Regulators subsection, and more specifically to the DC DC Switching Regulators section. As a DC-DC switching regulator, the LM2677SX-ADJ integrates a control block, with current sensing and voltage regulator loops. It is versatile, due to its adjustable output voltage and fixed switching frequency, and is characterized by low power dissipation.

Features

The LM2677SX-ADJ is a series of buck switching regulators, intended for use in boost, buck and VWL(Voltage Minimizer) topologies. Its output voltage range is adjustable, with a 1.21 V to 24 V maximum and a 0.8 V minimum limit. It has a 3-2.3 A adjustable peak output current. The switching frequency can be set between 100 kHz and 1.5 MHz and can be synchronized by an external clock signal if needed. It has a fast OVP and OCP response, with a Under Voltage Lock Out (UVLO) threshold of 10 V on the input pin.

The device also has an open loop soft start, that provides an adjustable output slew rate and prevents heavy in-rush current from the power supply. It also has a phase-locked loop (PLL) that can be used to phase lock the output frequency to an external clock. It also features thermal shutdown, over current and over temperature protection.

Applications

The LM2677SX-ADJ series is intended for general power supply applications, such as powering digital signal processors, video processors, surveillance cameras and other similar applications. It is especially suitable for applications where low power dissipation, adjustable output voltage and wide operating frequency range are needed.

Working Principle

In buck topology, the LM2677SX-ADJ converts a high input voltage to a regulated, lower output voltage. It does so byusing MOSFETs as the main power switches, enhancing the efficiency of the conversion process. The device is controlled by two different loops: the current loop - for controlling the peak current delivered to the load - and the voltage loop - for regulating the output voltage. The voltage reference is set by an external resistor divider and the peak current of the power switch is regulated by a 7-bit PWM comparator.

Both loops are connected to the error amplifier, which is responsible for generating the control voltage for the power switch driver. This control voltage is applied to the power switch, turning it on and off in order to maintain the desired voltage and current levels. The device also includes a soft start feature, which allows it to start without causing any sudden current surge.

The switching frequency of the LM2677SX-ADJ can be adjusted by changing the external clock frequency, or it can be synchronized with an external clock signal. The device also features thermal shutdown protection and an Internal Phase-locked Loop (PLL), which can be used to keep the output frequency locked with an external reference clock.

Conclusion

The LM2677SX-ADJ is a low power, adjustable DC-DC switching regulator from Texas Instruments, designed for power management and intended for general power supply applications. It has adjustable output voltage and peak current, along with a wide operating frequency range, making it suitable for a number of different applications. It is characterized by low power dissipation, fast over voltage and over current protection, as well as a soft start feature.