LTC3859ALHFE

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The LTC3859ALHFE is a fully integrated DC-DC controller and regulator designed to drive N-channel synchronous MOSFETs. This IC can be used as a wide input range DC/DC controller with integrated voltage regulation, switch current limit and programmable soft start. It is ideal for applications such as energy storage, point-of-load converters, and other high-efficiency DC-DC modules.

1. LTC3859ALHFE Application Field

The LTC3859ALHFE operates over input voltages ranging from 4 V to 48 V and can supply up to 2 A of output current. It features a high switching frequency, adjustable through external resistor. It provides accurate current limit control, adjustable soft start and voltage regulation with excellent transient response. It is ideally suited for driving low-side synchronous buck converter applications.

The solution provides an unprecedented level of integration and flexibility for managing power conversion. It is well suited for a wide range of applications, such as energy storage systems, point-of-load converters, automotive systems, telecom, industrial, HVAC control systems, renewable energy systems, and battery–operated applications.

2. LTC3859ALHFE Working Principle

When the LTC3859ALHFE IC is enabled it begins to work as a DC-DC regulator. With the help of the closed loop regulation capability and the current limit, the LTC3859ALHFE is able to limit the output current and maintain the output voltage with a steady value. Its output voltage is typically regulated within +/-1%.

The LTC3859ALHFE IC relies on an external input voltage, that is regulated by the voltage loop, the supply voltage, and the current loop. The voltage loop is composed of the internal voltage regulator, the error amplifier, an external resistor and an external capacitor. The sum of the input voltage, the voltage drop across the external resistor, and the voltage generated by the error amplifier must equal the output voltage.

The Current loop is made up of two transistors, one which is connected to the drain of the external MOSFET and the other is connected to a single current sense resistor. When the current will reach the peak current limit threshold, the current loop will stop the controller from sourcing additional current from the external MOSFET.

The Soft-start circuit allows for a controlled ramp slope of the output voltage. The soft-start pin is used to control the amount of current that flows into the Soft-start capacitor and as a result controls the rate at which the voltage ramps up.

The LTC3859ALHFE IC also offers programmable features such as the minimum on time, the fault status, and the external sense resistor value.

Conclusion

The LTC3859ALHFE is a fully integrated DC-DC controller and regulator designed to drive N-channel synchronous MOSFETs. It operates over input voltages ranging from 4 V to 48 V and it provides accurate current limit control, adjustable soft start and voltage regulation with excellent transient response, allowing for a wide range of applications. By having an internal voltage reference, an internal error amplifier, a soft-start circuit, and a current-sense circuit, the LTC3859ALHFE can regulate the output voltage, limit the output current, and provide a soft-start ramp to the output.

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