LT3845EFE#PBF

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LT3845EFE#PBF Application Field and Working Principle

The LT3845EFE#PBF Integrated Power Solution is a DC/DC switching controller that provides an active current-mode buck controller for off-line and DC-to-DC converter applications. This device integrates a fixed frequency, current-mode buck controller and a low voltage MOSFET driver into a single package, and is capable of providing maximum current output from as low as 18 V DC input. This Parts Wd MOFSETs has a high efficiency rating and is designed for faster transient response, which makes it ideal for applications such as LED lighting, adapter and isolated DC-DC converters, and telecommunication and PC board applications.

Overview

The LT3845EFE#PBF integrated power solution combined a fixed frequency, current-mode buck controller with a low voltage MOSFET driver in a single package. The typical input voltage range is from 18V to 400 V and the output voltage range is from 0.8V to 1.8V. The embedded current-mode controller enables fast transient response, while the low ON resistance driver is optimized for high efficiency conversion. The current-mode control architecture provides excellent load transient with fast and accurate loop compensation, allowing the device to operate over a wide input voltage range. The LT3845EFE#PBF also offers an adjustable current limit, overvoltage protection, and a wide temperature operating range.

Features

• Fixed frequency current mode controller
• High efficiency, low on resistance MOSFET driver
• Programmable frequency (150kHz to 1MHz)
• High output voltage accuracy
• Low quiescent current
• Output overload protection
• 2.5% reference accuracy
• Soft-start/enable
• Over-voltage protection
• Under-voltage Lockout
• Two 30 ns internal delay/sync control
• Thermal shutdown with hysteresis

Operation

The LT3845EFE#PBF is a DC-to-DC buck converter that converts an input DC voltage (VI) to a lower, regulated output voltage (VO). The device uses an external MOSFET switch to control the current flow from the input to the output. The operating frequency of the power supply is programmable from 150 kHz to 1 MHz with external resistor RSET. The currentmode control provides a fast transient response, allowing the part to be used in applications such as LED lighting, automotive, and high frequency switching supplies.

The input stage consists of an Enable pin that turns the power supply on and off. By pulling the EN pin low, the part will start to regulate the output voltage. An internal softstart capacitor (CSS) supplies a ramp to the oscillator control voltage, limiting the inrush current of the MOSFET switch without requiring an external capacitor. The device uses an externally adjustable current limit voltage by programming the current limit sense resistor. When the output current reaches the set limit, the part reduces the duty cycle until the current level is acceptable.

The MOSFET driver stage is designed for low side Nchannel MOSFETs that are optimized for high efficiency applications. It is compatible with 3.3V and 5V logic and offers a high current source/sink drivers with a high slew rate to reduce switching losses. The low input voltage over-voltage protection (OVLO) prevents the device from turning on when the input voltage is too high, and the under-voltage lockout (UVLO) prevents the device from turning on when the input voltage is too low.

Applications

• LED Lighting
• DC-to-DC Converters
• Adapter and Isolated DC-to-DC Converters
• Telecommunication and PC Board Applications

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