LTC3859EFE

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The LTC3859EFE is a DC-DC switching controller designed for high-current, non-isolated synchronous buck power converters. It features an integrated buck switch that can supply currents up to 75A, and operates over an input voltage range of 4V to 36V. It offers a high degree of flexibility to tailor its operation to the application’s specific needs and requirements.

The LTC3859EFE enables synchronous buck topologies such as step-down buck, step-up/down buck-boost, and inverting buck-boost. It features an internal clock and selectable frequency, so it can be easily configured for different operations. Operating at low frequencies reduces the power dissipation in the buck switch and lowers the external component count. Additionally, the LTC3859EFE has an internal regulator and can be operated from an auxiliary voltage source, allowing users to optimize their PCB layout with the minimum number of external components.

Features:

• Integrated High-Side and Low-Side N-Channel MOSFET Drivers
• Integrated Maximum Duty Cycle Control
• Voltage-Mode or Current-Mode Operation
• Synchronizable to an External Clock
• Selectable Frequency Operations
• Internal Regulator for Auxiliary Voltage
• Over-Current Protection
• Short- Circuits and Over-Temperature Protection

LTC3859EFE Application Fields

The LTC3859EFE is suitable for a wide range of industrial, motor drive and automotive applications, including motor drives, point-of-load regulators, DC/DC converters, battery chargers, automotive systems and DC/AC inverters. Thanks to its low-external component count, robust design and integrated protection mechanisms, the LTC3859EFE is an ideal choice to help maximize efficiency, system reliability and PCB size in high-density designs.

Working Principle

The LTC3859EFE operates in one of two selectable switching topologies: Step-Down Buck or Step-Up/Down Buck-Boost. It can also be configured as an inverting buck-boost. In either configuration, the controller uses an internal oscillator that controls the gate driver of the external MOSFETs.

In step-down buck operation, the LTC3859EFE senses the input voltage, V_IN, and the output voltage, V_OUT, to regulate the output voltage for a given output current. In step-up/down buck-boost operation, the LTC3859EFE senses only the input voltage and the output current to maintain a regulated output voltage. In both cases, the output voltage regulation is accomplished by varying the time the switch is on and off, resulting in a duty cycle, which is adjusted to compensate for variations in the output and input voltages.

The LTC3859EFE\'s integrated current-mode control loop compensates for changes in load current by evaluating the inductor current, either as a voltage across an external sense resistor or via an external current-sense amplifier input. The measured current is then compared to a current reference, and the resulting difference, or error signal, is used to adjust the duty cycle accordingly.

The LTC3859EFE includes protection circuitry to prevent over-current, over-temperature and short-circuit conditions. If any of the protection conditions are triggered, the controller will stop operating and initiate a soft-start cycle when the protection condition has cleared.

Conclusion

The LTC3859EFE is an ideal choice for non-isolated, high-current buck converter designs. Its easy-to-integrate design and low external component count make it well suited for a wide range of industrial, motor drive and automotive applications. In addition, it features protection mechanisms and a wide operating voltage range that improve system reliability and performance.

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