The **LTC3891** is a high-voltage synchronous buck DC/DC controller introduced by **Linear Technology Corporation**. This advanced device is designed to operate efficiently in demanding environments, with a standby current of just 50µA and a wide input voltage range of 4V to 60V. This makes it ideal for applications where high voltage transients are common, such as in automotive systems, heavy equipment, industrial control, robotics, and telecommunications.
The LTC3891 supports output currents up to 20A and delivers efficiencies as high as 95%, allowing for flexible voltage settings from 0.8V to 24V. Its robust design ensures reliable performance across various power sources and battery chemistries, including 12V, 24V, and 48V systems.
One of the standout features of the LTC3891 is its powerful 1.1Ω internal MOSFET gate driver, which enables efficient operation. The controller offers a flexible frequency range, operating at an optional fixed frequency between 50kHz and 900kHz, or synchronizing with an external clock from 75kHz to 850kHz via a phase-locked loop (PLL). It also provides multiple operational modes—continuous, pulse skip, and low-ripple Burst Mode—to optimize efficiency under light load conditions.
The device’s current-mode architecture simplifies loop compensation, ensures fast transient response, and delivers excellent voltage regulation. For current sensing, users can choose between measuring the DCR (direct current resistance) of the output inductor or using an optional sense resistor. Additionally, current foldback protection helps reduce heat generation during overload situations.
Other notable features include a short 95ns minimum on-time, enabling high step-down ratios at high efficiency, and up to 99% duty cycle for low dropout operation. An internal LDO supplies the gate driver from either the input voltage or an external EXTVCC pin, and a power good signal indicates system status.
The LTC3891 is available in two thermally enhanced packages: a 20-lead 3mm x 4mm QFN and a 20-lead TSSOP. It comes in three temperature grades: extended and industrial (-40°C to 125°C), automotive (-40°C to 150°C), and military (-55°C to 150°C). At 1,000-piece quantities, the unit costs $3.47 per piece.
**Key Performance Highlights:**
- Input Voltage Range: 4V to 60V
- Quiescent Current: 50µA
- Output Voltage Range: 0.8V to 24V
- Synchronous Rectification for Up to 95% Efficiency
- 95ns Minimum On-Time for High Step-Down Ratios
- DCR or RSENSE Current Detection
- Optional Low-Ripple Burst Mode, Pulse Skipping, or Continuous Operation
- Fixed Frequency Range: 50kHz to 900kHz
- PLL Synchronization: 75kHz to 850kHz
- Current-Mode Control for Fast Transient Response
- Adjustable Soft Start or Tracking
- Overvoltage and Overcurrent Foldback Protection
- Wide Temperature Grades: -40°C to 150°C
Whether you're working on automotive electronics, industrial power systems, or high-performance robotics, the LTC3891 offers a versatile and efficient solution for your DC/DC conversion needs.
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