The LTC3851 is a synchronous step-down switching regulator controller from Linear Technology. Its input range is 4V to 38V, making it suitable for regulating power from a variety of sources, including automotive batteries, 24V industrial supplies, and unregulated wall transformers. The LTC3851 features strong onboard drivers that allow the use of high power external MOSFETs to produce output currents up to 20A with output voltages ranging from 0.8V to 5.5V. The constant frequency peak current mode control architecture provides excellent line and load regulation along with load current sharing capability and dependable cycle-by-cycle current limiting. OPTI-LOOP® compensation simplifies loop stability design and provides well-behaved regulation over a broad range of operating conditions.
The document details the LTC3851, a versatile synchronous buck controller available in QFN or SSOP packages. It supports a wide input voltage range of 4V to 38V and can drive high-power external MOSFETs for output currents up to 20A with voltages from 0.8V to 5.5V.
Key features include constant frequency peak current mode control, OPTI-LOOP compensation, and three selectable current sense thresholds (30mV, 50mV, 75mV). The device offers multiple operating modes including Burst Mode for high efficiency at light loads and forced continuous conduction mode. It also includes fault protection such as foldback current limiting and output overvoltage detection.
| Input Voltage Range | 4V to 38V |
|---|---|
| Maximum Output Current | 20A |
| Output Voltage Range | 0.8V to 5.5V |
| Minimum On-Time | 90ns (typical) |
| Maximum Switching Frequency | 750kHz |
| Output Voltage Tolerance | +1% |
At light loads, it can be configured to operate in high efficiency Burst Mode operation or pulse-skipping mode.
The LTC3851 includes foldback current limiting, output overvoltage detection, and input undervoltage detection.