Features

• Synchronous Boost and Buck Controllers
• When Cascaded, Allows V_IN Above, Below or Equal to Regulated V_OUT
• Output Remains in Regulation Through Input Dips (e.g., Cold Crank) Down to 2.5V
• Wide Bias Input Voltage Range: 4.5V to 38V
• Low Input and Output Ripple
• Low EMI
• Fast Output Transient Response
• High Light Load Efficiency
• Low Operating I_Q: 33μA (Both Channels On)
• Low Operating I_Q: 28μA (Buck Channel On)
• R_SENSE or Lossless DCR Current Sensing
• Buck Output Voltage Range: 0.8V ≤ VOUT ≤ 24V
• Boost Output Voltage Up to 60V
• Phase-Lockable Frequency (75kHz to 850kHz)
• Small 32-Pin 5mm × 5mm QFN Package

Typical Application

Description

The LTC®7812 is a high performance synchronous Boost+Buck DC/DC switching regulator controller that drives all N-channel power MOSFET stages. It contains independent step-up (boost) and step-down (buck) controllers that can regulate two separate outputs or be cascaded to regulate an output voltage from an input voltage that can be above, below or equal to the output voltage. The LTC7812 operates from a wide 4.5V to 38V input supply range. When biased from the output of the boost regulator, the LTC7812 can operate from an input supply as low as 2.5V after start-up. The 33μA no-load quiescent current extends operating run time in battery-powered systems.

Unlike conventional buck-boost regulators, the LTC7812’s cascaded Boost+Buck solution has continuous, nonpulsating, input and output currents, substantially reducing voltage ripple and EMI. The LTC7812 has independent feedback and compensation points for the boost and buck regulation loops, enabling a fast output transient response that can be easily optimized externally.