Features

• Dual Buck Plus Single Boost Synchronous Controllers
• Wide Bias Input Voltage Range: 4.5V to 60V
• Outputs Remain in Regulation Through Cold Crank Down to a 2.2V Input Supply Voltage
• Buck and Boost Output Voltages Up to 60V
• Adjustable Gate Drive Level 5V to 10V (OPTI-DRIVE)
• No External Bootstrap Diodes Required
• Low Operating I_Q: 29μA (One Channel On)
• 100% Duty Cycle for Boost Synchronous MOSFET
• Phase-Lockable Frequency (75kHz to 850kHz)
• Programmable Fixed Frequency (50kHz to 900kHz)
• Very Low Dropout Operation: 99% Duty Cycle (Bucks)
• Low Shutdown I_Q: 3.6μA
• Fixed or Adjustable Boost Output Voltage Saves I_Q
• Small 38-Lead 5mm × 7mm QFN and TSSOP Packages

Typical Application

Description

The LTC®3899 is a high performance triple output (buck/ buck/boost) DC/DC switching regulator controller that drives all N-channel synchronous power MOSFET stages. The constant frequency current mode architecture allows a phase-lockable frequency of up to 850kHz. The LTC3899 operates from a wide 4.5V to 60V input supply range. When biased from the output of the boost converter or another auxiliary supply, the LTC3899 can operate from an input supply as low as 2.2V after start-up.

The gate drive for the LTC3899 can be programmed from 5V to 10V to allow the use of logic-level or standard-level FETs and to maximize efficiency. Internal switches in the top gate drivers eliminate the need for external bootstrap diodes. The 29μA no-load quiescent current extends operating run time in battery-powered systems. OPTI-LOOP® compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values.