Features

• Three High Efficiency DC/DC Converters:
  Buck-Boost (V_OUT: 1.8V to 5.25V, I_OUT: 1A)
  Dual Buck (V_OUT: 0.6V to V_IN, I_OUT: 600mA)
• 1.8V to 5.5V Input Voltage Range
• Pin-Selectable Burst Mode® Operation
• 30μA Total Quiescent Current in Burst Mode Operation
• Independent Power Good Indicator Outputs
• Integrated Soft-Start
• Thermal and Overcurrent Protection
• <2μA Current in Shutdown
• Small 4mm × 4mm QFN and Thermally Enhanced TSSOP Packages

Typical Application

Description

The LTC®3521 combines a 1A buck-boost DC/DC converter and dual 600mA synchronous buck DC/DC converters. The 1.1MHz switching frequency minimizes the solution footprint while maintaining high efficiency. All three converters feature soft-start and internal compensation to minimize the solution footprint and simplify the design process.

The buck converters are current mode controlled and utilize an internal synchronous rectifier to improve efficiency. The buck converters support 100% duty cycle operation to extend battery life. If the PWM pin is held low, the buck converters automatically transition from Burst Mode operation to PWM mode at high loads. With the PWM pin held high, the buck converters remain in low noise, 1.1MHz PWM mode.

The buck-boost converter features continuous conduction operation to maximize efficiency and minimize noise. At light loads, the buck-boost converter can be operated in Burst Mode operation to improve efficiency and reduce no-load standby current.

The LTC3521 provides a <2μA shutdown mode, overtemperature shutdown and current limit protection on all converters. The LTC3521 is available in a 24-pin 0.75mm × 4mm × 4mm QFN package, and a 20-pin thermally enhanced TSSOP package.