Features

• Dual High Efficiency DC/DC Converters:
  Buck-Boost (V_OUT: 2.2V to 5.25V, I_OUT = 1A at
  V_OUT = 3.3V, V_IN ≥ 3V)
  Buck (V_OUT: 0.8V to V_IN, I_OUT = 600mA)
• 2.2V to 5.5V Input Voltage Range
• Pin-Selectable Burst Mode® Operation
• Uncommitted Gain Block for LDO Controller, Battery Good Indication or Sequencing
• Programmable 100kHz to 2MHz Switching Frequency
• 55μA Total Quiescent Current for Both Converters in Burst Mode Operation
• Thermal and Overcurrent Protection
• <1μA Quiescent Current in Shutdown
• 24-Lead 4mm × 4mm QFN Package

Typical Application

Description

The LTC3520 combines 1A buck-boost and 600mA synchronous buck DC/DC converters in a tiny 4mm x 4mm package. A programmable switching frequency allows the efficiency to be optimized while minimizing the solution footprint. Both converters feature soft-start and current limit protection. The uncommitted gain block can be configured as an LDO or utilized as a battery-good comparator.

The buck converter is current mode controlled with internal synchronous rectification to improve efficiency. Pin-select- able Burst Mode operation can be enabled to improve light load efficiency, or the buck converter can be operated in low noise PWM mode for sensitive applications.

The buck-boost converter provides continuous conduction operation to maximize efficiency and minimize noise. At light loads, use of Burst Mode operation will improve efficiency.

The LTC3520 provides a <1µA shutdown mode and over- temperature shutdown on both converters. The LTC3520 is available in a low profile (0.75mm) 24-lead 4mm x 4mm QFN package.