Features

• Dual High Efficiency DC/DC Converters:
    Buck-Boost (VOUT: 2.2V to 5.25V, IOUT: 400mA for VIN > 3V, VOUT = 3.3V)
    Buck (VOUT: 0.6V to VIN, IOUT: 200mA)
• 2.4V to 5.5V Input Voltage Range
• Pin Selectable Burst Mode Operation
• 25µA Total Quiescent Current for Both Converters in Burst Mode Operation
• Independent Power Good Indicator Outputs
• Integrated Soft-Start
• Thermal and Overcurrent Protection
• <1µA Quiescent Current in Shutdown
• Small 0.75mm × 3mm × 3mm QFN Package

Typical Application

Description

The LTC3522 combines a 400mA buck-boost DC/DC converter with a 200mA synchronous buck DC/DC converter in a tiny 3mm × 3mm package. The 1MHz switching frequency minimizes the solution footprint while maintaining high efficiency. Both converters feature internal soft-start and compensation, simplifying the design process.

The buck converter is current mode controlled and utilizes an internal synchronous rectifier for high efficiency. The buck converter supports 100% duty cycle operation to extend battery life. If the PWM pin is held low, the buck converter automatically transitions from Burst Mode operation to PWM mode. With the PWM pin held high, the buck converter remains in low noise, 1MHz PWM mode.

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

The LTC3522 provides a 1µA shutdown mode, overtemperature shutdown and current limit protection on both converters. The LTC3522 is available in a 16-pin low profile 3mm × 3mm QFN package.