Features

• High Efficiency Dual Step-Down Outputs: Up to 96%
• 300mA Output Current per Channel at VIN = 3V
• Automatic Low Ripple Burst Mode Operation (20mVP-P).
• Only 40µA Quiescent Current During Operation (Both Channels)
• 2.25MHz Constant-Frequency Operation
• 2.5V to 5.5V Input Voltage Range
• Low Dropout Operation: 100% Duty Cycle
• Internally Compensated for All Ceramic Capacitors
• Independent Internal Soft-Start for Each Channel
• Current Mode Operation for Excellent Line and Load Transient Response
• 0.6V Reference Allows Low Output Voltages
• Short-Circuit Protected
• Ultralow Shutdown Current: IQ < 1µA
• Low Profi le (0.75mm) 8-Lead 3mm × 2mm DFN Package

Typical Application

Description

The LTC3547 is a dual, 2.25MHz, constant-frequency, synchronous step-down DC/DC converter in a tiny 3mm × 2mm DFN package. 100% duty cycle provides low dropout operation, extending battery life in portable systems. Low output voltages are supported with the 0.6V feedback reference voltage. Each regulator can supply 300mA continuous output current.

The input voltage range is 2.5V to 5.5V, making it ideal for Li-Ion and USB powered applications. Supply current during operation is only 40µA and drops to < 1µA in shutdown. Automatic Burst Mode® operation increases efficiency at light loads, further extending battery life.

An internally set 2.25MHz switching frequency allows the use of tiny surface mount inductors and capacitors. Internal soft-start reduces inrush current during startup. All outputs are internally compensated to work with ceramic capacitors. The LTC3547 is available in a low profile (0.75mm) 3mm × 2mm DFN package.The LTC3547is also available in a fixed output voltage configuration,eliminating the need for the external feedback networks