Features

• High Efficiency: Up to 95%
• Four Independent Regulators Provide Up to 300mA, 200mA, 200mA and 100mA Output Current
• 2.25V to 5.5V Input Voltage Range
• 2.25MHz Constant-Frequency Operation
• No Schottky Diodes Required
• Extremely Low Channel-to-Channel Transient Crosstalk
• Low Ripple (20mVP-P) Burst Mode Operation:
  IQ = 70µA (All Channels On)
• 0.8V Reference Allows Low Output Voltages
• Shutdown Mode Draws <1µA Supply Current
• Current Mode Operation for Excellent Line and Load Transient Response
• Overtemperature Protected
• Low Profile (3mm × 3mm) 16-Lead QFN Package

Typical Application

Description

The LTC3544 is a quad, high efficiency, monolithic synchronous buck regulator using a constant-frequency, current mode architecture. The four regulators operate independently with separate run pins. The 2.25V to 5.5V input voltage range makes the LTC3544 well suited for single Li-Ion/polymer battery-powered applications. 100% duty cycle provides low dropout operation, extending battery runtime in portable systems. Low ripple Burst Mode® operation increases efficiency at light loads, further extending battery runtime with typically only 20mV of ripple.

Switching frequency is internally set to 2.25MHz, allowing the use of small surface mount inductors and capacitors. The internal synchronous switches increase efficiency and eliminate the need for external Schottky diodes. Low output voltages are easily supported with the 0.8V feedback reference voltage.

The LTC3544 is available in a low profile (0.75mm) (3mm × 3mm) QFN package.