Features

• High Efficiency: Up to 95%
• Low Ripple (<35mV_P-P) Burst Mode Operation;
  I_Q = 40μA
• 2.25MHz Constant Frequency Operation
• High Switch Current: 0.7A and 1.2A
• No Schottky Diodes Required
• Low R_DS(ON) Internal Switches: 0.35Ω
• Current Mode Operation for Excellent Line and Load Transient Response
• Short-Circuit Protected
• Low Dropout Operation: 100% Duty Cycle
• Ultralow Shutdown Current: I_Q <1μA
• Output Voltages from 5V down to 0.6V
• Power-On Reset Output
• Externally Synchronizable Oscillator
• Optional External Soft-Start
• Small Thermally Enhanced MSOP and 3mm × 3mm DFN Packages

Typical Application

Description

The LTC®3548A is a dual, constant frequency, synchronous step-down DC/DC converter. Intended for low power applications, it operates from a 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, enabling the use of tiny, low cost capacitors and inductors 1mm or less in height. Each output voltage is adjustable from 0.6V to 5V. Internal synchronous 0.35Ω, 0.7A/1.2A power switches provide high efficiency without the need for external Schottky diodes.

A user-selectable mode input is provided to allow the user to trade-off ripple noise for low power efficiency. Burst Mode® operation provides the highest efficiency at light loads, while pulse-skipping mode provides the lowest ripple noise at light loads.

To further maximize battery life, the P-channel MOSFETs are turned on continuously in dropout (100% duty cycle), and both channels draw a total quiescent current of only 40μA. In shutdown, the device draws <1μA.