Features

• High Efficiency: Up to 95%
• Very Low Quiescent Current: Only 40μA
• Low Output Ripple Burst Mode® Operation
• 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
• Small Thermally Enhanced MSOP and 3mm × 3mm DFN Packages

Typical Application

Description

The LTC®3548 is a dual, constant frequency, synchronous step down DC/DC converter. Intended for low power applications, it operates from 2.5V to 5.5V input voltage range and has a constant 2.25MHz switching frequency, allowing the use of tiny, low cost capacitors and inductors with a profile ≤1mm. 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 noise ripple for low power efficiency. Burst Mode operation provides high efficiency at light loads, while Pulse-Skipping Mode provides low noise ripple at light loads.

To further maximize battery runtime, 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.