Dual Synchronous, 400mA/800mA, 2.25MHz Step-Down DC/DC Regulator

The LTC3548 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.

Features

LTC3548A

Improved Burst Mode, Improved ESD, 2 Adjustable Outputs

LTC3548-2

One Fixed 1.8V Output, 1 Adjustable

LTC3548-1

Fixed 1.8V and 1.575V Outputs

LTC3548

2 Adjustable Outputs

Applications

* PDAs/Palmtop PCs

* Digital Cameras

* Cellular Phones

* Portable Media Players

* PC Cards

* Wireless and DSL Modems

* 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 RDS(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: IQ < 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