LTC3569: Triple Synchronous Step-Down DC/DC Converter with Dynamically Adjustable Outputs

LTC3569: Triple Synchronous Step-Down DC/DC Converter with Dynamically Adjustable Outputs

MILPITAS, CA – January 29, 2009 – Linear Technology announces the LTC3569, a triple channel, high efficiency 3MHz synchronous buck regulator that delivers up 1.2A of continuous output current from one channel and 600mA from each of the other two channels. Using a constant frequency current mode architecture, the LTC3569 operates from an input voltage range of 2.5V to 5.5V, making it ideal for single-cell Li-Ion/polymer, or multicell alkaline/NiCad/NiMH applications. Each of the three output voltages are independently programmable, by lowering the feedback voltage of each channel from 800mV to 425mV (in 25mV increments) by toggling the EN pin, enabling dynamic adjustment of each channel’s output voltage. Additionally, each of the 600mA regulators can act as slave power stages to each other or to the 1.2A channel to support higher currents, thereby providing additional design flexibility.

The LTC3569’s switching frequency can be programmed between 1MHz and 3MHz or set at 2.25MHz, enabling the designer to optimize efficiency while avoiding critical noise-sensitive frequency bands. The combination of its 3mm x 3mm QFN-20 (or TSSOP- 16E) package and high switching frequency keeps external inductors and capacitors small, providing a very compact and thermally efficient footprint.

The LTC3569’s internal synchronous switches offer efficiencies as high as 95% while Burst Mode® operation minimizes quiescent current to only 100uA (all three channels) in no-load conditions. For applications demanding the lowest possible noise, the LTC3569 can run in a pulse skipping mode to minimize output ripple. The LTC3569 offers a Power Good indicator and is synchronizable to an external clock (1.2MHz to 3MHz) other features include internal compensation, over-temperature and short circuit protection.

The LTC3569EUD is available in a 3mm x 3mm QFN-20 package, and the LTC3569EFE is offered in a 16-lead thermally enhanced TSSOP package. Pricing starts at $3.10 and $3.20 each respectively, in 1,000-piece quantities. Industrial grade versions, the LTC3569IUD and LTC3569IFE, are tested and guaranteed to operate to the -40°C to 85°C operating junction temperature and are priced at $3.65 and $3.75 each respectively, in 1,000-piece quantities. All versions are available from stock. For more information, visit www.linear.com.

Summary of Features: LTC3569

Three Independent Current Mode Buck DC/DC Regulators (1.2A & 2x 600mA)

Single Pin Programmable VFB Servo Voltages from 800mV Down to 425mV (in 25mV Steps)

Pull VFB High to Make Each 600mA Buck a Slave for Higher Current Operation

Pulse Skip or Burst Mode Operation

Programmable (1MHz to 3MHz) or Fixed 2.25MHz

VIN Range 2.5V to 5.5V

Synchronizable (1.2MHz to 3MHz)

All Regulators Internally Compensated

PGOOD Output Flag

Quiescent Current

Zero Shutdown Current

Overtemperature & Short-Circuit Protection

Tiny 3mm × 3mm 20-Lead QFN &Thermally Enhanced TSSOP FE-16 Packages ■