Monolithic Dual Tracking 3A Step-Down Switching Regulator

The LT3501 is a dual current mode PWM step-down DC/DC converter with two internal 3.5A switches. Independent input voltage, feedback, soft-start and power good pins for each channel simplify complex power supply tracking/sequencing requirements.

Both converters are synchronized to either a common external clock input or a resistor programmable fi xed 250kHz to 1.5MHz internal oscillator. At all frequencies, a 180° phase relationship between channels is maintained, reducing voltage ripple and component size. Programmable frequency allows for optimization between effi ciency and external component size.

Minimum input-to-output voltage ratios are improved by allowing the switch to stay on through multiple clock cycles, only switching off when the boost capacitor needs recharging, resulting in ~95% maximum duty cycle.

Each output can be independently disabled using its own soft-start pin, or by using the SHDN pin the entire part can be placed in a low quiescent current shutdown mode.

The LT3501 is available in a 20-lead TSSOP package with exposed leadframe for low thermal resistance.

Applications

* DSP Power Supplies

* Disc Drives

* DSL/Cable Modems

* Wall Transformer Regulation

* Distributed Power Regulation

* Wide Input Range: 3.1V to 25V

* Two Switching Regulators with 3A Output Capability

* Independent Supply to Each Regulator

* Adjustable/Synchronizable Fixed Frequency Operation from 250kHz to 1.5MHz

* Antiphase Switching

* Outputs Can be Paralleled

* Independent, Sequential, Ratiometric or Absolute Tracking Between Outputs

* Independent Soft-Start and Power Good Pins

* Enhanced Short-Circuit Protection

* Low Dropout: 95% Maximum Duty Cycle

* Low Shutdown Current: <10µA

* 20-Lead TSSOP Package with Exposed Leadframe