Dual 550kHz Synchronous Switching Regulator Controller with 5-Bit VID and 150mA LDO

The LTC1705 is a complete power supply controller for Intel Mobile Pentium processors. It includes two switching regulator controllers, each designed to drive a pair of N-channel MOSFETs in a voltage mode feedback, synchronous buck configuration, to provide the core and I/O supplies. The core controller includes a 5-bit DAC that conforms to the Intel Mobile VID specification. The IC also includes a low dropout linear regulator (LDO) that delivers up to 150mA of output current to provide the CLK supply. The LTC1705 uses a constant-frequency 550kHz PWM architecture, minimizing external component size and cost, as well as optimizing load transient performance. It provides better than 1.25% DC accuracy at its core output, and 2% at I/0 and CLK outputs. The high performance feedback loops allow the circuit to keep total output regulation within ±5% under all transient conditions. An open-drain PGOOD flag indicates that all three outputs are within ±10% of their regulated values. A shutdown circuit disables all three outputs if the RUN/SS pin is pulled to ground. In this mode, the LTC1705 supply current drops to below 100µA.

Applications

* Complete Power Supply Controller for Intel Mobile Pentium® Processors

* Intel Mobile Pentium Core, I/O, Clock Supplies

* Multiple Logic Supply Generator

* Three Regulated Outputs: Core, I/O and CLK in One Package

* Integrated Intel Mobile 5-Bit VID DAC

* No External Current Sense Resistors

* All N-Channel External MOSFET Architecture

* 550kHz Switching Frequency Minimizes External Component Size and Cost

* Integrated 150mA LDO Linear Regulator

* Excellent DC Accuracy: 1.25% for Core, 2% for I/O and CLK Supplies

* PGOOD Flag Monitors All Three Outputs

* High Efficiency Over Wide Load Current Range

* Low Shutdown Current: < 100µA

* Switchers Run Out-of-Phase to Minimize CIN

* Small 28-Pin Narrow SSOP Package