Dual 550kHz Synchronous 2-Phase Switching Regulator Controller with 5-Bit VID

The LTC1873 is a dual switching regulator controller optimized for high efficiency with low input voltages. It includes two complete, on-chip, independent switching regulator controllers. Each is designed to drive a pair of external N-channel MOSFETs in a voltage mode feedback, synchronous buck configuration. The LTC1873 includes digital output voltage adjustment on side 1 that conforms to the Intel Desktop VID specification. A constant-frequency, true PWM design minimizes external component size and cost and optimizes load transient performance. The synchronous buck architecture automatically shifts to discontinuous and then to Burst Mode™ operation as the output load decreases, ensuring maximum efficiency over a wide range of load currents.

The LTC1873 features an onboard reference trimmed to 1% and delivers better than 1.5% regulation at the converter outputs over all combinations of line, load and temperature. Each channel can be enabled independently; with both channels disabled, the LTC1873 shuts down and supply current drops below 100µA.

Applications

* Microprocessor Core and I/O Supplies

* Multiple Logic Supply Generator

* High Efficiency Power Conversion

* Chipset Power Supply

* Two Independent PWM Controllers in One Package

* Side 1 Output Is Compliant with Intel Desktop VRM 8.4 Specifications (Includes 5-Bit VID DAC)

* 1.3V to 3.5V Output Voltage with 50mV/100mV Steps

* Two Sides Run Out-of-Phase to Minimize CIN

* All N-Channel External MOSFET Architecture

* No External Current Sense Resistors Required

* Precison Internal 0.8V ±1% Reference

* 550kHz Switching Frequency Minimizes External Component Size

* Very Fast Transient Response

* Up to 25A Output Current per Channel

* Low Shutdown Current: < 100µA

* Small 28-Pin SSOP Package