2-Phase, 5-Bit Adjustable,High Efficiency, Synchronous Step-Down Switching Regulator

The LTC1709 is a 2-phase, VID programmable, synchronous step-down switching regulator controller that drives all N-channel external power MOSFET stages in a fixed frequency architecture. The 2-phase controller drives its two output stages out of phase at frequencies up to 300kHz to minimize the RMS ripple currents in both input and output capacitors. The 2-phase technique effectively multiplies the fundamental frequency by two, improving transient response while operating each channel at a optimum frequency for efficiency. Thermal design is also simplified.

An internal differential amplifier provides true remote sensing of the regulated supply’s positive and negative output terminals as required in high current applications.

The RUN/SS pin provides soft-start and optional timed, short-circuit shutdown. Current foldback limits MOSFET dissipaton during short-circuit conditions when overcurrent latchoff is disabled. OPTI-LOOP compensation allows the transient response to be optimized for a wide range of output capacitors and ESR values.

Vout Range

VRM

LTC1709

1.3V to 3.5V

VRM8.4

LTC1709-7

0.925V to 2V

Mobile

LTC1709-8

1.3V to 3.5V

VRM8.4

LTC1709-85

1.05V to 1.825V

VRM8.5

LTC1709-9

1.1V to 1.85V

VRM9.0

Applications

* Desktop Computers

* Internet/Network Servers

* Large Memory Arrays

* DC Power Distribution Systems

* Battery Chargers

* Two Ouput Stages Operate Antiphase Reducing Input Capacitance and Power Supply Noise

* 5-Bit VID Control (VRM 8.4 Compliant)

VOUT: 1.3V to 3.5V in 50mV/100mV Steps

* Current Mode Control Ensures Current Sharing

* True Remote Sensing Differential Amplifier

* OPTI-LOOP™ Compensation Minimizes COUT

* Programmable Fixed Frequency: 150kHz to 300kHz—Effective 300kHz to 600kHz Switching Frequency