Features

• Two Ouput Stages Operate Antiphase Reducing
  Input Capacitance and Power Supply Noise
• 5-Bit VID Control (VRM 8.4 Compliant)
  V_OUT: 1.3V to 3.5V in 50mV/100mV Steps
• Current Mode Control Ensures Current Sharing
• True Remote Sensing Differential Amplifier
• OPTI-LOOP™ Compensation Minimizes C_OUT
• Programmable Fixed Frequency: 150kHz to
  300kHz—Effective 300kHz to 600kHz Switching
  Frequency
• ±1% Output Voltage Accuracy
• Wide V_IN Range: 4V to 36V Operation
• Adjustable Soft-Start Current Ramping
• Internal Current Foldback
• Short-Circuit Shutdown Timer with Defeat Option
• Overvoltage Soft-Latch Eliminates Nuisance Trips
• Low Shutdown Current: 20µA
• Small 36-Lead Narrow (0.209") SSOP Package

Typical Application

Description

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.