Features

• Output Stages Operate Antiphase
• ±1% Output Voltage Accuracy
• 6-Bit IMVP-IV VID Code: V_OUT = 0.7V to 1.708V
• Intel Compatible Power Saving Mode (PSIB)
• Stage Shedding Improves Low Current Efficiency
• Power Good Output with Adaptive Masking
• Lossless Voltage Positioning
• Dual Input Supply Capability for Load Sharing
• Resistor Programmable V_OUT at Boot-Up and Deeper Sleep State
• Resistor Programmable Deep Sleep Offset
• Programmable Fixed Frequency: 210kHz to 550kHz
• Adjustable Soft-Start Current Ramping
• Foldback Output Current Limit
• Short-Circuit Shutdown Timer with Defeat Option
• Overvoltage Protection
• Available in 36-Lead SSOP (0.209 Wide) and 38-Lead (5mm × 7mm) Packages

Typical Application

Description

The LTC3735 is a 2-phase synchronous step-down switching regulator controller that drives all N-channel power MOSFETs in a constant frequency architecture. The output voltage is programmable by six VID bits during normal operation and by external resistors during initial boot-up and deeper sleep state. The LTC3735 drives its two output stages out-of-phase at frequencies up to 550kHz to minimize the RMS ripple currents in both input and output capacitors. This antiphase technique also doubles the apparent switching frequency, improving the transient response while operating each phase at an optimum frequency for efficiency. Thermal design is further simplified by cycle-by-cycle current sharing between the two phases.

An Intel compatible PSIB input is provided to select between two modes of operation. Fully enhanced synchronous mode achieves a very small output ripple and very fast transient response while power saving mode realizes very high efficiency. OPTI-LOOP® compensation allows the transient response to be optimized for a wide range of output capacitance and ESR values.