Features

• No Current Sense Resistors Required
• Out-of-Phase Controllers Reduce Required Input Capacitance
• Tracking Function
• Wide V_IN Range: 2.75V to 9.8V
• 0.6V ±1% Voltage Reference
• High Current Limit
• Constant Frequency Current Mode Operation
• Low Dropout Operation: 100% Duty Cycle
• True PLL for Frequency Locking or Adjustment
• Selectable Pulse Skipping/Forced Continuous Operation
• Auxiliary Winding Regulation
• Internal Soft-Start Circuitry
• Power Good Output Voltage Monitor
• Output Overvoltage Protection
• Micropower Shutdown: I_Q = 9μA
• Tiny Low Profile (4mm × 4mm) QFN and narrow SSOP packages.

Typical Application

Description

The LTC®3736-2 is a 2-phase dual synchronous step-down switching regulator controller with tracking that drives external complementary power MOSFETs using few external components. The constant frequency current mode architecture with MOSFET VDS sensing eliminates the need for sense resistors and improves efficiency. Power loss and noise due to the ESR of the input capacitance are minimized by operating the two controllers out of phase.

Pulse skipping operation provides high efficiency at light loads. 100% duty cycle capability provides low dropout operation, extending operating time in battery-powered systems.

The switching frequency can be programmed up to 750kHz, allowing the use of small surface mount inductors and capacitors. For noise sensitive applications, the LTC3736-2 switching frequency can be externally synchronized from 250kHz to 850kHz. An internal soft-start, which can be lengthened externally, smoothly ramps the output voltage during start-up.

The LTC3736-2 is available in the tiny thermally enhanced (4mm × 4mm) QFN and 24-lead narrow SSOP packages.