Features

• Wide Output Voltage Range:
  0.8V < or = V_OUT < or = 14V
• Out-of-Phase Controllers Reduce Required Input Capacitance and Power Supply Induced Noise
• OPTI-LOOP® Compensation Minimizes C_OUT
• ±1% Output Voltage Accuracy
• Power Good Output Voltage Monitor
• Phase-Lockable Fixed Frequency 250kHz to 550kHz
• Latched Short-Circuit Shutdown (LTC3727 Only)
• Dual N-Channel MOSFET Synchronous Drive
• Wide V_IN Range: 4V to 36V Operation
• Very Low Dropout Operation: 99% Duty Cycle
• Adjustable Soft-Start Current Ramping
• Foldback Output Current Limiting
• Output Overvoltage Protection
• Low Shutdown I_Q: 20µA
• Selectable Constant Frequency or Burst Mode® Operation
• Small 28-Lead SSOP Package
• LTC3727-1 Also Available in the 5mm x 5mm QFN Package

Typical Application

Description

The LTC3727/LTC3727-1 are high performance dual step-down switching regulator controllers that drive all N-channel synchronous power MOSFET stages. A constant frequency current mode architecture allows phase-lockable frequency of up to 550kHz. Power loss and noise due to the ESR of the input capacitors are minimized by operating the two controller output stages out of phase.

OPTI-LOOP compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. There is a precision 0.8V reference and a power good output indicator. A wide 4V to 30V (36V maximum) input supply range encompasses all battery chemistries.

A RUN/SS pin for each controller provides soft-start, and on the LTC3727GN, optional timed, short-circuit shutdown. Current foldback limits MOSFET heat dissipation during short-circuit conditions when overcurrent latchoff is disabled. Output overvoltage protection circuitry latches on the bottom MOSFET until V_OUT returns to normal. The FCB mode pin can select among Burst Mode, constant frequency mode and continuous inductor current mode or regulate a secondary winding.