Low I, 60V Synchronous Step-Down Controller

The LTC3891 is a high performance step-down switching regulator DC/DC controller that drives an all N-channel synchronous power MOSFET stage. A constant frequency current mode architecture allows a phase-lockable frequency of up to 750kHz.

The 50μA no-load quiescent current extends operating run time in battery-powered systems. OPTI-LOOP® compensation allows the transient response to be optimized over a wide range of output capacitance and ESR values. The LTC3891 features a precision 0.8V reference and power good output indicator. A wide 4V to 60V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries. The output voltage of the LTC3891 can be programmed between 0.8V to 24V.

The TRACK/SS pin ramps the output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The PLLIN/MODE pin selects among Burst Mode operation, pulse-skipping mode, or continuous conduction mode at light loads.

Applications

* Automotive Always-On Systems

* Battery Powered Digital Devices

* Distributed DC Power Systems

* Wide VIN Range: 4V to 60V (65V Abs Max)

* Low Operating IQ: 50μA

* Wide Output Voltage Range: 0.8V ≤ VOUT ≤ 24V

* RSENSE or DCR Current Sensing

* Phase-Lockable Frequency (75kHz to 750kHz)

* Programmable Fixed Frequency (50kHz to 900kHz)

* Selectable Continuous, Pulse-Skipping or Low Ripple Burst Mode® Operation at Light Load

* Selectable Current Limit

* Very Low Dropout Operation: 99% Duty Cycle

* Adjustable Output Voltage Soft-Start or Tracking

* Power Good Output Voltage Monitor

* Output Overvoltage Protection

* Low Shutdown IQ: < 14μA

* Internal LDO Powers Gate Drive from VIN or EXTVCC

* No Current Foldback During Start-Up

* Small 20-Pin 3mm × 4mm QFN and TSSOP Packages