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LTC3857EUH Integrated Circuits Linear Technology

2016-7-27
           

LTC3857EUH

 

DESCRIPTION

The  LTC®3857  is  a  high  performance  dual  step-down  switching  regulator  controller  that  drives  all  N-channel  synchronous power MOSFET stages. A constant frequency current  mode  architecture  allows  a  phase-lockable  fre-quency of up to 850kHz. Power loss and noise due to the ESR of the input capacitor ESR are minimized by operating the two controller output stages out of phase.

The 50μA no-load quiescent current extends operating run time in battery-powered systems. The LTC3857 features a precision 0.8V reference and power good output indicators. A wide 4V to 38V input supply range encompasses a wide range of intermediate bus voltages and battery chemistries.

Independent TRACK/SS pins for each controller ramp the output voltages during start-up. Current foldback limits MOSFET heat dissipation during short-circuit conditions. The PLLIN/MODE pin selects among Burst Mode opera-tion, pulse-skipping mode, or continuous inductor current mode at light loads. 

For a leaded 28-lead SSOP package with a fixed current limit and one PGOOD output, without phase modulation or a clock output, see the LTC3857-1 data sheet.


FEATURES

Low Operating IQ: 50μA One Channel On

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

Wide VIN Range: 4V to 38V 40V Abs Max

RSENSE or DCR Current Sensing

Out-of-Phase Controllers Reduce Required Input Capacitance and

Power Supply Induced Noise

OPTI-LOOP® Compensation Minimizes COUT

Phase-Lockable Frequency 75kHz-850kHz

Programmable Fixed Frequency 50kHz-900kHz

Selectable Continuous, Pulse-Skipping or Low Ripple Burst Mode®

Operation at Light Loads

Selectable Current Limit

Very Low Dropout Operation: 99% Duty Cycle

Adjustable Output Voltage Soft-Start or Tracking

Power Good Output Voltage Monitors

Output Overvoltage Protection

Low Shutdown IQ : <8μA

Internal LDO Powers Gate Drive from VIN or EXTVCC

No Current Foldback During Start-up

5mm  × 5mm QFN Package

 

APPLICATIONS

Automotive Always-On Systems

Battery Operated Digital Devices

Distributed DC Power Systems

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